1 /*
   2  * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.tools.javac.code;
  27 
  28 import java.lang.ref.SoftReference;
  29 import java.util.HashSet;
  30 import java.util.HashMap;
  31 import java.util.Locale;
  32 import java.util.Map;
  33 import java.util.Optional;
  34 import java.util.Set;
  35 import java.util.WeakHashMap;
  36 import java.util.function.BiFunction;
  37 import java.util.function.BiPredicate;
  38 import java.util.function.Function;
  39 import java.util.function.Predicate;
  40 import java.util.stream.Collector;
  41 
  42 import javax.tools.JavaFileObject;
  43 
  44 import com.sun.tools.javac.code.Attribute.RetentionPolicy;
  45 import com.sun.tools.javac.code.Lint.LintCategory;
  46 import com.sun.tools.javac.code.Source.Feature;
  47 import com.sun.tools.javac.code.Type.UndetVar.InferenceBound;
  48 import com.sun.tools.javac.code.TypeMetadata.Annotations;
  49 import com.sun.tools.javac.comp.AttrContext;
  50 import com.sun.tools.javac.comp.Check;
  51 import com.sun.tools.javac.comp.Enter;
  52 import com.sun.tools.javac.comp.Env;
  53 import com.sun.tools.javac.jvm.ClassFile;
  54 import com.sun.tools.javac.util.*;
  55 
  56 import static com.sun.tools.javac.code.BoundKind.*;
  57 import static com.sun.tools.javac.code.Flags.*;
  58 import static com.sun.tools.javac.code.Kinds.Kind.*;
  59 import static com.sun.tools.javac.code.Scope.*;
  60 import static com.sun.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;
  61 import static com.sun.tools.javac.code.Symbol.*;
  62 import static com.sun.tools.javac.code.Type.*;
  63 import static com.sun.tools.javac.code.TypeTag.*;
  64 import static com.sun.tools.javac.jvm.ClassFile.externalize;
  65 import com.sun.tools.javac.resources.CompilerProperties.Fragments;
  66 
  67 /**
  68  * Utility class containing various operations on types.
  69  *
  70  * <p>Unless other names are more illustrative, the following naming
  71  * conventions should be observed in this file:
  72  *
  73  * <dl>
  74  * <dt>t</dt>
  75  * <dd>If the first argument to an operation is a type, it should be named t.</dd>
  76  * <dt>s</dt>
  77  * <dd>Similarly, if the second argument to an operation is a type, it should be named s.</dd>
  78  * <dt>ts</dt>
  79  * <dd>If an operations takes a list of types, the first should be named ts.</dd>
  80  * <dt>ss</dt>
  81  * <dd>A second list of types should be named ss.</dd>
  82  * </dl>
  83  *
  84  * <p><b>This is NOT part of any supported API.
  85  * If you write code that depends on this, you do so at your own risk.
  86  * This code and its internal interfaces are subject to change or
  87  * deletion without notice.</b>
  88  */
  89 public class Types {
  90     protected static final Context.Key<Types> typesKey = new Context.Key<>();
  91 
  92     final Symtab syms;
  93     final JavacMessages messages;
  94     final Names names;
  95     final Check chk;
  96     final Enter enter;
  97     JCDiagnostic.Factory diags;
  98     List<Warner> warnStack = List.nil();
  99     final Name capturedName;
 100 
 101     public final Warner noWarnings;
 102 
 103     // <editor-fold defaultstate="collapsed" desc="Instantiating">
 104     public static Types instance(Context context) {
 105         Types instance = context.get(typesKey);
 106         if (instance == null)
 107             instance = new Types(context);
 108         return instance;
 109     }
 110 
 111     @SuppressWarnings("this-escape")
 112     protected Types(Context context) {
 113         context.put(typesKey, this);
 114         syms = Symtab.instance(context);
 115         names = Names.instance(context);
 116         Source source = Source.instance(context);
 117         chk = Check.instance(context);
 118         enter = Enter.instance(context);
 119         capturedName = names.fromString("<captured wildcard>");
 120         messages = JavacMessages.instance(context);
 121         diags = JCDiagnostic.Factory.instance(context);
 122         noWarnings = new Warner(null) {
 123             @Override
 124             public String toString() {
 125                 return "NO_WARNINGS";
 126             }
 127         };
 128     }
 129     // </editor-fold>
 130 
 131     // <editor-fold defaultstate="collapsed" desc="bounds">
 132     /**
 133      * Get a wildcard's upper bound, returning non-wildcards unchanged.
 134      * @param t a type argument, either a wildcard or a type
 135      */
 136     public Type wildUpperBound(Type t) {
 137         if (t.hasTag(WILDCARD)) {
 138             WildcardType w = (WildcardType) t;
 139             if (w.isSuperBound())
 140                 return w.bound == null ? syms.objectType : w.bound.getUpperBound();
 141             else
 142                 return wildUpperBound(w.type);
 143         }
 144         else return t;
 145     }
 146 
 147     /**
 148      * Get a capture variable's upper bound, returning other types unchanged.
 149      * @param t a type
 150      */
 151     public Type cvarUpperBound(Type t) {
 152         if (t.hasTag(TYPEVAR)) {
 153             TypeVar v = (TypeVar) t;
 154             return v.isCaptured() ? cvarUpperBound(v.getUpperBound()) : v;
 155         }
 156         else return t;
 157     }
 158 
 159     /**
 160      * Get a wildcard's lower bound, returning non-wildcards unchanged.
 161      * @param t a type argument, either a wildcard or a type
 162      */
 163     public Type wildLowerBound(Type t) {
 164         if (t.hasTag(WILDCARD)) {
 165             WildcardType w = (WildcardType) t;
 166             return w.isExtendsBound() ? syms.botType : wildLowerBound(w.type);
 167         }
 168         else return t;
 169     }
 170 
 171     /**
 172      * Get a capture variable's lower bound, returning other types unchanged.
 173      * @param t a type
 174      */
 175     public Type cvarLowerBound(Type t) {
 176         if (t.hasTag(TYPEVAR) && ((TypeVar) t).isCaptured()) {
 177             return cvarLowerBound(t.getLowerBound());
 178         }
 179         else return t;
 180     }
 181 
 182     /**
 183      * Recursively skip type-variables until a class/array type is found; capture conversion is then
 184      * (optionally) applied to the resulting type. This is useful for i.e. computing a site that is
 185      * suitable for a method lookup.
 186      */
 187     public Type skipTypeVars(Type site, boolean capture) {
 188         while (site.hasTag(TYPEVAR)) {
 189             site = site.getUpperBound();
 190         }
 191         return capture ? capture(site) : site;
 192     }
 193     // </editor-fold>
 194 
 195     // <editor-fold defaultstate="collapsed" desc="projections">
 196 
 197     /**
 198      * A projection kind. See {@link TypeProjection}
 199      */
 200     enum ProjectionKind {
 201         UPWARDS() {
 202             @Override
 203             ProjectionKind complement() {
 204                 return DOWNWARDS;
 205             }
 206         },
 207         DOWNWARDS() {
 208             @Override
 209             ProjectionKind complement() {
 210                 return UPWARDS;
 211             }
 212         };
 213 
 214         abstract ProjectionKind complement();
 215     }
 216 
 217     /**
 218      * This visitor performs upwards and downwards projections on types.
 219      *
 220      * A projection is defined as a function that takes a type T, a set of type variables V and that
 221      * produces another type S.
 222      *
 223      * An upwards projection maps a type T into a type S such that (i) T has no variables in V,
 224      * and (ii) S is an upper bound of T.
 225      *
 226      * A downwards projection maps a type T into a type S such that (i) T has no variables in V,
 227      * and (ii) S is a lower bound of T.
 228      *
 229      * Note that projections are only allowed to touch variables in V. Therefore, it is possible for
 230      * a projection to leave its input type unchanged if it does not contain any variables in V.
 231      *
 232      * Moreover, note that while an upwards projection is always defined (every type as an upper bound),
 233      * a downwards projection is not always defined.
 234      *
 235      * Examples:
 236      *
 237      * {@code upwards(List<#CAP1>, [#CAP1]) = List<? extends String>, where #CAP1 <: String }
 238      * {@code downwards(List<#CAP2>, [#CAP2]) = List<? super String>, where #CAP2 :> String }
 239      * {@code upwards(List<#CAP1>, [#CAP2]) = List<#CAP1> }
 240      * {@code downwards(List<#CAP1>, [#CAP1]) = not defined }
 241      */
 242     class TypeProjection extends TypeMapping<ProjectionKind> {
 243 
 244         List<Type> vars;
 245         Set<Type> seen = new HashSet<>();
 246 
 247         public TypeProjection(List<Type> vars) {
 248             this.vars = vars;
 249         }
 250 
 251         @Override
 252         public Type visitClassType(ClassType t, ProjectionKind pkind) {
 253             if (t.isCompound()) {
 254                 List<Type> components = directSupertypes(t);
 255                 List<Type> components1 = components.map(c -> c.map(this, pkind));
 256                 if (components == components1) return t;
 257                 else return makeIntersectionType(components1);
 258             } else {
 259                 Type outer = t.getEnclosingType();
 260                 Type outer1 = visit(outer, pkind);
 261                 List<Type> typarams = t.getTypeArguments();
 262                 List<Type> formals = t.tsym.type.getTypeArguments();
 263                 ListBuffer<Type> typarams1 = new ListBuffer<>();
 264                 boolean changed = false;
 265                 for (Type actual : typarams) {
 266                     Type t2 = mapTypeArgument(t, formals.head.getUpperBound(), actual, pkind);
 267                     if (t2.hasTag(BOT)) {
 268                         //not defined
 269                         return syms.botType;
 270                     }
 271                     typarams1.add(t2);
 272                     changed |= actual != t2;
 273                     formals = formals.tail;
 274                 }
 275                 if (outer1 == outer && !changed) return t;
 276                 else return new ClassType(outer1, typarams1.toList(), t.tsym, t.getMetadata()) {
 277                     @Override
 278                     protected boolean needsStripping() {
 279                         return true;
 280                     }
 281                 };
 282             }
 283         }
 284 
 285         @Override
 286         public Type visitArrayType(ArrayType t, ProjectionKind s) {
 287             Type elemtype = t.elemtype;
 288             Type elemtype1 = visit(elemtype, s);
 289             if (elemtype1 == elemtype) {
 290                 return t;
 291             } else if (elemtype1.hasTag(BOT)) {
 292                 //undefined
 293                 return syms.botType;
 294             } else {
 295                 return new ArrayType(elemtype1, t.tsym, t.metadata) {
 296                     @Override
 297                     protected boolean needsStripping() {
 298                         return true;
 299                     }
 300                 };
 301             }
 302         }
 303 
 304         @Override
 305         public Type visitTypeVar(TypeVar t, ProjectionKind pkind) {
 306             if (vars.contains(t)) {
 307                 if (seen.add(t)) {
 308                     try {
 309                         final Type bound;
 310                         switch (pkind) {
 311                             case UPWARDS:
 312                                 bound = t.getUpperBound();
 313                                 break;
 314                             case DOWNWARDS:
 315                                 bound = (t.getLowerBound() == null) ?
 316                                         syms.botType :
 317                                         t.getLowerBound();
 318                                 break;
 319                             default:
 320                                 Assert.error();
 321                                 return null;
 322                         }
 323                         return bound.map(this, pkind);
 324                     } finally {
 325                         seen.remove(t);
 326                     }
 327                 } else {
 328                     //cycle
 329                     return pkind == ProjectionKind.UPWARDS ?
 330                             syms.objectType : syms.botType;
 331                 }
 332             } else {
 333                 return t;
 334             }
 335         }
 336 
 337         private Type mapTypeArgument(Type site, Type declaredBound, Type t, ProjectionKind pkind) {
 338             return t.containsAny(vars) ?
 339                     t.map(new TypeArgumentProjection(site, declaredBound), pkind) :
 340                     t;
 341         }
 342 
 343         class TypeArgumentProjection extends TypeMapping<ProjectionKind> {
 344 
 345             Type site;
 346             Type declaredBound;
 347 
 348             TypeArgumentProjection(Type site, Type declaredBound) {
 349                 this.site = site;
 350                 this.declaredBound = declaredBound;
 351             }
 352 
 353             @Override
 354             public Type visitType(Type t, ProjectionKind pkind) {
 355                 //type argument is some type containing restricted vars
 356                 if (pkind == ProjectionKind.DOWNWARDS) {
 357                     //not defined
 358                     return syms.botType;
 359                 }
 360                 Type upper = t.map(TypeProjection.this, ProjectionKind.UPWARDS);
 361                 Type lower = t.map(TypeProjection.this, ProjectionKind.DOWNWARDS);
 362                 List<Type> formals = site.tsym.type.getTypeArguments();
 363                 BoundKind bk;
 364                 Type bound;
 365                 if (!isSameType(upper, syms.objectType) &&
 366                         (declaredBound.containsAny(formals) ||
 367                          !isSubtype(declaredBound, upper))) {
 368                     bound = upper;
 369                     bk = EXTENDS;
 370                 } else if (!lower.hasTag(BOT)) {
 371                     bound = lower;
 372                     bk = SUPER;
 373                 } else {
 374                     bound = syms.objectType;
 375                     bk = UNBOUND;
 376                 }
 377                 return makeWildcard(bound, bk);
 378             }
 379 
 380             @Override
 381             public Type visitWildcardType(WildcardType wt, ProjectionKind pkind) {
 382                 //type argument is some wildcard whose bound contains restricted vars
 383                 Type bound = syms.botType;
 384                 BoundKind bk = wt.kind;
 385                 switch (wt.kind) {
 386                     case EXTENDS:
 387                         bound = wt.type.map(TypeProjection.this, pkind);
 388                         if (bound.hasTag(BOT)) {
 389                             return syms.botType;
 390                         }
 391                         break;
 392                     case SUPER:
 393                         bound = wt.type.map(TypeProjection.this, pkind.complement());
 394                         if (bound.hasTag(BOT)) {
 395                             bound = syms.objectType;
 396                             bk = UNBOUND;
 397                         }
 398                         break;
 399                 }
 400                 return makeWildcard(bound, bk);
 401             }
 402 
 403             private Type makeWildcard(Type bound, BoundKind bk) {
 404                 return new WildcardType(bound, bk, syms.boundClass) {
 405                     @Override
 406                     protected boolean needsStripping() {
 407                         return true;
 408                     }
 409                 };
 410             }
 411         }
 412     }
 413 
 414     /**
 415      * Computes an upward projection of given type, and vars. See {@link TypeProjection}.
 416      *
 417      * @param t the type to be projected
 418      * @param vars the set of type variables to be mapped
 419      * @return the type obtained as result of the projection
 420      */
 421     public Type upward(Type t, List<Type> vars) {
 422         return t.map(new TypeProjection(vars), ProjectionKind.UPWARDS);
 423     }
 424 
 425     /**
 426      * Computes the set of captured variables mentioned in a given type. See {@link CaptureScanner}.
 427      * This routine is typically used to computed the input set of variables to be used during
 428      * an upwards projection (see {@link Types#upward(Type, List)}).
 429      *
 430      * @param t the type where occurrences of captured variables have to be found
 431      * @return the set of captured variables found in t
 432      */
 433     public List<Type> captures(Type t) {
 434         CaptureScanner cs = new CaptureScanner();
 435         Set<Type> captures = new HashSet<>();
 436         cs.visit(t, captures);
 437         return List.from(captures);
 438     }
 439 
 440     /**
 441      * This visitor scans a type recursively looking for occurrences of captured type variables.
 442      */
 443     class CaptureScanner extends SimpleVisitor<Void, Set<Type>> {
 444 
 445         @Override
 446         public Void visitType(Type t, Set<Type> types) {
 447             return null;
 448         }
 449 
 450         @Override
 451         public Void visitClassType(ClassType t, Set<Type> seen) {
 452             if (t.isCompound()) {
 453                 directSupertypes(t).forEach(s -> visit(s, seen));
 454             } else {
 455                 t.allparams().forEach(ta -> visit(ta, seen));
 456             }
 457             return null;
 458         }
 459 
 460         @Override
 461         public Void visitArrayType(ArrayType t, Set<Type> seen) {
 462             return visit(t.elemtype, seen);
 463         }
 464 
 465         @Override
 466         public Void visitWildcardType(WildcardType t, Set<Type> seen) {
 467             visit(t.type, seen);
 468             return null;
 469         }
 470 
 471         @Override
 472         public Void visitTypeVar(TypeVar t, Set<Type> seen) {
 473             if ((t.tsym.flags() & Flags.SYNTHETIC) != 0 && seen.add(t)) {
 474                 visit(t.getUpperBound(), seen);
 475             }
 476             return null;
 477         }
 478 
 479         @Override
 480         public Void visitCapturedType(CapturedType t, Set<Type> seen) {
 481             if (seen.add(t)) {
 482                 visit(t.getUpperBound(), seen);
 483                 visit(t.getLowerBound(), seen);
 484             }
 485             return null;
 486         }
 487     }
 488 
 489     // </editor-fold>
 490 
 491     // <editor-fold defaultstate="collapsed" desc="isUnbounded">
 492     /**
 493      * Checks that all the arguments to a class are unbounded
 494      * wildcards or something else that doesn't make any restrictions
 495      * on the arguments. If a class isUnbounded, a raw super- or
 496      * subclass can be cast to it without a warning.
 497      * @param t a type
 498      * @return true iff the given type is unbounded or raw
 499      */
 500     public boolean isUnbounded(Type t) {
 501         return isUnbounded.visit(t);
 502     }
 503     // where
 504         private final UnaryVisitor<Boolean> isUnbounded = new UnaryVisitor<Boolean>() {
 505 
 506             public Boolean visitType(Type t, Void ignored) {
 507                 return true;
 508             }
 509 
 510             @Override
 511             public Boolean visitClassType(ClassType t, Void ignored) {
 512                 List<Type> parms = t.tsym.type.allparams();
 513                 List<Type> args = t.allparams();
 514                 while (parms.nonEmpty()) {
 515                     WildcardType unb = new WildcardType(syms.objectType,
 516                                                         BoundKind.UNBOUND,
 517                                                         syms.boundClass,
 518                                                         (TypeVar)parms.head);
 519                     if (!containsType(args.head, unb))
 520                         return false;
 521                     parms = parms.tail;
 522                     args = args.tail;
 523                 }
 524                 return true;
 525             }
 526         };
 527     // </editor-fold>
 528 
 529     // <editor-fold defaultstate="collapsed" desc="asSub">
 530     /**
 531      * Return the least specific subtype of t that starts with symbol
 532      * sym.  If none exists, return null.  The least specific subtype
 533      * is determined as follows:
 534      *
 535      * <p>If there is exactly one parameterized instance of sym that is a
 536      * subtype of t, that parameterized instance is returned.<br>
 537      * Otherwise, if the plain type or raw type `sym' is a subtype of
 538      * type t, the type `sym' itself is returned.  Otherwise, null is
 539      * returned.
 540      */
 541     public Type asSub(Type t, Symbol sym) {
 542         return asSub.visit(t, sym);
 543     }
 544     // where
 545         private final SimpleVisitor<Type,Symbol> asSub = new SimpleVisitor<Type,Symbol>() {
 546 
 547             public Type visitType(Type t, Symbol sym) {
 548                 return null;
 549             }
 550 
 551             @Override
 552             public Type visitClassType(ClassType t, Symbol sym) {
 553                 if (t.tsym == sym)
 554                     return t;
 555                 Type base = asSuper(sym.type, t.tsym);
 556                 if (base == null)
 557                     return null;
 558                 ListBuffer<Type> from = new ListBuffer<>();
 559                 ListBuffer<Type> to = new ListBuffer<>();
 560                 try {
 561                     adapt(base, t, from, to);
 562                 } catch (AdaptFailure ex) {
 563                     return null;
 564                 }
 565                 Type res = subst(sym.type, from.toList(), to.toList());
 566                 if (!isSubtype(res, t))
 567                     return null;
 568                 ListBuffer<Type> openVars = new ListBuffer<>();
 569                 for (List<Type> l = sym.type.allparams();
 570                      l.nonEmpty(); l = l.tail)
 571                     if (res.contains(l.head) && !t.contains(l.head))
 572                         openVars.append(l.head);
 573                 if (openVars.nonEmpty()) {
 574                     if (t.isRaw()) {
 575                         // The subtype of a raw type is raw
 576                         res = erasure(res);
 577                     } else {
 578                         // Unbound type arguments default to ?
 579                         List<Type> opens = openVars.toList();
 580                         ListBuffer<Type> qs = new ListBuffer<>();
 581                         for (List<Type> iter = opens; iter.nonEmpty(); iter = iter.tail) {
 582                             qs.append(new WildcardType(syms.objectType, BoundKind.UNBOUND,
 583                                                        syms.boundClass, (TypeVar) iter.head));
 584                         }
 585                         res = subst(res, opens, qs.toList());
 586                     }
 587                 }
 588                 return res;
 589             }
 590 
 591             @Override
 592             public Type visitErrorType(ErrorType t, Symbol sym) {
 593                 return t;
 594             }
 595         };
 596     // </editor-fold>
 597 
 598     // <editor-fold defaultstate="collapsed" desc="isConvertible">
 599     /**
 600      * Is t a subtype of or convertible via boxing/unboxing
 601      * conversion to s?
 602      */
 603     public boolean isConvertible(Type t, Type s, Warner warn) {
 604         if (t.hasTag(ERROR)) {
 605             return true;
 606         }
 607         boolean tPrimitive = t.isPrimitive();
 608         boolean sPrimitive = s.isPrimitive();
 609         if (tPrimitive == sPrimitive) {
 610             return isSubtypeUnchecked(t, s, warn);
 611         }
 612         boolean tUndet = t.hasTag(UNDETVAR);
 613         boolean sUndet = s.hasTag(UNDETVAR);
 614 
 615         if (tUndet || sUndet) {
 616             return tUndet ?
 617                     isSubtype(t, boxedTypeOrType(s)) :
 618                     isSubtype(boxedTypeOrType(t), s);
 619         }
 620 
 621         return tPrimitive
 622             ? isSubtype(boxedClass(t).type, s)
 623             : isSubtype(unboxedType(t), s);
 624     }
 625 
 626     /**
 627      * Is t a subtype of or convertible via boxing/unboxing
 628      * conversions to s?
 629      */
 630     public boolean isConvertible(Type t, Type s) {
 631         return isConvertible(t, s, noWarnings);
 632     }
 633     // </editor-fold>
 634 
 635     // <editor-fold defaultstate="collapsed" desc="findSam">
 636 
 637     /**
 638      * Exception used to report a function descriptor lookup failure. The exception
 639      * wraps a diagnostic that can be used to generate more details error
 640      * messages.
 641      */
 642     public static class FunctionDescriptorLookupError extends RuntimeException {
 643         private static final long serialVersionUID = 0;
 644 
 645         transient JCDiagnostic diagnostic;
 646 
 647         FunctionDescriptorLookupError() {
 648             this.diagnostic = null;
 649         }
 650 
 651         FunctionDescriptorLookupError setMessage(JCDiagnostic diag) {
 652             this.diagnostic = diag;
 653             return this;
 654         }
 655 
 656         public JCDiagnostic getDiagnostic() {
 657             return diagnostic;
 658         }
 659 
 660         @Override
 661         public Throwable fillInStackTrace() {
 662             // This is an internal exception; the stack trace is irrelevant.
 663             return this;
 664         }
 665     }
 666 
 667     /**
 668      * A cache that keeps track of function descriptors associated with given
 669      * functional interfaces.
 670      */
 671     class DescriptorCache {
 672 
 673         private WeakHashMap<TypeSymbol, Entry> _map = new WeakHashMap<>();
 674 
 675         class FunctionDescriptor {
 676             Symbol descSym;
 677 
 678             FunctionDescriptor(Symbol descSym) {
 679                 this.descSym = descSym;
 680             }
 681 
 682             public Symbol getSymbol() {
 683                 return descSym;
 684             }
 685 
 686             public Type getType(Type site) {
 687                 site = removeWildcards(site);
 688                 if (site.isIntersection()) {
 689                     IntersectionClassType ict = (IntersectionClassType)site;
 690                     for (Type component : ict.getExplicitComponents()) {
 691                         if (!chk.checkValidGenericType(component)) {
 692                             //if the inferred functional interface type is not well-formed,
 693                             //or if it's not a subtype of the original target, issue an error
 694                             throw failure(diags.fragment(Fragments.NoSuitableFunctionalIntfInst(site)));
 695                         }
 696                     }
 697                 } else {
 698                     if (!chk.checkValidGenericType(site)) {
 699                         //if the inferred functional interface type is not well-formed,
 700                         //or if it's not a subtype of the original target, issue an error
 701                         throw failure(diags.fragment(Fragments.NoSuitableFunctionalIntfInst(site)));
 702                     }
 703                 }
 704                 return memberType(site, descSym);
 705             }
 706         }
 707 
 708         class Entry {
 709             final FunctionDescriptor cachedDescRes;
 710             final int prevMark;
 711 
 712             public Entry(FunctionDescriptor cachedDescRes,
 713                     int prevMark) {
 714                 this.cachedDescRes = cachedDescRes;
 715                 this.prevMark = prevMark;
 716             }
 717 
 718             boolean matches(int mark) {
 719                 return  this.prevMark == mark;
 720             }
 721         }
 722 
 723         FunctionDescriptor get(TypeSymbol origin) throws FunctionDescriptorLookupError {
 724             Entry e = _map.get(origin);
 725             CompoundScope members = membersClosure(origin.type, false);
 726             if (e == null ||
 727                     !e.matches(members.getMark())) {
 728                 FunctionDescriptor descRes = findDescriptorInternal(origin, members);
 729                 _map.put(origin, new Entry(descRes, members.getMark()));
 730                 return descRes;
 731             }
 732             else {
 733                 return e.cachedDescRes;
 734             }
 735         }
 736 
 737         /**
 738          * Compute the function descriptor associated with a given functional interface
 739          */
 740         public FunctionDescriptor findDescriptorInternal(TypeSymbol origin,
 741                 CompoundScope membersCache) throws FunctionDescriptorLookupError {
 742             if (!origin.isInterface() || (origin.flags() & ANNOTATION) != 0 || origin.isSealed()) {
 743                 //t must be an interface
 744                 throw failure("not.a.functional.intf", origin);
 745             }
 746 
 747             final ListBuffer<Symbol> abstracts = new ListBuffer<>();
 748             for (Symbol sym : membersCache.getSymbols(new DescriptorFilter(origin))) {
 749                 Type mtype = memberType(origin.type, sym);
 750                 if (abstracts.isEmpty()) {
 751                     abstracts.append(sym);
 752                 } else if ((sym.name == abstracts.first().name &&
 753                         overrideEquivalent(mtype, memberType(origin.type, abstracts.first())))) {
 754                     if (!abstracts.stream().filter(msym -> msym.owner.isSubClass(sym.enclClass(), Types.this))
 755                             .map(msym -> memberType(origin.type, msym))
 756                             .anyMatch(abstractMType -> isSubSignature(abstractMType, mtype))) {
 757                         abstracts.append(sym);
 758                     }
 759                 } else {
 760                     //the target method(s) should be the only abstract members of t
 761                     throw failure("not.a.functional.intf.1",  origin,
 762                             diags.fragment(Fragments.IncompatibleAbstracts(Kinds.kindName(origin), origin)));
 763                 }
 764             }
 765             if (abstracts.isEmpty()) {
 766                 //t must define a suitable non-generic method
 767                 throw failure("not.a.functional.intf.1", origin,
 768                             diags.fragment(Fragments.NoAbstracts(Kinds.kindName(origin), origin)));
 769             } else if (abstracts.size() == 1) {
 770                 return new FunctionDescriptor(abstracts.first());
 771             } else { // size > 1
 772                 FunctionDescriptor descRes = mergeDescriptors(origin, abstracts.toList());
 773                 if (descRes == null) {
 774                     //we can get here if the functional interface is ill-formed
 775                     ListBuffer<JCDiagnostic> descriptors = new ListBuffer<>();
 776                     for (Symbol desc : abstracts) {
 777                         String key = desc.type.getThrownTypes().nonEmpty() ?
 778                                 "descriptor.throws" : "descriptor";
 779                         descriptors.append(diags.fragment(key, desc.name,
 780                                 desc.type.getParameterTypes(),
 781                                 desc.type.getReturnType(),
 782                                 desc.type.getThrownTypes()));
 783                     }
 784                     JCDiagnostic msg =
 785                             diags.fragment(Fragments.IncompatibleDescsInFunctionalIntf(Kinds.kindName(origin),
 786                                                                                        origin));
 787                     JCDiagnostic.MultilineDiagnostic incompatibleDescriptors =
 788                             new JCDiagnostic.MultilineDiagnostic(msg, descriptors.toList());
 789                     throw failure(incompatibleDescriptors);
 790                 }
 791                 return descRes;
 792             }
 793         }
 794 
 795         /**
 796          * Compute a synthetic type for the target descriptor given a list
 797          * of override-equivalent methods in the functional interface type.
 798          * The resulting method type is a method type that is override-equivalent
 799          * and return-type substitutable with each method in the original list.
 800          */
 801         private FunctionDescriptor mergeDescriptors(TypeSymbol origin, List<Symbol> methodSyms) {
 802             return mergeAbstracts(methodSyms, origin.type, false)
 803                     .map(bestSoFar -> new FunctionDescriptor(bestSoFar.baseSymbol()) {
 804                         @Override
 805                         public Type getType(Type origin) {
 806                             Type mt = memberType(origin, getSymbol());
 807                             return createMethodTypeWithThrown(mt, bestSoFar.type.getThrownTypes());
 808                         }
 809                     }).orElse(null);
 810         }
 811 
 812         FunctionDescriptorLookupError failure(String msg, Object... args) {
 813             return failure(diags.fragment(msg, args));
 814         }
 815 
 816         FunctionDescriptorLookupError failure(JCDiagnostic diag) {
 817             return new FunctionDescriptorLookupError().setMessage(diag);
 818         }
 819     }
 820 
 821     private DescriptorCache descCache = new DescriptorCache();
 822 
 823     /**
 824      * Find the method descriptor associated to this class symbol - if the
 825      * symbol 'origin' is not a functional interface, an exception is thrown.
 826      */
 827     public Symbol findDescriptorSymbol(TypeSymbol origin) throws FunctionDescriptorLookupError {
 828         return descCache.get(origin).getSymbol();
 829     }
 830 
 831     /**
 832      * Find the type of the method descriptor associated to this class symbol -
 833      * if the symbol 'origin' is not a functional interface, an exception is thrown.
 834      */
 835     public Type findDescriptorType(Type origin) throws FunctionDescriptorLookupError {
 836         return descCache.get(origin.tsym).getType(origin);
 837     }
 838 
 839     /**
 840      * Is given type a functional interface?
 841      */
 842     public boolean isFunctionalInterface(TypeSymbol tsym) {
 843         try {
 844             findDescriptorSymbol(tsym);
 845             return true;
 846         } catch (FunctionDescriptorLookupError ex) {
 847             return false;
 848         }
 849     }
 850 
 851     public boolean isFunctionalInterface(Type site) {
 852         try {
 853             findDescriptorType(site);
 854             return true;
 855         } catch (FunctionDescriptorLookupError ex) {
 856             return false;
 857         }
 858     }
 859 
 860     public Type removeWildcards(Type site) {
 861         if (site.getTypeArguments().stream().anyMatch(t -> t.hasTag(WILDCARD))) {
 862             //compute non-wildcard parameterization - JLS 9.9
 863             List<Type> actuals = site.getTypeArguments();
 864             List<Type> formals = site.tsym.type.getTypeArguments();
 865             ListBuffer<Type> targs = new ListBuffer<>();
 866             for (Type formal : formals) {
 867                 Type actual = actuals.head;
 868                 Type bound = formal.getUpperBound();
 869                 if (actuals.head.hasTag(WILDCARD)) {
 870                     WildcardType wt = (WildcardType)actual;
 871                     //check that bound does not contain other formals
 872                     if (bound.containsAny(formals)) {
 873                         targs.add(wt.type);
 874                     } else {
 875                         //compute new type-argument based on declared bound and wildcard bound
 876                         switch (wt.kind) {
 877                             case UNBOUND:
 878                                 targs.add(bound);
 879                                 break;
 880                             case EXTENDS:
 881                                 targs.add(glb(bound, wt.type));
 882                                 break;
 883                             case SUPER:
 884                                 targs.add(wt.type);
 885                                 break;
 886                             default:
 887                                 Assert.error("Cannot get here!");
 888                         }
 889                     }
 890                 } else {
 891                     //not a wildcard - the new type argument remains unchanged
 892                     targs.add(actual);
 893                 }
 894                 actuals = actuals.tail;
 895             }
 896             return subst(site.tsym.type, formals, targs.toList());
 897         } else {
 898             return site;
 899         }
 900     }
 901 
 902     /**
 903      * Create a symbol for a class that implements a given functional interface
 904      * and overrides its functional descriptor. This routine is used for two
 905      * main purposes: (i) checking well-formedness of a functional interface;
 906      * (ii) perform functional interface bridge calculation.
 907      */
 908     public ClassSymbol makeFunctionalInterfaceClass(Env<AttrContext> env, Name name, Type target, long cflags) {
 909         if (target == null || target == syms.unknownType) {
 910             return null;
 911         }
 912         Symbol descSym = findDescriptorSymbol(target.tsym);
 913         Type descType = findDescriptorType(target);
 914         ClassSymbol csym = new ClassSymbol(cflags, name, env.enclClass.sym.outermostClass());
 915         csym.completer = Completer.NULL_COMPLETER;
 916         csym.members_field = WriteableScope.create(csym);
 917         MethodSymbol instDescSym = new MethodSymbol(descSym.flags(), descSym.name, descType, csym);
 918         csym.members_field.enter(instDescSym);
 919         Type.ClassType ctype = new Type.ClassType(Type.noType, List.nil(), csym);
 920         ctype.supertype_field = syms.objectType;
 921         ctype.interfaces_field = target.isIntersection() ?
 922                 directSupertypes(target) :
 923                 List.of(target);
 924         csym.type = ctype;
 925         csym.sourcefile = ((ClassSymbol)csym.owner).sourcefile;
 926         return csym;
 927     }
 928 
 929     /**
 930      * Find the minimal set of methods that are overridden by the functional
 931      * descriptor in 'origin'. All returned methods are assumed to have different
 932      * erased signatures.
 933      */
 934     public List<Symbol> functionalInterfaceBridges(TypeSymbol origin) {
 935         Assert.check(isFunctionalInterface(origin));
 936         Symbol descSym = findDescriptorSymbol(origin);
 937         CompoundScope members = membersClosure(origin.type, false);
 938         ListBuffer<Symbol> overridden = new ListBuffer<>();
 939         outer: for (Symbol m2 : members.getSymbolsByName(descSym.name, bridgeFilter)) {
 940             if (m2 == descSym) continue;
 941             else if (descSym.overrides(m2, origin, Types.this, false)) {
 942                 for (Symbol m3 : overridden) {
 943                     if (isSameType(m3.erasure(Types.this), m2.erasure(Types.this)) ||
 944                             (m3.overrides(m2, origin, Types.this, false) &&
 945                             (pendingBridges((ClassSymbol)origin, m3.enclClass()) ||
 946                             (((MethodSymbol)m2).binaryImplementation((ClassSymbol)m3.owner, Types.this) != null)))) {
 947                         continue outer;
 948                     }
 949                 }
 950                 overridden.add(m2);
 951             }
 952         }
 953         return overridden.toList();
 954     }
 955     //where
 956         // Use anonymous class instead of lambda expression intentionally,
 957         // because the variable `names` has modifier: final.
 958         private Predicate<Symbol> bridgeFilter = new Predicate<Symbol>() {
 959             public boolean test(Symbol t) {
 960                 return t.kind == MTH &&
 961                         t.name != names.init &&
 962                         t.name != names.clinit &&
 963                         (t.flags() & SYNTHETIC) == 0;
 964             }
 965         };
 966 
 967         private boolean pendingBridges(ClassSymbol origin, TypeSymbol s) {
 968             //a symbol will be completed from a classfile if (a) symbol has
 969             //an associated file object with CLASS kind and (b) the symbol has
 970             //not been entered
 971             if (origin.classfile != null &&
 972                     origin.classfile.getKind() == JavaFileObject.Kind.CLASS &&
 973                     enter.getEnv(origin) == null) {
 974                 return false;
 975             }
 976             if (origin == s) {
 977                 return true;
 978             }
 979             for (Type t : interfaces(origin.type)) {
 980                 if (pendingBridges((ClassSymbol)t.tsym, s)) {
 981                     return true;
 982                 }
 983             }
 984             return false;
 985         }
 986     // </editor-fold>
 987 
 988    /**
 989     * Scope filter used to skip methods that should be ignored (such as methods
 990     * overridden by j.l.Object) during function interface conversion interface check
 991     */
 992     class DescriptorFilter implements Predicate<Symbol> {
 993 
 994        TypeSymbol origin;
 995 
 996        DescriptorFilter(TypeSymbol origin) {
 997            this.origin = origin;
 998        }
 999 
1000        @Override
1001        public boolean test(Symbol sym) {
1002            return sym.kind == MTH &&
1003                    (sym.flags() & (ABSTRACT | DEFAULT)) == ABSTRACT &&
1004                    !overridesObjectMethod(origin, sym) &&
1005                    (interfaceCandidates(origin.type, (MethodSymbol)sym).head.flags() & DEFAULT) == 0;
1006        }
1007     }
1008 
1009     // <editor-fold defaultstate="collapsed" desc="isSubtype">
1010     /**
1011      * Is t an unchecked subtype of s?
1012      */
1013     public boolean isSubtypeUnchecked(Type t, Type s) {
1014         return isSubtypeUnchecked(t, s, noWarnings);
1015     }
1016     /**
1017      * Is t an unchecked subtype of s?
1018      */
1019     public boolean isSubtypeUnchecked(Type t, Type s, Warner warn) {
1020         boolean result = isSubtypeUncheckedInternal(t, s, true, warn);
1021         if (result) {
1022             checkUnsafeVarargsConversion(t, s, warn);
1023         }
1024         return result;
1025     }
1026     //where
1027         private boolean isSubtypeUncheckedInternal(Type t, Type s, boolean capture, Warner warn) {
1028             if (t.hasTag(ARRAY) && s.hasTag(ARRAY)) {
1029                 if (((ArrayType)t).elemtype.isPrimitive()) {
1030                     return isSameType(elemtype(t), elemtype(s));
1031                 } else {
1032                     return isSubtypeUncheckedInternal(elemtype(t), elemtype(s), false, warn);
1033                 }
1034             } else if (isSubtype(t, s, capture)) {
1035                 return true;
1036             } else if (t.hasTag(TYPEVAR)) {
1037                 return isSubtypeUncheckedInternal(t.getUpperBound(), s, false, warn);
1038             } else if (!s.isRaw()) {
1039                 Type t2 = asSuper(t, s.tsym);
1040                 if (t2 != null && t2.isRaw()) {
1041                     if (isReifiable(s)) {
1042                         warn.silentWarn(LintCategory.UNCHECKED);
1043                     } else {
1044                         warn.warn(LintCategory.UNCHECKED);
1045                     }
1046                     return true;
1047                 }
1048             }
1049             return false;
1050         }
1051 
1052         private void checkUnsafeVarargsConversion(Type t, Type s, Warner warn) {
1053             if (!t.hasTag(ARRAY) || isReifiable(t)) {
1054                 return;
1055             }
1056             ArrayType from = (ArrayType)t;
1057             boolean shouldWarn = false;
1058             switch (s.getTag()) {
1059                 case ARRAY:
1060                     ArrayType to = (ArrayType)s;
1061                     shouldWarn = from.isVarargs() &&
1062                             !to.isVarargs() &&
1063                             !isReifiable(from);
1064                     break;
1065                 case CLASS:
1066                     shouldWarn = from.isVarargs();
1067                     break;
1068             }
1069             if (shouldWarn) {
1070                 warn.warn(LintCategory.VARARGS);
1071             }
1072         }
1073 
1074     /**
1075      * Is t a subtype of s?<br>
1076      * (not defined for Method and ForAll types)
1077      */
1078     public final boolean isSubtype(Type t, Type s) {
1079         return isSubtype(t, s, true);
1080     }
1081     public final boolean isSubtypeNoCapture(Type t, Type s) {
1082         return isSubtype(t, s, false);
1083     }
1084     public boolean isSubtype(Type t, Type s, boolean capture) {
1085         if (t.equalsIgnoreMetadata(s))
1086             return true;
1087         if (s.isPartial())
1088             return isSuperType(s, t);
1089 
1090         if (s.isCompound()) {
1091             for (Type s2 : interfaces(s).prepend(supertype(s))) {
1092                 if (!isSubtype(t, s2, capture))
1093                     return false;
1094             }
1095             return true;
1096         }
1097 
1098         // Generally, if 's' is a lower-bounded type variable, recur on lower bound; but
1099         // for inference variables and intersections, we need to keep 's'
1100         // (see JLS 4.10.2 for intersections and 18.2.3 for inference vars)
1101         if (!t.hasTag(UNDETVAR) && !t.isCompound()) {
1102             // TODO: JDK-8039198, bounds checking sometimes passes in a wildcard as s
1103             Type lower = cvarLowerBound(wildLowerBound(s));
1104             if (s != lower && !lower.hasTag(BOT))
1105                 return isSubtype(capture ? capture(t) : t, lower, false);
1106         }
1107 
1108         return isSubtype.visit(capture ? capture(t) : t, s);
1109     }
1110     // where
1111         private TypeRelation isSubtype = new TypeRelation()
1112         {
1113             @Override
1114             public Boolean visitType(Type t, Type s) {
1115                 switch (t.getTag()) {
1116                  case BYTE:
1117                      return (!s.hasTag(CHAR) && t.getTag().isSubRangeOf(s.getTag()));
1118                  case CHAR:
1119                      return (!s.hasTag(SHORT) && t.getTag().isSubRangeOf(s.getTag()));
1120                  case SHORT: case INT: case LONG:
1121                  case FLOAT: case DOUBLE:
1122                      return t.getTag().isSubRangeOf(s.getTag());
1123                  case BOOLEAN: case VOID:
1124                      return t.hasTag(s.getTag());
1125                  case TYPEVAR:
1126                      return isSubtypeNoCapture(t.getUpperBound(), s);
1127                  case BOT:
1128                      return
1129                          s.hasTag(BOT) || s.hasTag(CLASS) ||
1130                          s.hasTag(ARRAY) || s.hasTag(TYPEVAR);
1131                  case WILDCARD: //we shouldn't be here - avoids crash (see 7034495)
1132                  case NONE:
1133                      return false;
1134                  default:
1135                      throw new AssertionError("isSubtype " + t.getTag());
1136                  }
1137             }
1138 
1139             private Set<TypePair> cache = new HashSet<>();
1140 
1141             private boolean containsTypeRecursive(Type t, Type s) {
1142                 TypePair pair = new TypePair(t, s);
1143                 if (cache.add(pair)) {
1144                     try {
1145                         return containsType(t.getTypeArguments(),
1146                                             s.getTypeArguments());
1147                     } finally {
1148                         cache.remove(pair);
1149                     }
1150                 } else {
1151                     return containsType(t.getTypeArguments(),
1152                                         rewriteSupers(s).getTypeArguments());
1153                 }
1154             }
1155 
1156             private Type rewriteSupers(Type t) {
1157                 if (!t.isParameterized())
1158                     return t;
1159                 ListBuffer<Type> from = new ListBuffer<>();
1160                 ListBuffer<Type> to = new ListBuffer<>();
1161                 adaptSelf(t, from, to);
1162                 if (from.isEmpty())
1163                     return t;
1164                 ListBuffer<Type> rewrite = new ListBuffer<>();
1165                 boolean changed = false;
1166                 for (Type orig : to.toList()) {
1167                     Type s = rewriteSupers(orig);
1168                     if (s.isSuperBound() && !s.isExtendsBound()) {
1169                         s = new WildcardType(syms.objectType,
1170                                              BoundKind.UNBOUND,
1171                                              syms.boundClass,
1172                                              s.getMetadata());
1173                         changed = true;
1174                     } else if (s != orig) {
1175                         s = new WildcardType(wildUpperBound(s),
1176                                              BoundKind.EXTENDS,
1177                                              syms.boundClass,
1178                                              s.getMetadata());
1179                         changed = true;
1180                     }
1181                     rewrite.append(s);
1182                 }
1183                 if (changed)
1184                     return subst(t.tsym.type, from.toList(), rewrite.toList());
1185                 else
1186                     return t;
1187             }
1188 
1189             @Override
1190             public Boolean visitClassType(ClassType t, Type s) {
1191                 Type sup = asSuper(t, s.tsym);
1192                 if (sup == null) return false;
1193                 // If t is an intersection, sup might not be a class type
1194                 if (!sup.hasTag(CLASS)) return isSubtypeNoCapture(sup, s);
1195                 return sup.tsym == s.tsym
1196                      // Check type variable containment
1197                     && (!s.isParameterized() || containsTypeRecursive(s, sup))
1198                     && isSubtypeNoCapture(sup.getEnclosingType(),
1199                                           s.getEnclosingType());
1200             }
1201 
1202             @Override
1203             public Boolean visitArrayType(ArrayType t, Type s) {
1204                 if (s.hasTag(ARRAY)) {
1205                     if (t.elemtype.isPrimitive())
1206                         return isSameType(t.elemtype, elemtype(s));
1207                     else
1208                         return isSubtypeNoCapture(t.elemtype, elemtype(s));
1209                 }
1210 
1211                 if (s.hasTag(CLASS)) {
1212                     Name sname = s.tsym.getQualifiedName();
1213                     return sname == names.java_lang_Object
1214                         || sname == names.java_lang_Cloneable
1215                         || sname == names.java_io_Serializable;
1216                 }
1217 
1218                 return false;
1219             }
1220 
1221             @Override
1222             public Boolean visitUndetVar(UndetVar t, Type s) {
1223                 //todo: test against origin needed? or replace with substitution?
1224                 if (t == s || t.qtype == s || s.hasTag(ERROR) || s.hasTag(UNKNOWN)) {
1225                     return true;
1226                 } else if (s.hasTag(BOT)) {
1227                     //if 's' is 'null' there's no instantiated type U for which
1228                     //U <: s (but 'null' itself, which is not a valid type)
1229                     return false;
1230                 }
1231 
1232                 t.addBound(InferenceBound.UPPER, s, Types.this);
1233                 return true;
1234             }
1235 
1236             @Override
1237             public Boolean visitErrorType(ErrorType t, Type s) {
1238                 return true;
1239             }
1240         };
1241 
1242     /**
1243      * Is t a subtype of every type in given list `ts'?<br>
1244      * (not defined for Method and ForAll types)<br>
1245      * Allows unchecked conversions.
1246      */
1247     public boolean isSubtypeUnchecked(Type t, List<Type> ts, Warner warn) {
1248         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1249             if (!isSubtypeUnchecked(t, l.head, warn))
1250                 return false;
1251         return true;
1252     }
1253 
1254     /**
1255      * Are corresponding elements of ts subtypes of ss?  If lists are
1256      * of different length, return false.
1257      */
1258     public boolean isSubtypes(List<Type> ts, List<Type> ss) {
1259         while (ts.tail != null && ss.tail != null
1260                /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
1261                isSubtype(ts.head, ss.head)) {
1262             ts = ts.tail;
1263             ss = ss.tail;
1264         }
1265         return ts.tail == null && ss.tail == null;
1266         /*inlined: ts.isEmpty() && ss.isEmpty();*/
1267     }
1268 
1269     /**
1270      * Are corresponding elements of ts subtypes of ss, allowing
1271      * unchecked conversions?  If lists are of different length,
1272      * return false.
1273      **/
1274     public boolean isSubtypesUnchecked(List<Type> ts, List<Type> ss, Warner warn) {
1275         while (ts.tail != null && ss.tail != null
1276                /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
1277                isSubtypeUnchecked(ts.head, ss.head, warn)) {
1278             ts = ts.tail;
1279             ss = ss.tail;
1280         }
1281         return ts.tail == null && ss.tail == null;
1282         /*inlined: ts.isEmpty() && ss.isEmpty();*/
1283     }
1284     // </editor-fold>
1285 
1286     // <editor-fold defaultstate="collapsed" desc="isSuperType">
1287     /**
1288      * Is t a supertype of s?
1289      */
1290     public boolean isSuperType(Type t, Type s) {
1291         switch (t.getTag()) {
1292         case ERROR:
1293             return true;
1294         case UNDETVAR: {
1295             UndetVar undet = (UndetVar)t;
1296             if (t == s ||
1297                 undet.qtype == s ||
1298                 s.hasTag(ERROR) ||
1299                 s.hasTag(BOT)) {
1300                 return true;
1301             }
1302             undet.addBound(InferenceBound.LOWER, s, this);
1303             return true;
1304         }
1305         default:
1306             return isSubtype(s, t);
1307         }
1308     }
1309     // </editor-fold>
1310 
1311     // <editor-fold defaultstate="collapsed" desc="isSameType">
1312     /**
1313      * Are corresponding elements of the lists the same type?  If
1314      * lists are of different length, return false.
1315      */
1316     public boolean isSameTypes(List<Type> ts, List<Type> ss) {
1317         while (ts.tail != null && ss.tail != null
1318                /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
1319                isSameType(ts.head, ss.head)) {
1320             ts = ts.tail;
1321             ss = ss.tail;
1322         }
1323         return ts.tail == null && ss.tail == null;
1324         /*inlined: ts.isEmpty() && ss.isEmpty();*/
1325     }
1326 
1327     /**
1328      * A polymorphic signature method (JLS 15.12.3) is a method that
1329      *   (i) is declared in the java.lang.invoke.MethodHandle/VarHandle classes;
1330      *  (ii) takes a single variable arity parameter;
1331      * (iii) whose declared type is Object[];
1332      *  (iv) has any return type, Object signifying a polymorphic return type; and
1333      *   (v) is native.
1334     */
1335    public boolean isSignaturePolymorphic(MethodSymbol msym) {
1336        List<Type> argtypes = msym.type.getParameterTypes();
1337        return (msym.flags_field & NATIVE) != 0 &&
1338               (msym.owner == syms.methodHandleType.tsym || msym.owner == syms.varHandleType.tsym) &&
1339                argtypes.length() == 1 &&
1340                argtypes.head.hasTag(TypeTag.ARRAY) &&
1341                ((ArrayType)argtypes.head).elemtype.tsym == syms.objectType.tsym;
1342    }
1343 
1344     /**
1345      * Is t the same type as s?
1346      */
1347     public boolean isSameType(Type t, Type s) {
1348         return isSameTypeVisitor.visit(t, s);
1349     }
1350     // where
1351 
1352         /**
1353          * Type-equality relation - type variables are considered
1354          * equals if they share the same object identity.
1355          */
1356         TypeRelation isSameTypeVisitor = new TypeRelation() {
1357 
1358             public Boolean visitType(Type t, Type s) {
1359                 if (t.equalsIgnoreMetadata(s))
1360                     return true;
1361 
1362                 if (s.isPartial())
1363                     return visit(s, t);
1364 
1365                 switch (t.getTag()) {
1366                 case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
1367                 case DOUBLE: case BOOLEAN: case VOID: case BOT: case NONE:
1368                     return t.hasTag(s.getTag());
1369                 case TYPEVAR: {
1370                     if (s.hasTag(TYPEVAR)) {
1371                         //type-substitution does not preserve type-var types
1372                         //check that type var symbols and bounds are indeed the same
1373                         return t == s;
1374                     }
1375                     else {
1376                         //special case for s == ? super X, where upper(s) = u
1377                         //check that u == t, where u has been set by Type.withTypeVar
1378                         return s.isSuperBound() &&
1379                                 !s.isExtendsBound() &&
1380                                 visit(t, wildUpperBound(s));
1381                     }
1382                 }
1383                 default:
1384                     throw new AssertionError("isSameType " + t.getTag());
1385                 }
1386             }
1387 
1388             @Override
1389             public Boolean visitWildcardType(WildcardType t, Type s) {
1390                 if (!s.hasTag(WILDCARD)) {
1391                     return false;
1392                 } else {
1393                     WildcardType t2 = (WildcardType)s;
1394                     return (t.kind == t2.kind || (t.isExtendsBound() && s.isExtendsBound())) &&
1395                             isSameType(t.type, t2.type);
1396                 }
1397             }
1398 
1399             @Override
1400             public Boolean visitClassType(ClassType t, Type s) {
1401                 if (t == s)
1402                     return true;
1403 
1404                 if (s.isPartial())
1405                     return visit(s, t);
1406 
1407                 if (s.isSuperBound() && !s.isExtendsBound())
1408                     return visit(t, wildUpperBound(s)) && visit(t, wildLowerBound(s));
1409 
1410                 if (t.isCompound() && s.isCompound()) {
1411                     if (!visit(supertype(t), supertype(s)))
1412                         return false;
1413 
1414                     Map<Symbol,Type> tMap = new HashMap<>();
1415                     for (Type ti : interfaces(t)) {
1416                         tMap.put(ti.tsym, ti);
1417                     }
1418                     for (Type si : interfaces(s)) {
1419                         if (!tMap.containsKey(si.tsym))
1420                             return false;
1421                         Type ti = tMap.remove(si.tsym);
1422                         if (!visit(ti, si))
1423                             return false;
1424                     }
1425                     return tMap.isEmpty();
1426                 }
1427                 return t.tsym == s.tsym
1428                     && visit(t.getEnclosingType(), s.getEnclosingType())
1429                     && containsTypeEquivalent(t.getTypeArguments(), s.getTypeArguments());
1430             }
1431 
1432             @Override
1433             public Boolean visitArrayType(ArrayType t, Type s) {
1434                 if (t == s)
1435                     return true;
1436 
1437                 if (s.isPartial())
1438                     return visit(s, t);
1439 
1440                 return s.hasTag(ARRAY)
1441                     && containsTypeEquivalent(t.elemtype, elemtype(s));
1442             }
1443 
1444             @Override
1445             public Boolean visitMethodType(MethodType t, Type s) {
1446                 // isSameType for methods does not take thrown
1447                 // exceptions into account!
1448                 return hasSameArgs(t, s) && visit(t.getReturnType(), s.getReturnType());
1449             }
1450 
1451             @Override
1452             public Boolean visitPackageType(PackageType t, Type s) {
1453                 return t == s;
1454             }
1455 
1456             @Override
1457             public Boolean visitForAll(ForAll t, Type s) {
1458                 if (!s.hasTag(FORALL)) {
1459                     return false;
1460                 }
1461 
1462                 ForAll forAll = (ForAll)s;
1463                 return hasSameBounds(t, forAll)
1464                     && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
1465             }
1466 
1467             @Override
1468             public Boolean visitUndetVar(UndetVar t, Type s) {
1469                 if (s.hasTag(WILDCARD)) {
1470                     // FIXME, this might be leftovers from before capture conversion
1471                     return false;
1472                 }
1473 
1474                 if (t == s || t.qtype == s || s.hasTag(ERROR) || s.hasTag(UNKNOWN)) {
1475                     return true;
1476                 }
1477 
1478                 t.addBound(InferenceBound.EQ, s, Types.this);
1479 
1480                 return true;
1481             }
1482 
1483             @Override
1484             public Boolean visitErrorType(ErrorType t, Type s) {
1485                 return true;
1486             }
1487         };
1488 
1489     // </editor-fold>
1490 
1491     // <editor-fold defaultstate="collapsed" desc="Contains Type">
1492     public boolean containedBy(Type t, Type s) {
1493         switch (t.getTag()) {
1494         case UNDETVAR:
1495             if (s.hasTag(WILDCARD)) {
1496                 UndetVar undetvar = (UndetVar)t;
1497                 WildcardType wt = (WildcardType)s;
1498                 switch(wt.kind) {
1499                     case UNBOUND:
1500                         break;
1501                     case EXTENDS: {
1502                         Type bound = wildUpperBound(s);
1503                         undetvar.addBound(InferenceBound.UPPER, bound, this);
1504                         break;
1505                     }
1506                     case SUPER: {
1507                         Type bound = wildLowerBound(s);
1508                         undetvar.addBound(InferenceBound.LOWER, bound, this);
1509                         break;
1510                     }
1511                 }
1512                 return true;
1513             } else {
1514                 return isSameType(t, s);
1515             }
1516         case ERROR:
1517             return true;
1518         default:
1519             return containsType(s, t);
1520         }
1521     }
1522 
1523     boolean containsType(List<Type> ts, List<Type> ss) {
1524         while (ts.nonEmpty() && ss.nonEmpty()
1525                && containsType(ts.head, ss.head)) {
1526             ts = ts.tail;
1527             ss = ss.tail;
1528         }
1529         return ts.isEmpty() && ss.isEmpty();
1530     }
1531 
1532     /**
1533      * Check if t contains s.
1534      *
1535      * <p>T contains S if:
1536      *
1537      * <p>{@code L(T) <: L(S) && U(S) <: U(T)}
1538      *
1539      * <p>This relation is only used by ClassType.isSubtype(), that
1540      * is,
1541      *
1542      * <p>{@code C<S> <: C<T> if T contains S.}
1543      *
1544      * <p>Because of F-bounds, this relation can lead to infinite
1545      * recursion.  Thus we must somehow break that recursion.  Notice
1546      * that containsType() is only called from ClassType.isSubtype().
1547      * Since the arguments have already been checked against their
1548      * bounds, we know:
1549      *
1550      * <p>{@code U(S) <: U(T) if T is "super" bound (U(T) *is* the bound)}
1551      *
1552      * <p>{@code L(T) <: L(S) if T is "extends" bound (L(T) is bottom)}
1553      *
1554      * @param t a type
1555      * @param s a type
1556      */
1557     public boolean containsType(Type t, Type s) {
1558         return containsType.visit(t, s);
1559     }
1560     // where
1561         private TypeRelation containsType = new TypeRelation() {
1562 
1563             public Boolean visitType(Type t, Type s) {
1564                 if (s.isPartial())
1565                     return containedBy(s, t);
1566                 else
1567                     return isSameType(t, s);
1568             }
1569 
1570 //            void debugContainsType(WildcardType t, Type s) {
1571 //                System.err.println();
1572 //                System.err.format(" does %s contain %s?%n", t, s);
1573 //                System.err.format(" %s U(%s) <: U(%s) %s = %s%n",
1574 //                                  wildUpperBound(s), s, t, wildUpperBound(t),
1575 //                                  t.isSuperBound()
1576 //                                  || isSubtypeNoCapture(wildUpperBound(s), wildUpperBound(t)));
1577 //                System.err.format(" %s L(%s) <: L(%s) %s = %s%n",
1578 //                                  wildLowerBound(t), t, s, wildLowerBound(s),
1579 //                                  t.isExtendsBound()
1580 //                                  || isSubtypeNoCapture(wildLowerBound(t), wildLowerBound(s)));
1581 //                System.err.println();
1582 //            }
1583 
1584             @Override
1585             public Boolean visitWildcardType(WildcardType t, Type s) {
1586                 if (s.isPartial())
1587                     return containedBy(s, t);
1588                 else {
1589 //                    debugContainsType(t, s);
1590                     return isSameWildcard(t, s)
1591                         || isCaptureOf(s, t)
1592                         || ((t.isExtendsBound() || isSubtypeNoCapture(wildLowerBound(t), wildLowerBound(s))) &&
1593                             (t.isSuperBound() || isSubtypeNoCapture(wildUpperBound(s), wildUpperBound(t))));
1594                 }
1595             }
1596 
1597             @Override
1598             public Boolean visitUndetVar(UndetVar t, Type s) {
1599                 if (!s.hasTag(WILDCARD)) {
1600                     return isSameType(t, s);
1601                 } else {
1602                     return false;
1603                 }
1604             }
1605 
1606             @Override
1607             public Boolean visitErrorType(ErrorType t, Type s) {
1608                 return true;
1609             }
1610         };
1611 
1612     public boolean isCaptureOf(Type s, WildcardType t) {
1613         if (!s.hasTag(TYPEVAR) || !((TypeVar)s).isCaptured())
1614             return false;
1615         return isSameWildcard(t, ((CapturedType)s).wildcard);
1616     }
1617 
1618     public boolean isSameWildcard(WildcardType t, Type s) {
1619         if (!s.hasTag(WILDCARD))
1620             return false;
1621         WildcardType w = (WildcardType)s;
1622         return w.kind == t.kind && w.type == t.type;
1623     }
1624 
1625     public boolean containsTypeEquivalent(List<Type> ts, List<Type> ss) {
1626         while (ts.nonEmpty() && ss.nonEmpty()
1627                && containsTypeEquivalent(ts.head, ss.head)) {
1628             ts = ts.tail;
1629             ss = ss.tail;
1630         }
1631         return ts.isEmpty() && ss.isEmpty();
1632     }
1633     // </editor-fold>
1634 
1635     // <editor-fold defaultstate="collapsed" desc="isCastable">
1636     public boolean isCastable(Type t, Type s) {
1637         return isCastable(t, s, noWarnings);
1638     }
1639 
1640     /**
1641      * Is t castable to s?<br>
1642      * s is assumed to be an erased type.<br>
1643      * (not defined for Method and ForAll types).
1644      */
1645     public boolean isCastable(Type t, Type s, Warner warn) {
1646         // if same type
1647         if (t == s)
1648             return true;
1649         // if one of the types is primitive
1650         if (t.isPrimitive() != s.isPrimitive()) {
1651             t = skipTypeVars(t, false);
1652             return (isConvertible(t, s, warn)
1653                     || (s.isPrimitive() &&
1654                         isSubtype(boxedClass(s).type, t)));
1655         }
1656         boolean result;
1657         if (warn != warnStack.head) {
1658             try {
1659                 warnStack = warnStack.prepend(warn);
1660                 checkUnsafeVarargsConversion(t, s, warn);
1661                 result = isCastable.visit(t,s);
1662             } finally {
1663                 warnStack = warnStack.tail;
1664             }
1665         } else {
1666             result = isCastable.visit(t,s);
1667         }
1668         if (result && t.hasTag(CLASS) && t.tsym.kind.matches(Kinds.KindSelector.TYP)
1669                 && s.hasTag(CLASS) && s.tsym.kind.matches(Kinds.KindSelector.TYP)
1670                 && (t.tsym.isSealed() || s.tsym.isSealed())) {
1671             return (t.isCompound() || s.isCompound()) ?
1672                     true :
1673                     !(new DisjointChecker().areDisjoint((ClassSymbol)t.tsym, (ClassSymbol)s.tsym));
1674         }
1675         return result;
1676     }
1677     // where
1678         class DisjointChecker {
1679             Set<Pair<ClassSymbol, ClassSymbol>> pairsSeen = new HashSet<>();
1680             private boolean areDisjoint(ClassSymbol ts, ClassSymbol ss) {
1681                 Pair<ClassSymbol, ClassSymbol> newPair = new Pair<>(ts, ss);
1682                 /* if we are seeing the same pair again then there is an issue with the sealed hierarchy
1683                  * bail out, a detailed error will be reported downstream
1684                  */
1685                 if (!pairsSeen.add(newPair))
1686                     return false;
1687                 if (isSubtype(erasure(ts.type), erasure(ss.type))) {
1688                     return false;
1689                 }
1690                 if (isSubtype(erasure(ts.type), erasure(ss.type))) {
1691                     return false;
1692                 }
1693                 // if both are classes or both are interfaces, shortcut
1694                 if (ts.isInterface() == ss.isInterface() && isSubtype(erasure(ss.type), erasure(ts.type))) {
1695                     return false;
1696                 }
1697                 if (ts.isInterface() && !ss.isInterface()) {
1698                     /* so ts is interface but ss is a class
1699                      * an interface is disjoint from a class if the class is disjoint form the interface
1700                      */
1701                     return areDisjoint(ss, ts);
1702                 }
1703                 // a final class that is not subtype of ss is disjoint
1704                 if (!ts.isInterface() && ts.isFinal()) {
1705                     return true;
1706                 }
1707                 // if at least one is sealed
1708                 if (ts.isSealed() || ss.isSealed()) {
1709                     // permitted subtypes have to be disjoint with the other symbol
1710                     ClassSymbol sealedOne = ts.isSealed() ? ts : ss;
1711                     ClassSymbol other = sealedOne == ts ? ss : ts;
1712                     return sealedOne.getPermittedSubclasses().stream().allMatch(type -> areDisjoint((ClassSymbol)type.tsym, other));
1713                 }
1714                 return false;
1715             }
1716         }
1717 
1718         private TypeRelation isCastable = new TypeRelation() {
1719 
1720             public Boolean visitType(Type t, Type s) {
1721                 if (s.hasTag(ERROR) || t.hasTag(NONE))
1722                     return true;
1723 
1724                 switch (t.getTag()) {
1725                 case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
1726                 case DOUBLE:
1727                     return s.isNumeric();
1728                 case BOOLEAN:
1729                     return s.hasTag(BOOLEAN);
1730                 case VOID:
1731                     return false;
1732                 case BOT:
1733                     return isSubtype(t, s);
1734                 default:
1735                     throw new AssertionError();
1736                 }
1737             }
1738 
1739             @Override
1740             public Boolean visitWildcardType(WildcardType t, Type s) {
1741                 return isCastable(wildUpperBound(t), s, warnStack.head);
1742             }
1743 
1744             @Override
1745             public Boolean visitClassType(ClassType t, Type s) {
1746                 if (s.hasTag(ERROR) || s.hasTag(BOT))
1747                     return true;
1748 
1749                 if (s.hasTag(TYPEVAR)) {
1750                     if (isCastable(t, s.getUpperBound(), noWarnings)) {
1751                         warnStack.head.warn(LintCategory.UNCHECKED);
1752                         return true;
1753                     } else {
1754                         return false;
1755                     }
1756                 }
1757 
1758                 if (t.isCompound() || s.isCompound()) {
1759                     return !t.isCompound() ?
1760                             visitCompoundType((ClassType)s, t, true) :
1761                             visitCompoundType(t, s, false);
1762                 }
1763 
1764                 if (s.hasTag(CLASS) || s.hasTag(ARRAY)) {
1765                     boolean upcast;
1766                     if ((upcast = isSubtype(erasure(t), erasure(s)))
1767                         || isSubtype(erasure(s), erasure(t))) {
1768                         if (!upcast && s.hasTag(ARRAY)) {
1769                             if (!isReifiable(s))
1770                                 warnStack.head.warn(LintCategory.UNCHECKED);
1771                             return true;
1772                         } else if (s.isRaw()) {
1773                             return true;
1774                         } else if (t.isRaw()) {
1775                             if (!isUnbounded(s))
1776                                 warnStack.head.warn(LintCategory.UNCHECKED);
1777                             return true;
1778                         }
1779                         // Assume |a| <: |b|
1780                         final Type a = upcast ? t : s;
1781                         final Type b = upcast ? s : t;
1782                         final boolean HIGH = true;
1783                         final boolean LOW = false;
1784                         final boolean DONT_REWRITE_TYPEVARS = false;
1785                         Type aHigh = rewriteQuantifiers(a, HIGH, DONT_REWRITE_TYPEVARS);
1786                         Type aLow  = rewriteQuantifiers(a, LOW,  DONT_REWRITE_TYPEVARS);
1787                         Type bHigh = rewriteQuantifiers(b, HIGH, DONT_REWRITE_TYPEVARS);
1788                         Type bLow  = rewriteQuantifiers(b, LOW,  DONT_REWRITE_TYPEVARS);
1789                         Type lowSub = asSub(bLow, aLow.tsym);
1790                         Type highSub = (lowSub == null) ? null : asSub(bHigh, aHigh.tsym);
1791                         if (highSub == null) {
1792                             final boolean REWRITE_TYPEVARS = true;
1793                             aHigh = rewriteQuantifiers(a, HIGH, REWRITE_TYPEVARS);
1794                             aLow  = rewriteQuantifiers(a, LOW,  REWRITE_TYPEVARS);
1795                             bHigh = rewriteQuantifiers(b, HIGH, REWRITE_TYPEVARS);
1796                             bLow  = rewriteQuantifiers(b, LOW,  REWRITE_TYPEVARS);
1797                             lowSub = asSub(bLow, aLow.tsym);
1798                             highSub = (lowSub == null) ? null : asSub(bHigh, aHigh.tsym);
1799                         }
1800                         if (highSub != null) {
1801                             if (!(a.tsym == highSub.tsym && a.tsym == lowSub.tsym)) {
1802                                 Assert.error(a.tsym + " != " + highSub.tsym + " != " + lowSub.tsym);
1803                             }
1804                             if (!disjointTypes(aHigh.allparams(), highSub.allparams())
1805                                 && !disjointTypes(aHigh.allparams(), lowSub.allparams())
1806                                 && !disjointTypes(aLow.allparams(), highSub.allparams())
1807                                 && !disjointTypes(aLow.allparams(), lowSub.allparams())) {
1808                                 if (upcast ? giveWarning(a, b) :
1809                                     giveWarning(b, a))
1810                                     warnStack.head.warn(LintCategory.UNCHECKED);
1811                                 return true;
1812                             }
1813                         }
1814                         if (isReifiable(s))
1815                             return isSubtypeUnchecked(a, b);
1816                         else
1817                             return isSubtypeUnchecked(a, b, warnStack.head);
1818                     }
1819 
1820                     // Sidecast
1821                     if (s.hasTag(CLASS)) {
1822                         if ((s.tsym.flags() & INTERFACE) != 0) {
1823                             return ((t.tsym.flags() & FINAL) == 0)
1824                                 ? sideCast(t, s, warnStack.head)
1825                                 : sideCastFinal(t, s, warnStack.head);
1826                         } else if ((t.tsym.flags() & INTERFACE) != 0) {
1827                             return ((s.tsym.flags() & FINAL) == 0)
1828                                 ? sideCast(t, s, warnStack.head)
1829                                 : sideCastFinal(t, s, warnStack.head);
1830                         } else {
1831                             // unrelated class types
1832                             return false;
1833                         }
1834                     }
1835                 }
1836                 return false;
1837             }
1838 
1839             boolean visitCompoundType(ClassType ct, Type s, boolean reverse) {
1840                 Warner warn = noWarnings;
1841                 for (Type c : directSupertypes(ct)) {
1842                     warn.clear();
1843                     if (reverse ? !isCastable(s, c, warn) : !isCastable(c, s, warn))
1844                         return false;
1845                 }
1846                 if (warn.hasLint(LintCategory.UNCHECKED))
1847                     warnStack.head.warn(LintCategory.UNCHECKED);
1848                 return true;
1849             }
1850 
1851             @Override
1852             public Boolean visitArrayType(ArrayType t, Type s) {
1853                 switch (s.getTag()) {
1854                 case ERROR:
1855                 case BOT:
1856                     return true;
1857                 case TYPEVAR:
1858                     if (isCastable(s, t, noWarnings)) {
1859                         warnStack.head.warn(LintCategory.UNCHECKED);
1860                         return true;
1861                     } else {
1862                         return false;
1863                     }
1864                 case CLASS:
1865                     return isSubtype(t, s);
1866                 case ARRAY:
1867                     if (elemtype(t).isPrimitive() || elemtype(s).isPrimitive()) {
1868                         return elemtype(t).hasTag(elemtype(s).getTag());
1869                     } else {
1870                         return isCastable(elemtype(t), elemtype(s), warnStack.head);
1871                     }
1872                 default:
1873                     return false;
1874                 }
1875             }
1876 
1877             @Override
1878             public Boolean visitTypeVar(TypeVar t, Type s) {
1879                 switch (s.getTag()) {
1880                 case ERROR:
1881                 case BOT:
1882                     return true;
1883                 case TYPEVAR:
1884                     if (isSubtype(t, s)) {
1885                         return true;
1886                     } else if (isCastable(t.getUpperBound(), s, noWarnings)) {
1887                         warnStack.head.warn(LintCategory.UNCHECKED);
1888                         return true;
1889                     } else {
1890                         return false;
1891                     }
1892                 default:
1893                     return isCastable(t.getUpperBound(), s, warnStack.head);
1894                 }
1895             }
1896 
1897             @Override
1898             public Boolean visitErrorType(ErrorType t, Type s) {
1899                 return true;
1900             }
1901         };
1902     // </editor-fold>
1903 
1904     // <editor-fold defaultstate="collapsed" desc="disjointTypes">
1905     public boolean disjointTypes(List<Type> ts, List<Type> ss) {
1906         while (ts.tail != null && ss.tail != null) {
1907             if (disjointType(ts.head, ss.head)) return true;
1908             ts = ts.tail;
1909             ss = ss.tail;
1910         }
1911         return false;
1912     }
1913 
1914     /**
1915      * Two types or wildcards are considered disjoint if it can be
1916      * proven that no type can be contained in both. It is
1917      * conservative in that it is allowed to say that two types are
1918      * not disjoint, even though they actually are.
1919      *
1920      * The type {@code C<X>} is castable to {@code C<Y>} exactly if
1921      * {@code X} and {@code Y} are not disjoint.
1922      */
1923     public boolean disjointType(Type t, Type s) {
1924         return disjointType.visit(t, s);
1925     }
1926     // where
1927         private TypeRelation disjointType = new TypeRelation() {
1928 
1929             private Set<TypePair> cache = new HashSet<>();
1930 
1931             @Override
1932             public Boolean visitType(Type t, Type s) {
1933                 if (s.hasTag(WILDCARD))
1934                     return visit(s, t);
1935                 else
1936                     return notSoftSubtypeRecursive(t, s) || notSoftSubtypeRecursive(s, t);
1937             }
1938 
1939             private boolean isCastableRecursive(Type t, Type s) {
1940                 TypePair pair = new TypePair(t, s);
1941                 if (cache.add(pair)) {
1942                     try {
1943                         return Types.this.isCastable(t, s);
1944                     } finally {
1945                         cache.remove(pair);
1946                     }
1947                 } else {
1948                     return true;
1949                 }
1950             }
1951 
1952             private boolean notSoftSubtypeRecursive(Type t, Type s) {
1953                 TypePair pair = new TypePair(t, s);
1954                 if (cache.add(pair)) {
1955                     try {
1956                         return Types.this.notSoftSubtype(t, s);
1957                     } finally {
1958                         cache.remove(pair);
1959                     }
1960                 } else {
1961                     return false;
1962                 }
1963             }
1964 
1965             @Override
1966             public Boolean visitWildcardType(WildcardType t, Type s) {
1967                 if (t.isUnbound())
1968                     return false;
1969 
1970                 if (!s.hasTag(WILDCARD)) {
1971                     if (t.isExtendsBound())
1972                         return notSoftSubtypeRecursive(s, t.type);
1973                     else
1974                         return notSoftSubtypeRecursive(t.type, s);
1975                 }
1976 
1977                 if (s.isUnbound())
1978                     return false;
1979 
1980                 if (t.isExtendsBound()) {
1981                     if (s.isExtendsBound())
1982                         return !isCastableRecursive(t.type, wildUpperBound(s));
1983                     else if (s.isSuperBound())
1984                         return notSoftSubtypeRecursive(wildLowerBound(s), t.type);
1985                 } else if (t.isSuperBound()) {
1986                     if (s.isExtendsBound())
1987                         return notSoftSubtypeRecursive(t.type, wildUpperBound(s));
1988                 }
1989                 return false;
1990             }
1991         };
1992     // </editor-fold>
1993 
1994     // <editor-fold defaultstate="collapsed" desc="cvarLowerBounds">
1995     public List<Type> cvarLowerBounds(List<Type> ts) {
1996         return ts.map(cvarLowerBoundMapping);
1997     }
1998         private final TypeMapping<Void> cvarLowerBoundMapping = new TypeMapping<Void>() {
1999             @Override
2000             public Type visitCapturedType(CapturedType t, Void _unused) {
2001                 return cvarLowerBound(t);
2002             }
2003         };
2004     // </editor-fold>
2005 
2006     // <editor-fold defaultstate="collapsed" desc="notSoftSubtype">
2007     /**
2008      * This relation answers the question: is impossible that
2009      * something of type `t' can be a subtype of `s'? This is
2010      * different from the question "is `t' not a subtype of `s'?"
2011      * when type variables are involved: Integer is not a subtype of T
2012      * where {@code <T extends Number>} but it is not true that Integer cannot
2013      * possibly be a subtype of T.
2014      */
2015     public boolean notSoftSubtype(Type t, Type s) {
2016         if (t == s) return false;
2017         if (t.hasTag(TYPEVAR)) {
2018             TypeVar tv = (TypeVar) t;
2019             return !isCastable(tv.getUpperBound(),
2020                                relaxBound(s),
2021                                noWarnings);
2022         }
2023         if (!s.hasTag(WILDCARD))
2024             s = cvarUpperBound(s);
2025 
2026         return !isSubtype(t, relaxBound(s));
2027     }
2028 
2029     private Type relaxBound(Type t) {
2030         return (t.hasTag(TYPEVAR)) ?
2031                 rewriteQuantifiers(skipTypeVars(t, false), true, true) :
2032                 t;
2033     }
2034     // </editor-fold>
2035 
2036     // <editor-fold defaultstate="collapsed" desc="isReifiable">
2037     public boolean isReifiable(Type t) {
2038         return isReifiable.visit(t);
2039     }
2040     // where
2041         private UnaryVisitor<Boolean> isReifiable = new UnaryVisitor<Boolean>() {
2042 
2043             public Boolean visitType(Type t, Void ignored) {
2044                 return true;
2045             }
2046 
2047             @Override
2048             public Boolean visitClassType(ClassType t, Void ignored) {
2049                 if (t.isCompound())
2050                     return false;
2051                 else {
2052                     if (!t.isParameterized())
2053                         return true;
2054 
2055                     for (Type param : t.allparams()) {
2056                         if (!param.isUnbound())
2057                             return false;
2058                     }
2059                     return true;
2060                 }
2061             }
2062 
2063             @Override
2064             public Boolean visitArrayType(ArrayType t, Void ignored) {
2065                 return visit(t.elemtype);
2066             }
2067 
2068             @Override
2069             public Boolean visitTypeVar(TypeVar t, Void ignored) {
2070                 return false;
2071             }
2072         };
2073     // </editor-fold>
2074 
2075     // <editor-fold defaultstate="collapsed" desc="Array Utils">
2076     public boolean isArray(Type t) {
2077         while (t.hasTag(WILDCARD))
2078             t = wildUpperBound(t);
2079         return t.hasTag(ARRAY);
2080     }
2081 
2082     /**
2083      * The element type of an array.
2084      */
2085     public Type elemtype(Type t) {
2086         switch (t.getTag()) {
2087         case WILDCARD:
2088             return elemtype(wildUpperBound(t));
2089         case ARRAY:
2090             return ((ArrayType)t).elemtype;
2091         case FORALL:
2092             return elemtype(((ForAll)t).qtype);
2093         case ERROR:
2094             return t;
2095         default:
2096             return null;
2097         }
2098     }
2099 
2100     public Type elemtypeOrType(Type t) {
2101         Type elemtype = elemtype(t);
2102         return elemtype != null ?
2103             elemtype :
2104             t;
2105     }
2106 
2107     /**
2108      * Mapping to take element type of an arraytype
2109      */
2110     private TypeMapping<Void> elemTypeFun = new TypeMapping<Void>() {
2111         @Override
2112         public Type visitArrayType(ArrayType t, Void _unused) {
2113             return t.elemtype;
2114         }
2115 
2116         @Override
2117         public Type visitTypeVar(TypeVar t, Void _unused) {
2118             return visit(skipTypeVars(t, false));
2119         }
2120     };
2121 
2122     /**
2123      * The number of dimensions of an array type.
2124      */
2125     public int dimensions(Type t) {
2126         int result = 0;
2127         while (t.hasTag(ARRAY)) {
2128             result++;
2129             t = elemtype(t);
2130         }
2131         return result;
2132     }
2133 
2134     /**
2135      * Returns an ArrayType with the component type t
2136      *
2137      * @param t The component type of the ArrayType
2138      * @return the ArrayType for the given component
2139      */
2140     public ArrayType makeArrayType(Type t) {
2141         return makeArrayType(t, 1);
2142     }
2143 
2144     public ArrayType makeArrayType(Type t, int dimensions) {
2145         if (t.hasTag(VOID) || t.hasTag(PACKAGE)) {
2146             Assert.error("Type t must not be a VOID or PACKAGE type, " + t.toString());
2147         }
2148         ArrayType result = new ArrayType(t, syms.arrayClass);
2149         for (int i = 1; i < dimensions; i++) {
2150             result = new ArrayType(result, syms.arrayClass);
2151         }
2152         return result;
2153     }
2154     // </editor-fold>
2155 
2156     // <editor-fold defaultstate="collapsed" desc="asSuper">
2157     /**
2158      * Return the (most specific) base type of t that starts with the
2159      * given symbol.  If none exists, return null.
2160      *
2161      * Caveat Emptor: Since javac represents the class of all arrays with a singleton
2162      * symbol Symtab.arrayClass, which by being a singleton cannot hold any discriminant,
2163      * this method could yield surprising answers when invoked on arrays. For example when
2164      * invoked with t being byte [] and sym being t.sym itself, asSuper would answer null.
2165      *
2166      * @param t a type
2167      * @param sym a symbol
2168      */
2169     public Type asSuper(Type t, Symbol sym) {
2170         /* Some examples:
2171          *
2172          * (Enum<E>, Comparable) => Comparable<E>
2173          * (c.s.s.d.AttributeTree.ValueKind, Enum) => Enum<c.s.s.d.AttributeTree.ValueKind>
2174          * (c.s.s.t.ExpressionTree, c.s.s.t.Tree) => c.s.s.t.Tree
2175          * (j.u.List<capture#160 of ? extends c.s.s.d.DocTree>, Iterable) =>
2176          *     Iterable<capture#160 of ? extends c.s.s.d.DocTree>
2177          */
2178         if (sym.type == syms.objectType) { //optimization
2179             return syms.objectType;
2180         }
2181         return asSuper.visit(t, sym);
2182     }
2183     // where
2184         private SimpleVisitor<Type,Symbol> asSuper = new SimpleVisitor<Type,Symbol>() {
2185 
2186             private Set<Symbol> seenTypes = new HashSet<>();
2187 
2188             public Type visitType(Type t, Symbol sym) {
2189                 return null;
2190             }
2191 
2192             @Override
2193             public Type visitClassType(ClassType t, Symbol sym) {
2194                 if (t.tsym == sym)
2195                     return t;
2196 
2197                 Symbol c = t.tsym;
2198                 if (!seenTypes.add(c)) {
2199                     return null;
2200                 }
2201                 try {
2202                     Type st = supertype(t);
2203                     if (st.hasTag(CLASS) || st.hasTag(TYPEVAR)) {
2204                         Type x = asSuper(st, sym);
2205                         if (x != null)
2206                             return x;
2207                     }
2208                     if ((sym.flags() & INTERFACE) != 0) {
2209                         for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
2210                             if (!l.head.hasTag(ERROR)) {
2211                                 Type x = asSuper(l.head, sym);
2212                                 if (x != null)
2213                                     return x;
2214                             }
2215                         }
2216                     }
2217                     return null;
2218                 } finally {
2219                     seenTypes.remove(c);
2220                 }
2221             }
2222 
2223             @Override
2224             public Type visitArrayType(ArrayType t, Symbol sym) {
2225                 return isSubtype(t, sym.type) ? sym.type : null;
2226             }
2227 
2228             @Override
2229             public Type visitTypeVar(TypeVar t, Symbol sym) {
2230                 if (t.tsym == sym)
2231                     return t;
2232                 else
2233                     return asSuper(t.getUpperBound(), sym);
2234             }
2235 
2236             @Override
2237             public Type visitErrorType(ErrorType t, Symbol sym) {
2238                 return t;
2239             }
2240         };
2241 
2242     /**
2243      * Return the base type of t or any of its outer types that starts
2244      * with the given symbol.  If none exists, return null.
2245      *
2246      * @param t a type
2247      * @param sym a symbol
2248      */
2249     public Type asOuterSuper(Type t, Symbol sym) {
2250         switch (t.getTag()) {
2251         case CLASS:
2252             do {
2253                 Type s = asSuper(t, sym);
2254                 if (s != null) return s;
2255                 t = t.getEnclosingType();
2256             } while (t.hasTag(CLASS));
2257             return null;
2258         case ARRAY:
2259             return isSubtype(t, sym.type) ? sym.type : null;
2260         case TYPEVAR:
2261             return asSuper(t, sym);
2262         case ERROR:
2263             return t;
2264         default:
2265             return null;
2266         }
2267     }
2268 
2269     /**
2270      * Return the base type of t or any of its enclosing types that
2271      * starts with the given symbol.  If none exists, return null.
2272      *
2273      * @param t a type
2274      * @param sym a symbol
2275      */
2276     public Type asEnclosingSuper(Type t, Symbol sym) {
2277         switch (t.getTag()) {
2278         case CLASS:
2279             do {
2280                 Type s = asSuper(t, sym);
2281                 if (s != null) return s;
2282                 Type outer = t.getEnclosingType();
2283                 t = (outer.hasTag(CLASS)) ? outer :
2284                     (t.tsym.owner.enclClass() != null) ? t.tsym.owner.enclClass().type :
2285                     Type.noType;
2286             } while (t.hasTag(CLASS));
2287             return null;
2288         case ARRAY:
2289             return isSubtype(t, sym.type) ? sym.type : null;
2290         case TYPEVAR:
2291             return asSuper(t, sym);
2292         case ERROR:
2293             return t;
2294         default:
2295             return null;
2296         }
2297     }
2298     // </editor-fold>
2299 
2300     // <editor-fold defaultstate="collapsed" desc="memberType">
2301     /**
2302      * The type of given symbol, seen as a member of t.
2303      *
2304      * @param t a type
2305      * @param sym a symbol
2306      */
2307     public Type memberType(Type t, Symbol sym) {
2308         return (sym.flags() & STATIC) != 0
2309             ? sym.type
2310             : memberType.visit(t, sym);
2311         }
2312     // where
2313         private SimpleVisitor<Type,Symbol> memberType = new SimpleVisitor<Type,Symbol>() {
2314 
2315             public Type visitType(Type t, Symbol sym) {
2316                 return sym.type;
2317             }
2318 
2319             @Override
2320             public Type visitWildcardType(WildcardType t, Symbol sym) {
2321                 return memberType(wildUpperBound(t), sym);
2322             }
2323 
2324             @Override
2325             public Type visitClassType(ClassType t, Symbol sym) {
2326                 Symbol owner = sym.owner;
2327                 long flags = sym.flags();
2328                 if (((flags & STATIC) == 0) && owner.type.isParameterized()) {
2329                     Type base = asOuterSuper(t, owner);
2330                     //if t is an intersection type T = CT & I1 & I2 ... & In
2331                     //its supertypes CT, I1, ... In might contain wildcards
2332                     //so we need to go through capture conversion
2333                     base = t.isCompound() ? capture(base) : base;
2334                     if (base != null) {
2335                         List<Type> ownerParams = owner.type.allparams();
2336                         List<Type> baseParams = base.allparams();
2337                         if (ownerParams.nonEmpty()) {
2338                             if (baseParams.isEmpty()) {
2339                                 // then base is a raw type
2340                                 return erasure(sym.type);
2341                             } else {
2342                                 return subst(sym.type, ownerParams, baseParams);
2343                             }
2344                         }
2345                     }
2346                 }
2347                 return sym.type;
2348             }
2349 
2350             @Override
2351             public Type visitTypeVar(TypeVar t, Symbol sym) {
2352                 return memberType(t.getUpperBound(), sym);
2353             }
2354 
2355             @Override
2356             public Type visitErrorType(ErrorType t, Symbol sym) {
2357                 return t;
2358             }
2359         };
2360     // </editor-fold>
2361 
2362     // <editor-fold defaultstate="collapsed" desc="isAssignable">
2363     public boolean isAssignable(Type t, Type s) {
2364         return isAssignable(t, s, noWarnings);
2365     }
2366 
2367     /**
2368      * Is t assignable to s?<br>
2369      * Equivalent to subtype except for constant values and raw
2370      * types.<br>
2371      * (not defined for Method and ForAll types)
2372      */
2373     public boolean isAssignable(Type t, Type s, Warner warn) {
2374         if (t.hasTag(ERROR))
2375             return true;
2376         if (t.getTag().isSubRangeOf(INT) && t.constValue() != null) {
2377             int value = ((Number)t.constValue()).intValue();
2378             switch (s.getTag()) {
2379             case BYTE:
2380             case CHAR:
2381             case SHORT:
2382             case INT:
2383                 if (s.getTag().checkRange(value))
2384                     return true;
2385                 break;
2386             case CLASS:
2387                 switch (unboxedType(s).getTag()) {
2388                 case BYTE:
2389                 case CHAR:
2390                 case SHORT:
2391                     return isAssignable(t, unboxedType(s), warn);
2392                 }
2393                 break;
2394             }
2395         }
2396         return isConvertible(t, s, warn);
2397     }
2398     // </editor-fold>
2399 
2400     // <editor-fold defaultstate="collapsed" desc="erasure">
2401     /**
2402      * The erasure of t {@code |t|} -- the type that results when all
2403      * type parameters in t are deleted.
2404      */
2405     public Type erasure(Type t) {
2406         return eraseNotNeeded(t) ? t : erasure(t, false);
2407     }
2408     //where
2409     private boolean eraseNotNeeded(Type t) {
2410         // We don't want to erase primitive types and String type as that
2411         // operation is idempotent. Also, erasing these could result in loss
2412         // of information such as constant values attached to such types.
2413         return (t.isPrimitive()) || (syms.stringType.tsym == t.tsym);
2414     }
2415 
2416     private Type erasure(Type t, boolean recurse) {
2417         if (t.isPrimitive()) {
2418             return t; /* fast special case */
2419         } else {
2420             Type out = erasure.visit(t, recurse);
2421             return out;
2422         }
2423     }
2424     // where
2425         private TypeMapping<Boolean> erasure = new StructuralTypeMapping<Boolean>() {
2426             @SuppressWarnings("fallthrough")
2427             private Type combineMetadata(final Type s,
2428                                          final Type t) {
2429                 if (t.getMetadata().nonEmpty()) {
2430                     switch (s.getTag()) {
2431                         case CLASS:
2432                             if (s instanceof UnionClassType ||
2433                                 s instanceof IntersectionClassType) {
2434                                 return s;
2435                             }
2436                             //fall-through
2437                         case BYTE, CHAR, SHORT, LONG, FLOAT, INT, DOUBLE, BOOLEAN,
2438                              ARRAY, MODULE, TYPEVAR, WILDCARD, BOT:
2439                             return s.dropMetadata(Annotations.class);
2440                         case VOID, METHOD, PACKAGE, FORALL, DEFERRED,
2441                              NONE, ERROR, UNKNOWN, UNDETVAR, UNINITIALIZED_THIS,
2442                              UNINITIALIZED_OBJECT:
2443                             return s;
2444                         default:
2445                             throw new AssertionError(s.getTag().name());
2446                     }
2447                 } else {
2448                     return s;
2449                 }
2450             }
2451 
2452             public Type visitType(Type t, Boolean recurse) {
2453                 if (t.isPrimitive())
2454                     return t; /*fast special case*/
2455                 else {
2456                     //other cases already handled
2457                     return combineMetadata(t, t);
2458                 }
2459             }
2460 
2461             @Override
2462             public Type visitWildcardType(WildcardType t, Boolean recurse) {
2463                 Type erased = erasure(wildUpperBound(t), recurse);
2464                 return combineMetadata(erased, t);
2465             }
2466 
2467             @Override
2468             public Type visitClassType(ClassType t, Boolean recurse) {
2469                 Type erased = t.tsym.erasure(Types.this);
2470                 if (recurse) {
2471                     erased = new ErasedClassType(erased.getEnclosingType(),erased.tsym,
2472                             t.dropMetadata(Annotations.class).getMetadata());
2473                     return erased;
2474                 } else {
2475                     return combineMetadata(erased, t);
2476                 }
2477             }
2478 
2479             @Override
2480             public Type visitTypeVar(TypeVar t, Boolean recurse) {
2481                 Type erased = erasure(t.getUpperBound(), recurse);
2482                 return combineMetadata(erased, t);
2483             }
2484         };
2485 
2486     public List<Type> erasure(List<Type> ts) {
2487         return erasure.visit(ts, false);
2488     }
2489 
2490     public Type erasureRecursive(Type t) {
2491         return erasure(t, true);
2492     }
2493 
2494     public List<Type> erasureRecursive(List<Type> ts) {
2495         return erasure.visit(ts, true);
2496     }
2497     // </editor-fold>
2498 
2499     // <editor-fold defaultstate="collapsed" desc="makeIntersectionType">
2500     /**
2501      * Make an intersection type from non-empty list of types.  The list should be ordered according to
2502      * {@link TypeSymbol#precedes(TypeSymbol, Types)}. Note that this might cause a symbol completion.
2503      * Hence, this version of makeIntersectionType may not be called during a classfile read.
2504      *
2505      * @param bounds    the types from which the intersection type is formed
2506      */
2507     public IntersectionClassType makeIntersectionType(List<Type> bounds) {
2508         return makeIntersectionType(bounds, bounds.head.tsym.isInterface());
2509     }
2510 
2511     /**
2512      * Make an intersection type from non-empty list of types.  The list should be ordered according to
2513      * {@link TypeSymbol#precedes(TypeSymbol, Types)}. This does not cause symbol completion as
2514      * an extra parameter indicates as to whether all bounds are interfaces - in which case the
2515      * supertype is implicitly assumed to be 'Object'.
2516      *
2517      * @param bounds        the types from which the intersection type is formed
2518      * @param allInterfaces are all bounds interface types?
2519      */
2520     public IntersectionClassType makeIntersectionType(List<Type> bounds, boolean allInterfaces) {
2521         Assert.check(bounds.nonEmpty());
2522         Type firstExplicitBound = bounds.head;
2523         if (allInterfaces) {
2524             bounds = bounds.prepend(syms.objectType);
2525         }
2526         ClassSymbol bc =
2527             new ClassSymbol(ABSTRACT|PUBLIC|SYNTHETIC|COMPOUND|ACYCLIC,
2528                             Type.moreInfo
2529                                 ? names.fromString(bounds.toString())
2530                                 : names.empty,
2531                             null,
2532                             syms.noSymbol);
2533         IntersectionClassType intersectionType = new IntersectionClassType(bounds, bc, allInterfaces);
2534         bc.type = intersectionType;
2535         bc.erasure_field = (bounds.head.hasTag(TYPEVAR)) ?
2536                 syms.objectType : // error condition, recover
2537                 erasure(firstExplicitBound);
2538         bc.members_field = WriteableScope.create(bc);
2539         return intersectionType;
2540     }
2541     // </editor-fold>
2542 
2543     // <editor-fold defaultstate="collapsed" desc="supertype">
2544     public Type supertype(Type t) {
2545         return supertype.visit(t);
2546     }
2547     // where
2548         private UnaryVisitor<Type> supertype = new UnaryVisitor<Type>() {
2549 
2550             public Type visitType(Type t, Void ignored) {
2551                 // A note on wildcards: there is no good way to
2552                 // determine a supertype for a lower-bounded wildcard.
2553                 return Type.noType;
2554             }
2555 
2556             @Override
2557             public Type visitClassType(ClassType t, Void ignored) {
2558                 if (t.supertype_field == null) {
2559                     Type supertype = ((ClassSymbol)t.tsym).getSuperclass();
2560                     // An interface has no superclass; its supertype is Object.
2561                     if (t.isInterface())
2562                         supertype = ((ClassType)t.tsym.type).supertype_field;
2563                     if (t.supertype_field == null) {
2564                         List<Type> actuals = classBound(t).allparams();
2565                         List<Type> formals = t.tsym.type.allparams();
2566                         if (t.hasErasedSupertypes()) {
2567                             t.supertype_field = erasureRecursive(supertype);
2568                         } else if (formals.nonEmpty()) {
2569                             t.supertype_field = subst(supertype, formals, actuals);
2570                         }
2571                         else {
2572                             t.supertype_field = supertype;
2573                         }
2574                     }
2575                 }
2576                 return t.supertype_field;
2577             }
2578 
2579             /**
2580              * The supertype is always a class type. If the type
2581              * variable's bounds start with a class type, this is also
2582              * the supertype.  Otherwise, the supertype is
2583              * java.lang.Object.
2584              */
2585             @Override
2586             public Type visitTypeVar(TypeVar t, Void ignored) {
2587                 if (t.getUpperBound().hasTag(TYPEVAR) ||
2588                     (!t.getUpperBound().isCompound() && !t.getUpperBound().isInterface())) {
2589                     return t.getUpperBound();
2590                 } else {
2591                     return supertype(t.getUpperBound());
2592                 }
2593             }
2594 
2595             @Override
2596             public Type visitArrayType(ArrayType t, Void ignored) {
2597                 if (t.elemtype.isPrimitive() || isSameType(t.elemtype, syms.objectType))
2598                     return arraySuperType();
2599                 else
2600                     return new ArrayType(supertype(t.elemtype), t.tsym);
2601             }
2602 
2603             @Override
2604             public Type visitErrorType(ErrorType t, Void ignored) {
2605                 return Type.noType;
2606             }
2607         };
2608     // </editor-fold>
2609 
2610     // <editor-fold defaultstate="collapsed" desc="interfaces">
2611     /**
2612      * Return the interfaces implemented by this class.
2613      */
2614     public List<Type> interfaces(Type t) {
2615         return interfaces.visit(t);
2616     }
2617     // where
2618         private UnaryVisitor<List<Type>> interfaces = new UnaryVisitor<List<Type>>() {
2619 
2620             public List<Type> visitType(Type t, Void ignored) {
2621                 return List.nil();
2622             }
2623 
2624             @Override
2625             public List<Type> visitClassType(ClassType t, Void ignored) {
2626                 if (t.interfaces_field == null) {
2627                     List<Type> interfaces = ((ClassSymbol)t.tsym).getInterfaces();
2628                     if (t.interfaces_field == null) {
2629                         // If t.interfaces_field is null, then t must
2630                         // be a parameterized type (not to be confused
2631                         // with a generic type declaration).
2632                         // Terminology:
2633                         //    Parameterized type: List<String>
2634                         //    Generic type declaration: class List<E> { ... }
2635                         // So t corresponds to List<String> and
2636                         // t.tsym.type corresponds to List<E>.
2637                         // The reason t must be parameterized type is
2638                         // that completion will happen as a side
2639                         // effect of calling
2640                         // ClassSymbol.getInterfaces.  Since
2641                         // t.interfaces_field is null after
2642                         // completion, we can assume that t is not the
2643                         // type of a class/interface declaration.
2644                         Assert.check(t != t.tsym.type, t);
2645                         List<Type> actuals = t.allparams();
2646                         List<Type> formals = t.tsym.type.allparams();
2647                         if (t.hasErasedSupertypes()) {
2648                             t.interfaces_field = erasureRecursive(interfaces);
2649                         } else if (formals.nonEmpty()) {
2650                             t.interfaces_field = subst(interfaces, formals, actuals);
2651                         }
2652                         else {
2653                             t.interfaces_field = interfaces;
2654                         }
2655                     }
2656                 }
2657                 return t.interfaces_field;
2658             }
2659 
2660             @Override
2661             public List<Type> visitTypeVar(TypeVar t, Void ignored) {
2662                 if (t.getUpperBound().isCompound())
2663                     return interfaces(t.getUpperBound());
2664 
2665                 if (t.getUpperBound().isInterface())
2666                     return List.of(t.getUpperBound());
2667 
2668                 return List.nil();
2669             }
2670         };
2671 
2672     public List<Type> directSupertypes(Type t) {
2673         return directSupertypes.visit(t);
2674     }
2675     // where
2676         private final UnaryVisitor<List<Type>> directSupertypes = new UnaryVisitor<List<Type>>() {
2677 
2678             public List<Type> visitType(final Type type, final Void ignored) {
2679                 if (!type.isIntersection()) {
2680                     final Type sup = supertype(type);
2681                     return (sup == Type.noType || sup == type || sup == null)
2682                         ? interfaces(type)
2683                         : interfaces(type).prepend(sup);
2684                 } else {
2685                     return ((IntersectionClassType)type).getExplicitComponents();
2686                 }
2687             }
2688         };
2689 
2690     public boolean isDirectSuperInterface(TypeSymbol isym, TypeSymbol origin) {
2691         for (Type i2 : interfaces(origin.type)) {
2692             if (isym == i2.tsym) return true;
2693         }
2694         return false;
2695     }
2696     // </editor-fold>
2697 
2698     // <editor-fold defaultstate="collapsed" desc="isDerivedRaw">
2699     Map<Type,Boolean> isDerivedRawCache = new HashMap<>();
2700 
2701     public boolean isDerivedRaw(Type t) {
2702         Boolean result = isDerivedRawCache.get(t);
2703         if (result == null) {
2704             result = isDerivedRawInternal(t);
2705             isDerivedRawCache.put(t, result);
2706         }
2707         return result;
2708     }
2709 
2710     public boolean isDerivedRawInternal(Type t) {
2711         if (t.isErroneous())
2712             return false;
2713         return
2714             t.isRaw() ||
2715             supertype(t) != Type.noType && isDerivedRaw(supertype(t)) ||
2716             isDerivedRaw(interfaces(t));
2717     }
2718 
2719     public boolean isDerivedRaw(List<Type> ts) {
2720         List<Type> l = ts;
2721         while (l.nonEmpty() && !isDerivedRaw(l.head)) l = l.tail;
2722         return l.nonEmpty();
2723     }
2724     // </editor-fold>
2725 
2726     // <editor-fold defaultstate="collapsed" desc="setBounds">
2727     /**
2728      * Same as {@link Types#setBounds(TypeVar, List, boolean)}, except that third parameter is computed directly,
2729      * as follows: if all all bounds are interface types, the computed supertype is Object,otherwise
2730      * the supertype is simply left null (in this case, the supertype is assumed to be the head of
2731      * the bound list passed as second argument). Note that this check might cause a symbol completion.
2732      * Hence, this version of setBounds may not be called during a classfile read.
2733      *
2734      * @param t         a type variable
2735      * @param bounds    the bounds, must be nonempty
2736      */
2737     public void setBounds(TypeVar t, List<Type> bounds) {
2738         setBounds(t, bounds, bounds.head.tsym.isInterface());
2739     }
2740 
2741     /**
2742      * Set the bounds field of the given type variable to reflect a (possibly multiple) list of bounds.
2743      * This does not cause symbol completion as an extra parameter indicates as to whether all bounds
2744      * are interfaces - in which case the supertype is implicitly assumed to be 'Object'.
2745      *
2746      * @param t             a type variable
2747      * @param bounds        the bounds, must be nonempty
2748      * @param allInterfaces are all bounds interface types?
2749      */
2750     public void setBounds(TypeVar t, List<Type> bounds, boolean allInterfaces) {
2751         t.setUpperBound( bounds.tail.isEmpty() ?
2752                 bounds.head :
2753                 makeIntersectionType(bounds, allInterfaces) );
2754         t.rank_field = -1;
2755     }
2756     // </editor-fold>
2757 
2758     // <editor-fold defaultstate="collapsed" desc="getBounds">
2759     /**
2760      * Return list of bounds of the given type variable.
2761      */
2762     public List<Type> getBounds(TypeVar t) {
2763         if (t.getUpperBound().hasTag(NONE))
2764             return List.nil();
2765         else if (t.getUpperBound().isErroneous() || !t.getUpperBound().isCompound())
2766             return List.of(t.getUpperBound());
2767         else if ((erasure(t).tsym.flags() & INTERFACE) == 0)
2768             return interfaces(t).prepend(supertype(t));
2769         else
2770             // No superclass was given in bounds.
2771             // In this case, supertype is Object, erasure is first interface.
2772             return interfaces(t);
2773     }
2774     // </editor-fold>
2775 
2776     // <editor-fold defaultstate="collapsed" desc="classBound">
2777     /**
2778      * If the given type is a (possibly selected) type variable,
2779      * return the bounding class of this type, otherwise return the
2780      * type itself.
2781      */
2782     public Type classBound(Type t) {
2783         return classBound.visit(t);
2784     }
2785     // where
2786         private UnaryVisitor<Type> classBound = new UnaryVisitor<Type>() {
2787 
2788             public Type visitType(Type t, Void ignored) {
2789                 return t;
2790             }
2791 
2792             @Override
2793             public Type visitClassType(ClassType t, Void ignored) {
2794                 Type outer1 = classBound(t.getEnclosingType());
2795                 if (outer1 != t.getEnclosingType())
2796                     return new ClassType(outer1, t.getTypeArguments(), t.tsym,
2797                                          t.getMetadata());
2798                 else
2799                     return t;
2800             }
2801 
2802             @Override
2803             public Type visitTypeVar(TypeVar t, Void ignored) {
2804                 return classBound(supertype(t));
2805             }
2806 
2807             @Override
2808             public Type visitErrorType(ErrorType t, Void ignored) {
2809                 return t;
2810             }
2811         };
2812     // </editor-fold>
2813 
2814     // <editor-fold defaultstate="collapsed" desc="subsignature / override equivalence">
2815     /**
2816      * Returns true iff the first signature is a <em>subsignature</em>
2817      * of the other.  This is <b>not</b> an equivalence
2818      * relation.
2819      *
2820      * @jls 8.4.2 Method Signature
2821      * @see #overrideEquivalent(Type t, Type s)
2822      * @param t first signature (possibly raw).
2823      * @param s second signature (could be subjected to erasure).
2824      * @return true if t is a subsignature of s.
2825      */
2826     public boolean isSubSignature(Type t, Type s) {
2827         return hasSameArgs(t, s, true) || hasSameArgs(t, erasure(s), true);
2828     }
2829 
2830     /**
2831      * Returns true iff these signatures are related by <em>override
2832      * equivalence</em>.  This is the natural extension of
2833      * isSubSignature to an equivalence relation.
2834      *
2835      * @jls 8.4.2 Method Signature
2836      * @see #isSubSignature(Type t, Type s)
2837      * @param t a signature (possible raw, could be subjected to
2838      * erasure).
2839      * @param s a signature (possible raw, could be subjected to
2840      * erasure).
2841      * @return true if either argument is a subsignature of the other.
2842      */
2843     public boolean overrideEquivalent(Type t, Type s) {
2844         return hasSameArgs(t, s) ||
2845             hasSameArgs(t, erasure(s)) || hasSameArgs(erasure(t), s);
2846     }
2847 
2848     public boolean overridesObjectMethod(TypeSymbol origin, Symbol msym) {
2849         for (Symbol sym : syms.objectType.tsym.members().getSymbolsByName(msym.name)) {
2850             if (msym.overrides(sym, origin, Types.this, true)) {
2851                 return true;
2852             }
2853         }
2854         return false;
2855     }
2856 
2857     /**
2858      * This enum defines the strategy for implementing most specific return type check
2859      * during the most specific and functional interface checks.
2860      */
2861     public enum MostSpecificReturnCheck {
2862         /**
2863          * Return r1 is more specific than r2 if {@code r1 <: r2}. Extra care required for (i) handling
2864          * method type variables (if either method is generic) and (ii) subtyping should be replaced
2865          * by type-equivalence for primitives. This is essentially an inlined version of
2866          * {@link Types#resultSubtype(Type, Type, Warner)}, where the assignability check has been
2867          * replaced with a strict subtyping check.
2868          */
2869         BASIC() {
2870             @Override
2871             public boolean test(Type mt1, Type mt2, Types types) {
2872                 List<Type> tvars = mt1.getTypeArguments();
2873                 List<Type> svars = mt2.getTypeArguments();
2874                 Type t = mt1.getReturnType();
2875                 Type s = types.subst(mt2.getReturnType(), svars, tvars);
2876                 return types.isSameType(t, s) ||
2877                     !t.isPrimitive() &&
2878                     !s.isPrimitive() &&
2879                     types.isSubtype(t, s);
2880             }
2881         },
2882         /**
2883          * Return r1 is more specific than r2 if r1 is return-type-substitutable for r2.
2884          */
2885         RTS() {
2886             @Override
2887             public boolean test(Type mt1, Type mt2, Types types) {
2888                 return types.returnTypeSubstitutable(mt1, mt2);
2889             }
2890         };
2891 
2892         public abstract boolean test(Type mt1, Type mt2, Types types);
2893     }
2894 
2895     /**
2896      * Merge multiple abstract methods. The preferred method is a method that is a subsignature
2897      * of all the other signatures and whose return type is more specific {@link MostSpecificReturnCheck}.
2898      * The resulting preferred method has a throws clause that is the intersection of the merged
2899      * methods' clauses.
2900      */
2901     public Optional<Symbol> mergeAbstracts(List<Symbol> ambiguousInOrder, Type site, boolean sigCheck) {
2902         //first check for preconditions
2903         boolean shouldErase = false;
2904         List<Type> erasedParams = ambiguousInOrder.head.erasure(this).getParameterTypes();
2905         for (Symbol s : ambiguousInOrder) {
2906             if ((s.flags() & ABSTRACT) == 0 ||
2907                     (sigCheck && !isSameTypes(erasedParams, s.erasure(this).getParameterTypes()))) {
2908                 return Optional.empty();
2909             } else if (s.type.hasTag(FORALL)) {
2910                 shouldErase = true;
2911             }
2912         }
2913         //then merge abstracts
2914         for (MostSpecificReturnCheck mostSpecificReturnCheck : MostSpecificReturnCheck.values()) {
2915             outer: for (Symbol s : ambiguousInOrder) {
2916                 Type mt = memberType(site, s);
2917                 List<Type> allThrown = mt.getThrownTypes();
2918                 for (Symbol s2 : ambiguousInOrder) {
2919                     if (s != s2) {
2920                         Type mt2 = memberType(site, s2);
2921                         if (!isSubSignature(mt, mt2) ||
2922                                 !mostSpecificReturnCheck.test(mt, mt2, this)) {
2923                             //ambiguity cannot be resolved
2924                             continue outer;
2925                         } else {
2926                             List<Type> thrownTypes2 = mt2.getThrownTypes();
2927                             if (!mt.hasTag(FORALL) && shouldErase) {
2928                                 thrownTypes2 = erasure(thrownTypes2);
2929                             } else if (mt.hasTag(FORALL)) {
2930                                 //subsignature implies that if most specific is generic, then all other
2931                                 //methods are too
2932                                 Assert.check(mt2.hasTag(FORALL));
2933                                 // if both are generic methods, adjust thrown types ahead of intersection computation
2934                                 thrownTypes2 = subst(thrownTypes2, mt2.getTypeArguments(), mt.getTypeArguments());
2935                             }
2936                             allThrown = chk.intersect(allThrown, thrownTypes2);
2937                         }
2938                     }
2939                 }
2940                 return (allThrown == mt.getThrownTypes()) ?
2941                         Optional.of(s) :
2942                         Optional.of(new MethodSymbol(
2943                                 s.flags(),
2944                                 s.name,
2945                                 createMethodTypeWithThrown(s.type, allThrown),
2946                                 s.owner) {
2947                             @Override
2948                             public Symbol baseSymbol() {
2949                                 return s;
2950                             }
2951                         });
2952             }
2953         }
2954         return Optional.empty();
2955     }
2956 
2957     // <editor-fold defaultstate="collapsed" desc="Determining method implementation in given site">
2958     class ImplementationCache {
2959 
2960         private WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, Entry>>> _map = new WeakHashMap<>();
2961 
2962         class Entry {
2963             final MethodSymbol cachedImpl;
2964             final Predicate<Symbol> implFilter;
2965             final boolean checkResult;
2966             final int prevMark;
2967 
2968             public Entry(MethodSymbol cachedImpl,
2969                     Predicate<Symbol> scopeFilter,
2970                     boolean checkResult,
2971                     int prevMark) {
2972                 this.cachedImpl = cachedImpl;
2973                 this.implFilter = scopeFilter;
2974                 this.checkResult = checkResult;
2975                 this.prevMark = prevMark;
2976             }
2977 
2978             boolean matches(Predicate<Symbol> scopeFilter, boolean checkResult, int mark) {
2979                 return this.implFilter == scopeFilter &&
2980                         this.checkResult == checkResult &&
2981                         this.prevMark == mark;
2982             }
2983         }
2984 
2985         MethodSymbol get(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Predicate<Symbol> implFilter) {
2986             SoftReference<Map<TypeSymbol, Entry>> ref_cache = _map.get(ms);
2987             Map<TypeSymbol, Entry> cache = ref_cache != null ? ref_cache.get() : null;
2988             if (cache == null) {
2989                 cache = new HashMap<>();
2990                 _map.put(ms, new SoftReference<>(cache));
2991             }
2992             Entry e = cache.get(origin);
2993             CompoundScope members = membersClosure(origin.type, true);
2994             if (e == null ||
2995                     !e.matches(implFilter, checkResult, members.getMark())) {
2996                 MethodSymbol impl = implementationInternal(ms, origin, checkResult, implFilter);
2997                 cache.put(origin, new Entry(impl, implFilter, checkResult, members.getMark()));
2998                 return impl;
2999             }
3000             else {
3001                 return e.cachedImpl;
3002             }
3003         }
3004 
3005         private MethodSymbol implementationInternal(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Predicate<Symbol> implFilter) {
3006             for (Type t = origin.type; t.hasTag(CLASS) || t.hasTag(TYPEVAR); t = supertype(t)) {
3007                 t = skipTypeVars(t, false);
3008                 TypeSymbol c = t.tsym;
3009                 Symbol bestSoFar = null;
3010                 for (Symbol sym : c.members().getSymbolsByName(ms.name, implFilter)) {
3011                     if (sym != null && sym.overrides(ms, origin, Types.this, checkResult)) {
3012                         bestSoFar = sym;
3013                         if ((sym.flags() & ABSTRACT) == 0) {
3014                             //if concrete impl is found, exit immediately
3015                             break;
3016                         }
3017                     }
3018                 }
3019                 if (bestSoFar != null) {
3020                     //return either the (only) concrete implementation or the first abstract one
3021                     return (MethodSymbol)bestSoFar;
3022                 }
3023             }
3024             return null;
3025         }
3026     }
3027 
3028     private ImplementationCache implCache = new ImplementationCache();
3029 
3030     public MethodSymbol implementation(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Predicate<Symbol> implFilter) {
3031         return implCache.get(ms, origin, checkResult, implFilter);
3032     }
3033     // </editor-fold>
3034 
3035     // <editor-fold defaultstate="collapsed" desc="compute transitive closure of all members in given site">
3036     class MembersClosureCache extends SimpleVisitor<Scope.CompoundScope, Void> {
3037 
3038         private Map<TypeSymbol, CompoundScope> _map = new HashMap<>();
3039 
3040         Set<TypeSymbol> seenTypes = new HashSet<>();
3041 
3042         class MembersScope extends CompoundScope {
3043 
3044             CompoundScope scope;
3045 
3046             public MembersScope(CompoundScope scope) {
3047                 super(scope.owner);
3048                 this.scope = scope;
3049             }
3050 
3051             Predicate<Symbol> combine(Predicate<Symbol> sf) {
3052                 return s -> !s.owner.isInterface() && (sf == null || sf.test(s));
3053             }
3054 
3055             @Override
3056             public Iterable<Symbol> getSymbols(Predicate<Symbol> sf, LookupKind lookupKind) {
3057                 return scope.getSymbols(combine(sf), lookupKind);
3058             }
3059 
3060             @Override
3061             public Iterable<Symbol> getSymbolsByName(Name name, Predicate<Symbol> sf, LookupKind lookupKind) {
3062                 return scope.getSymbolsByName(name, combine(sf), lookupKind);
3063             }
3064 
3065             @Override
3066             public int getMark() {
3067                 return scope.getMark();
3068             }
3069         }
3070 
3071         CompoundScope nilScope;
3072 
3073         /** members closure visitor methods **/
3074 
3075         public CompoundScope visitType(Type t, Void _unused) {
3076             if (nilScope == null) {
3077                 nilScope = new CompoundScope(syms.noSymbol);
3078             }
3079             return nilScope;
3080         }
3081 
3082         @Override
3083         public CompoundScope visitClassType(ClassType t, Void _unused) {
3084             if (!seenTypes.add(t.tsym)) {
3085                 //this is possible when an interface is implemented in multiple
3086                 //superclasses, or when a class hierarchy is circular - in such
3087                 //cases we don't need to recurse (empty scope is returned)
3088                 return new CompoundScope(t.tsym);
3089             }
3090             try {
3091                 seenTypes.add(t.tsym);
3092                 ClassSymbol csym = (ClassSymbol)t.tsym;
3093                 CompoundScope membersClosure = _map.get(csym);
3094                 if (membersClosure == null) {
3095                     membersClosure = new CompoundScope(csym);
3096                     for (Type i : interfaces(t)) {
3097                         membersClosure.prependSubScope(visit(i, null));
3098                     }
3099                     membersClosure.prependSubScope(visit(supertype(t), null));
3100                     membersClosure.prependSubScope(csym.members());
3101                     _map.put(csym, membersClosure);
3102                 }
3103                 return membersClosure;
3104             }
3105             finally {
3106                 seenTypes.remove(t.tsym);
3107             }
3108         }
3109 
3110         @Override
3111         public CompoundScope visitTypeVar(TypeVar t, Void _unused) {
3112             return visit(t.getUpperBound(), null);
3113         }
3114     }
3115 
3116     private MembersClosureCache membersCache = new MembersClosureCache();
3117 
3118     public CompoundScope membersClosure(Type site, boolean skipInterface) {
3119         CompoundScope cs = membersCache.visit(site, null);
3120         Assert.checkNonNull(cs, () -> "type " + site);
3121         return skipInterface ? membersCache.new MembersScope(cs) : cs;
3122     }
3123     // </editor-fold>
3124 
3125 
3126     /** Return first abstract member of class `sym'.
3127      */
3128     public MethodSymbol firstUnimplementedAbstract(ClassSymbol sym) {
3129         try {
3130             return firstUnimplementedAbstractImpl(sym, sym);
3131         } catch (CompletionFailure ex) {
3132             chk.completionError(enter.getEnv(sym).tree.pos(), ex);
3133             return null;
3134         }
3135     }
3136         //where:
3137         private MethodSymbol firstUnimplementedAbstractImpl(ClassSymbol impl, ClassSymbol c) {
3138             MethodSymbol undef = null;
3139             // Do not bother to search in classes that are not abstract,
3140             // since they cannot have abstract members.
3141             if (c == impl || (c.flags() & (ABSTRACT | INTERFACE)) != 0) {
3142                 Scope s = c.members();
3143                 for (Symbol sym : s.getSymbols(NON_RECURSIVE)) {
3144                     if (sym.kind == MTH &&
3145                         (sym.flags() & (ABSTRACT|DEFAULT|PRIVATE)) == ABSTRACT) {
3146                         MethodSymbol absmeth = (MethodSymbol)sym;
3147                         MethodSymbol implmeth = absmeth.implementation(impl, this, true);
3148                         if (implmeth == null || implmeth == absmeth) {
3149                             //look for default implementations
3150                             MethodSymbol prov = interfaceCandidates(impl.type, absmeth).head;
3151                             if (prov != null && prov.overrides(absmeth, impl, this, true)) {
3152                                 implmeth = prov;
3153                             }
3154                         }
3155                         if (implmeth == null || implmeth == absmeth) {
3156                             undef = absmeth;
3157                             break;
3158                         }
3159                     }
3160                 }
3161                 if (undef == null) {
3162                     Type st = supertype(c.type);
3163                     if (st.hasTag(CLASS))
3164                         undef = firstUnimplementedAbstractImpl(impl, (ClassSymbol)st.tsym);
3165                 }
3166                 for (List<Type> l = interfaces(c.type);
3167                      undef == null && l.nonEmpty();
3168                      l = l.tail) {
3169                     undef = firstUnimplementedAbstractImpl(impl, (ClassSymbol)l.head.tsym);
3170                 }
3171             }
3172             return undef;
3173         }
3174 
3175     public class CandidatesCache {
3176         public Map<Entry, List<MethodSymbol>> cache = new WeakHashMap<>();
3177 
3178         class Entry {
3179             Type site;
3180             MethodSymbol msym;
3181 
3182             Entry(Type site, MethodSymbol msym) {
3183                 this.site = site;
3184                 this.msym = msym;
3185             }
3186 
3187             @Override
3188             public boolean equals(Object obj) {
3189                 return (obj instanceof Entry entry)
3190                         && entry.msym == msym
3191                         && isSameType(site, entry.site);
3192             }
3193 
3194             @Override
3195             public int hashCode() {
3196                 return Types.this.hashCode(site) & ~msym.hashCode();
3197             }
3198         }
3199 
3200         public List<MethodSymbol> get(Entry e) {
3201             return cache.get(e);
3202         }
3203 
3204         public void put(Entry e, List<MethodSymbol> msymbols) {
3205             cache.put(e, msymbols);
3206         }
3207     }
3208 
3209     public CandidatesCache candidatesCache = new CandidatesCache();
3210 
3211     //where
3212     public List<MethodSymbol> interfaceCandidates(Type site, MethodSymbol ms) {
3213         CandidatesCache.Entry e = candidatesCache.new Entry(site, ms);
3214         List<MethodSymbol> candidates = candidatesCache.get(e);
3215         if (candidates == null) {
3216             Predicate<Symbol> filter = new MethodFilter(ms, site);
3217             List<MethodSymbol> candidates2 = List.nil();
3218             for (Symbol s : membersClosure(site, false).getSymbols(filter)) {
3219                 if (!site.tsym.isInterface() && !s.owner.isInterface()) {
3220                     return List.of((MethodSymbol)s);
3221                 } else if (!candidates2.contains(s)) {
3222                     candidates2 = candidates2.prepend((MethodSymbol)s);
3223                 }
3224             }
3225             candidates = prune(candidates2);
3226             candidatesCache.put(e, candidates);
3227         }
3228         return candidates;
3229     }
3230 
3231     public List<MethodSymbol> prune(List<MethodSymbol> methods) {
3232         ListBuffer<MethodSymbol> methodsMin = new ListBuffer<>();
3233         for (MethodSymbol m1 : methods) {
3234             boolean isMin_m1 = true;
3235             for (MethodSymbol m2 : methods) {
3236                 if (m1 == m2) continue;
3237                 if (m2.owner != m1.owner &&
3238                         asSuper(m2.owner.type, m1.owner) != null) {
3239                     isMin_m1 = false;
3240                     break;
3241                 }
3242             }
3243             if (isMin_m1)
3244                 methodsMin.append(m1);
3245         }
3246         return methodsMin.toList();
3247     }
3248     // where
3249             private class MethodFilter implements Predicate<Symbol> {
3250 
3251                 Symbol msym;
3252                 Type site;
3253 
3254                 MethodFilter(Symbol msym, Type site) {
3255                     this.msym = msym;
3256                     this.site = site;
3257                 }
3258 
3259                 @Override
3260                 public boolean test(Symbol s) {
3261                     return s.kind == MTH &&
3262                             s.name == msym.name &&
3263                             (s.flags() & SYNTHETIC) == 0 &&
3264                             s.isInheritedIn(site.tsym, Types.this) &&
3265                             overrideEquivalent(memberType(site, s), memberType(site, msym));
3266                 }
3267             }
3268     // </editor-fold>
3269 
3270     /**
3271      * Does t have the same arguments as s?  It is assumed that both
3272      * types are (possibly polymorphic) method types.  Monomorphic
3273      * method types "have the same arguments", if their argument lists
3274      * are equal.  Polymorphic method types "have the same arguments",
3275      * if they have the same arguments after renaming all type
3276      * variables of one to corresponding type variables in the other,
3277      * where correspondence is by position in the type parameter list.
3278      */
3279     public boolean hasSameArgs(Type t, Type s) {
3280         return hasSameArgs(t, s, true);
3281     }
3282 
3283     public boolean hasSameArgs(Type t, Type s, boolean strict) {
3284         return hasSameArgs(t, s, strict ? hasSameArgs_strict : hasSameArgs_nonstrict);
3285     }
3286 
3287     private boolean hasSameArgs(Type t, Type s, TypeRelation hasSameArgs) {
3288         return hasSameArgs.visit(t, s);
3289     }
3290     // where
3291         private class HasSameArgs extends TypeRelation {
3292 
3293             boolean strict;
3294 
3295             public HasSameArgs(boolean strict) {
3296                 this.strict = strict;
3297             }
3298 
3299             public Boolean visitType(Type t, Type s) {
3300                 throw new AssertionError();
3301             }
3302 
3303             @Override
3304             public Boolean visitMethodType(MethodType t, Type s) {
3305                 return s.hasTag(METHOD)
3306                     && containsTypeEquivalent(t.argtypes, s.getParameterTypes());
3307             }
3308 
3309             @Override
3310             public Boolean visitForAll(ForAll t, Type s) {
3311                 if (!s.hasTag(FORALL))
3312                     return strict ? false : visitMethodType(t.asMethodType(), s);
3313 
3314                 ForAll forAll = (ForAll)s;
3315                 return hasSameBounds(t, forAll)
3316                     && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
3317             }
3318 
3319             @Override
3320             public Boolean visitErrorType(ErrorType t, Type s) {
3321                 return false;
3322             }
3323         }
3324 
3325     TypeRelation hasSameArgs_strict = new HasSameArgs(true);
3326         TypeRelation hasSameArgs_nonstrict = new HasSameArgs(false);
3327 
3328     // </editor-fold>
3329 
3330     // <editor-fold defaultstate="collapsed" desc="subst">
3331     public List<Type> subst(List<Type> ts,
3332                             List<Type> from,
3333                             List<Type> to) {
3334         return ts.map(new Subst(from, to));
3335     }
3336 
3337     /**
3338      * Substitute all occurrences of a type in `from' with the
3339      * corresponding type in `to' in 't'. Match lists `from' and `to'
3340      * from the right: If lists have different length, discard leading
3341      * elements of the longer list.
3342      */
3343     public Type subst(Type t, List<Type> from, List<Type> to) {
3344         return t.map(new Subst(from, to));
3345     }
3346 
3347     private class Subst extends StructuralTypeMapping<Void> {
3348         List<Type> from;
3349         List<Type> to;
3350 
3351         public Subst(List<Type> from, List<Type> to) {
3352             int fromLength = from.length();
3353             int toLength = to.length();
3354             while (fromLength > toLength) {
3355                 fromLength--;
3356                 from = from.tail;
3357             }
3358             while (fromLength < toLength) {
3359                 toLength--;
3360                 to = to.tail;
3361             }
3362             this.from = from;
3363             this.to = to;
3364         }
3365 
3366         @Override
3367         public Type visitTypeVar(TypeVar t, Void ignored) {
3368             for (List<Type> from = this.from, to = this.to;
3369                  from.nonEmpty();
3370                  from = from.tail, to = to.tail) {
3371                 if (t.equalsIgnoreMetadata(from.head)) {
3372                     return to.head.withTypeVar(t);
3373                 }
3374             }
3375             return t;
3376         }
3377 
3378         @Override
3379         public Type visitClassType(ClassType t, Void ignored) {
3380             if (!t.isCompound()) {
3381                 return super.visitClassType(t, ignored);
3382             } else {
3383                 Type st = visit(supertype(t));
3384                 List<Type> is = visit(interfaces(t), ignored);
3385                 if (st == supertype(t) && is == interfaces(t))
3386                     return t;
3387                 else
3388                     return makeIntersectionType(is.prepend(st));
3389             }
3390         }
3391 
3392         @Override
3393         public Type visitWildcardType(WildcardType t, Void ignored) {
3394             WildcardType t2 = (WildcardType)super.visitWildcardType(t, ignored);
3395             if (t2 != t && t.isExtendsBound() && t2.type.isExtendsBound()) {
3396                 t2.type = wildUpperBound(t2.type);
3397             }
3398             return t2;
3399         }
3400 
3401         @Override
3402         public Type visitForAll(ForAll t, Void ignored) {
3403             if (Type.containsAny(to, t.tvars)) {
3404                 //perform alpha-renaming of free-variables in 't'
3405                 //if 'to' types contain variables that are free in 't'
3406                 List<Type> freevars = newInstances(t.tvars);
3407                 t = new ForAll(freevars,
3408                                Types.this.subst(t.qtype, t.tvars, freevars));
3409             }
3410             List<Type> tvars1 = substBounds(t.tvars, from, to);
3411             Type qtype1 = visit(t.qtype);
3412             if (tvars1 == t.tvars && qtype1 == t.qtype) {
3413                 return t;
3414             } else if (tvars1 == t.tvars) {
3415                 return new ForAll(tvars1, qtype1) {
3416                     @Override
3417                     public boolean needsStripping() {
3418                         return true;
3419                     }
3420                 };
3421             } else {
3422                 return new ForAll(tvars1, Types.this.subst(qtype1, t.tvars, tvars1)) {
3423                     @Override
3424                     public boolean needsStripping() {
3425                         return true;
3426                     }
3427                 };
3428             }
3429         }
3430     }
3431 
3432     public List<Type> substBounds(List<Type> tvars,
3433                                   List<Type> from,
3434                                   List<Type> to) {
3435         if (tvars.isEmpty())
3436             return tvars;
3437         ListBuffer<Type> newBoundsBuf = new ListBuffer<>();
3438         boolean changed = false;
3439         // calculate new bounds
3440         for (Type t : tvars) {
3441             TypeVar tv = (TypeVar) t;
3442             Type bound = subst(tv.getUpperBound(), from, to);
3443             if (bound != tv.getUpperBound())
3444                 changed = true;
3445             newBoundsBuf.append(bound);
3446         }
3447         if (!changed)
3448             return tvars;
3449         ListBuffer<Type> newTvars = new ListBuffer<>();
3450         // create new type variables without bounds
3451         for (Type t : tvars) {
3452             newTvars.append(new TypeVar(t.tsym, null, syms.botType,
3453                                         t.getMetadata()));
3454         }
3455         // the new bounds should use the new type variables in place
3456         // of the old
3457         List<Type> newBounds = newBoundsBuf.toList();
3458         from = tvars;
3459         to = newTvars.toList();
3460         for (; !newBounds.isEmpty(); newBounds = newBounds.tail) {
3461             newBounds.head = subst(newBounds.head, from, to);
3462         }
3463         newBounds = newBoundsBuf.toList();
3464         // set the bounds of new type variables to the new bounds
3465         for (Type t : newTvars.toList()) {
3466             TypeVar tv = (TypeVar) t;
3467             tv.setUpperBound( newBounds.head );
3468             newBounds = newBounds.tail;
3469         }
3470         return newTvars.toList();
3471     }
3472 
3473     public TypeVar substBound(TypeVar t, List<Type> from, List<Type> to) {
3474         Type bound1 = subst(t.getUpperBound(), from, to);
3475         if (bound1 == t.getUpperBound())
3476             return t;
3477         else {
3478             // create new type variable without bounds
3479             TypeVar tv = new TypeVar(t.tsym, null, syms.botType,
3480                                      t.getMetadata());
3481             // the new bound should use the new type variable in place
3482             // of the old
3483             tv.setUpperBound( subst(bound1, List.of(t), List.of(tv)) );
3484             return tv;
3485         }
3486     }
3487     // </editor-fold>
3488 
3489     // <editor-fold defaultstate="collapsed" desc="hasSameBounds">
3490     /**
3491      * Does t have the same bounds for quantified variables as s?
3492      */
3493     public boolean hasSameBounds(ForAll t, ForAll s) {
3494         List<Type> l1 = t.tvars;
3495         List<Type> l2 = s.tvars;
3496         while (l1.nonEmpty() && l2.nonEmpty() &&
3497                isSameType(l1.head.getUpperBound(),
3498                           subst(l2.head.getUpperBound(),
3499                                 s.tvars,
3500                                 t.tvars))) {
3501             l1 = l1.tail;
3502             l2 = l2.tail;
3503         }
3504         return l1.isEmpty() && l2.isEmpty();
3505     }
3506     // </editor-fold>
3507 
3508     // <editor-fold defaultstate="collapsed" desc="newInstances">
3509     /** Create new vector of type variables from list of variables
3510      *  changing all recursive bounds from old to new list.
3511      */
3512     public List<Type> newInstances(List<Type> tvars) {
3513         List<Type> tvars1 = tvars.map(newInstanceFun);
3514         for (List<Type> l = tvars1; l.nonEmpty(); l = l.tail) {
3515             TypeVar tv = (TypeVar) l.head;
3516             tv.setUpperBound( subst(tv.getUpperBound(), tvars, tvars1) );
3517         }
3518         return tvars1;
3519     }
3520         private static final TypeMapping<Void> newInstanceFun = new TypeMapping<Void>() {
3521             @Override
3522             public TypeVar visitTypeVar(TypeVar t, Void _unused) {
3523                 return new TypeVar(t.tsym, t.getUpperBound(), t.getLowerBound(), t.getMetadata());
3524             }
3525         };
3526     // </editor-fold>
3527 
3528     public Type createMethodTypeWithParameters(Type original, List<Type> newParams) {
3529         return original.accept(methodWithParameters, newParams);
3530     }
3531     // where
3532         private final MapVisitor<List<Type>> methodWithParameters = new MapVisitor<List<Type>>() {
3533             public Type visitType(Type t, List<Type> newParams) {
3534                 throw new IllegalArgumentException("Not a method type: " + t);
3535             }
3536             public Type visitMethodType(MethodType t, List<Type> newParams) {
3537                 return new MethodType(newParams, t.restype, t.thrown, t.tsym);
3538             }
3539             public Type visitForAll(ForAll t, List<Type> newParams) {
3540                 return new ForAll(t.tvars, t.qtype.accept(this, newParams));
3541             }
3542         };
3543 
3544     public Type createMethodTypeWithThrown(Type original, List<Type> newThrown) {
3545         return original.accept(methodWithThrown, newThrown);
3546     }
3547     // where
3548         private final MapVisitor<List<Type>> methodWithThrown = new MapVisitor<List<Type>>() {
3549             public Type visitType(Type t, List<Type> newThrown) {
3550                 throw new IllegalArgumentException("Not a method type: " + t);
3551             }
3552             public Type visitMethodType(MethodType t, List<Type> newThrown) {
3553                 return new MethodType(t.argtypes, t.restype, newThrown, t.tsym);
3554             }
3555             public Type visitForAll(ForAll t, List<Type> newThrown) {
3556                 return new ForAll(t.tvars, t.qtype.accept(this, newThrown));
3557             }
3558         };
3559 
3560     public Type createMethodTypeWithReturn(Type original, Type newReturn) {
3561         return original.accept(methodWithReturn, newReturn);
3562     }
3563     // where
3564         private final MapVisitor<Type> methodWithReturn = new MapVisitor<Type>() {
3565             public Type visitType(Type t, Type newReturn) {
3566                 throw new IllegalArgumentException("Not a method type: " + t);
3567             }
3568             public Type visitMethodType(MethodType t, Type newReturn) {
3569                 return new MethodType(t.argtypes, newReturn, t.thrown, t.tsym) {
3570                     @Override
3571                     public Type baseType() {
3572                         return t;
3573                     }
3574                 };
3575             }
3576             public Type visitForAll(ForAll t, Type newReturn) {
3577                 return new ForAll(t.tvars, t.qtype.accept(this, newReturn)) {
3578                     @Override
3579                     public Type baseType() {
3580                         return t;
3581                     }
3582                 };
3583             }
3584         };
3585 
3586     // <editor-fold defaultstate="collapsed" desc="createErrorType">
3587     public Type createErrorType(Type originalType) {
3588         return new ErrorType(originalType, syms.errSymbol);
3589     }
3590 
3591     public Type createErrorType(ClassSymbol c, Type originalType) {
3592         return new ErrorType(c, originalType);
3593     }
3594 
3595     public Type createErrorType(Name name, TypeSymbol container, Type originalType) {
3596         return new ErrorType(name, container, originalType);
3597     }
3598     // </editor-fold>
3599 
3600     // <editor-fold defaultstate="collapsed" desc="rank">
3601     /**
3602      * The rank of a class is the length of the longest path between
3603      * the class and java.lang.Object in the class inheritance
3604      * graph. Undefined for all but reference types.
3605      */
3606     public int rank(Type t) {
3607         switch(t.getTag()) {
3608         case CLASS: {
3609             ClassType cls = (ClassType)t;
3610             if (cls.rank_field < 0) {
3611                 Name fullname = cls.tsym.getQualifiedName();
3612                 if (fullname == names.java_lang_Object)
3613                     cls.rank_field = 0;
3614                 else {
3615                     int r = rank(supertype(cls));
3616                     for (List<Type> l = interfaces(cls);
3617                          l.nonEmpty();
3618                          l = l.tail) {
3619                         if (rank(l.head) > r)
3620                             r = rank(l.head);
3621                     }
3622                     cls.rank_field = r + 1;
3623                 }
3624             }
3625             return cls.rank_field;
3626         }
3627         case TYPEVAR: {
3628             TypeVar tvar = (TypeVar)t;
3629             if (tvar.rank_field < 0) {
3630                 int r = rank(supertype(tvar));
3631                 for (List<Type> l = interfaces(tvar);
3632                      l.nonEmpty();
3633                      l = l.tail) {
3634                     if (rank(l.head) > r) r = rank(l.head);
3635                 }
3636                 tvar.rank_field = r + 1;
3637             }
3638             return tvar.rank_field;
3639         }
3640         case ERROR:
3641         case NONE:
3642             return 0;
3643         default:
3644             throw new AssertionError();
3645         }
3646     }
3647     // </editor-fold>
3648 
3649     /**
3650      * Helper method for generating a string representation of a given type
3651      * accordingly to a given locale
3652      */
3653     public String toString(Type t, Locale locale) {
3654         return Printer.createStandardPrinter(messages).visit(t, locale);
3655     }
3656 
3657     /**
3658      * Helper method for generating a string representation of a given type
3659      * accordingly to a given locale
3660      */
3661     public String toString(Symbol t, Locale locale) {
3662         return Printer.createStandardPrinter(messages).visit(t, locale);
3663     }
3664 
3665     // <editor-fold defaultstate="collapsed" desc="toString">
3666     /**
3667      * This toString is slightly more descriptive than the one on Type.
3668      *
3669      * @deprecated Types.toString(Type t, Locale l) provides better support
3670      * for localization
3671      */
3672     @Deprecated
3673     public String toString(Type t) {
3674         if (t.hasTag(FORALL)) {
3675             ForAll forAll = (ForAll)t;
3676             return typaramsString(forAll.tvars) + forAll.qtype;
3677         }
3678         return "" + t;
3679     }
3680     // where
3681         private String typaramsString(List<Type> tvars) {
3682             StringBuilder s = new StringBuilder();
3683             s.append('<');
3684             boolean first = true;
3685             for (Type t : tvars) {
3686                 if (!first) s.append(", ");
3687                 first = false;
3688                 appendTyparamString(((TypeVar)t), s);
3689             }
3690             s.append('>');
3691             return s.toString();
3692         }
3693         private void appendTyparamString(TypeVar t, StringBuilder buf) {
3694             buf.append(t);
3695             if (t.getUpperBound() == null ||
3696                 t.getUpperBound().tsym.getQualifiedName() == names.java_lang_Object)
3697                 return;
3698             buf.append(" extends "); // Java syntax; no need for i18n
3699             Type bound = t.getUpperBound();
3700             if (!bound.isCompound()) {
3701                 buf.append(bound);
3702             } else if ((erasure(t).tsym.flags() & INTERFACE) == 0) {
3703                 buf.append(supertype(t));
3704                 for (Type intf : interfaces(t)) {
3705                     buf.append('&');
3706                     buf.append(intf);
3707                 }
3708             } else {
3709                 // No superclass was given in bounds.
3710                 // In this case, supertype is Object, erasure is first interface.
3711                 boolean first = true;
3712                 for (Type intf : interfaces(t)) {
3713                     if (!first) buf.append('&');
3714                     first = false;
3715                     buf.append(intf);
3716                 }
3717             }
3718         }
3719     // </editor-fold>
3720 
3721     // <editor-fold defaultstate="collapsed" desc="Determining least upper bounds of types">
3722     /**
3723      * A cache for closures.
3724      *
3725      * <p>A closure is a list of all the supertypes and interfaces of
3726      * a class or interface type, ordered by ClassSymbol.precedes
3727      * (that is, subclasses come first, arbitrarily but fixed
3728      * otherwise).
3729      */
3730     private Map<Type,List<Type>> closureCache = new HashMap<>();
3731 
3732     /**
3733      * Returns the closure of a class or interface type.
3734      */
3735     public List<Type> closure(Type t) {
3736         List<Type> cl = closureCache.get(t);
3737         if (cl == null) {
3738             Type st = supertype(t);
3739             if (!t.isCompound()) {
3740                 if (st.hasTag(CLASS)) {
3741                     cl = insert(closure(st), t);
3742                 } else if (st.hasTag(TYPEVAR)) {
3743                     cl = closure(st).prepend(t);
3744                 } else {
3745                     cl = List.of(t);
3746                 }
3747             } else {
3748                 cl = closure(supertype(t));
3749             }
3750             for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail)
3751                 cl = union(cl, closure(l.head));
3752             closureCache.put(t, cl);
3753         }
3754         return cl;
3755     }
3756 
3757     /**
3758      * Collect types into a new closure (using a {@code ClosureHolder})
3759      */
3760     public Collector<Type, ClosureHolder, List<Type>> closureCollector(boolean minClosure, BiPredicate<Type, Type> shouldSkip) {
3761         return Collector.of(() -> new ClosureHolder(minClosure, shouldSkip),
3762                 ClosureHolder::add,
3763                 ClosureHolder::merge,
3764                 ClosureHolder::closure);
3765     }
3766     //where
3767         class ClosureHolder {
3768             List<Type> closure;
3769             final boolean minClosure;
3770             final BiPredicate<Type, Type> shouldSkip;
3771 
3772             ClosureHolder(boolean minClosure, BiPredicate<Type, Type> shouldSkip) {
3773                 this.closure = List.nil();
3774                 this.minClosure = minClosure;
3775                 this.shouldSkip = shouldSkip;
3776             }
3777 
3778             void add(Type type) {
3779                 closure = insert(closure, type, shouldSkip);
3780             }
3781 
3782             ClosureHolder merge(ClosureHolder other) {
3783                 closure = union(closure, other.closure, shouldSkip);
3784                 return this;
3785             }
3786 
3787             List<Type> closure() {
3788                 return minClosure ? closureMin(closure) : closure;
3789             }
3790         }
3791 
3792     BiPredicate<Type, Type> basicClosureSkip = (t1, t2) -> t1.tsym == t2.tsym;
3793 
3794     /**
3795      * Insert a type in a closure
3796      */
3797     public List<Type> insert(List<Type> cl, Type t, BiPredicate<Type, Type> shouldSkip) {
3798         if (cl.isEmpty()) {
3799             return cl.prepend(t);
3800         } else if (shouldSkip.test(t, cl.head)) {
3801             return cl;
3802         } else if (t.tsym.precedes(cl.head.tsym, this)) {
3803             return cl.prepend(t);
3804         } else {
3805             // t comes after head, or the two are unrelated
3806             return insert(cl.tail, t, shouldSkip).prepend(cl.head);
3807         }
3808     }
3809 
3810     public List<Type> insert(List<Type> cl, Type t) {
3811         return insert(cl, t, basicClosureSkip);
3812     }
3813 
3814     /**
3815      * Form the union of two closures
3816      */
3817     public List<Type> union(List<Type> cl1, List<Type> cl2, BiPredicate<Type, Type> shouldSkip) {
3818         if (cl1.isEmpty()) {
3819             return cl2;
3820         } else if (cl2.isEmpty()) {
3821             return cl1;
3822         } else if (shouldSkip.test(cl1.head, cl2.head)) {
3823             return union(cl1.tail, cl2.tail, shouldSkip).prepend(cl1.head);
3824         } else if (cl2.head.tsym.precedes(cl1.head.tsym, this)) {
3825             return union(cl1, cl2.tail, shouldSkip).prepend(cl2.head);
3826         } else {
3827             return union(cl1.tail, cl2, shouldSkip).prepend(cl1.head);
3828         }
3829     }
3830 
3831     public List<Type> union(List<Type> cl1, List<Type> cl2) {
3832         return union(cl1, cl2, basicClosureSkip);
3833     }
3834 
3835     /**
3836      * Intersect two closures
3837      */
3838     public List<Type> intersect(List<Type> cl1, List<Type> cl2) {
3839         if (cl1 == cl2)
3840             return cl1;
3841         if (cl1.isEmpty() || cl2.isEmpty())
3842             return List.nil();
3843         if (cl1.head.tsym.precedes(cl2.head.tsym, this))
3844             return intersect(cl1.tail, cl2);
3845         if (cl2.head.tsym.precedes(cl1.head.tsym, this))
3846             return intersect(cl1, cl2.tail);
3847         if (isSameType(cl1.head, cl2.head))
3848             return intersect(cl1.tail, cl2.tail).prepend(cl1.head);
3849         if (cl1.head.tsym == cl2.head.tsym &&
3850             cl1.head.hasTag(CLASS) && cl2.head.hasTag(CLASS)) {
3851             if (cl1.head.isParameterized() && cl2.head.isParameterized()) {
3852                 Type merge = merge(cl1.head,cl2.head);
3853                 return intersect(cl1.tail, cl2.tail).prepend(merge);
3854             }
3855             if (cl1.head.isRaw() || cl2.head.isRaw())
3856                 return intersect(cl1.tail, cl2.tail).prepend(erasure(cl1.head));
3857         }
3858         return intersect(cl1.tail, cl2.tail);
3859     }
3860     // where
3861         class TypePair {
3862             final Type t1;
3863             final Type t2;;
3864 
3865             TypePair(Type t1, Type t2) {
3866                 this.t1 = t1;
3867                 this.t2 = t2;
3868             }
3869             @Override
3870             public int hashCode() {
3871                 return 127 * Types.this.hashCode(t1) + Types.this.hashCode(t2);
3872             }
3873             @Override
3874             public boolean equals(Object obj) {
3875                 return (obj instanceof TypePair typePair)
3876                         && isSameType(t1, typePair.t1)
3877                         && isSameType(t2, typePair.t2);
3878             }
3879         }
3880         Set<TypePair> mergeCache = new HashSet<>();
3881         private Type merge(Type c1, Type c2) {
3882             ClassType class1 = (ClassType) c1;
3883             List<Type> act1 = class1.getTypeArguments();
3884             ClassType class2 = (ClassType) c2;
3885             List<Type> act2 = class2.getTypeArguments();
3886             ListBuffer<Type> merged = new ListBuffer<>();
3887             List<Type> typarams = class1.tsym.type.getTypeArguments();
3888 
3889             while (act1.nonEmpty() && act2.nonEmpty() && typarams.nonEmpty()) {
3890                 if (containsType(act1.head, act2.head)) {
3891                     merged.append(act1.head);
3892                 } else if (containsType(act2.head, act1.head)) {
3893                     merged.append(act2.head);
3894                 } else {
3895                     TypePair pair = new TypePair(c1, c2);
3896                     Type m;
3897                     if (mergeCache.add(pair)) {
3898                         m = new WildcardType(lub(wildUpperBound(act1.head),
3899                                                  wildUpperBound(act2.head)),
3900                                              BoundKind.EXTENDS,
3901                                              syms.boundClass);
3902                         mergeCache.remove(pair);
3903                     } else {
3904                         m = new WildcardType(syms.objectType,
3905                                              BoundKind.UNBOUND,
3906                                              syms.boundClass);
3907                     }
3908                     merged.append(m.withTypeVar(typarams.head));
3909                 }
3910                 act1 = act1.tail;
3911                 act2 = act2.tail;
3912                 typarams = typarams.tail;
3913             }
3914             Assert.check(act1.isEmpty() && act2.isEmpty() && typarams.isEmpty());
3915             // There is no spec detailing how type annotations are to
3916             // be inherited.  So set it to noAnnotations for now
3917             return new ClassType(class1.getEnclosingType(), merged.toList(),
3918                                  class1.tsym, List.nil());
3919         }
3920 
3921     /**
3922      * Return the minimum type of a closure, a compound type if no
3923      * unique minimum exists.
3924      */
3925     private Type compoundMin(List<Type> cl) {
3926         if (cl.isEmpty()) return syms.objectType;
3927         List<Type> compound = closureMin(cl);
3928         if (compound.isEmpty())
3929             return null;
3930         else if (compound.tail.isEmpty())
3931             return compound.head;
3932         else
3933             return makeIntersectionType(compound);
3934     }
3935 
3936     /**
3937      * Return the minimum types of a closure, suitable for computing
3938      * compoundMin or glb.
3939      */
3940     private List<Type> closureMin(List<Type> cl) {
3941         ListBuffer<Type> classes = new ListBuffer<>();
3942         ListBuffer<Type> interfaces = new ListBuffer<>();
3943         Set<Type> toSkip = new HashSet<>();
3944         while (!cl.isEmpty()) {
3945             Type current = cl.head;
3946             boolean keep = !toSkip.contains(current);
3947             if (keep && current.hasTag(TYPEVAR)) {
3948                 // skip lower-bounded variables with a subtype in cl.tail
3949                 for (Type t : cl.tail) {
3950                     if (isSubtypeNoCapture(t, current)) {
3951                         keep = false;
3952                         break;
3953                     }
3954                 }
3955             }
3956             if (keep) {
3957                 if (current.isInterface())
3958                     interfaces.append(current);
3959                 else
3960                     classes.append(current);
3961                 for (Type t : cl.tail) {
3962                     // skip supertypes of 'current' in cl.tail
3963                     if (isSubtypeNoCapture(current, t))
3964                         toSkip.add(t);
3965                 }
3966             }
3967             cl = cl.tail;
3968         }
3969         return classes.appendList(interfaces).toList();
3970     }
3971 
3972     /**
3973      * Return the least upper bound of list of types.  if the lub does
3974      * not exist return null.
3975      */
3976     public Type lub(List<Type> ts) {
3977         return lub(ts.toArray(new Type[ts.length()]));
3978     }
3979 
3980     /**
3981      * Return the least upper bound (lub) of set of types.  If the lub
3982      * does not exist return the type of null (bottom).
3983      */
3984     public Type lub(Type... ts) {
3985         final int UNKNOWN_BOUND = 0;
3986         final int ARRAY_BOUND = 1;
3987         final int CLASS_BOUND = 2;
3988 
3989         int[] kinds = new int[ts.length];
3990 
3991         int boundkind = UNKNOWN_BOUND;
3992         for (int i = 0 ; i < ts.length ; i++) {
3993             Type t = ts[i];
3994             switch (t.getTag()) {
3995             case CLASS:
3996                 boundkind |= kinds[i] = CLASS_BOUND;
3997                 break;
3998             case ARRAY:
3999                 boundkind |= kinds[i] = ARRAY_BOUND;
4000                 break;
4001             case  TYPEVAR:
4002                 do {
4003                     t = t.getUpperBound();
4004                 } while (t.hasTag(TYPEVAR));
4005                 if (t.hasTag(ARRAY)) {
4006                     boundkind |= kinds[i] = ARRAY_BOUND;
4007                 } else {
4008                     boundkind |= kinds[i] = CLASS_BOUND;
4009                 }
4010                 break;
4011             default:
4012                 kinds[i] = UNKNOWN_BOUND;
4013                 if (t.isPrimitive())
4014                     return syms.errType;
4015             }
4016         }
4017         switch (boundkind) {
4018         case 0:
4019             return syms.botType;
4020 
4021         case ARRAY_BOUND:
4022             // calculate lub(A[], B[])
4023             Type[] elements = new Type[ts.length];
4024             for (int i = 0 ; i < ts.length ; i++) {
4025                 Type elem = elements[i] = elemTypeFun.apply(ts[i]);
4026                 if (elem.isPrimitive()) {
4027                     // if a primitive type is found, then return
4028                     // arraySuperType unless all the types are the
4029                     // same
4030                     Type first = ts[0];
4031                     for (int j = 1 ; j < ts.length ; j++) {
4032                         if (!isSameType(first, ts[j])) {
4033                              // lub(int[], B[]) is Cloneable & Serializable
4034                             return arraySuperType();
4035                         }
4036                     }
4037                     // all the array types are the same, return one
4038                     // lub(int[], int[]) is int[]
4039                     return first;
4040                 }
4041             }
4042             // lub(A[], B[]) is lub(A, B)[]
4043             return new ArrayType(lub(elements), syms.arrayClass);
4044 
4045         case CLASS_BOUND:
4046             // calculate lub(A, B)
4047             int startIdx = 0;
4048             for (int i = 0; i < ts.length ; i++) {
4049                 Type t = ts[i];
4050                 if (t.hasTag(CLASS) || t.hasTag(TYPEVAR)) {
4051                     break;
4052                 } else {
4053                     startIdx++;
4054                 }
4055             }
4056             Assert.check(startIdx < ts.length);
4057             //step 1 - compute erased candidate set (EC)
4058             List<Type> cl = erasedSupertypes(ts[startIdx]);
4059             for (int i = startIdx + 1 ; i < ts.length ; i++) {
4060                 Type t = ts[i];
4061                 if (t.hasTag(CLASS) || t.hasTag(TYPEVAR))
4062                     cl = intersect(cl, erasedSupertypes(t));
4063             }
4064             //step 2 - compute minimal erased candidate set (MEC)
4065             List<Type> mec = closureMin(cl);
4066             //step 3 - for each element G in MEC, compute lci(Inv(G))
4067             List<Type> candidates = List.nil();
4068             for (Type erasedSupertype : mec) {
4069                 List<Type> lci = List.of(asSuper(ts[startIdx], erasedSupertype.tsym));
4070                 for (int i = startIdx + 1 ; i < ts.length ; i++) {
4071                     Type superType = asSuper(ts[i], erasedSupertype.tsym);
4072                     lci = intersect(lci, superType != null ? List.of(superType) : List.nil());
4073                 }
4074                 candidates = candidates.appendList(lci);
4075             }
4076             //step 4 - let MEC be { G1, G2 ... Gn }, then we have that
4077             //lub = lci(Inv(G1)) & lci(Inv(G2)) & ... & lci(Inv(Gn))
4078             return compoundMin(candidates);
4079 
4080         default:
4081             // calculate lub(A, B[])
4082             List<Type> classes = List.of(arraySuperType());
4083             for (int i = 0 ; i < ts.length ; i++) {
4084                 if (kinds[i] != ARRAY_BOUND) // Filter out any arrays
4085                     classes = classes.prepend(ts[i]);
4086             }
4087             // lub(A, B[]) is lub(A, arraySuperType)
4088             return lub(classes);
4089         }
4090     }
4091     // where
4092         List<Type> erasedSupertypes(Type t) {
4093             ListBuffer<Type> buf = new ListBuffer<>();
4094             for (Type sup : closure(t)) {
4095                 if (sup.hasTag(TYPEVAR)) {
4096                     buf.append(sup);
4097                 } else {
4098                     buf.append(erasure(sup));
4099                 }
4100             }
4101             return buf.toList();
4102         }
4103 
4104         private Type arraySuperType;
4105         private Type arraySuperType() {
4106             // initialized lazily to avoid problems during compiler startup
4107             if (arraySuperType == null) {
4108                 // JLS 10.8: all arrays implement Cloneable and Serializable.
4109                 arraySuperType = makeIntersectionType(List.of(syms.serializableType,
4110                         syms.cloneableType), true);
4111             }
4112             return arraySuperType;
4113         }
4114     // </editor-fold>
4115 
4116     // <editor-fold defaultstate="collapsed" desc="Greatest lower bound">
4117     public Type glb(List<Type> ts) {
4118         Type t1 = ts.head;
4119         for (Type t2 : ts.tail) {
4120             if (t1.isErroneous())
4121                 return t1;
4122             t1 = glb(t1, t2);
4123         }
4124         return t1;
4125     }
4126     //where
4127     public Type glb(Type t, Type s) {
4128         if (s == null)
4129             return t;
4130         else if (t.isPrimitive() || s.isPrimitive())
4131             return syms.errType;
4132         else if (isSubtypeNoCapture(t, s))
4133             return t;
4134         else if (isSubtypeNoCapture(s, t))
4135             return s;
4136 
4137         List<Type> closure = union(closure(t), closure(s));
4138         return glbFlattened(closure, t);
4139     }
4140     //where
4141     /**
4142      * Perform glb for a list of non-primitive, non-error, non-compound types;
4143      * redundant elements are removed.  Bounds should be ordered according to
4144      * {@link Symbol#precedes(TypeSymbol,Types)}.
4145      *
4146      * @param flatBounds List of type to glb
4147      * @param errT Original type to use if the result is an error type
4148      */
4149     private Type glbFlattened(List<Type> flatBounds, Type errT) {
4150         List<Type> bounds = closureMin(flatBounds);
4151 
4152         if (bounds.isEmpty()) {             // length == 0
4153             return syms.objectType;
4154         } else if (bounds.tail.isEmpty()) { // length == 1
4155             return bounds.head;
4156         } else {                            // length > 1
4157             int classCount = 0;
4158             List<Type> cvars = List.nil();
4159             List<Type> lowers = List.nil();
4160             for (Type bound : bounds) {
4161                 if (!bound.isInterface()) {
4162                     classCount++;
4163                     Type lower = cvarLowerBound(bound);
4164                     if (bound != lower && !lower.hasTag(BOT)) {
4165                         cvars = cvars.append(bound);
4166                         lowers = lowers.append(lower);
4167                     }
4168                 }
4169             }
4170             if (classCount > 1) {
4171                 if (lowers.isEmpty()) {
4172                     return createErrorType(errT);
4173                 } else {
4174                     // try again with lower bounds included instead of capture variables
4175                     List<Type> newBounds = bounds.diff(cvars).appendList(lowers);
4176                     return glb(newBounds);
4177                 }
4178             }
4179         }
4180         return makeIntersectionType(bounds);
4181     }
4182     // </editor-fold>
4183 
4184     // <editor-fold defaultstate="collapsed" desc="hashCode">
4185     /**
4186      * Compute a hash code on a type.
4187      */
4188     public int hashCode(Type t) {
4189         return hashCode(t, false);
4190     }
4191 
4192     public int hashCode(Type t, boolean strict) {
4193         return strict ?
4194                 hashCodeStrictVisitor.visit(t) :
4195                 hashCodeVisitor.visit(t);
4196     }
4197     // where
4198         private static final HashCodeVisitor hashCodeVisitor = new HashCodeVisitor();
4199         private static final HashCodeVisitor hashCodeStrictVisitor = new HashCodeVisitor() {
4200             @Override
4201             public Integer visitTypeVar(TypeVar t, Void ignored) {
4202                 return System.identityHashCode(t);
4203             }
4204         };
4205 
4206         private static class HashCodeVisitor extends UnaryVisitor<Integer> {
4207             public Integer visitType(Type t, Void ignored) {
4208                 return t.getTag().ordinal();
4209             }
4210 
4211             @Override
4212             public Integer visitClassType(ClassType t, Void ignored) {
4213                 int result = visit(t.getEnclosingType());
4214                 result *= 127;
4215                 result += t.tsym.flatName().hashCode();
4216                 for (Type s : t.getTypeArguments()) {
4217                     result *= 127;
4218                     result += visit(s);
4219                 }
4220                 return result;
4221             }
4222 
4223             @Override
4224             public Integer visitMethodType(MethodType t, Void ignored) {
4225                 int h = METHOD.ordinal();
4226                 for (List<Type> thisargs = t.argtypes;
4227                      thisargs.tail != null;
4228                      thisargs = thisargs.tail)
4229                     h = (h << 5) + visit(thisargs.head);
4230                 return (h << 5) + visit(t.restype);
4231             }
4232 
4233             @Override
4234             public Integer visitWildcardType(WildcardType t, Void ignored) {
4235                 int result = t.kind.hashCode();
4236                 if (t.type != null) {
4237                     result *= 127;
4238                     result += visit(t.type);
4239                 }
4240                 return result;
4241             }
4242 
4243             @Override
4244             public Integer visitArrayType(ArrayType t, Void ignored) {
4245                 return visit(t.elemtype) + 12;
4246             }
4247 
4248             @Override
4249             public Integer visitTypeVar(TypeVar t, Void ignored) {
4250                 return System.identityHashCode(t);
4251             }
4252 
4253             @Override
4254             public Integer visitUndetVar(UndetVar t, Void ignored) {
4255                 return System.identityHashCode(t);
4256             }
4257 
4258             @Override
4259             public Integer visitErrorType(ErrorType t, Void ignored) {
4260                 return 0;
4261             }
4262         }
4263     // </editor-fold>
4264 
4265     // <editor-fold defaultstate="collapsed" desc="Return-Type-Substitutable">
4266     /**
4267      * Does t have a result that is a subtype of the result type of s,
4268      * suitable for covariant returns?  It is assumed that both types
4269      * are (possibly polymorphic) method types.  Monomorphic method
4270      * types are handled in the obvious way.  Polymorphic method types
4271      * require renaming all type variables of one to corresponding
4272      * type variables in the other, where correspondence is by
4273      * position in the type parameter list. */
4274     public boolean resultSubtype(Type t, Type s, Warner warner) {
4275         List<Type> tvars = t.getTypeArguments();
4276         List<Type> svars = s.getTypeArguments();
4277         Type tres = t.getReturnType();
4278         Type sres = subst(s.getReturnType(), svars, tvars);
4279         return covariantReturnType(tres, sres, warner);
4280     }
4281 
4282     /**
4283      * Return-Type-Substitutable.
4284      * @jls 8.4.5 Method Result
4285      */
4286     public boolean returnTypeSubstitutable(Type r1, Type r2) {
4287         if (hasSameArgs(r1, r2))
4288             return resultSubtype(r1, r2, noWarnings);
4289         else
4290             return covariantReturnType(r1.getReturnType(),
4291                                        erasure(r2.getReturnType()),
4292                                        noWarnings);
4293     }
4294 
4295     public boolean returnTypeSubstitutable(Type r1,
4296                                            Type r2, Type r2res,
4297                                            Warner warner) {
4298         if (isSameType(r1.getReturnType(), r2res))
4299             return true;
4300         if (r1.getReturnType().isPrimitive() || r2res.isPrimitive())
4301             return false;
4302 
4303         if (hasSameArgs(r1, r2))
4304             return covariantReturnType(r1.getReturnType(), r2res, warner);
4305         if (isSubtypeUnchecked(r1.getReturnType(), r2res, warner))
4306             return true;
4307         if (!isSubtype(r1.getReturnType(), erasure(r2res)))
4308             return false;
4309         warner.warn(LintCategory.UNCHECKED);
4310         return true;
4311     }
4312 
4313     /**
4314      * Is t an appropriate return type in an overrider for a
4315      * method that returns s?
4316      */
4317     public boolean covariantReturnType(Type t, Type s, Warner warner) {
4318         return
4319             isSameType(t, s) ||
4320             !t.isPrimitive() &&
4321             !s.isPrimitive() &&
4322             isAssignable(t, s, warner);
4323     }
4324     // </editor-fold>
4325 
4326     // <editor-fold defaultstate="collapsed" desc="Box/unbox support">
4327     /**
4328      * Return the class that boxes the given primitive.
4329      */
4330     public ClassSymbol boxedClass(Type t) {
4331         return syms.enterClass(syms.java_base, syms.boxedName[t.getTag().ordinal()]);
4332     }
4333 
4334     /**
4335      * Return the boxed type if 't' is primitive, otherwise return 't' itself.
4336      */
4337     public Type boxedTypeOrType(Type t) {
4338         return t.isPrimitive() ?
4339             boxedClass(t).type :
4340             t;
4341     }
4342 
4343     /**
4344      * Return the primitive type corresponding to a boxed type.
4345      */
4346     public Type unboxedType(Type t) {
4347         if (t.hasTag(ERROR))
4348             return Type.noType;
4349         for (int i=0; i<syms.boxedName.length; i++) {
4350             Name box = syms.boxedName[i];
4351             if (box != null &&
4352                 asSuper(t, syms.enterClass(syms.java_base, box)) != null)
4353                 return syms.typeOfTag[i];
4354         }
4355         return Type.noType;
4356     }
4357 
4358     /**
4359      * Return the unboxed type if 't' is a boxed class, otherwise return 't' itself.
4360      */
4361     public Type unboxedTypeOrType(Type t) {
4362         Type unboxedType = unboxedType(t);
4363         return unboxedType.hasTag(NONE) ? t : unboxedType;
4364     }
4365     // </editor-fold>
4366 
4367     // <editor-fold defaultstate="collapsed" desc="Capture conversion">
4368     /*
4369      * JLS 5.1.10 Capture Conversion:
4370      *
4371      * Let G name a generic type declaration with n formal type
4372      * parameters A1 ... An with corresponding bounds U1 ... Un. There
4373      * exists a capture conversion from G<T1 ... Tn> to G<S1 ... Sn>,
4374      * where, for 1 <= i <= n:
4375      *
4376      * + If Ti is a wildcard type argument (4.5.1) of the form ? then
4377      *   Si is a fresh type variable whose upper bound is
4378      *   Ui[A1 := S1, ..., An := Sn] and whose lower bound is the null
4379      *   type.
4380      *
4381      * + If Ti is a wildcard type argument of the form ? extends Bi,
4382      *   then Si is a fresh type variable whose upper bound is
4383      *   glb(Bi, Ui[A1 := S1, ..., An := Sn]) and whose lower bound is
4384      *   the null type, where glb(V1,... ,Vm) is V1 & ... & Vm. It is
4385      *   a compile-time error if for any two classes (not interfaces)
4386      *   Vi and Vj,Vi is not a subclass of Vj or vice versa.
4387      *
4388      * + If Ti is a wildcard type argument of the form ? super Bi,
4389      *   then Si is a fresh type variable whose upper bound is
4390      *   Ui[A1 := S1, ..., An := Sn] and whose lower bound is Bi.
4391      *
4392      * + Otherwise, Si = Ti.
4393      *
4394      * Capture conversion on any type other than a parameterized type
4395      * (4.5) acts as an identity conversion (5.1.1). Capture
4396      * conversions never require a special action at run time and
4397      * therefore never throw an exception at run time.
4398      *
4399      * Capture conversion is not applied recursively.
4400      */
4401     /**
4402      * Capture conversion as specified by the JLS.
4403      */
4404 
4405     public List<Type> capture(List<Type> ts) {
4406         List<Type> buf = List.nil();
4407         for (Type t : ts) {
4408             buf = buf.prepend(capture(t));
4409         }
4410         return buf.reverse();
4411     }
4412 
4413     public Type capture(Type t) {
4414         if (!t.hasTag(CLASS)) {
4415             return t;
4416         }
4417         if (t.getEnclosingType() != Type.noType) {
4418             Type capturedEncl = capture(t.getEnclosingType());
4419             if (capturedEncl != t.getEnclosingType()) {
4420                 Type type1 = memberType(capturedEncl, t.tsym);
4421                 t = subst(type1, t.tsym.type.getTypeArguments(), t.getTypeArguments());
4422             }
4423         }
4424         ClassType cls = (ClassType)t;
4425         if (cls.isRaw() || !cls.isParameterized())
4426             return cls;
4427 
4428         ClassType G = (ClassType)cls.asElement().asType();
4429         List<Type> A = G.getTypeArguments();
4430         List<Type> T = cls.getTypeArguments();
4431         List<Type> S = freshTypeVariables(T);
4432 
4433         List<Type> currentA = A;
4434         List<Type> currentT = T;
4435         List<Type> currentS = S;
4436         boolean captured = false;
4437         while (!currentA.isEmpty() &&
4438                !currentT.isEmpty() &&
4439                !currentS.isEmpty()) {
4440             if (currentS.head != currentT.head) {
4441                 captured = true;
4442                 WildcardType Ti = (WildcardType)currentT.head;
4443                 Type Ui = currentA.head.getUpperBound();
4444                 CapturedType Si = (CapturedType)currentS.head;
4445                 if (Ui == null)
4446                     Ui = syms.objectType;
4447                 switch (Ti.kind) {
4448                 case UNBOUND:
4449                     Si.setUpperBound( subst(Ui, A, S) );
4450                     Si.lower = syms.botType;
4451                     break;
4452                 case EXTENDS:
4453                     Si.setUpperBound( glb(Ti.getExtendsBound(), subst(Ui, A, S)) );
4454                     Si.lower = syms.botType;
4455                     break;
4456                 case SUPER:
4457                     Si.setUpperBound( subst(Ui, A, S) );
4458                     Si.lower = Ti.getSuperBound();
4459                     break;
4460                 }
4461                 Type tmpBound = Si.getUpperBound().hasTag(UNDETVAR) ? ((UndetVar)Si.getUpperBound()).qtype : Si.getUpperBound();
4462                 Type tmpLower = Si.lower.hasTag(UNDETVAR) ? ((UndetVar)Si.lower).qtype : Si.lower;
4463                 if (!Si.getUpperBound().hasTag(ERROR) &&
4464                     !Si.lower.hasTag(ERROR) &&
4465                     isSameType(tmpBound, tmpLower)) {
4466                     currentS.head = Si.getUpperBound();
4467                 }
4468             }
4469             currentA = currentA.tail;
4470             currentT = currentT.tail;
4471             currentS = currentS.tail;
4472         }
4473         if (!currentA.isEmpty() || !currentT.isEmpty() || !currentS.isEmpty())
4474             return erasure(t); // some "rare" type involved
4475 
4476         if (captured)
4477             return new ClassType(cls.getEnclosingType(), S, cls.tsym,
4478                                  cls.getMetadata());
4479         else
4480             return t;
4481     }
4482     // where
4483         public List<Type> freshTypeVariables(List<Type> types) {
4484             ListBuffer<Type> result = new ListBuffer<>();
4485             for (Type t : types) {
4486                 if (t.hasTag(WILDCARD)) {
4487                     Type bound = ((WildcardType)t).getExtendsBound();
4488                     if (bound == null)
4489                         bound = syms.objectType;
4490                     result.append(new CapturedType(capturedName,
4491                                                    syms.noSymbol,
4492                                                    bound,
4493                                                    syms.botType,
4494                                                    (WildcardType)t));
4495                 } else {
4496                     result.append(t);
4497                 }
4498             }
4499             return result.toList();
4500         }
4501     // </editor-fold>
4502 
4503     // <editor-fold defaultstate="collapsed" desc="Internal utility methods">
4504     private boolean sideCast(Type from, Type to, Warner warn) {
4505         // We are casting from type $from$ to type $to$, which are
4506         // non-final unrelated types.  This method
4507         // tries to reject a cast by transferring type parameters
4508         // from $to$ to $from$ by common superinterfaces.
4509         boolean reverse = false;
4510         Type target = to;
4511         if ((to.tsym.flags() & INTERFACE) == 0) {
4512             Assert.check((from.tsym.flags() & INTERFACE) != 0);
4513             reverse = true;
4514             to = from;
4515             from = target;
4516         }
4517         List<Type> commonSupers = superClosure(to, erasure(from));
4518         boolean giveWarning = commonSupers.isEmpty();
4519         // The arguments to the supers could be unified here to
4520         // get a more accurate analysis
4521         while (commonSupers.nonEmpty()) {
4522             Type t1 = asSuper(from, commonSupers.head.tsym);
4523             Type t2 = commonSupers.head; // same as asSuper(to, commonSupers.head.tsym);
4524             if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
4525                 return false;
4526             giveWarning = giveWarning || (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2));
4527             commonSupers = commonSupers.tail;
4528         }
4529         if (giveWarning && !isReifiable(reverse ? from : to))
4530             warn.warn(LintCategory.UNCHECKED);
4531         return true;
4532     }
4533 
4534     private boolean sideCastFinal(Type from, Type to, Warner warn) {
4535         // We are casting from type $from$ to type $to$, which are
4536         // unrelated types one of which is final and the other of
4537         // which is an interface.  This method
4538         // tries to reject a cast by transferring type parameters
4539         // from the final class to the interface.
4540         boolean reverse = false;
4541         Type target = to;
4542         if ((to.tsym.flags() & INTERFACE) == 0) {
4543             Assert.check((from.tsym.flags() & INTERFACE) != 0);
4544             reverse = true;
4545             to = from;
4546             from = target;
4547         }
4548         Assert.check((from.tsym.flags() & FINAL) != 0);
4549         Type t1 = asSuper(from, to.tsym);
4550         if (t1 == null) return false;
4551         Type t2 = to;
4552         if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
4553             return false;
4554         if (!isReifiable(target) &&
4555             (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2)))
4556             warn.warn(LintCategory.UNCHECKED);
4557         return true;
4558     }
4559 
4560     private boolean giveWarning(Type from, Type to) {
4561         List<Type> bounds = to.isCompound() ?
4562                 directSupertypes(to) : List.of(to);
4563         for (Type b : bounds) {
4564             Type subFrom = asSub(from, b.tsym);
4565             if (b.isParameterized() &&
4566                     (!(isUnbounded(b) ||
4567                     isSubtype(from, b) ||
4568                     ((subFrom != null) && containsType(b.allparams(), subFrom.allparams()))))) {
4569                 return true;
4570             }
4571         }
4572         return false;
4573     }
4574 
4575     private List<Type> superClosure(Type t, Type s) {
4576         List<Type> cl = List.nil();
4577         for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
4578             if (isSubtype(s, erasure(l.head))) {
4579                 cl = insert(cl, l.head);
4580             } else {
4581                 cl = union(cl, superClosure(l.head, s));
4582             }
4583         }
4584         return cl;
4585     }
4586 
4587     private boolean containsTypeEquivalent(Type t, Type s) {
4588         return isSameType(t, s) || // shortcut
4589             containsType(t, s) && containsType(s, t);
4590     }
4591 
4592     // <editor-fold defaultstate="collapsed" desc="adapt">
4593     /**
4594      * Adapt a type by computing a substitution which maps a source
4595      * type to a target type.
4596      *
4597      * @param source    the source type
4598      * @param target    the target type
4599      * @param from      the type variables of the computed substitution
4600      * @param to        the types of the computed substitution.
4601      */
4602     public void adapt(Type source,
4603                        Type target,
4604                        ListBuffer<Type> from,
4605                        ListBuffer<Type> to) throws AdaptFailure {
4606         new Adapter(from, to).adapt(source, target);
4607     }
4608 
4609     class Adapter extends SimpleVisitor<Void, Type> {
4610 
4611         ListBuffer<Type> from;
4612         ListBuffer<Type> to;
4613         Map<Symbol,Type> mapping;
4614 
4615         Adapter(ListBuffer<Type> from, ListBuffer<Type> to) {
4616             this.from = from;
4617             this.to = to;
4618             mapping = new HashMap<>();
4619         }
4620 
4621         public void adapt(Type source, Type target) throws AdaptFailure {
4622             visit(source, target);
4623             List<Type> fromList = from.toList();
4624             List<Type> toList = to.toList();
4625             while (!fromList.isEmpty()) {
4626                 Type val = mapping.get(fromList.head.tsym);
4627                 if (toList.head != val)
4628                     toList.head = val;
4629                 fromList = fromList.tail;
4630                 toList = toList.tail;
4631             }
4632         }
4633 
4634         @Override
4635         public Void visitClassType(ClassType source, Type target) throws AdaptFailure {
4636             if (target.hasTag(CLASS))
4637                 adaptRecursive(source.allparams(), target.allparams());
4638             return null;
4639         }
4640 
4641         @Override
4642         public Void visitArrayType(ArrayType source, Type target) throws AdaptFailure {
4643             if (target.hasTag(ARRAY))
4644                 adaptRecursive(elemtype(source), elemtype(target));
4645             return null;
4646         }
4647 
4648         @Override
4649         public Void visitWildcardType(WildcardType source, Type target) throws AdaptFailure {
4650             if (source.isExtendsBound())
4651                 adaptRecursive(wildUpperBound(source), wildUpperBound(target));
4652             else if (source.isSuperBound())
4653                 adaptRecursive(wildLowerBound(source), wildLowerBound(target));
4654             return null;
4655         }
4656 
4657         @Override
4658         public Void visitTypeVar(TypeVar source, Type target) throws AdaptFailure {
4659             // Check to see if there is
4660             // already a mapping for $source$, in which case
4661             // the old mapping will be merged with the new
4662             Type val = mapping.get(source.tsym);
4663             if (val != null) {
4664                 if (val.isSuperBound() && target.isSuperBound()) {
4665                     val = isSubtype(wildLowerBound(val), wildLowerBound(target))
4666                         ? target : val;
4667                 } else if (val.isExtendsBound() && target.isExtendsBound()) {
4668                     val = isSubtype(wildUpperBound(val), wildUpperBound(target))
4669                         ? val : target;
4670                 } else if (!isSameType(val, target)) {
4671                     throw new AdaptFailure();
4672                 }
4673             } else {
4674                 val = target;
4675                 from.append(source);
4676                 to.append(target);
4677             }
4678             mapping.put(source.tsym, val);
4679             return null;
4680         }
4681 
4682         @Override
4683         public Void visitType(Type source, Type target) {
4684             return null;
4685         }
4686 
4687         private Set<TypePair> cache = new HashSet<>();
4688 
4689         private void adaptRecursive(Type source, Type target) {
4690             TypePair pair = new TypePair(source, target);
4691             if (cache.add(pair)) {
4692                 try {
4693                     visit(source, target);
4694                 } finally {
4695                     cache.remove(pair);
4696                 }
4697             }
4698         }
4699 
4700         private void adaptRecursive(List<Type> source, List<Type> target) {
4701             if (source.length() == target.length()) {
4702                 while (source.nonEmpty()) {
4703                     adaptRecursive(source.head, target.head);
4704                     source = source.tail;
4705                     target = target.tail;
4706                 }
4707             }
4708         }
4709     }
4710 
4711     public static class AdaptFailure extends RuntimeException {
4712         static final long serialVersionUID = -7490231548272701566L;
4713     }
4714 
4715     private void adaptSelf(Type t,
4716                            ListBuffer<Type> from,
4717                            ListBuffer<Type> to) {
4718         try {
4719             //if (t.tsym.type != t)
4720                 adapt(t.tsym.type, t, from, to);
4721         } catch (AdaptFailure ex) {
4722             // Adapt should never fail calculating a mapping from
4723             // t.tsym.type to t as there can be no merge problem.
4724             throw new AssertionError(ex);
4725         }
4726     }
4727     // </editor-fold>
4728 
4729     /**
4730      * Rewrite all type variables (universal quantifiers) in the given
4731      * type to wildcards (existential quantifiers).  This is used to
4732      * determine if a cast is allowed.  For example, if high is true
4733      * and {@code T <: Number}, then {@code List<T>} is rewritten to
4734      * {@code List<?  extends Number>}.  Since {@code List<Integer> <:
4735      * List<? extends Number>} a {@code List<T>} can be cast to {@code
4736      * List<Integer>} with a warning.
4737      * @param t a type
4738      * @param high if true return an upper bound; otherwise a lower
4739      * bound
4740      * @param rewriteTypeVars only rewrite captured wildcards if false;
4741      * otherwise rewrite all type variables
4742      * @return the type rewritten with wildcards (existential
4743      * quantifiers) only
4744      */
4745     private Type rewriteQuantifiers(Type t, boolean high, boolean rewriteTypeVars) {
4746         return new Rewriter(high, rewriteTypeVars).visit(t);
4747     }
4748 
4749     class Rewriter extends UnaryVisitor<Type> {
4750 
4751         boolean high;
4752         boolean rewriteTypeVars;
4753 
4754         Rewriter(boolean high, boolean rewriteTypeVars) {
4755             this.high = high;
4756             this.rewriteTypeVars = rewriteTypeVars;
4757         }
4758 
4759         @Override
4760         public Type visitClassType(ClassType t, Void s) {
4761             ListBuffer<Type> rewritten = new ListBuffer<>();
4762             boolean changed = false;
4763             for (Type arg : t.allparams()) {
4764                 Type bound = visit(arg);
4765                 if (arg != bound) {
4766                     changed = true;
4767                 }
4768                 rewritten.append(bound);
4769             }
4770             if (changed)
4771                 return subst(t.tsym.type,
4772                         t.tsym.type.allparams(),
4773                         rewritten.toList());
4774             else
4775                 return t;
4776         }
4777 
4778         public Type visitType(Type t, Void s) {
4779             return t;
4780         }
4781 
4782         @Override
4783         public Type visitCapturedType(CapturedType t, Void s) {
4784             Type w_bound = t.wildcard.type;
4785             Type bound = w_bound.contains(t) ?
4786                         erasure(w_bound) :
4787                         visit(w_bound);
4788             return rewriteAsWildcardType(visit(bound), t.wildcard.bound, t.wildcard.kind);
4789         }
4790 
4791         @Override
4792         public Type visitTypeVar(TypeVar t, Void s) {
4793             if (rewriteTypeVars) {
4794                 Type bound = t.getUpperBound().contains(t) ?
4795                         erasure(t.getUpperBound()) :
4796                         visit(t.getUpperBound());
4797                 return rewriteAsWildcardType(bound, t, EXTENDS);
4798             } else {
4799                 return t;
4800             }
4801         }
4802 
4803         @Override
4804         public Type visitWildcardType(WildcardType t, Void s) {
4805             Type bound2 = visit(t.type);
4806             return t.type == bound2 ? t : rewriteAsWildcardType(bound2, t.bound, t.kind);
4807         }
4808 
4809         private Type rewriteAsWildcardType(Type bound, TypeVar formal, BoundKind bk) {
4810             switch (bk) {
4811                case EXTENDS: return high ?
4812                        makeExtendsWildcard(B(bound), formal) :
4813                        makeExtendsWildcard(syms.objectType, formal);
4814                case SUPER: return high ?
4815                        makeSuperWildcard(syms.botType, formal) :
4816                        makeSuperWildcard(B(bound), formal);
4817                case UNBOUND: return makeExtendsWildcard(syms.objectType, formal);
4818                default:
4819                    Assert.error("Invalid bound kind " + bk);
4820                    return null;
4821             }
4822         }
4823 
4824         Type B(Type t) {
4825             while (t.hasTag(WILDCARD)) {
4826                 WildcardType w = (WildcardType)t;
4827                 t = high ?
4828                     w.getExtendsBound() :
4829                     w.getSuperBound();
4830                 if (t == null) {
4831                     t = high ? syms.objectType : syms.botType;
4832                 }
4833             }
4834             return t;
4835         }
4836     }
4837 
4838 
4839     /**
4840      * Create a wildcard with the given upper (extends) bound; create
4841      * an unbounded wildcard if bound is Object.
4842      *
4843      * @param bound the upper bound
4844      * @param formal the formal type parameter that will be
4845      * substituted by the wildcard
4846      */
4847     private WildcardType makeExtendsWildcard(Type bound, TypeVar formal) {
4848         if (bound == syms.objectType) {
4849             return new WildcardType(syms.objectType,
4850                                     BoundKind.UNBOUND,
4851                                     syms.boundClass,
4852                                     formal);
4853         } else {
4854             return new WildcardType(bound,
4855                                     BoundKind.EXTENDS,
4856                                     syms.boundClass,
4857                                     formal);
4858         }
4859     }
4860 
4861     /**
4862      * Create a wildcard with the given lower (super) bound; create an
4863      * unbounded wildcard if bound is bottom (type of {@code null}).
4864      *
4865      * @param bound the lower bound
4866      * @param formal the formal type parameter that will be
4867      * substituted by the wildcard
4868      */
4869     private WildcardType makeSuperWildcard(Type bound, TypeVar formal) {
4870         if (bound.hasTag(BOT)) {
4871             return new WildcardType(syms.objectType,
4872                                     BoundKind.UNBOUND,
4873                                     syms.boundClass,
4874                                     formal);
4875         } else {
4876             return new WildcardType(bound,
4877                                     BoundKind.SUPER,
4878                                     syms.boundClass,
4879                                     formal);
4880         }
4881     }
4882 
4883     /**
4884      * A wrapper for a type that allows use in sets.
4885      */
4886     public static class UniqueType {
4887         public final Type type;
4888         final Types types;
4889         private boolean encodeTypeSig;
4890 
4891         public UniqueType(Type type, Types types, boolean encodeTypeSig) {
4892             this.type = type;
4893             this.types = types;
4894             this.encodeTypeSig = encodeTypeSig;
4895         }
4896 
4897         public UniqueType(Type type, Types types) {
4898             this(type, types, true);
4899         }
4900 
4901         public int hashCode() {
4902             return types.hashCode(type);
4903         }
4904 
4905         public boolean equals(Object obj) {
4906             return (obj instanceof UniqueType uniqueType) &&
4907                     types.isSameType(type, uniqueType.type);
4908         }
4909 
4910         public boolean encodeTypeSig() {
4911             return encodeTypeSig;
4912         }
4913 
4914         public String toString() {
4915             return type.toString();
4916         }
4917 
4918     }
4919     // </editor-fold>
4920 
4921     // <editor-fold defaultstate="collapsed" desc="Visitors">
4922     /**
4923      * A default visitor for types.  All visitor methods except
4924      * visitType are implemented by delegating to visitType.  Concrete
4925      * subclasses must provide an implementation of visitType and can
4926      * override other methods as needed.
4927      *
4928      * @param <R> the return type of the operation implemented by this
4929      * visitor; use Void if no return type is needed.
4930      * @param <S> the type of the second argument (the first being the
4931      * type itself) of the operation implemented by this visitor; use
4932      * Void if a second argument is not needed.
4933      */
4934     public abstract static class DefaultTypeVisitor<R,S> implements Type.Visitor<R,S> {
4935         public final R visit(Type t, S s)               { return t.accept(this, s); }
4936         public R visitClassType(ClassType t, S s)       { return visitType(t, s); }
4937         public R visitWildcardType(WildcardType t, S s) { return visitType(t, s); }
4938         public R visitArrayType(ArrayType t, S s)       { return visitType(t, s); }
4939         public R visitMethodType(MethodType t, S s)     { return visitType(t, s); }
4940         public R visitPackageType(PackageType t, S s)   { return visitType(t, s); }
4941         public R visitModuleType(ModuleType t, S s)     { return visitType(t, s); }
4942         public R visitTypeVar(TypeVar t, S s)           { return visitType(t, s); }
4943         public R visitCapturedType(CapturedType t, S s) { return visitType(t, s); }
4944         public R visitForAll(ForAll t, S s)             { return visitType(t, s); }
4945         public R visitUndetVar(UndetVar t, S s)         { return visitType(t, s); }
4946         public R visitErrorType(ErrorType t, S s)       { return visitType(t, s); }
4947     }
4948 
4949     /**
4950      * A default visitor for symbols.  All visitor methods except
4951      * visitSymbol are implemented by delegating to visitSymbol.  Concrete
4952      * subclasses must provide an implementation of visitSymbol and can
4953      * override other methods as needed.
4954      *
4955      * @param <R> the return type of the operation implemented by this
4956      * visitor; use Void if no return type is needed.
4957      * @param <S> the type of the second argument (the first being the
4958      * symbol itself) of the operation implemented by this visitor; use
4959      * Void if a second argument is not needed.
4960      */
4961     public abstract static class DefaultSymbolVisitor<R,S> implements Symbol.Visitor<R,S> {
4962         public final R visit(Symbol s, S arg)                   { return s.accept(this, arg); }
4963         public R visitClassSymbol(ClassSymbol s, S arg)         { return visitSymbol(s, arg); }
4964         public R visitMethodSymbol(MethodSymbol s, S arg)       { return visitSymbol(s, arg); }
4965         public R visitOperatorSymbol(OperatorSymbol s, S arg)   { return visitSymbol(s, arg); }
4966         public R visitPackageSymbol(PackageSymbol s, S arg)     { return visitSymbol(s, arg); }
4967         public R visitTypeSymbol(TypeSymbol s, S arg)           { return visitSymbol(s, arg); }
4968         public R visitVarSymbol(VarSymbol s, S arg)             { return visitSymbol(s, arg); }
4969     }
4970 
4971     /**
4972      * A <em>simple</em> visitor for types.  This visitor is simple as
4973      * captured wildcards, for-all types (generic methods), and
4974      * undetermined type variables (part of inference) are hidden.
4975      * Captured wildcards are hidden by treating them as type
4976      * variables and the rest are hidden by visiting their qtypes.
4977      *
4978      * @param <R> the return type of the operation implemented by this
4979      * visitor; use Void if no return type is needed.
4980      * @param <S> the type of the second argument (the first being the
4981      * type itself) of the operation implemented by this visitor; use
4982      * Void if a second argument is not needed.
4983      */
4984     public abstract static class SimpleVisitor<R,S> extends DefaultTypeVisitor<R,S> {
4985         @Override
4986         public R visitCapturedType(CapturedType t, S s) {
4987             return visitTypeVar(t, s);
4988         }
4989         @Override
4990         public R visitForAll(ForAll t, S s) {
4991             return visit(t.qtype, s);
4992         }
4993         @Override
4994         public R visitUndetVar(UndetVar t, S s) {
4995             return visit(t.qtype, s);
4996         }
4997     }
4998 
4999     /**
5000      * A plain relation on types.  That is a 2-ary function on the
5001      * form Type&nbsp;&times;&nbsp;Type&nbsp;&rarr;&nbsp;Boolean.
5002      * <!-- In plain text: Type x Type -> Boolean -->
5003      */
5004     public abstract static class TypeRelation extends SimpleVisitor<Boolean,Type> {}
5005 
5006     /**
5007      * A convenience visitor for implementing operations that only
5008      * require one argument (the type itself), that is, unary
5009      * operations.
5010      *
5011      * @param <R> the return type of the operation implemented by this
5012      * visitor; use Void if no return type is needed.
5013      */
5014     public abstract static class UnaryVisitor<R> extends SimpleVisitor<R,Void> {
5015         public final R visit(Type t) { return t.accept(this, null); }
5016     }
5017 
5018     /**
5019      * A visitor for implementing a mapping from types to types.  The
5020      * default behavior of this class is to implement the identity
5021      * mapping (mapping a type to itself).  This can be overridden in
5022      * subclasses.
5023      *
5024      * @param <S> the type of the second argument (the first being the
5025      * type itself) of this mapping; use Void if a second argument is
5026      * not needed.
5027      */
5028     public static class MapVisitor<S> extends DefaultTypeVisitor<Type,S> {
5029         public final Type visit(Type t) { return t.accept(this, null); }
5030         public Type visitType(Type t, S s) { return t; }
5031     }
5032 
5033     /**
5034      * An abstract class for mappings from types to types (see {@link Type#map(TypeMapping)}.
5035      * This class implements the functional interface {@code Function}, that allows it to be used
5036      * fluently in stream-like processing.
5037      */
5038     public static class TypeMapping<S> extends MapVisitor<S> implements Function<Type, Type> {
5039         @Override
5040         public Type apply(Type type) { return visit(type); }
5041 
5042         List<Type> visit(List<Type> ts, S s) {
5043             return ts.map(t -> visit(t, s));
5044         }
5045 
5046         @Override
5047         public Type visitCapturedType(CapturedType t, S s) {
5048             return visitTypeVar(t, s);
5049         }
5050     }
5051     // </editor-fold>
5052 
5053     // <editor-fold defaultstate="collapsed" desc="Unconditionality">
5054     /** Check unconditionality between any combination of reference or primitive types.
5055      *
5056      *  Rules:
5057      *    an identity conversion
5058      *    a widening reference conversion
5059      *    a widening primitive conversion (delegates to `checkUnconditionallyExactPrimitives`)
5060      *    a boxing conversion
5061      *    a boxing conversion followed by a widening reference conversion
5062      *
5063      *  @param source     Source primitive or reference type
5064      *  @param target     Target primitive or reference type
5065      */
5066     public boolean isUnconditionallyExact(Type source, Type target) {
5067         if (isSameType(source, target)) {
5068             return true;
5069         }
5070 
5071         return target.isPrimitive()
5072                 ? isUnconditionallyExactPrimitives(source, target)
5073                 : isSubtype(boxedTypeOrType(erasure(source)), target);
5074     }
5075 
5076     /** Check unconditionality between primitive types.
5077      *
5078      *  - widening from one integral type to another,
5079      *  - widening from one floating point type to another,
5080      *  - widening from byte, short, or char to a floating point type,
5081      *  - widening from int to double.
5082      *
5083      *  @param selectorType     Type of selector
5084      *  @param targetType       Target type
5085      */
5086     public boolean isUnconditionallyExactPrimitives(Type selectorType, Type targetType) {
5087         if (isSameType(selectorType, targetType)) {
5088             return true;
5089         }
5090 
5091         return (selectorType.isPrimitive() && targetType.isPrimitive()) &&
5092                 ((selectorType.hasTag(BYTE) && !targetType.hasTag(CHAR)) ||
5093                  (selectorType.hasTag(SHORT) && (selectorType.getTag().isStrictSubRangeOf(targetType.getTag()))) ||
5094                  (selectorType.hasTag(CHAR)  && (selectorType.getTag().isStrictSubRangeOf(targetType.getTag())))  ||
5095                  (selectorType.hasTag(INT)   && (targetType.hasTag(DOUBLE) || targetType.hasTag(LONG))) ||
5096                  (selectorType.hasTag(FLOAT) && (selectorType.getTag().isStrictSubRangeOf(targetType.getTag()))));
5097     }
5098     // </editor-fold>
5099 
5100     // <editor-fold defaultstate="collapsed" desc="Annotation support">
5101 
5102     public RetentionPolicy getRetention(Attribute.Compound a) {
5103         return getRetention(a.type.tsym);
5104     }
5105 
5106     public RetentionPolicy getRetention(TypeSymbol sym) {
5107         RetentionPolicy vis = RetentionPolicy.CLASS; // the default
5108         Attribute.Compound c = sym.attribute(syms.retentionType.tsym);
5109         if (c != null) {
5110             Attribute value = c.member(names.value);
5111             if (value != null && value instanceof Attribute.Enum attributeEnum) {
5112                 Name levelName = attributeEnum.value.name;
5113                 if (levelName == names.SOURCE) vis = RetentionPolicy.SOURCE;
5114                 else if (levelName == names.CLASS) vis = RetentionPolicy.CLASS;
5115                 else if (levelName == names.RUNTIME) vis = RetentionPolicy.RUNTIME;
5116                 else ;// /* fail soft */ throw new AssertionError(levelName);
5117             }
5118         }
5119         return vis;
5120     }
5121     // </editor-fold>
5122 
5123     // <editor-fold defaultstate="collapsed" desc="Signature Generation">
5124 
5125     public abstract static class SignatureGenerator {
5126 
5127         public static class InvalidSignatureException extends RuntimeException {
5128             private static final long serialVersionUID = 0;
5129 
5130             private final transient Type type;
5131 
5132             InvalidSignatureException(Type type) {
5133                 this.type = type;
5134             }
5135 
5136             public Type type() {
5137                 return type;
5138             }
5139 
5140             @Override
5141             public Throwable fillInStackTrace() {
5142                 // This is an internal exception; the stack trace is irrelevant.
5143                 return this;
5144             }
5145         }
5146 
5147         private final Types types;
5148 
5149         protected abstract void append(char ch);
5150         protected abstract void append(byte[] ba);
5151         protected abstract void append(Name name);
5152         protected void classReference(ClassSymbol c) { /* by default: no-op */ }
5153 
5154         protected SignatureGenerator(Types types) {
5155             this.types = types;
5156         }
5157 
5158         protected void reportIllegalSignature(Type t) {
5159             throw new InvalidSignatureException(t);
5160         }
5161 
5162         /**
5163          * Assemble signature of given type in string buffer.
5164          */
5165         public void assembleSig(Type type) {
5166             switch (type.getTag()) {
5167                 case BYTE:
5168                     append('B');
5169                     break;
5170                 case SHORT:
5171                     append('S');
5172                     break;
5173                 case CHAR:
5174                     append('C');
5175                     break;
5176                 case INT:
5177                     append('I');
5178                     break;
5179                 case LONG:
5180                     append('J');
5181                     break;
5182                 case FLOAT:
5183                     append('F');
5184                     break;
5185                 case DOUBLE:
5186                     append('D');
5187                     break;
5188                 case BOOLEAN:
5189                     append('Z');
5190                     break;
5191                 case VOID:
5192                     append('V');
5193                     break;
5194                 case CLASS:
5195                     if (type.isCompound()) {
5196                         reportIllegalSignature(type);
5197                     }
5198                     append('L');
5199                     assembleClassSig(type);
5200                     append(';');
5201                     break;
5202                 case ARRAY:
5203                     ArrayType at = (ArrayType) type;
5204                     append('[');
5205                     assembleSig(at.elemtype);
5206                     break;
5207                 case METHOD:
5208                     MethodType mt = (MethodType) type;
5209                     append('(');
5210                     assembleSig(mt.argtypes);
5211                     append(')');
5212                     assembleSig(mt.restype);
5213                     if (hasTypeVar(mt.thrown)) {
5214                         for (List<Type> l = mt.thrown; l.nonEmpty(); l = l.tail) {
5215                             append('^');
5216                             assembleSig(l.head);
5217                         }
5218                     }
5219                     break;
5220                 case WILDCARD: {
5221                     Type.WildcardType ta = (Type.WildcardType) type;
5222                     switch (ta.kind) {
5223                         case SUPER:
5224                             append('-');
5225                             assembleSig(ta.type);
5226                             break;
5227                         case EXTENDS:
5228                             append('+');
5229                             assembleSig(ta.type);
5230                             break;
5231                         case UNBOUND:
5232                             append('*');
5233                             break;
5234                         default:
5235                             throw new AssertionError(ta.kind);
5236                     }
5237                     break;
5238                 }
5239                 case TYPEVAR:
5240                     if (((TypeVar)type).isCaptured()) {
5241                         reportIllegalSignature(type);
5242                     }
5243                     append('T');
5244                     append(type.tsym.name);
5245                     append(';');
5246                     break;
5247                 case FORALL:
5248                     Type.ForAll ft = (Type.ForAll) type;
5249                     assembleParamsSig(ft.tvars);
5250                     assembleSig(ft.qtype);
5251                     break;
5252                 default:
5253                     throw new AssertionError("typeSig " + type.getTag());
5254             }
5255         }
5256 
5257         public boolean hasTypeVar(List<Type> l) {
5258             while (l.nonEmpty()) {
5259                 if (l.head.hasTag(TypeTag.TYPEVAR)) {
5260                     return true;
5261                 }
5262                 l = l.tail;
5263             }
5264             return false;
5265         }
5266 
5267         public void assembleClassSig(Type type) {
5268             ClassType ct = (ClassType) type;
5269             ClassSymbol c = (ClassSymbol) ct.tsym;
5270             classReference(c);
5271             Type outer = ct.getEnclosingType();
5272             if (outer.allparams().nonEmpty()) {
5273                 boolean rawOuter =
5274                         c.owner.kind == MTH || // either a local class
5275                         c.name == types.names.empty; // or anonymous
5276                 assembleClassSig(rawOuter
5277                         ? types.erasure(outer)
5278                         : outer);
5279                 append(rawOuter ? '$' : '.');
5280                 Assert.check(c.flatname.startsWith(c.owner.enclClass().flatname));
5281                 append(rawOuter
5282                         ? c.flatname.subName(c.owner.enclClass().flatname.length() + 1)
5283                         : c.name);
5284             } else {
5285                 append(externalize(c.flatname));
5286             }
5287             if (ct.getTypeArguments().nonEmpty()) {
5288                 append('<');
5289                 assembleSig(ct.getTypeArguments());
5290                 append('>');
5291             }
5292         }
5293 
5294         public void assembleParamsSig(List<Type> typarams) {
5295             append('<');
5296             for (List<Type> ts = typarams; ts.nonEmpty(); ts = ts.tail) {
5297                 Type.TypeVar tvar = (Type.TypeVar) ts.head;
5298                 append(tvar.tsym.name);
5299                 List<Type> bounds = types.getBounds(tvar);
5300                 if ((bounds.head.tsym.flags() & INTERFACE) != 0) {
5301                     append(':');
5302                 }
5303                 for (List<Type> l = bounds; l.nonEmpty(); l = l.tail) {
5304                     append(':');
5305                     assembleSig(l.head);
5306                 }
5307             }
5308             append('>');
5309         }
5310 
5311         public void assembleSig(List<Type> types) {
5312             for (List<Type> ts = types; ts.nonEmpty(); ts = ts.tail) {
5313                 assembleSig(ts.head);
5314             }
5315         }
5316     }
5317 
5318     public Type constantType(LoadableConstant c) {
5319         switch (c.poolTag()) {
5320             case ClassFile.CONSTANT_Class:
5321                 return syms.classType;
5322             case ClassFile.CONSTANT_String:
5323                 return syms.stringType;
5324             case ClassFile.CONSTANT_Integer:
5325                 return syms.intType;
5326             case ClassFile.CONSTANT_Float:
5327                 return syms.floatType;
5328             case ClassFile.CONSTANT_Long:
5329                 return syms.longType;
5330             case ClassFile.CONSTANT_Double:
5331                 return syms.doubleType;
5332             case ClassFile.CONSTANT_MethodHandle:
5333                 return syms.methodHandleType;
5334             case ClassFile.CONSTANT_MethodType:
5335                 return syms.methodTypeType;
5336             case ClassFile.CONSTANT_Dynamic:
5337                 return ((DynamicVarSymbol)c).type;
5338             default:
5339                 throw new AssertionError("Not a loadable constant: " + c.poolTag());
5340         }
5341     }
5342     // </editor-fold>
5343 
5344     public void newRound() {
5345         descCache._map.clear();
5346         isDerivedRawCache.clear();
5347         implCache._map.clear();
5348         membersCache._map.clear();
5349         closureCache.clear();
5350     }
5351 }