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.permitted.stream().allMatch(sym -> areDisjoint((ClassSymbol)sym, 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             private Type combineMetadata(final Type s,
2427                                          final Type t) {
2428                 if (t.getMetadata().nonEmpty()) {
2429                     switch (s.getKind()) {
2430                         case OTHER:
2431                         case UNION:
2432                         case INTERSECTION:
2433                         case PACKAGE:
2434                         case EXECUTABLE:
2435                         case NONE:
2436                         case VOID:
2437                         case ERROR:
2438                             return s;
2439                         default: return s.cloneWithMetadata(t.getMetadata()).dropMetadata(Annotations.class);
2440                     }
2441                 } else {
2442                     return s;
2443                 }
2444             }
2445 
2446             public Type visitType(Type t, Boolean recurse) {
2447                 if (t.isPrimitive())
2448                     return t; /*fast special case*/
2449                 else {
2450                     //other cases already handled
2451                     return combineMetadata(t, t);
2452                 }
2453             }
2454 
2455             @Override
2456             public Type visitWildcardType(WildcardType t, Boolean recurse) {
2457                 Type erased = erasure(wildUpperBound(t), recurse);
2458                 return combineMetadata(erased, t);
2459             }
2460 
2461             @Override
2462             public Type visitClassType(ClassType t, Boolean recurse) {
2463                 Type erased = t.tsym.erasure(Types.this);
2464                 if (recurse) {
2465                     erased = new ErasedClassType(erased.getEnclosingType(),erased.tsym,
2466                             t.dropMetadata(Annotations.class).getMetadata());
2467                     return erased;
2468                 } else {
2469                     return combineMetadata(erased, t);
2470                 }
2471             }
2472 
2473             @Override
2474             public Type visitTypeVar(TypeVar t, Boolean recurse) {
2475                 Type erased = erasure(t.getUpperBound(), recurse);
2476                 return combineMetadata(erased, t);
2477             }
2478         };
2479 
2480     public List<Type> erasure(List<Type> ts) {
2481         return erasure.visit(ts, false);
2482     }
2483 
2484     public Type erasureRecursive(Type t) {
2485         return erasure(t, true);
2486     }
2487 
2488     public List<Type> erasureRecursive(List<Type> ts) {
2489         return erasure.visit(ts, true);
2490     }
2491     // </editor-fold>
2492 
2493     // <editor-fold defaultstate="collapsed" desc="makeIntersectionType">
2494     /**
2495      * Make an intersection type from non-empty list of types.  The list should be ordered according to
2496      * {@link TypeSymbol#precedes(TypeSymbol, Types)}. Note that this might cause a symbol completion.
2497      * Hence, this version of makeIntersectionType may not be called during a classfile read.
2498      *
2499      * @param bounds    the types from which the intersection type is formed
2500      */
2501     public IntersectionClassType makeIntersectionType(List<Type> bounds) {
2502         return makeIntersectionType(bounds, bounds.head.tsym.isInterface());
2503     }
2504 
2505     /**
2506      * Make an intersection type from non-empty list of types.  The list should be ordered according to
2507      * {@link TypeSymbol#precedes(TypeSymbol, Types)}. This does not cause symbol completion as
2508      * an extra parameter indicates as to whether all bounds are interfaces - in which case the
2509      * supertype is implicitly assumed to be 'Object'.
2510      *
2511      * @param bounds        the types from which the intersection type is formed
2512      * @param allInterfaces are all bounds interface types?
2513      */
2514     public IntersectionClassType makeIntersectionType(List<Type> bounds, boolean allInterfaces) {
2515         Assert.check(bounds.nonEmpty());
2516         Type firstExplicitBound = bounds.head;
2517         if (allInterfaces) {
2518             bounds = bounds.prepend(syms.objectType);
2519         }
2520         ClassSymbol bc =
2521             new ClassSymbol(ABSTRACT|PUBLIC|SYNTHETIC|COMPOUND|ACYCLIC,
2522                             Type.moreInfo
2523                                 ? names.fromString(bounds.toString())
2524                                 : names.empty,
2525                             null,
2526                             syms.noSymbol);
2527         IntersectionClassType intersectionType = new IntersectionClassType(bounds, bc, allInterfaces);
2528         bc.type = intersectionType;
2529         bc.erasure_field = (bounds.head.hasTag(TYPEVAR)) ?
2530                 syms.objectType : // error condition, recover
2531                 erasure(firstExplicitBound);
2532         bc.members_field = WriteableScope.create(bc);
2533         return intersectionType;
2534     }
2535     // </editor-fold>
2536 
2537     // <editor-fold defaultstate="collapsed" desc="supertype">
2538     public Type supertype(Type t) {
2539         return supertype.visit(t);
2540     }
2541     // where
2542         private UnaryVisitor<Type> supertype = new UnaryVisitor<Type>() {
2543 
2544             public Type visitType(Type t, Void ignored) {
2545                 // A note on wildcards: there is no good way to
2546                 // determine a supertype for a lower-bounded wildcard.
2547                 return Type.noType;
2548             }
2549 
2550             @Override
2551             public Type visitClassType(ClassType t, Void ignored) {
2552                 if (t.supertype_field == null) {
2553                     Type supertype = ((ClassSymbol)t.tsym).getSuperclass();
2554                     // An interface has no superclass; its supertype is Object.
2555                     if (t.isInterface())
2556                         supertype = ((ClassType)t.tsym.type).supertype_field;
2557                     if (t.supertype_field == null) {
2558                         List<Type> actuals = classBound(t).allparams();
2559                         List<Type> formals = t.tsym.type.allparams();
2560                         if (t.hasErasedSupertypes()) {
2561                             t.supertype_field = erasureRecursive(supertype);
2562                         } else if (formals.nonEmpty()) {
2563                             t.supertype_field = subst(supertype, formals, actuals);
2564                         }
2565                         else {
2566                             t.supertype_field = supertype;
2567                         }
2568                     }
2569                 }
2570                 return t.supertype_field;
2571             }
2572 
2573             /**
2574              * The supertype is always a class type. If the type
2575              * variable's bounds start with a class type, this is also
2576              * the supertype.  Otherwise, the supertype is
2577              * java.lang.Object.
2578              */
2579             @Override
2580             public Type visitTypeVar(TypeVar t, Void ignored) {
2581                 if (t.getUpperBound().hasTag(TYPEVAR) ||
2582                     (!t.getUpperBound().isCompound() && !t.getUpperBound().isInterface())) {
2583                     return t.getUpperBound();
2584                 } else {
2585                     return supertype(t.getUpperBound());
2586                 }
2587             }
2588 
2589             @Override
2590             public Type visitArrayType(ArrayType t, Void ignored) {
2591                 if (t.elemtype.isPrimitive() || isSameType(t.elemtype, syms.objectType))
2592                     return arraySuperType();
2593                 else
2594                     return new ArrayType(supertype(t.elemtype), t.tsym);
2595             }
2596 
2597             @Override
2598             public Type visitErrorType(ErrorType t, Void ignored) {
2599                 return Type.noType;
2600             }
2601         };
2602     // </editor-fold>
2603 
2604     // <editor-fold defaultstate="collapsed" desc="interfaces">
2605     /**
2606      * Return the interfaces implemented by this class.
2607      */
2608     public List<Type> interfaces(Type t) {
2609         return interfaces.visit(t);
2610     }
2611     // where
2612         private UnaryVisitor<List<Type>> interfaces = new UnaryVisitor<List<Type>>() {
2613 
2614             public List<Type> visitType(Type t, Void ignored) {
2615                 return List.nil();
2616             }
2617 
2618             @Override
2619             public List<Type> visitClassType(ClassType t, Void ignored) {
2620                 if (t.interfaces_field == null) {
2621                     List<Type> interfaces = ((ClassSymbol)t.tsym).getInterfaces();
2622                     if (t.interfaces_field == null) {
2623                         // If t.interfaces_field is null, then t must
2624                         // be a parameterized type (not to be confused
2625                         // with a generic type declaration).
2626                         // Terminology:
2627                         //    Parameterized type: List<String>
2628                         //    Generic type declaration: class List<E> { ... }
2629                         // So t corresponds to List<String> and
2630                         // t.tsym.type corresponds to List<E>.
2631                         // The reason t must be parameterized type is
2632                         // that completion will happen as a side
2633                         // effect of calling
2634                         // ClassSymbol.getInterfaces.  Since
2635                         // t.interfaces_field is null after
2636                         // completion, we can assume that t is not the
2637                         // type of a class/interface declaration.
2638                         Assert.check(t != t.tsym.type, t);
2639                         List<Type> actuals = t.allparams();
2640                         List<Type> formals = t.tsym.type.allparams();
2641                         if (t.hasErasedSupertypes()) {
2642                             t.interfaces_field = erasureRecursive(interfaces);
2643                         } else if (formals.nonEmpty()) {
2644                             t.interfaces_field = subst(interfaces, formals, actuals);
2645                         }
2646                         else {
2647                             t.interfaces_field = interfaces;
2648                         }
2649                     }
2650                 }
2651                 return t.interfaces_field;
2652             }
2653 
2654             @Override
2655             public List<Type> visitTypeVar(TypeVar t, Void ignored) {
2656                 if (t.getUpperBound().isCompound())
2657                     return interfaces(t.getUpperBound());
2658 
2659                 if (t.getUpperBound().isInterface())
2660                     return List.of(t.getUpperBound());
2661 
2662                 return List.nil();
2663             }
2664         };
2665 
2666     public List<Type> directSupertypes(Type t) {
2667         return directSupertypes.visit(t);
2668     }
2669     // where
2670         private final UnaryVisitor<List<Type>> directSupertypes = new UnaryVisitor<List<Type>>() {
2671 
2672             public List<Type> visitType(final Type type, final Void ignored) {
2673                 if (!type.isIntersection()) {
2674                     final Type sup = supertype(type);
2675                     return (sup == Type.noType || sup == type || sup == null)
2676                         ? interfaces(type)
2677                         : interfaces(type).prepend(sup);
2678                 } else {
2679                     return ((IntersectionClassType)type).getExplicitComponents();
2680                 }
2681             }
2682         };
2683 
2684     public boolean isDirectSuperInterface(TypeSymbol isym, TypeSymbol origin) {
2685         for (Type i2 : interfaces(origin.type)) {
2686             if (isym == i2.tsym) return true;
2687         }
2688         return false;
2689     }
2690     // </editor-fold>
2691 
2692     // <editor-fold defaultstate="collapsed" desc="isDerivedRaw">
2693     Map<Type,Boolean> isDerivedRawCache = new HashMap<>();
2694 
2695     public boolean isDerivedRaw(Type t) {
2696         Boolean result = isDerivedRawCache.get(t);
2697         if (result == null) {
2698             result = isDerivedRawInternal(t);
2699             isDerivedRawCache.put(t, result);
2700         }
2701         return result;
2702     }
2703 
2704     public boolean isDerivedRawInternal(Type t) {
2705         if (t.isErroneous())
2706             return false;
2707         return
2708             t.isRaw() ||
2709             supertype(t) != Type.noType && isDerivedRaw(supertype(t)) ||
2710             isDerivedRaw(interfaces(t));
2711     }
2712 
2713     public boolean isDerivedRaw(List<Type> ts) {
2714         List<Type> l = ts;
2715         while (l.nonEmpty() && !isDerivedRaw(l.head)) l = l.tail;
2716         return l.nonEmpty();
2717     }
2718     // </editor-fold>
2719 
2720     // <editor-fold defaultstate="collapsed" desc="setBounds">
2721     /**
2722      * Same as {@link Types#setBounds(TypeVar, List, boolean)}, except that third parameter is computed directly,
2723      * as follows: if all all bounds are interface types, the computed supertype is Object,otherwise
2724      * the supertype is simply left null (in this case, the supertype is assumed to be the head of
2725      * the bound list passed as second argument). Note that this check might cause a symbol completion.
2726      * Hence, this version of setBounds may not be called during a classfile read.
2727      *
2728      * @param t         a type variable
2729      * @param bounds    the bounds, must be nonempty
2730      */
2731     public void setBounds(TypeVar t, List<Type> bounds) {
2732         setBounds(t, bounds, bounds.head.tsym.isInterface());
2733     }
2734 
2735     /**
2736      * Set the bounds field of the given type variable to reflect a (possibly multiple) list of bounds.
2737      * This does not cause symbol completion as an extra parameter indicates as to whether all bounds
2738      * are interfaces - in which case the supertype is implicitly assumed to be 'Object'.
2739      *
2740      * @param t             a type variable
2741      * @param bounds        the bounds, must be nonempty
2742      * @param allInterfaces are all bounds interface types?
2743      */
2744     public void setBounds(TypeVar t, List<Type> bounds, boolean allInterfaces) {
2745         t.setUpperBound( bounds.tail.isEmpty() ?
2746                 bounds.head :
2747                 makeIntersectionType(bounds, allInterfaces) );
2748         t.rank_field = -1;
2749     }
2750     // </editor-fold>
2751 
2752     // <editor-fold defaultstate="collapsed" desc="getBounds">
2753     /**
2754      * Return list of bounds of the given type variable.
2755      */
2756     public List<Type> getBounds(TypeVar t) {
2757         if (t.getUpperBound().hasTag(NONE))
2758             return List.nil();
2759         else if (t.getUpperBound().isErroneous() || !t.getUpperBound().isCompound())
2760             return List.of(t.getUpperBound());
2761         else if ((erasure(t).tsym.flags() & INTERFACE) == 0)
2762             return interfaces(t).prepend(supertype(t));
2763         else
2764             // No superclass was given in bounds.
2765             // In this case, supertype is Object, erasure is first interface.
2766             return interfaces(t);
2767     }
2768     // </editor-fold>
2769 
2770     // <editor-fold defaultstate="collapsed" desc="classBound">
2771     /**
2772      * If the given type is a (possibly selected) type variable,
2773      * return the bounding class of this type, otherwise return the
2774      * type itself.
2775      */
2776     public Type classBound(Type t) {
2777         return classBound.visit(t);
2778     }
2779     // where
2780         private UnaryVisitor<Type> classBound = new UnaryVisitor<Type>() {
2781 
2782             public Type visitType(Type t, Void ignored) {
2783                 return t;
2784             }
2785 
2786             @Override
2787             public Type visitClassType(ClassType t, Void ignored) {
2788                 Type outer1 = classBound(t.getEnclosingType());
2789                 if (outer1 != t.getEnclosingType())
2790                     return new ClassType(outer1, t.getTypeArguments(), t.tsym,
2791                                          t.getMetadata());
2792                 else
2793                     return t;
2794             }
2795 
2796             @Override
2797             public Type visitTypeVar(TypeVar t, Void ignored) {
2798                 return classBound(supertype(t));
2799             }
2800 
2801             @Override
2802             public Type visitErrorType(ErrorType t, Void ignored) {
2803                 return t;
2804             }
2805         };
2806     // </editor-fold>
2807 
2808     // <editor-fold defaultstate="collapsed" desc="subsignature / override equivalence">
2809     /**
2810      * Returns true iff the first signature is a <em>subsignature</em>
2811      * of the other.  This is <b>not</b> an equivalence
2812      * relation.
2813      *
2814      * @jls 8.4.2 Method Signature
2815      * @see #overrideEquivalent(Type t, Type s)
2816      * @param t first signature (possibly raw).
2817      * @param s second signature (could be subjected to erasure).
2818      * @return true if t is a subsignature of s.
2819      */
2820     public boolean isSubSignature(Type t, Type s) {
2821         return hasSameArgs(t, s, true) || hasSameArgs(t, erasure(s), true);
2822     }
2823 
2824     /**
2825      * Returns true iff these signatures are related by <em>override
2826      * equivalence</em>.  This is the natural extension of
2827      * isSubSignature to an equivalence relation.
2828      *
2829      * @jls 8.4.2 Method Signature
2830      * @see #isSubSignature(Type t, Type s)
2831      * @param t a signature (possible raw, could be subjected to
2832      * erasure).
2833      * @param s a signature (possible raw, could be subjected to
2834      * erasure).
2835      * @return true if either argument is a subsignature of the other.
2836      */
2837     public boolean overrideEquivalent(Type t, Type s) {
2838         return hasSameArgs(t, s) ||
2839             hasSameArgs(t, erasure(s)) || hasSameArgs(erasure(t), s);
2840     }
2841 
2842     public boolean overridesObjectMethod(TypeSymbol origin, Symbol msym) {
2843         for (Symbol sym : syms.objectType.tsym.members().getSymbolsByName(msym.name)) {
2844             if (msym.overrides(sym, origin, Types.this, true)) {
2845                 return true;
2846             }
2847         }
2848         return false;
2849     }
2850 
2851     /**
2852      * This enum defines the strategy for implementing most specific return type check
2853      * during the most specific and functional interface checks.
2854      */
2855     public enum MostSpecificReturnCheck {
2856         /**
2857          * Return r1 is more specific than r2 if {@code r1 <: r2}. Extra care required for (i) handling
2858          * method type variables (if either method is generic) and (ii) subtyping should be replaced
2859          * by type-equivalence for primitives. This is essentially an inlined version of
2860          * {@link Types#resultSubtype(Type, Type, Warner)}, where the assignability check has been
2861          * replaced with a strict subtyping check.
2862          */
2863         BASIC() {
2864             @Override
2865             public boolean test(Type mt1, Type mt2, Types types) {
2866                 List<Type> tvars = mt1.getTypeArguments();
2867                 List<Type> svars = mt2.getTypeArguments();
2868                 Type t = mt1.getReturnType();
2869                 Type s = types.subst(mt2.getReturnType(), svars, tvars);
2870                 return types.isSameType(t, s) ||
2871                     !t.isPrimitive() &&
2872                     !s.isPrimitive() &&
2873                     types.isSubtype(t, s);
2874             }
2875         },
2876         /**
2877          * Return r1 is more specific than r2 if r1 is return-type-substitutable for r2.
2878          */
2879         RTS() {
2880             @Override
2881             public boolean test(Type mt1, Type mt2, Types types) {
2882                 return types.returnTypeSubstitutable(mt1, mt2);
2883             }
2884         };
2885 
2886         public abstract boolean test(Type mt1, Type mt2, Types types);
2887     }
2888 
2889     /**
2890      * Merge multiple abstract methods. The preferred method is a method that is a subsignature
2891      * of all the other signatures and whose return type is more specific {@link MostSpecificReturnCheck}.
2892      * The resulting preferred method has a throws clause that is the intersection of the merged
2893      * methods' clauses.
2894      */
2895     public Optional<Symbol> mergeAbstracts(List<Symbol> ambiguousInOrder, Type site, boolean sigCheck) {
2896         //first check for preconditions
2897         boolean shouldErase = false;
2898         List<Type> erasedParams = ambiguousInOrder.head.erasure(this).getParameterTypes();
2899         for (Symbol s : ambiguousInOrder) {
2900             if ((s.flags() & ABSTRACT) == 0 ||
2901                     (sigCheck && !isSameTypes(erasedParams, s.erasure(this).getParameterTypes()))) {
2902                 return Optional.empty();
2903             } else if (s.type.hasTag(FORALL)) {
2904                 shouldErase = true;
2905             }
2906         }
2907         //then merge abstracts
2908         for (MostSpecificReturnCheck mostSpecificReturnCheck : MostSpecificReturnCheck.values()) {
2909             outer: for (Symbol s : ambiguousInOrder) {
2910                 Type mt = memberType(site, s);
2911                 List<Type> allThrown = mt.getThrownTypes();
2912                 for (Symbol s2 : ambiguousInOrder) {
2913                     if (s != s2) {
2914                         Type mt2 = memberType(site, s2);
2915                         if (!isSubSignature(mt, mt2) ||
2916                                 !mostSpecificReturnCheck.test(mt, mt2, this)) {
2917                             //ambiguity cannot be resolved
2918                             continue outer;
2919                         } else {
2920                             List<Type> thrownTypes2 = mt2.getThrownTypes();
2921                             if (!mt.hasTag(FORALL) && shouldErase) {
2922                                 thrownTypes2 = erasure(thrownTypes2);
2923                             } else if (mt.hasTag(FORALL)) {
2924                                 //subsignature implies that if most specific is generic, then all other
2925                                 //methods are too
2926                                 Assert.check(mt2.hasTag(FORALL));
2927                                 // if both are generic methods, adjust thrown types ahead of intersection computation
2928                                 thrownTypes2 = subst(thrownTypes2, mt2.getTypeArguments(), mt.getTypeArguments());
2929                             }
2930                             allThrown = chk.intersect(allThrown, thrownTypes2);
2931                         }
2932                     }
2933                 }
2934                 return (allThrown == mt.getThrownTypes()) ?
2935                         Optional.of(s) :
2936                         Optional.of(new MethodSymbol(
2937                                 s.flags(),
2938                                 s.name,
2939                                 createMethodTypeWithThrown(s.type, allThrown),
2940                                 s.owner) {
2941                             @Override
2942                             public Symbol baseSymbol() {
2943                                 return s;
2944                             }
2945                         });
2946             }
2947         }
2948         return Optional.empty();
2949     }
2950 
2951     // <editor-fold defaultstate="collapsed" desc="Determining method implementation in given site">
2952     class ImplementationCache {
2953 
2954         private WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, Entry>>> _map = new WeakHashMap<>();
2955 
2956         class Entry {
2957             final MethodSymbol cachedImpl;
2958             final Predicate<Symbol> implFilter;
2959             final boolean checkResult;
2960             final int prevMark;
2961 
2962             public Entry(MethodSymbol cachedImpl,
2963                     Predicate<Symbol> scopeFilter,
2964                     boolean checkResult,
2965                     int prevMark) {
2966                 this.cachedImpl = cachedImpl;
2967                 this.implFilter = scopeFilter;
2968                 this.checkResult = checkResult;
2969                 this.prevMark = prevMark;
2970             }
2971 
2972             boolean matches(Predicate<Symbol> scopeFilter, boolean checkResult, int mark) {
2973                 return this.implFilter == scopeFilter &&
2974                         this.checkResult == checkResult &&
2975                         this.prevMark == mark;
2976             }
2977         }
2978 
2979         MethodSymbol get(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Predicate<Symbol> implFilter) {
2980             SoftReference<Map<TypeSymbol, Entry>> ref_cache = _map.get(ms);
2981             Map<TypeSymbol, Entry> cache = ref_cache != null ? ref_cache.get() : null;
2982             if (cache == null) {
2983                 cache = new HashMap<>();
2984                 _map.put(ms, new SoftReference<>(cache));
2985             }
2986             Entry e = cache.get(origin);
2987             CompoundScope members = membersClosure(origin.type, true);
2988             if (e == null ||
2989                     !e.matches(implFilter, checkResult, members.getMark())) {
2990                 MethodSymbol impl = implementationInternal(ms, origin, checkResult, implFilter);
2991                 cache.put(origin, new Entry(impl, implFilter, checkResult, members.getMark()));
2992                 return impl;
2993             }
2994             else {
2995                 return e.cachedImpl;
2996             }
2997         }
2998 
2999         private MethodSymbol implementationInternal(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Predicate<Symbol> implFilter) {
3000             for (Type t = origin.type; t.hasTag(CLASS) || t.hasTag(TYPEVAR); t = supertype(t)) {
3001                 t = skipTypeVars(t, false);
3002                 TypeSymbol c = t.tsym;
3003                 Symbol bestSoFar = null;
3004                 for (Symbol sym : c.members().getSymbolsByName(ms.name, implFilter)) {
3005                     if (sym != null && sym.overrides(ms, origin, Types.this, checkResult)) {
3006                         bestSoFar = sym;
3007                         if ((sym.flags() & ABSTRACT) == 0) {
3008                             //if concrete impl is found, exit immediately
3009                             break;
3010                         }
3011                     }
3012                 }
3013                 if (bestSoFar != null) {
3014                     //return either the (only) concrete implementation or the first abstract one
3015                     return (MethodSymbol)bestSoFar;
3016                 }
3017             }
3018             return null;
3019         }
3020     }
3021 
3022     private ImplementationCache implCache = new ImplementationCache();
3023 
3024     public MethodSymbol implementation(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Predicate<Symbol> implFilter) {
3025         return implCache.get(ms, origin, checkResult, implFilter);
3026     }
3027     // </editor-fold>
3028 
3029     // <editor-fold defaultstate="collapsed" desc="compute transitive closure of all members in given site">
3030     class MembersClosureCache extends SimpleVisitor<Scope.CompoundScope, Void> {
3031 
3032         private Map<TypeSymbol, CompoundScope> _map = new HashMap<>();
3033 
3034         Set<TypeSymbol> seenTypes = new HashSet<>();
3035 
3036         class MembersScope extends CompoundScope {
3037 
3038             CompoundScope scope;
3039 
3040             public MembersScope(CompoundScope scope) {
3041                 super(scope.owner);
3042                 this.scope = scope;
3043             }
3044 
3045             Predicate<Symbol> combine(Predicate<Symbol> sf) {
3046                 return s -> !s.owner.isInterface() && (sf == null || sf.test(s));
3047             }
3048 
3049             @Override
3050             public Iterable<Symbol> getSymbols(Predicate<Symbol> sf, LookupKind lookupKind) {
3051                 return scope.getSymbols(combine(sf), lookupKind);
3052             }
3053 
3054             @Override
3055             public Iterable<Symbol> getSymbolsByName(Name name, Predicate<Symbol> sf, LookupKind lookupKind) {
3056                 return scope.getSymbolsByName(name, combine(sf), lookupKind);
3057             }
3058 
3059             @Override
3060             public int getMark() {
3061                 return scope.getMark();
3062             }
3063         }
3064 
3065         CompoundScope nilScope;
3066 
3067         /** members closure visitor methods **/
3068 
3069         public CompoundScope visitType(Type t, Void _unused) {
3070             if (nilScope == null) {
3071                 nilScope = new CompoundScope(syms.noSymbol);
3072             }
3073             return nilScope;
3074         }
3075 
3076         @Override
3077         public CompoundScope visitClassType(ClassType t, Void _unused) {
3078             if (!seenTypes.add(t.tsym)) {
3079                 //this is possible when an interface is implemented in multiple
3080                 //superclasses, or when a class hierarchy is circular - in such
3081                 //cases we don't need to recurse (empty scope is returned)
3082                 return new CompoundScope(t.tsym);
3083             }
3084             try {
3085                 seenTypes.add(t.tsym);
3086                 ClassSymbol csym = (ClassSymbol)t.tsym;
3087                 CompoundScope membersClosure = _map.get(csym);
3088                 if (membersClosure == null) {
3089                     membersClosure = new CompoundScope(csym);
3090                     for (Type i : interfaces(t)) {
3091                         membersClosure.prependSubScope(visit(i, null));
3092                     }
3093                     membersClosure.prependSubScope(visit(supertype(t), null));
3094                     membersClosure.prependSubScope(csym.members());
3095                     _map.put(csym, membersClosure);
3096                 }
3097                 return membersClosure;
3098             }
3099             finally {
3100                 seenTypes.remove(t.tsym);
3101             }
3102         }
3103 
3104         @Override
3105         public CompoundScope visitTypeVar(TypeVar t, Void _unused) {
3106             return visit(t.getUpperBound(), null);
3107         }
3108     }
3109 
3110     private MembersClosureCache membersCache = new MembersClosureCache();
3111 
3112     public CompoundScope membersClosure(Type site, boolean skipInterface) {
3113         CompoundScope cs = membersCache.visit(site, null);
3114         Assert.checkNonNull(cs, () -> "type " + site);
3115         return skipInterface ? membersCache.new MembersScope(cs) : cs;
3116     }
3117     // </editor-fold>
3118 
3119 
3120     /** Return first abstract member of class `sym'.
3121      */
3122     public MethodSymbol firstUnimplementedAbstract(ClassSymbol sym) {
3123         try {
3124             return firstUnimplementedAbstractImpl(sym, sym);
3125         } catch (CompletionFailure ex) {
3126             chk.completionError(enter.getEnv(sym).tree.pos(), ex);
3127             return null;
3128         }
3129     }
3130         //where:
3131         private MethodSymbol firstUnimplementedAbstractImpl(ClassSymbol impl, ClassSymbol c) {
3132             MethodSymbol undef = null;
3133             // Do not bother to search in classes that are not abstract,
3134             // since they cannot have abstract members.
3135             if (c == impl || (c.flags() & (ABSTRACT | INTERFACE)) != 0) {
3136                 Scope s = c.members();
3137                 for (Symbol sym : s.getSymbols(NON_RECURSIVE)) {
3138                     if (sym.kind == MTH &&
3139                         (sym.flags() & (ABSTRACT|DEFAULT|PRIVATE)) == ABSTRACT) {
3140                         MethodSymbol absmeth = (MethodSymbol)sym;
3141                         MethodSymbol implmeth = absmeth.implementation(impl, this, true);
3142                         if (implmeth == null || implmeth == absmeth) {
3143                             //look for default implementations
3144                             MethodSymbol prov = interfaceCandidates(impl.type, absmeth).head;
3145                             if (prov != null && prov.overrides(absmeth, impl, this, true)) {
3146                                 implmeth = prov;
3147                             }
3148                         }
3149                         if (implmeth == null || implmeth == absmeth) {
3150                             undef = absmeth;
3151                             break;
3152                         }
3153                     }
3154                 }
3155                 if (undef == null) {
3156                     Type st = supertype(c.type);
3157                     if (st.hasTag(CLASS))
3158                         undef = firstUnimplementedAbstractImpl(impl, (ClassSymbol)st.tsym);
3159                 }
3160                 for (List<Type> l = interfaces(c.type);
3161                      undef == null && l.nonEmpty();
3162                      l = l.tail) {
3163                     undef = firstUnimplementedAbstractImpl(impl, (ClassSymbol)l.head.tsym);
3164                 }
3165             }
3166             return undef;
3167         }
3168 
3169     public class CandidatesCache {
3170         public Map<Entry, List<MethodSymbol>> cache = new WeakHashMap<>();
3171 
3172         class Entry {
3173             Type site;
3174             MethodSymbol msym;
3175 
3176             Entry(Type site, MethodSymbol msym) {
3177                 this.site = site;
3178                 this.msym = msym;
3179             }
3180 
3181             @Override
3182             public boolean equals(Object obj) {
3183                 return (obj instanceof Entry entry)
3184                         && entry.msym == msym
3185                         && isSameType(site, entry.site);
3186             }
3187 
3188             @Override
3189             public int hashCode() {
3190                 return Types.this.hashCode(site) & ~msym.hashCode();
3191             }
3192         }
3193 
3194         public List<MethodSymbol> get(Entry e) {
3195             return cache.get(e);
3196         }
3197 
3198         public void put(Entry e, List<MethodSymbol> msymbols) {
3199             cache.put(e, msymbols);
3200         }
3201     }
3202 
3203     public CandidatesCache candidatesCache = new CandidatesCache();
3204 
3205     //where
3206     public List<MethodSymbol> interfaceCandidates(Type site, MethodSymbol ms) {
3207         CandidatesCache.Entry e = candidatesCache.new Entry(site, ms);
3208         List<MethodSymbol> candidates = candidatesCache.get(e);
3209         if (candidates == null) {
3210             Predicate<Symbol> filter = new MethodFilter(ms, site);
3211             List<MethodSymbol> candidates2 = List.nil();
3212             for (Symbol s : membersClosure(site, false).getSymbols(filter)) {
3213                 if (!site.tsym.isInterface() && !s.owner.isInterface()) {
3214                     return List.of((MethodSymbol)s);
3215                 } else if (!candidates2.contains(s)) {
3216                     candidates2 = candidates2.prepend((MethodSymbol)s);
3217                 }
3218             }
3219             candidates = prune(candidates2);
3220             candidatesCache.put(e, candidates);
3221         }
3222         return candidates;
3223     }
3224 
3225     public List<MethodSymbol> prune(List<MethodSymbol> methods) {
3226         ListBuffer<MethodSymbol> methodsMin = new ListBuffer<>();
3227         for (MethodSymbol m1 : methods) {
3228             boolean isMin_m1 = true;
3229             for (MethodSymbol m2 : methods) {
3230                 if (m1 == m2) continue;
3231                 if (m2.owner != m1.owner &&
3232                         asSuper(m2.owner.type, m1.owner) != null) {
3233                     isMin_m1 = false;
3234                     break;
3235                 }
3236             }
3237             if (isMin_m1)
3238                 methodsMin.append(m1);
3239         }
3240         return methodsMin.toList();
3241     }
3242     // where
3243             private class MethodFilter implements Predicate<Symbol> {
3244 
3245                 Symbol msym;
3246                 Type site;
3247 
3248                 MethodFilter(Symbol msym, Type site) {
3249                     this.msym = msym;
3250                     this.site = site;
3251                 }
3252 
3253                 @Override
3254                 public boolean test(Symbol s) {
3255                     return s.kind == MTH &&
3256                             s.name == msym.name &&
3257                             (s.flags() & SYNTHETIC) == 0 &&
3258                             s.isInheritedIn(site.tsym, Types.this) &&
3259                             overrideEquivalent(memberType(site, s), memberType(site, msym));
3260                 }
3261             }
3262     // </editor-fold>
3263 
3264     /**
3265      * Does t have the same arguments as s?  It is assumed that both
3266      * types are (possibly polymorphic) method types.  Monomorphic
3267      * method types "have the same arguments", if their argument lists
3268      * are equal.  Polymorphic method types "have the same arguments",
3269      * if they have the same arguments after renaming all type
3270      * variables of one to corresponding type variables in the other,
3271      * where correspondence is by position in the type parameter list.
3272      */
3273     public boolean hasSameArgs(Type t, Type s) {
3274         return hasSameArgs(t, s, true);
3275     }
3276 
3277     public boolean hasSameArgs(Type t, Type s, boolean strict) {
3278         return hasSameArgs(t, s, strict ? hasSameArgs_strict : hasSameArgs_nonstrict);
3279     }
3280 
3281     private boolean hasSameArgs(Type t, Type s, TypeRelation hasSameArgs) {
3282         return hasSameArgs.visit(t, s);
3283     }
3284     // where
3285         private class HasSameArgs extends TypeRelation {
3286 
3287             boolean strict;
3288 
3289             public HasSameArgs(boolean strict) {
3290                 this.strict = strict;
3291             }
3292 
3293             public Boolean visitType(Type t, Type s) {
3294                 throw new AssertionError();
3295             }
3296 
3297             @Override
3298             public Boolean visitMethodType(MethodType t, Type s) {
3299                 return s.hasTag(METHOD)
3300                     && containsTypeEquivalent(t.argtypes, s.getParameterTypes());
3301             }
3302 
3303             @Override
3304             public Boolean visitForAll(ForAll t, Type s) {
3305                 if (!s.hasTag(FORALL))
3306                     return strict ? false : visitMethodType(t.asMethodType(), s);
3307 
3308                 ForAll forAll = (ForAll)s;
3309                 return hasSameBounds(t, forAll)
3310                     && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
3311             }
3312 
3313             @Override
3314             public Boolean visitErrorType(ErrorType t, Type s) {
3315                 return false;
3316             }
3317         }
3318 
3319     TypeRelation hasSameArgs_strict = new HasSameArgs(true);
3320         TypeRelation hasSameArgs_nonstrict = new HasSameArgs(false);
3321 
3322     // </editor-fold>
3323 
3324     // <editor-fold defaultstate="collapsed" desc="subst">
3325     public List<Type> subst(List<Type> ts,
3326                             List<Type> from,
3327                             List<Type> to) {
3328         return ts.map(new Subst(from, to));
3329     }
3330 
3331     /**
3332      * Substitute all occurrences of a type in `from' with the
3333      * corresponding type in `to' in 't'. Match lists `from' and `to'
3334      * from the right: If lists have different length, discard leading
3335      * elements of the longer list.
3336      */
3337     public Type subst(Type t, List<Type> from, List<Type> to) {
3338         return t.map(new Subst(from, to));
3339     }
3340 
3341     private class Subst extends StructuralTypeMapping<Void> {
3342         List<Type> from;
3343         List<Type> to;
3344 
3345         public Subst(List<Type> from, List<Type> to) {
3346             int fromLength = from.length();
3347             int toLength = to.length();
3348             while (fromLength > toLength) {
3349                 fromLength--;
3350                 from = from.tail;
3351             }
3352             while (fromLength < toLength) {
3353                 toLength--;
3354                 to = to.tail;
3355             }
3356             this.from = from;
3357             this.to = to;
3358         }
3359 
3360         @Override
3361         public Type visitTypeVar(TypeVar t, Void ignored) {
3362             for (List<Type> from = this.from, to = this.to;
3363                  from.nonEmpty();
3364                  from = from.tail, to = to.tail) {
3365                 if (t.equalsIgnoreMetadata(from.head)) {
3366                     return to.head.withTypeVar(t);
3367                 }
3368             }
3369             return t;
3370         }
3371 
3372         @Override
3373         public Type visitClassType(ClassType t, Void ignored) {
3374             if (!t.isCompound()) {
3375                 return super.visitClassType(t, ignored);
3376             } else {
3377                 Type st = visit(supertype(t));
3378                 List<Type> is = visit(interfaces(t), ignored);
3379                 if (st == supertype(t) && is == interfaces(t))
3380                     return t;
3381                 else
3382                     return makeIntersectionType(is.prepend(st));
3383             }
3384         }
3385 
3386         @Override
3387         public Type visitWildcardType(WildcardType t, Void ignored) {
3388             WildcardType t2 = (WildcardType)super.visitWildcardType(t, ignored);
3389             if (t2 != t && t.isExtendsBound() && t2.type.isExtendsBound()) {
3390                 t2.type = wildUpperBound(t2.type);
3391             }
3392             return t2;
3393         }
3394 
3395         @Override
3396         public Type visitForAll(ForAll t, Void ignored) {
3397             if (Type.containsAny(to, t.tvars)) {
3398                 //perform alpha-renaming of free-variables in 't'
3399                 //if 'to' types contain variables that are free in 't'
3400                 List<Type> freevars = newInstances(t.tvars);
3401                 t = new ForAll(freevars,
3402                                Types.this.subst(t.qtype, t.tvars, freevars));
3403             }
3404             List<Type> tvars1 = substBounds(t.tvars, from, to);
3405             Type qtype1 = visit(t.qtype);
3406             if (tvars1 == t.tvars && qtype1 == t.qtype) {
3407                 return t;
3408             } else if (tvars1 == t.tvars) {
3409                 return new ForAll(tvars1, qtype1) {
3410                     @Override
3411                     public boolean needsStripping() {
3412                         return true;
3413                     }
3414                 };
3415             } else {
3416                 return new ForAll(tvars1, Types.this.subst(qtype1, t.tvars, tvars1)) {
3417                     @Override
3418                     public boolean needsStripping() {
3419                         return true;
3420                     }
3421                 };
3422             }
3423         }
3424     }
3425 
3426     public List<Type> substBounds(List<Type> tvars,
3427                                   List<Type> from,
3428                                   List<Type> to) {
3429         if (tvars.isEmpty())
3430             return tvars;
3431         ListBuffer<Type> newBoundsBuf = new ListBuffer<>();
3432         boolean changed = false;
3433         // calculate new bounds
3434         for (Type t : tvars) {
3435             TypeVar tv = (TypeVar) t;
3436             Type bound = subst(tv.getUpperBound(), from, to);
3437             if (bound != tv.getUpperBound())
3438                 changed = true;
3439             newBoundsBuf.append(bound);
3440         }
3441         if (!changed)
3442             return tvars;
3443         ListBuffer<Type> newTvars = new ListBuffer<>();
3444         // create new type variables without bounds
3445         for (Type t : tvars) {
3446             newTvars.append(new TypeVar(t.tsym, null, syms.botType,
3447                                         t.getMetadata()));
3448         }
3449         // the new bounds should use the new type variables in place
3450         // of the old
3451         List<Type> newBounds = newBoundsBuf.toList();
3452         from = tvars;
3453         to = newTvars.toList();
3454         for (; !newBounds.isEmpty(); newBounds = newBounds.tail) {
3455             newBounds.head = subst(newBounds.head, from, to);
3456         }
3457         newBounds = newBoundsBuf.toList();
3458         // set the bounds of new type variables to the new bounds
3459         for (Type t : newTvars.toList()) {
3460             TypeVar tv = (TypeVar) t;
3461             tv.setUpperBound( newBounds.head );
3462             newBounds = newBounds.tail;
3463         }
3464         return newTvars.toList();
3465     }
3466 
3467     public TypeVar substBound(TypeVar t, List<Type> from, List<Type> to) {
3468         Type bound1 = subst(t.getUpperBound(), from, to);
3469         if (bound1 == t.getUpperBound())
3470             return t;
3471         else {
3472             // create new type variable without bounds
3473             TypeVar tv = new TypeVar(t.tsym, null, syms.botType,
3474                                      t.getMetadata());
3475             // the new bound should use the new type variable in place
3476             // of the old
3477             tv.setUpperBound( subst(bound1, List.of(t), List.of(tv)) );
3478             return tv;
3479         }
3480     }
3481     // </editor-fold>
3482 
3483     // <editor-fold defaultstate="collapsed" desc="hasSameBounds">
3484     /**
3485      * Does t have the same bounds for quantified variables as s?
3486      */
3487     public boolean hasSameBounds(ForAll t, ForAll s) {
3488         List<Type> l1 = t.tvars;
3489         List<Type> l2 = s.tvars;
3490         while (l1.nonEmpty() && l2.nonEmpty() &&
3491                isSameType(l1.head.getUpperBound(),
3492                           subst(l2.head.getUpperBound(),
3493                                 s.tvars,
3494                                 t.tvars))) {
3495             l1 = l1.tail;
3496             l2 = l2.tail;
3497         }
3498         return l1.isEmpty() && l2.isEmpty();
3499     }
3500     // </editor-fold>
3501 
3502     // <editor-fold defaultstate="collapsed" desc="newInstances">
3503     /** Create new vector of type variables from list of variables
3504      *  changing all recursive bounds from old to new list.
3505      */
3506     public List<Type> newInstances(List<Type> tvars) {
3507         List<Type> tvars1 = tvars.map(newInstanceFun);
3508         for (List<Type> l = tvars1; l.nonEmpty(); l = l.tail) {
3509             TypeVar tv = (TypeVar) l.head;
3510             tv.setUpperBound( subst(tv.getUpperBound(), tvars, tvars1) );
3511         }
3512         return tvars1;
3513     }
3514         private static final TypeMapping<Void> newInstanceFun = new TypeMapping<Void>() {
3515             @Override
3516             public TypeVar visitTypeVar(TypeVar t, Void _unused) {
3517                 return new TypeVar(t.tsym, t.getUpperBound(), t.getLowerBound(), t.getMetadata());
3518             }
3519         };
3520     // </editor-fold>
3521 
3522     public Type createMethodTypeWithParameters(Type original, List<Type> newParams) {
3523         return original.accept(methodWithParameters, newParams);
3524     }
3525     // where
3526         private final MapVisitor<List<Type>> methodWithParameters = new MapVisitor<List<Type>>() {
3527             public Type visitType(Type t, List<Type> newParams) {
3528                 throw new IllegalArgumentException("Not a method type: " + t);
3529             }
3530             public Type visitMethodType(MethodType t, List<Type> newParams) {
3531                 return new MethodType(newParams, t.restype, t.thrown, t.tsym);
3532             }
3533             public Type visitForAll(ForAll t, List<Type> newParams) {
3534                 return new ForAll(t.tvars, t.qtype.accept(this, newParams));
3535             }
3536         };
3537 
3538     public Type createMethodTypeWithThrown(Type original, List<Type> newThrown) {
3539         return original.accept(methodWithThrown, newThrown);
3540     }
3541     // where
3542         private final MapVisitor<List<Type>> methodWithThrown = new MapVisitor<List<Type>>() {
3543             public Type visitType(Type t, List<Type> newThrown) {
3544                 throw new IllegalArgumentException("Not a method type: " + t);
3545             }
3546             public Type visitMethodType(MethodType t, List<Type> newThrown) {
3547                 return new MethodType(t.argtypes, t.restype, newThrown, t.tsym);
3548             }
3549             public Type visitForAll(ForAll t, List<Type> newThrown) {
3550                 return new ForAll(t.tvars, t.qtype.accept(this, newThrown));
3551             }
3552         };
3553 
3554     public Type createMethodTypeWithReturn(Type original, Type newReturn) {
3555         return original.accept(methodWithReturn, newReturn);
3556     }
3557     // where
3558         private final MapVisitor<Type> methodWithReturn = new MapVisitor<Type>() {
3559             public Type visitType(Type t, Type newReturn) {
3560                 throw new IllegalArgumentException("Not a method type: " + t);
3561             }
3562             public Type visitMethodType(MethodType t, Type newReturn) {
3563                 return new MethodType(t.argtypes, newReturn, t.thrown, t.tsym) {
3564                     @Override
3565                     public Type baseType() {
3566                         return t;
3567                     }
3568                 };
3569             }
3570             public Type visitForAll(ForAll t, Type newReturn) {
3571                 return new ForAll(t.tvars, t.qtype.accept(this, newReturn)) {
3572                     @Override
3573                     public Type baseType() {
3574                         return t;
3575                     }
3576                 };
3577             }
3578         };
3579 
3580     // <editor-fold defaultstate="collapsed" desc="createErrorType">
3581     public Type createErrorType(Type originalType) {
3582         return new ErrorType(originalType, syms.errSymbol);
3583     }
3584 
3585     public Type createErrorType(ClassSymbol c, Type originalType) {
3586         return new ErrorType(c, originalType);
3587     }
3588 
3589     public Type createErrorType(Name name, TypeSymbol container, Type originalType) {
3590         return new ErrorType(name, container, originalType);
3591     }
3592     // </editor-fold>
3593 
3594     // <editor-fold defaultstate="collapsed" desc="rank">
3595     /**
3596      * The rank of a class is the length of the longest path between
3597      * the class and java.lang.Object in the class inheritance
3598      * graph. Undefined for all but reference types.
3599      */
3600     public int rank(Type t) {
3601         switch(t.getTag()) {
3602         case CLASS: {
3603             ClassType cls = (ClassType)t;
3604             if (cls.rank_field < 0) {
3605                 Name fullname = cls.tsym.getQualifiedName();
3606                 if (fullname == names.java_lang_Object)
3607                     cls.rank_field = 0;
3608                 else {
3609                     int r = rank(supertype(cls));
3610                     for (List<Type> l = interfaces(cls);
3611                          l.nonEmpty();
3612                          l = l.tail) {
3613                         if (rank(l.head) > r)
3614                             r = rank(l.head);
3615                     }
3616                     cls.rank_field = r + 1;
3617                 }
3618             }
3619             return cls.rank_field;
3620         }
3621         case TYPEVAR: {
3622             TypeVar tvar = (TypeVar)t;
3623             if (tvar.rank_field < 0) {
3624                 int r = rank(supertype(tvar));
3625                 for (List<Type> l = interfaces(tvar);
3626                      l.nonEmpty();
3627                      l = l.tail) {
3628                     if (rank(l.head) > r) r = rank(l.head);
3629                 }
3630                 tvar.rank_field = r + 1;
3631             }
3632             return tvar.rank_field;
3633         }
3634         case ERROR:
3635         case NONE:
3636             return 0;
3637         default:
3638             throw new AssertionError();
3639         }
3640     }
3641     // </editor-fold>
3642 
3643     /**
3644      * Helper method for generating a string representation of a given type
3645      * accordingly to a given locale
3646      */
3647     public String toString(Type t, Locale locale) {
3648         return Printer.createStandardPrinter(messages).visit(t, locale);
3649     }
3650 
3651     /**
3652      * Helper method for generating a string representation of a given type
3653      * accordingly to a given locale
3654      */
3655     public String toString(Symbol t, Locale locale) {
3656         return Printer.createStandardPrinter(messages).visit(t, locale);
3657     }
3658 
3659     // <editor-fold defaultstate="collapsed" desc="toString">
3660     /**
3661      * This toString is slightly more descriptive than the one on Type.
3662      *
3663      * @deprecated Types.toString(Type t, Locale l) provides better support
3664      * for localization
3665      */
3666     @Deprecated
3667     public String toString(Type t) {
3668         if (t.hasTag(FORALL)) {
3669             ForAll forAll = (ForAll)t;
3670             return typaramsString(forAll.tvars) + forAll.qtype;
3671         }
3672         return "" + t;
3673     }
3674     // where
3675         private String typaramsString(List<Type> tvars) {
3676             StringBuilder s = new StringBuilder();
3677             s.append('<');
3678             boolean first = true;
3679             for (Type t : tvars) {
3680                 if (!first) s.append(", ");
3681                 first = false;
3682                 appendTyparamString(((TypeVar)t), s);
3683             }
3684             s.append('>');
3685             return s.toString();
3686         }
3687         private void appendTyparamString(TypeVar t, StringBuilder buf) {
3688             buf.append(t);
3689             if (t.getUpperBound() == null ||
3690                 t.getUpperBound().tsym.getQualifiedName() == names.java_lang_Object)
3691                 return;
3692             buf.append(" extends "); // Java syntax; no need for i18n
3693             Type bound = t.getUpperBound();
3694             if (!bound.isCompound()) {
3695                 buf.append(bound);
3696             } else if ((erasure(t).tsym.flags() & INTERFACE) == 0) {
3697                 buf.append(supertype(t));
3698                 for (Type intf : interfaces(t)) {
3699                     buf.append('&');
3700                     buf.append(intf);
3701                 }
3702             } else {
3703                 // No superclass was given in bounds.
3704                 // In this case, supertype is Object, erasure is first interface.
3705                 boolean first = true;
3706                 for (Type intf : interfaces(t)) {
3707                     if (!first) buf.append('&');
3708                     first = false;
3709                     buf.append(intf);
3710                 }
3711             }
3712         }
3713     // </editor-fold>
3714 
3715     // <editor-fold defaultstate="collapsed" desc="Determining least upper bounds of types">
3716     /**
3717      * A cache for closures.
3718      *
3719      * <p>A closure is a list of all the supertypes and interfaces of
3720      * a class or interface type, ordered by ClassSymbol.precedes
3721      * (that is, subclasses come first, arbitrarily but fixed
3722      * otherwise).
3723      */
3724     private Map<Type,List<Type>> closureCache = new HashMap<>();
3725 
3726     /**
3727      * Returns the closure of a class or interface type.
3728      */
3729     public List<Type> closure(Type t) {
3730         List<Type> cl = closureCache.get(t);
3731         if (cl == null) {
3732             Type st = supertype(t);
3733             if (!t.isCompound()) {
3734                 if (st.hasTag(CLASS)) {
3735                     cl = insert(closure(st), t);
3736                 } else if (st.hasTag(TYPEVAR)) {
3737                     cl = closure(st).prepend(t);
3738                 } else {
3739                     cl = List.of(t);
3740                 }
3741             } else {
3742                 cl = closure(supertype(t));
3743             }
3744             for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail)
3745                 cl = union(cl, closure(l.head));
3746             closureCache.put(t, cl);
3747         }
3748         return cl;
3749     }
3750 
3751     /**
3752      * Collect types into a new closure (using a {@code ClosureHolder})
3753      */
3754     public Collector<Type, ClosureHolder, List<Type>> closureCollector(boolean minClosure, BiPredicate<Type, Type> shouldSkip) {
3755         return Collector.of(() -> new ClosureHolder(minClosure, shouldSkip),
3756                 ClosureHolder::add,
3757                 ClosureHolder::merge,
3758                 ClosureHolder::closure);
3759     }
3760     //where
3761         class ClosureHolder {
3762             List<Type> closure;
3763             final boolean minClosure;
3764             final BiPredicate<Type, Type> shouldSkip;
3765 
3766             ClosureHolder(boolean minClosure, BiPredicate<Type, Type> shouldSkip) {
3767                 this.closure = List.nil();
3768                 this.minClosure = minClosure;
3769                 this.shouldSkip = shouldSkip;
3770             }
3771 
3772             void add(Type type) {
3773                 closure = insert(closure, type, shouldSkip);
3774             }
3775 
3776             ClosureHolder merge(ClosureHolder other) {
3777                 closure = union(closure, other.closure, shouldSkip);
3778                 return this;
3779             }
3780 
3781             List<Type> closure() {
3782                 return minClosure ? closureMin(closure) : closure;
3783             }
3784         }
3785 
3786     BiPredicate<Type, Type> basicClosureSkip = (t1, t2) -> t1.tsym == t2.tsym;
3787 
3788     /**
3789      * Insert a type in a closure
3790      */
3791     public List<Type> insert(List<Type> cl, Type t, BiPredicate<Type, Type> shouldSkip) {
3792         if (cl.isEmpty()) {
3793             return cl.prepend(t);
3794         } else if (shouldSkip.test(t, cl.head)) {
3795             return cl;
3796         } else if (t.tsym.precedes(cl.head.tsym, this)) {
3797             return cl.prepend(t);
3798         } else {
3799             // t comes after head, or the two are unrelated
3800             return insert(cl.tail, t, shouldSkip).prepend(cl.head);
3801         }
3802     }
3803 
3804     public List<Type> insert(List<Type> cl, Type t) {
3805         return insert(cl, t, basicClosureSkip);
3806     }
3807 
3808     /**
3809      * Form the union of two closures
3810      */
3811     public List<Type> union(List<Type> cl1, List<Type> cl2, BiPredicate<Type, Type> shouldSkip) {
3812         if (cl1.isEmpty()) {
3813             return cl2;
3814         } else if (cl2.isEmpty()) {
3815             return cl1;
3816         } else if (shouldSkip.test(cl1.head, cl2.head)) {
3817             return union(cl1.tail, cl2.tail, shouldSkip).prepend(cl1.head);
3818         } else if (cl2.head.tsym.precedes(cl1.head.tsym, this)) {
3819             return union(cl1, cl2.tail, shouldSkip).prepend(cl2.head);
3820         } else {
3821             return union(cl1.tail, cl2, shouldSkip).prepend(cl1.head);
3822         }
3823     }
3824 
3825     public List<Type> union(List<Type> cl1, List<Type> cl2) {
3826         return union(cl1, cl2, basicClosureSkip);
3827     }
3828 
3829     /**
3830      * Intersect two closures
3831      */
3832     public List<Type> intersect(List<Type> cl1, List<Type> cl2) {
3833         if (cl1 == cl2)
3834             return cl1;
3835         if (cl1.isEmpty() || cl2.isEmpty())
3836             return List.nil();
3837         if (cl1.head.tsym.precedes(cl2.head.tsym, this))
3838             return intersect(cl1.tail, cl2);
3839         if (cl2.head.tsym.precedes(cl1.head.tsym, this))
3840             return intersect(cl1, cl2.tail);
3841         if (isSameType(cl1.head, cl2.head))
3842             return intersect(cl1.tail, cl2.tail).prepend(cl1.head);
3843         if (cl1.head.tsym == cl2.head.tsym &&
3844             cl1.head.hasTag(CLASS) && cl2.head.hasTag(CLASS)) {
3845             if (cl1.head.isParameterized() && cl2.head.isParameterized()) {
3846                 Type merge = merge(cl1.head,cl2.head);
3847                 return intersect(cl1.tail, cl2.tail).prepend(merge);
3848             }
3849             if (cl1.head.isRaw() || cl2.head.isRaw())
3850                 return intersect(cl1.tail, cl2.tail).prepend(erasure(cl1.head));
3851         }
3852         return intersect(cl1.tail, cl2.tail);
3853     }
3854     // where
3855         class TypePair {
3856             final Type t1;
3857             final Type t2;;
3858 
3859             TypePair(Type t1, Type t2) {
3860                 this.t1 = t1;
3861                 this.t2 = t2;
3862             }
3863             @Override
3864             public int hashCode() {
3865                 return 127 * Types.this.hashCode(t1) + Types.this.hashCode(t2);
3866             }
3867             @Override
3868             public boolean equals(Object obj) {
3869                 return (obj instanceof TypePair typePair)
3870                         && isSameType(t1, typePair.t1)
3871                         && isSameType(t2, typePair.t2);
3872             }
3873         }
3874         Set<TypePair> mergeCache = new HashSet<>();
3875         private Type merge(Type c1, Type c2) {
3876             ClassType class1 = (ClassType) c1;
3877             List<Type> act1 = class1.getTypeArguments();
3878             ClassType class2 = (ClassType) c2;
3879             List<Type> act2 = class2.getTypeArguments();
3880             ListBuffer<Type> merged = new ListBuffer<>();
3881             List<Type> typarams = class1.tsym.type.getTypeArguments();
3882 
3883             while (act1.nonEmpty() && act2.nonEmpty() && typarams.nonEmpty()) {
3884                 if (containsType(act1.head, act2.head)) {
3885                     merged.append(act1.head);
3886                 } else if (containsType(act2.head, act1.head)) {
3887                     merged.append(act2.head);
3888                 } else {
3889                     TypePair pair = new TypePair(c1, c2);
3890                     Type m;
3891                     if (mergeCache.add(pair)) {
3892                         m = new WildcardType(lub(wildUpperBound(act1.head),
3893                                                  wildUpperBound(act2.head)),
3894                                              BoundKind.EXTENDS,
3895                                              syms.boundClass);
3896                         mergeCache.remove(pair);
3897                     } else {
3898                         m = new WildcardType(syms.objectType,
3899                                              BoundKind.UNBOUND,
3900                                              syms.boundClass);
3901                     }
3902                     merged.append(m.withTypeVar(typarams.head));
3903                 }
3904                 act1 = act1.tail;
3905                 act2 = act2.tail;
3906                 typarams = typarams.tail;
3907             }
3908             Assert.check(act1.isEmpty() && act2.isEmpty() && typarams.isEmpty());
3909             // There is no spec detailing how type annotations are to
3910             // be inherited.  So set it to noAnnotations for now
3911             return new ClassType(class1.getEnclosingType(), merged.toList(),
3912                                  class1.tsym, List.nil());
3913         }
3914 
3915     /**
3916      * Return the minimum type of a closure, a compound type if no
3917      * unique minimum exists.
3918      */
3919     private Type compoundMin(List<Type> cl) {
3920         if (cl.isEmpty()) return syms.objectType;
3921         List<Type> compound = closureMin(cl);
3922         if (compound.isEmpty())
3923             return null;
3924         else if (compound.tail.isEmpty())
3925             return compound.head;
3926         else
3927             return makeIntersectionType(compound);
3928     }
3929 
3930     /**
3931      * Return the minimum types of a closure, suitable for computing
3932      * compoundMin or glb.
3933      */
3934     private List<Type> closureMin(List<Type> cl) {
3935         ListBuffer<Type> classes = new ListBuffer<>();
3936         ListBuffer<Type> interfaces = new ListBuffer<>();
3937         Set<Type> toSkip = new HashSet<>();
3938         while (!cl.isEmpty()) {
3939             Type current = cl.head;
3940             boolean keep = !toSkip.contains(current);
3941             if (keep && current.hasTag(TYPEVAR)) {
3942                 // skip lower-bounded variables with a subtype in cl.tail
3943                 for (Type t : cl.tail) {
3944                     if (isSubtypeNoCapture(t, current)) {
3945                         keep = false;
3946                         break;
3947                     }
3948                 }
3949             }
3950             if (keep) {
3951                 if (current.isInterface())
3952                     interfaces.append(current);
3953                 else
3954                     classes.append(current);
3955                 for (Type t : cl.tail) {
3956                     // skip supertypes of 'current' in cl.tail
3957                     if (isSubtypeNoCapture(current, t))
3958                         toSkip.add(t);
3959                 }
3960             }
3961             cl = cl.tail;
3962         }
3963         return classes.appendList(interfaces).toList();
3964     }
3965 
3966     /**
3967      * Return the least upper bound of list of types.  if the lub does
3968      * not exist return null.
3969      */
3970     public Type lub(List<Type> ts) {
3971         return lub(ts.toArray(new Type[ts.length()]));
3972     }
3973 
3974     /**
3975      * Return the least upper bound (lub) of set of types.  If the lub
3976      * does not exist return the type of null (bottom).
3977      */
3978     public Type lub(Type... ts) {
3979         final int UNKNOWN_BOUND = 0;
3980         final int ARRAY_BOUND = 1;
3981         final int CLASS_BOUND = 2;
3982 
3983         int[] kinds = new int[ts.length];
3984 
3985         int boundkind = UNKNOWN_BOUND;
3986         for (int i = 0 ; i < ts.length ; i++) {
3987             Type t = ts[i];
3988             switch (t.getTag()) {
3989             case CLASS:
3990                 boundkind |= kinds[i] = CLASS_BOUND;
3991                 break;
3992             case ARRAY:
3993                 boundkind |= kinds[i] = ARRAY_BOUND;
3994                 break;
3995             case  TYPEVAR:
3996                 do {
3997                     t = t.getUpperBound();
3998                 } while (t.hasTag(TYPEVAR));
3999                 if (t.hasTag(ARRAY)) {
4000                     boundkind |= kinds[i] = ARRAY_BOUND;
4001                 } else {
4002                     boundkind |= kinds[i] = CLASS_BOUND;
4003                 }
4004                 break;
4005             default:
4006                 kinds[i] = UNKNOWN_BOUND;
4007                 if (t.isPrimitive())
4008                     return syms.errType;
4009             }
4010         }
4011         switch (boundkind) {
4012         case 0:
4013             return syms.botType;
4014 
4015         case ARRAY_BOUND:
4016             // calculate lub(A[], B[])
4017             Type[] elements = new Type[ts.length];
4018             for (int i = 0 ; i < ts.length ; i++) {
4019                 Type elem = elements[i] = elemTypeFun.apply(ts[i]);
4020                 if (elem.isPrimitive()) {
4021                     // if a primitive type is found, then return
4022                     // arraySuperType unless all the types are the
4023                     // same
4024                     Type first = ts[0];
4025                     for (int j = 1 ; j < ts.length ; j++) {
4026                         if (!isSameType(first, ts[j])) {
4027                              // lub(int[], B[]) is Cloneable & Serializable
4028                             return arraySuperType();
4029                         }
4030                     }
4031                     // all the array types are the same, return one
4032                     // lub(int[], int[]) is int[]
4033                     return first;
4034                 }
4035             }
4036             // lub(A[], B[]) is lub(A, B)[]
4037             return new ArrayType(lub(elements), syms.arrayClass);
4038 
4039         case CLASS_BOUND:
4040             // calculate lub(A, B)
4041             int startIdx = 0;
4042             for (int i = 0; i < ts.length ; i++) {
4043                 Type t = ts[i];
4044                 if (t.hasTag(CLASS) || t.hasTag(TYPEVAR)) {
4045                     break;
4046                 } else {
4047                     startIdx++;
4048                 }
4049             }
4050             Assert.check(startIdx < ts.length);
4051             //step 1 - compute erased candidate set (EC)
4052             List<Type> cl = erasedSupertypes(ts[startIdx]);
4053             for (int i = startIdx + 1 ; i < ts.length ; i++) {
4054                 Type t = ts[i];
4055                 if (t.hasTag(CLASS) || t.hasTag(TYPEVAR))
4056                     cl = intersect(cl, erasedSupertypes(t));
4057             }
4058             //step 2 - compute minimal erased candidate set (MEC)
4059             List<Type> mec = closureMin(cl);
4060             //step 3 - for each element G in MEC, compute lci(Inv(G))
4061             List<Type> candidates = List.nil();
4062             for (Type erasedSupertype : mec) {
4063                 List<Type> lci = List.of(asSuper(ts[startIdx], erasedSupertype.tsym));
4064                 for (int i = startIdx + 1 ; i < ts.length ; i++) {
4065                     Type superType = asSuper(ts[i], erasedSupertype.tsym);
4066                     lci = intersect(lci, superType != null ? List.of(superType) : List.nil());
4067                 }
4068                 candidates = candidates.appendList(lci);
4069             }
4070             //step 4 - let MEC be { G1, G2 ... Gn }, then we have that
4071             //lub = lci(Inv(G1)) & lci(Inv(G2)) & ... & lci(Inv(Gn))
4072             return compoundMin(candidates);
4073 
4074         default:
4075             // calculate lub(A, B[])
4076             List<Type> classes = List.of(arraySuperType());
4077             for (int i = 0 ; i < ts.length ; i++) {
4078                 if (kinds[i] != ARRAY_BOUND) // Filter out any arrays
4079                     classes = classes.prepend(ts[i]);
4080             }
4081             // lub(A, B[]) is lub(A, arraySuperType)
4082             return lub(classes);
4083         }
4084     }
4085     // where
4086         List<Type> erasedSupertypes(Type t) {
4087             ListBuffer<Type> buf = new ListBuffer<>();
4088             for (Type sup : closure(t)) {
4089                 if (sup.hasTag(TYPEVAR)) {
4090                     buf.append(sup);
4091                 } else {
4092                     buf.append(erasure(sup));
4093                 }
4094             }
4095             return buf.toList();
4096         }
4097 
4098         private Type arraySuperType;
4099         private Type arraySuperType() {
4100             // initialized lazily to avoid problems during compiler startup
4101             if (arraySuperType == null) {
4102                 // JLS 10.8: all arrays implement Cloneable and Serializable.
4103                 arraySuperType = makeIntersectionType(List.of(syms.serializableType,
4104                         syms.cloneableType), true);
4105             }
4106             return arraySuperType;
4107         }
4108     // </editor-fold>
4109 
4110     // <editor-fold defaultstate="collapsed" desc="Greatest lower bound">
4111     public Type glb(List<Type> ts) {
4112         Type t1 = ts.head;
4113         for (Type t2 : ts.tail) {
4114             if (t1.isErroneous())
4115                 return t1;
4116             t1 = glb(t1, t2);
4117         }
4118         return t1;
4119     }
4120     //where
4121     public Type glb(Type t, Type s) {
4122         if (s == null)
4123             return t;
4124         else if (t.isPrimitive() || s.isPrimitive())
4125             return syms.errType;
4126         else if (isSubtypeNoCapture(t, s))
4127             return t;
4128         else if (isSubtypeNoCapture(s, t))
4129             return s;
4130 
4131         List<Type> closure = union(closure(t), closure(s));
4132         return glbFlattened(closure, t);
4133     }
4134     //where
4135     /**
4136      * Perform glb for a list of non-primitive, non-error, non-compound types;
4137      * redundant elements are removed.  Bounds should be ordered according to
4138      * {@link Symbol#precedes(TypeSymbol,Types)}.
4139      *
4140      * @param flatBounds List of type to glb
4141      * @param errT Original type to use if the result is an error type
4142      */
4143     private Type glbFlattened(List<Type> flatBounds, Type errT) {
4144         List<Type> bounds = closureMin(flatBounds);
4145 
4146         if (bounds.isEmpty()) {             // length == 0
4147             return syms.objectType;
4148         } else if (bounds.tail.isEmpty()) { // length == 1
4149             return bounds.head;
4150         } else {                            // length > 1
4151             int classCount = 0;
4152             List<Type> cvars = List.nil();
4153             List<Type> lowers = List.nil();
4154             for (Type bound : bounds) {
4155                 if (!bound.isInterface()) {
4156                     classCount++;
4157                     Type lower = cvarLowerBound(bound);
4158                     if (bound != lower && !lower.hasTag(BOT)) {
4159                         cvars = cvars.append(bound);
4160                         lowers = lowers.append(lower);
4161                     }
4162                 }
4163             }
4164             if (classCount > 1) {
4165                 if (lowers.isEmpty()) {
4166                     return createErrorType(errT);
4167                 } else {
4168                     // try again with lower bounds included instead of capture variables
4169                     List<Type> newBounds = bounds.diff(cvars).appendList(lowers);
4170                     return glb(newBounds);
4171                 }
4172             }
4173         }
4174         return makeIntersectionType(bounds);
4175     }
4176     // </editor-fold>
4177 
4178     // <editor-fold defaultstate="collapsed" desc="hashCode">
4179     /**
4180      * Compute a hash code on a type.
4181      */
4182     public int hashCode(Type t) {
4183         return hashCode(t, false);
4184     }
4185 
4186     public int hashCode(Type t, boolean strict) {
4187         return strict ?
4188                 hashCodeStrictVisitor.visit(t) :
4189                 hashCodeVisitor.visit(t);
4190     }
4191     // where
4192         private static final HashCodeVisitor hashCodeVisitor = new HashCodeVisitor();
4193         private static final HashCodeVisitor hashCodeStrictVisitor = new HashCodeVisitor() {
4194             @Override
4195             public Integer visitTypeVar(TypeVar t, Void ignored) {
4196                 return System.identityHashCode(t);
4197             }
4198         };
4199 
4200         private static class HashCodeVisitor extends UnaryVisitor<Integer> {
4201             public Integer visitType(Type t, Void ignored) {
4202                 return t.getTag().ordinal();
4203             }
4204 
4205             @Override
4206             public Integer visitClassType(ClassType t, Void ignored) {
4207                 int result = visit(t.getEnclosingType());
4208                 result *= 127;
4209                 result += t.tsym.flatName().hashCode();
4210                 for (Type s : t.getTypeArguments()) {
4211                     result *= 127;
4212                     result += visit(s);
4213                 }
4214                 return result;
4215             }
4216 
4217             @Override
4218             public Integer visitMethodType(MethodType t, Void ignored) {
4219                 int h = METHOD.ordinal();
4220                 for (List<Type> thisargs = t.argtypes;
4221                      thisargs.tail != null;
4222                      thisargs = thisargs.tail)
4223                     h = (h << 5) + visit(thisargs.head);
4224                 return (h << 5) + visit(t.restype);
4225             }
4226 
4227             @Override
4228             public Integer visitWildcardType(WildcardType t, Void ignored) {
4229                 int result = t.kind.hashCode();
4230                 if (t.type != null) {
4231                     result *= 127;
4232                     result += visit(t.type);
4233                 }
4234                 return result;
4235             }
4236 
4237             @Override
4238             public Integer visitArrayType(ArrayType t, Void ignored) {
4239                 return visit(t.elemtype) + 12;
4240             }
4241 
4242             @Override
4243             public Integer visitTypeVar(TypeVar t, Void ignored) {
4244                 return System.identityHashCode(t);
4245             }
4246 
4247             @Override
4248             public Integer visitUndetVar(UndetVar t, Void ignored) {
4249                 return System.identityHashCode(t);
4250             }
4251 
4252             @Override
4253             public Integer visitErrorType(ErrorType t, Void ignored) {
4254                 return 0;
4255             }
4256         }
4257     // </editor-fold>
4258 
4259     // <editor-fold defaultstate="collapsed" desc="Return-Type-Substitutable">
4260     /**
4261      * Does t have a result that is a subtype of the result type of s,
4262      * suitable for covariant returns?  It is assumed that both types
4263      * are (possibly polymorphic) method types.  Monomorphic method
4264      * types are handled in the obvious way.  Polymorphic method types
4265      * require renaming all type variables of one to corresponding
4266      * type variables in the other, where correspondence is by
4267      * position in the type parameter list. */
4268     public boolean resultSubtype(Type t, Type s, Warner warner) {
4269         List<Type> tvars = t.getTypeArguments();
4270         List<Type> svars = s.getTypeArguments();
4271         Type tres = t.getReturnType();
4272         Type sres = subst(s.getReturnType(), svars, tvars);
4273         return covariantReturnType(tres, sres, warner);
4274     }
4275 
4276     /**
4277      * Return-Type-Substitutable.
4278      * @jls 8.4.5 Method Result
4279      */
4280     public boolean returnTypeSubstitutable(Type r1, Type r2) {
4281         if (hasSameArgs(r1, r2))
4282             return resultSubtype(r1, r2, noWarnings);
4283         else
4284             return covariantReturnType(r1.getReturnType(),
4285                                        erasure(r2.getReturnType()),
4286                                        noWarnings);
4287     }
4288 
4289     public boolean returnTypeSubstitutable(Type r1,
4290                                            Type r2, Type r2res,
4291                                            Warner warner) {
4292         if (isSameType(r1.getReturnType(), r2res))
4293             return true;
4294         if (r1.getReturnType().isPrimitive() || r2res.isPrimitive())
4295             return false;
4296 
4297         if (hasSameArgs(r1, r2))
4298             return covariantReturnType(r1.getReturnType(), r2res, warner);
4299         if (isSubtypeUnchecked(r1.getReturnType(), r2res, warner))
4300             return true;
4301         if (!isSubtype(r1.getReturnType(), erasure(r2res)))
4302             return false;
4303         warner.warn(LintCategory.UNCHECKED);
4304         return true;
4305     }
4306 
4307     /**
4308      * Is t an appropriate return type in an overrider for a
4309      * method that returns s?
4310      */
4311     public boolean covariantReturnType(Type t, Type s, Warner warner) {
4312         return
4313             isSameType(t, s) ||
4314             !t.isPrimitive() &&
4315             !s.isPrimitive() &&
4316             isAssignable(t, s, warner);
4317     }
4318     // </editor-fold>
4319 
4320     // <editor-fold defaultstate="collapsed" desc="Box/unbox support">
4321     /**
4322      * Return the class that boxes the given primitive.
4323      */
4324     public ClassSymbol boxedClass(Type t) {
4325         return syms.enterClass(syms.java_base, syms.boxedName[t.getTag().ordinal()]);
4326     }
4327 
4328     /**
4329      * Return the boxed type if 't' is primitive, otherwise return 't' itself.
4330      */
4331     public Type boxedTypeOrType(Type t) {
4332         return t.isPrimitive() ?
4333             boxedClass(t).type :
4334             t;
4335     }
4336 
4337     /**
4338      * Return the primitive type corresponding to a boxed type.
4339      */
4340     public Type unboxedType(Type t) {
4341         if (t.hasTag(ERROR))
4342             return Type.noType;
4343         for (int i=0; i<syms.boxedName.length; i++) {
4344             Name box = syms.boxedName[i];
4345             if (box != null &&
4346                 asSuper(t, syms.enterClass(syms.java_base, box)) != null)
4347                 return syms.typeOfTag[i];
4348         }
4349         return Type.noType;
4350     }
4351 
4352     /**
4353      * Return the unboxed type if 't' is a boxed class, otherwise return 't' itself.
4354      */
4355     public Type unboxedTypeOrType(Type t) {
4356         Type unboxedType = unboxedType(t);
4357         return unboxedType.hasTag(NONE) ? t : unboxedType;
4358     }
4359     // </editor-fold>
4360 
4361     // <editor-fold defaultstate="collapsed" desc="Capture conversion">
4362     /*
4363      * JLS 5.1.10 Capture Conversion:
4364      *
4365      * Let G name a generic type declaration with n formal type
4366      * parameters A1 ... An with corresponding bounds U1 ... Un. There
4367      * exists a capture conversion from G<T1 ... Tn> to G<S1 ... Sn>,
4368      * where, for 1 <= i <= n:
4369      *
4370      * + If Ti is a wildcard type argument (4.5.1) of the form ? then
4371      *   Si is a fresh type variable whose upper bound is
4372      *   Ui[A1 := S1, ..., An := Sn] and whose lower bound is the null
4373      *   type.
4374      *
4375      * + If Ti is a wildcard type argument of the form ? extends Bi,
4376      *   then Si is a fresh type variable whose upper bound is
4377      *   glb(Bi, Ui[A1 := S1, ..., An := Sn]) and whose lower bound is
4378      *   the null type, where glb(V1,... ,Vm) is V1 & ... & Vm. It is
4379      *   a compile-time error if for any two classes (not interfaces)
4380      *   Vi and Vj,Vi is not a subclass of Vj or vice versa.
4381      *
4382      * + If Ti is a wildcard type argument of the form ? super Bi,
4383      *   then Si is a fresh type variable whose upper bound is
4384      *   Ui[A1 := S1, ..., An := Sn] and whose lower bound is Bi.
4385      *
4386      * + Otherwise, Si = Ti.
4387      *
4388      * Capture conversion on any type other than a parameterized type
4389      * (4.5) acts as an identity conversion (5.1.1). Capture
4390      * conversions never require a special action at run time and
4391      * therefore never throw an exception at run time.
4392      *
4393      * Capture conversion is not applied recursively.
4394      */
4395     /**
4396      * Capture conversion as specified by the JLS.
4397      */
4398 
4399     public List<Type> capture(List<Type> ts) {
4400         List<Type> buf = List.nil();
4401         for (Type t : ts) {
4402             buf = buf.prepend(capture(t));
4403         }
4404         return buf.reverse();
4405     }
4406 
4407     public Type capture(Type t) {
4408         if (!t.hasTag(CLASS)) {
4409             return t;
4410         }
4411         if (t.getEnclosingType() != Type.noType) {
4412             Type capturedEncl = capture(t.getEnclosingType());
4413             if (capturedEncl != t.getEnclosingType()) {
4414                 Type type1 = memberType(capturedEncl, t.tsym);
4415                 t = subst(type1, t.tsym.type.getTypeArguments(), t.getTypeArguments());
4416             }
4417         }
4418         ClassType cls = (ClassType)t;
4419         if (cls.isRaw() || !cls.isParameterized())
4420             return cls;
4421 
4422         ClassType G = (ClassType)cls.asElement().asType();
4423         List<Type> A = G.getTypeArguments();
4424         List<Type> T = cls.getTypeArguments();
4425         List<Type> S = freshTypeVariables(T);
4426 
4427         List<Type> currentA = A;
4428         List<Type> currentT = T;
4429         List<Type> currentS = S;
4430         boolean captured = false;
4431         while (!currentA.isEmpty() &&
4432                !currentT.isEmpty() &&
4433                !currentS.isEmpty()) {
4434             if (currentS.head != currentT.head) {
4435                 captured = true;
4436                 WildcardType Ti = (WildcardType)currentT.head;
4437                 Type Ui = currentA.head.getUpperBound();
4438                 CapturedType Si = (CapturedType)currentS.head;
4439                 if (Ui == null)
4440                     Ui = syms.objectType;
4441                 switch (Ti.kind) {
4442                 case UNBOUND:
4443                     Si.setUpperBound( subst(Ui, A, S) );
4444                     Si.lower = syms.botType;
4445                     break;
4446                 case EXTENDS:
4447                     Si.setUpperBound( glb(Ti.getExtendsBound(), subst(Ui, A, S)) );
4448                     Si.lower = syms.botType;
4449                     break;
4450                 case SUPER:
4451                     Si.setUpperBound( subst(Ui, A, S) );
4452                     Si.lower = Ti.getSuperBound();
4453                     break;
4454                 }
4455                 Type tmpBound = Si.getUpperBound().hasTag(UNDETVAR) ? ((UndetVar)Si.getUpperBound()).qtype : Si.getUpperBound();
4456                 Type tmpLower = Si.lower.hasTag(UNDETVAR) ? ((UndetVar)Si.lower).qtype : Si.lower;
4457                 if (!Si.getUpperBound().hasTag(ERROR) &&
4458                     !Si.lower.hasTag(ERROR) &&
4459                     isSameType(tmpBound, tmpLower)) {
4460                     currentS.head = Si.getUpperBound();
4461                 }
4462             }
4463             currentA = currentA.tail;
4464             currentT = currentT.tail;
4465             currentS = currentS.tail;
4466         }
4467         if (!currentA.isEmpty() || !currentT.isEmpty() || !currentS.isEmpty())
4468             return erasure(t); // some "rare" type involved
4469 
4470         if (captured)
4471             return new ClassType(cls.getEnclosingType(), S, cls.tsym,
4472                                  cls.getMetadata());
4473         else
4474             return t;
4475     }
4476     // where
4477         public List<Type> freshTypeVariables(List<Type> types) {
4478             ListBuffer<Type> result = new ListBuffer<>();
4479             for (Type t : types) {
4480                 if (t.hasTag(WILDCARD)) {
4481                     Type bound = ((WildcardType)t).getExtendsBound();
4482                     if (bound == null)
4483                         bound = syms.objectType;
4484                     result.append(new CapturedType(capturedName,
4485                                                    syms.noSymbol,
4486                                                    bound,
4487                                                    syms.botType,
4488                                                    (WildcardType)t));
4489                 } else {
4490                     result.append(t);
4491                 }
4492             }
4493             return result.toList();
4494         }
4495     // </editor-fold>
4496 
4497     // <editor-fold defaultstate="collapsed" desc="Internal utility methods">
4498     private boolean sideCast(Type from, Type to, Warner warn) {
4499         // We are casting from type $from$ to type $to$, which are
4500         // non-final unrelated types.  This method
4501         // tries to reject a cast by transferring type parameters
4502         // from $to$ to $from$ by common superinterfaces.
4503         boolean reverse = false;
4504         Type target = to;
4505         if ((to.tsym.flags() & INTERFACE) == 0) {
4506             Assert.check((from.tsym.flags() & INTERFACE) != 0);
4507             reverse = true;
4508             to = from;
4509             from = target;
4510         }
4511         List<Type> commonSupers = superClosure(to, erasure(from));
4512         boolean giveWarning = commonSupers.isEmpty();
4513         // The arguments to the supers could be unified here to
4514         // get a more accurate analysis
4515         while (commonSupers.nonEmpty()) {
4516             Type t1 = asSuper(from, commonSupers.head.tsym);
4517             Type t2 = commonSupers.head; // same as asSuper(to, commonSupers.head.tsym);
4518             if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
4519                 return false;
4520             giveWarning = giveWarning || (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2));
4521             commonSupers = commonSupers.tail;
4522         }
4523         if (giveWarning && !isReifiable(reverse ? from : to))
4524             warn.warn(LintCategory.UNCHECKED);
4525         return true;
4526     }
4527 
4528     private boolean sideCastFinal(Type from, Type to, Warner warn) {
4529         // We are casting from type $from$ to type $to$, which are
4530         // unrelated types one of which is final and the other of
4531         // which is an interface.  This method
4532         // tries to reject a cast by transferring type parameters
4533         // from the final class to the interface.
4534         boolean reverse = false;
4535         Type target = to;
4536         if ((to.tsym.flags() & INTERFACE) == 0) {
4537             Assert.check((from.tsym.flags() & INTERFACE) != 0);
4538             reverse = true;
4539             to = from;
4540             from = target;
4541         }
4542         Assert.check((from.tsym.flags() & FINAL) != 0);
4543         Type t1 = asSuper(from, to.tsym);
4544         if (t1 == null) return false;
4545         Type t2 = to;
4546         if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
4547             return false;
4548         if (!isReifiable(target) &&
4549             (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2)))
4550             warn.warn(LintCategory.UNCHECKED);
4551         return true;
4552     }
4553 
4554     private boolean giveWarning(Type from, Type to) {
4555         List<Type> bounds = to.isCompound() ?
4556                 directSupertypes(to) : List.of(to);
4557         for (Type b : bounds) {
4558             Type subFrom = asSub(from, b.tsym);
4559             if (b.isParameterized() &&
4560                     (!(isUnbounded(b) ||
4561                     isSubtype(from, b) ||
4562                     ((subFrom != null) && containsType(b.allparams(), subFrom.allparams()))))) {
4563                 return true;
4564             }
4565         }
4566         return false;
4567     }
4568 
4569     private List<Type> superClosure(Type t, Type s) {
4570         List<Type> cl = List.nil();
4571         for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
4572             if (isSubtype(s, erasure(l.head))) {
4573                 cl = insert(cl, l.head);
4574             } else {
4575                 cl = union(cl, superClosure(l.head, s));
4576             }
4577         }
4578         return cl;
4579     }
4580 
4581     private boolean containsTypeEquivalent(Type t, Type s) {
4582         return isSameType(t, s) || // shortcut
4583             containsType(t, s) && containsType(s, t);
4584     }
4585 
4586     // <editor-fold defaultstate="collapsed" desc="adapt">
4587     /**
4588      * Adapt a type by computing a substitution which maps a source
4589      * type to a target type.
4590      *
4591      * @param source    the source type
4592      * @param target    the target type
4593      * @param from      the type variables of the computed substitution
4594      * @param to        the types of the computed substitution.
4595      */
4596     public void adapt(Type source,
4597                        Type target,
4598                        ListBuffer<Type> from,
4599                        ListBuffer<Type> to) throws AdaptFailure {
4600         new Adapter(from, to).adapt(source, target);
4601     }
4602 
4603     class Adapter extends SimpleVisitor<Void, Type> {
4604 
4605         ListBuffer<Type> from;
4606         ListBuffer<Type> to;
4607         Map<Symbol,Type> mapping;
4608 
4609         Adapter(ListBuffer<Type> from, ListBuffer<Type> to) {
4610             this.from = from;
4611             this.to = to;
4612             mapping = new HashMap<>();
4613         }
4614 
4615         public void adapt(Type source, Type target) throws AdaptFailure {
4616             visit(source, target);
4617             List<Type> fromList = from.toList();
4618             List<Type> toList = to.toList();
4619             while (!fromList.isEmpty()) {
4620                 Type val = mapping.get(fromList.head.tsym);
4621                 if (toList.head != val)
4622                     toList.head = val;
4623                 fromList = fromList.tail;
4624                 toList = toList.tail;
4625             }
4626         }
4627 
4628         @Override
4629         public Void visitClassType(ClassType source, Type target) throws AdaptFailure {
4630             if (target.hasTag(CLASS))
4631                 adaptRecursive(source.allparams(), target.allparams());
4632             return null;
4633         }
4634 
4635         @Override
4636         public Void visitArrayType(ArrayType source, Type target) throws AdaptFailure {
4637             if (target.hasTag(ARRAY))
4638                 adaptRecursive(elemtype(source), elemtype(target));
4639             return null;
4640         }
4641 
4642         @Override
4643         public Void visitWildcardType(WildcardType source, Type target) throws AdaptFailure {
4644             if (source.isExtendsBound())
4645                 adaptRecursive(wildUpperBound(source), wildUpperBound(target));
4646             else if (source.isSuperBound())
4647                 adaptRecursive(wildLowerBound(source), wildLowerBound(target));
4648             return null;
4649         }
4650 
4651         @Override
4652         public Void visitTypeVar(TypeVar source, Type target) throws AdaptFailure {
4653             // Check to see if there is
4654             // already a mapping for $source$, in which case
4655             // the old mapping will be merged with the new
4656             Type val = mapping.get(source.tsym);
4657             if (val != null) {
4658                 if (val.isSuperBound() && target.isSuperBound()) {
4659                     val = isSubtype(wildLowerBound(val), wildLowerBound(target))
4660                         ? target : val;
4661                 } else if (val.isExtendsBound() && target.isExtendsBound()) {
4662                     val = isSubtype(wildUpperBound(val), wildUpperBound(target))
4663                         ? val : target;
4664                 } else if (!isSameType(val, target)) {
4665                     throw new AdaptFailure();
4666                 }
4667             } else {
4668                 val = target;
4669                 from.append(source);
4670                 to.append(target);
4671             }
4672             mapping.put(source.tsym, val);
4673             return null;
4674         }
4675 
4676         @Override
4677         public Void visitType(Type source, Type target) {
4678             return null;
4679         }
4680 
4681         private Set<TypePair> cache = new HashSet<>();
4682 
4683         private void adaptRecursive(Type source, Type target) {
4684             TypePair pair = new TypePair(source, target);
4685             if (cache.add(pair)) {
4686                 try {
4687                     visit(source, target);
4688                 } finally {
4689                     cache.remove(pair);
4690                 }
4691             }
4692         }
4693 
4694         private void adaptRecursive(List<Type> source, List<Type> target) {
4695             if (source.length() == target.length()) {
4696                 while (source.nonEmpty()) {
4697                     adaptRecursive(source.head, target.head);
4698                     source = source.tail;
4699                     target = target.tail;
4700                 }
4701             }
4702         }
4703     }
4704 
4705     public static class AdaptFailure extends RuntimeException {
4706         static final long serialVersionUID = -7490231548272701566L;
4707     }
4708 
4709     private void adaptSelf(Type t,
4710                            ListBuffer<Type> from,
4711                            ListBuffer<Type> to) {
4712         try {
4713             //if (t.tsym.type != t)
4714                 adapt(t.tsym.type, t, from, to);
4715         } catch (AdaptFailure ex) {
4716             // Adapt should never fail calculating a mapping from
4717             // t.tsym.type to t as there can be no merge problem.
4718             throw new AssertionError(ex);
4719         }
4720     }
4721     // </editor-fold>
4722 
4723     /**
4724      * Rewrite all type variables (universal quantifiers) in the given
4725      * type to wildcards (existential quantifiers).  This is used to
4726      * determine if a cast is allowed.  For example, if high is true
4727      * and {@code T <: Number}, then {@code List<T>} is rewritten to
4728      * {@code List<?  extends Number>}.  Since {@code List<Integer> <:
4729      * List<? extends Number>} a {@code List<T>} can be cast to {@code
4730      * List<Integer>} with a warning.
4731      * @param t a type
4732      * @param high if true return an upper bound; otherwise a lower
4733      * bound
4734      * @param rewriteTypeVars only rewrite captured wildcards if false;
4735      * otherwise rewrite all type variables
4736      * @return the type rewritten with wildcards (existential
4737      * quantifiers) only
4738      */
4739     private Type rewriteQuantifiers(Type t, boolean high, boolean rewriteTypeVars) {
4740         return new Rewriter(high, rewriteTypeVars).visit(t);
4741     }
4742 
4743     class Rewriter extends UnaryVisitor<Type> {
4744 
4745         boolean high;
4746         boolean rewriteTypeVars;
4747 
4748         Rewriter(boolean high, boolean rewriteTypeVars) {
4749             this.high = high;
4750             this.rewriteTypeVars = rewriteTypeVars;
4751         }
4752 
4753         @Override
4754         public Type visitClassType(ClassType t, Void s) {
4755             ListBuffer<Type> rewritten = new ListBuffer<>();
4756             boolean changed = false;
4757             for (Type arg : t.allparams()) {
4758                 Type bound = visit(arg);
4759                 if (arg != bound) {
4760                     changed = true;
4761                 }
4762                 rewritten.append(bound);
4763             }
4764             if (changed)
4765                 return subst(t.tsym.type,
4766                         t.tsym.type.allparams(),
4767                         rewritten.toList());
4768             else
4769                 return t;
4770         }
4771 
4772         public Type visitType(Type t, Void s) {
4773             return t;
4774         }
4775 
4776         @Override
4777         public Type visitCapturedType(CapturedType t, Void s) {
4778             Type w_bound = t.wildcard.type;
4779             Type bound = w_bound.contains(t) ?
4780                         erasure(w_bound) :
4781                         visit(w_bound);
4782             return rewriteAsWildcardType(visit(bound), t.wildcard.bound, t.wildcard.kind);
4783         }
4784 
4785         @Override
4786         public Type visitTypeVar(TypeVar t, Void s) {
4787             if (rewriteTypeVars) {
4788                 Type bound = t.getUpperBound().contains(t) ?
4789                         erasure(t.getUpperBound()) :
4790                         visit(t.getUpperBound());
4791                 return rewriteAsWildcardType(bound, t, EXTENDS);
4792             } else {
4793                 return t;
4794             }
4795         }
4796 
4797         @Override
4798         public Type visitWildcardType(WildcardType t, Void s) {
4799             Type bound2 = visit(t.type);
4800             return t.type == bound2 ? t : rewriteAsWildcardType(bound2, t.bound, t.kind);
4801         }
4802 
4803         private Type rewriteAsWildcardType(Type bound, TypeVar formal, BoundKind bk) {
4804             switch (bk) {
4805                case EXTENDS: return high ?
4806                        makeExtendsWildcard(B(bound), formal) :
4807                        makeExtendsWildcard(syms.objectType, formal);
4808                case SUPER: return high ?
4809                        makeSuperWildcard(syms.botType, formal) :
4810                        makeSuperWildcard(B(bound), formal);
4811                case UNBOUND: return makeExtendsWildcard(syms.objectType, formal);
4812                default:
4813                    Assert.error("Invalid bound kind " + bk);
4814                    return null;
4815             }
4816         }
4817 
4818         Type B(Type t) {
4819             while (t.hasTag(WILDCARD)) {
4820                 WildcardType w = (WildcardType)t;
4821                 t = high ?
4822                     w.getExtendsBound() :
4823                     w.getSuperBound();
4824                 if (t == null) {
4825                     t = high ? syms.objectType : syms.botType;
4826                 }
4827             }
4828             return t;
4829         }
4830     }
4831 
4832 
4833     /**
4834      * Create a wildcard with the given upper (extends) bound; create
4835      * an unbounded wildcard if bound is Object.
4836      *
4837      * @param bound the upper bound
4838      * @param formal the formal type parameter that will be
4839      * substituted by the wildcard
4840      */
4841     private WildcardType makeExtendsWildcard(Type bound, TypeVar formal) {
4842         if (bound == syms.objectType) {
4843             return new WildcardType(syms.objectType,
4844                                     BoundKind.UNBOUND,
4845                                     syms.boundClass,
4846                                     formal);
4847         } else {
4848             return new WildcardType(bound,
4849                                     BoundKind.EXTENDS,
4850                                     syms.boundClass,
4851                                     formal);
4852         }
4853     }
4854 
4855     /**
4856      * Create a wildcard with the given lower (super) bound; create an
4857      * unbounded wildcard if bound is bottom (type of {@code null}).
4858      *
4859      * @param bound the lower bound
4860      * @param formal the formal type parameter that will be
4861      * substituted by the wildcard
4862      */
4863     private WildcardType makeSuperWildcard(Type bound, TypeVar formal) {
4864         if (bound.hasTag(BOT)) {
4865             return new WildcardType(syms.objectType,
4866                                     BoundKind.UNBOUND,
4867                                     syms.boundClass,
4868                                     formal);
4869         } else {
4870             return new WildcardType(bound,
4871                                     BoundKind.SUPER,
4872                                     syms.boundClass,
4873                                     formal);
4874         }
4875     }
4876 
4877     /**
4878      * A wrapper for a type that allows use in sets.
4879      */
4880     public static class UniqueType {
4881         public final Type type;
4882         final Types types;
4883         private boolean encodeTypeSig;
4884 
4885         public UniqueType(Type type, Types types, boolean encodeTypeSig) {
4886             this.type = type;
4887             this.types = types;
4888             this.encodeTypeSig = encodeTypeSig;
4889         }
4890 
4891         public UniqueType(Type type, Types types) {
4892             this(type, types, true);
4893         }
4894 
4895         public int hashCode() {
4896             return types.hashCode(type);
4897         }
4898 
4899         public boolean equals(Object obj) {
4900             return (obj instanceof UniqueType uniqueType) &&
4901                     types.isSameType(type, uniqueType.type);
4902         }
4903 
4904         public boolean encodeTypeSig() {
4905             return encodeTypeSig;
4906         }
4907 
4908         public String toString() {
4909             return type.toString();
4910         }
4911 
4912     }
4913     // </editor-fold>
4914 
4915     // <editor-fold defaultstate="collapsed" desc="Visitors">
4916     /**
4917      * A default visitor for types.  All visitor methods except
4918      * visitType are implemented by delegating to visitType.  Concrete
4919      * subclasses must provide an implementation of visitType and can
4920      * override other methods as needed.
4921      *
4922      * @param <R> the return type of the operation implemented by this
4923      * visitor; use Void if no return type is needed.
4924      * @param <S> the type of the second argument (the first being the
4925      * type itself) of the operation implemented by this visitor; use
4926      * Void if a second argument is not needed.
4927      */
4928     public abstract static class DefaultTypeVisitor<R,S> implements Type.Visitor<R,S> {
4929         public final R visit(Type t, S s)               { return t.accept(this, s); }
4930         public R visitClassType(ClassType t, S s)       { return visitType(t, s); }
4931         public R visitWildcardType(WildcardType t, S s) { return visitType(t, s); }
4932         public R visitArrayType(ArrayType t, S s)       { return visitType(t, s); }
4933         public R visitMethodType(MethodType t, S s)     { return visitType(t, s); }
4934         public R visitPackageType(PackageType t, S s)   { return visitType(t, s); }
4935         public R visitModuleType(ModuleType t, S s)     { return visitType(t, s); }
4936         public R visitTypeVar(TypeVar t, S s)           { return visitType(t, s); }
4937         public R visitCapturedType(CapturedType t, S s) { return visitType(t, s); }
4938         public R visitForAll(ForAll t, S s)             { return visitType(t, s); }
4939         public R visitUndetVar(UndetVar t, S s)         { return visitType(t, s); }
4940         public R visitErrorType(ErrorType t, S s)       { return visitType(t, s); }
4941     }
4942 
4943     /**
4944      * A default visitor for symbols.  All visitor methods except
4945      * visitSymbol are implemented by delegating to visitSymbol.  Concrete
4946      * subclasses must provide an implementation of visitSymbol and can
4947      * override other methods as needed.
4948      *
4949      * @param <R> the return type of the operation implemented by this
4950      * visitor; use Void if no return type is needed.
4951      * @param <S> the type of the second argument (the first being the
4952      * symbol itself) of the operation implemented by this visitor; use
4953      * Void if a second argument is not needed.
4954      */
4955     public abstract static class DefaultSymbolVisitor<R,S> implements Symbol.Visitor<R,S> {
4956         public final R visit(Symbol s, S arg)                   { return s.accept(this, arg); }
4957         public R visitClassSymbol(ClassSymbol s, S arg)         { return visitSymbol(s, arg); }
4958         public R visitMethodSymbol(MethodSymbol s, S arg)       { return visitSymbol(s, arg); }
4959         public R visitOperatorSymbol(OperatorSymbol s, S arg)   { return visitSymbol(s, arg); }
4960         public R visitPackageSymbol(PackageSymbol s, S arg)     { return visitSymbol(s, arg); }
4961         public R visitTypeSymbol(TypeSymbol s, S arg)           { return visitSymbol(s, arg); }
4962         public R visitVarSymbol(VarSymbol s, S arg)             { return visitSymbol(s, arg); }
4963     }
4964 
4965     /**
4966      * A <em>simple</em> visitor for types.  This visitor is simple as
4967      * captured wildcards, for-all types (generic methods), and
4968      * undetermined type variables (part of inference) are hidden.
4969      * Captured wildcards are hidden by treating them as type
4970      * variables and the rest are hidden by visiting their qtypes.
4971      *
4972      * @param <R> the return type of the operation implemented by this
4973      * visitor; use Void if no return type is needed.
4974      * @param <S> the type of the second argument (the first being the
4975      * type itself) of the operation implemented by this visitor; use
4976      * Void if a second argument is not needed.
4977      */
4978     public abstract static class SimpleVisitor<R,S> extends DefaultTypeVisitor<R,S> {
4979         @Override
4980         public R visitCapturedType(CapturedType t, S s) {
4981             return visitTypeVar(t, s);
4982         }
4983         @Override
4984         public R visitForAll(ForAll t, S s) {
4985             return visit(t.qtype, s);
4986         }
4987         @Override
4988         public R visitUndetVar(UndetVar t, S s) {
4989             return visit(t.qtype, s);
4990         }
4991     }
4992 
4993     /**
4994      * A plain relation on types.  That is a 2-ary function on the
4995      * form Type&nbsp;&times;&nbsp;Type&nbsp;&rarr;&nbsp;Boolean.
4996      * <!-- In plain text: Type x Type -> Boolean -->
4997      */
4998     public abstract static class TypeRelation extends SimpleVisitor<Boolean,Type> {}
4999 
5000     /**
5001      * A convenience visitor for implementing operations that only
5002      * require one argument (the type itself), that is, unary
5003      * operations.
5004      *
5005      * @param <R> the return type of the operation implemented by this
5006      * visitor; use Void if no return type is needed.
5007      */
5008     public abstract static class UnaryVisitor<R> extends SimpleVisitor<R,Void> {
5009         public final R visit(Type t) { return t.accept(this, null); }
5010     }
5011 
5012     /**
5013      * A visitor for implementing a mapping from types to types.  The
5014      * default behavior of this class is to implement the identity
5015      * mapping (mapping a type to itself).  This can be overridden in
5016      * subclasses.
5017      *
5018      * @param <S> the type of the second argument (the first being the
5019      * type itself) of this mapping; use Void if a second argument is
5020      * not needed.
5021      */
5022     public static class MapVisitor<S> extends DefaultTypeVisitor<Type,S> {
5023         public final Type visit(Type t) { return t.accept(this, null); }
5024         public Type visitType(Type t, S s) { return t; }
5025     }
5026 
5027     /**
5028      * An abstract class for mappings from types to types (see {@link Type#map(TypeMapping)}.
5029      * This class implements the functional interface {@code Function}, that allows it to be used
5030      * fluently in stream-like processing.
5031      */
5032     public static class TypeMapping<S> extends MapVisitor<S> implements Function<Type, Type> {
5033         @Override
5034         public Type apply(Type type) { return visit(type); }
5035 
5036         List<Type> visit(List<Type> ts, S s) {
5037             return ts.map(t -> visit(t, s));
5038         }
5039 
5040         @Override
5041         public Type visitCapturedType(CapturedType t, S s) {
5042             return visitTypeVar(t, s);
5043         }
5044     }
5045     // </editor-fold>
5046 
5047 
5048     // <editor-fold defaultstate="collapsed" desc="Annotation support">
5049 
5050     public RetentionPolicy getRetention(Attribute.Compound a) {
5051         return getRetention(a.type.tsym);
5052     }
5053 
5054     public RetentionPolicy getRetention(TypeSymbol sym) {
5055         RetentionPolicy vis = RetentionPolicy.CLASS; // the default
5056         Attribute.Compound c = sym.attribute(syms.retentionType.tsym);
5057         if (c != null) {
5058             Attribute value = c.member(names.value);
5059             if (value != null && value instanceof Attribute.Enum attributeEnum) {
5060                 Name levelName = attributeEnum.value.name;
5061                 if (levelName == names.SOURCE) vis = RetentionPolicy.SOURCE;
5062                 else if (levelName == names.CLASS) vis = RetentionPolicy.CLASS;
5063                 else if (levelName == names.RUNTIME) vis = RetentionPolicy.RUNTIME;
5064                 else ;// /* fail soft */ throw new AssertionError(levelName);
5065             }
5066         }
5067         return vis;
5068     }
5069     // </editor-fold>
5070 
5071     // <editor-fold defaultstate="collapsed" desc="Signature Generation">
5072 
5073     public abstract static class SignatureGenerator {
5074 
5075         public static class InvalidSignatureException extends RuntimeException {
5076             private static final long serialVersionUID = 0;
5077 
5078             private final transient Type type;
5079 
5080             InvalidSignatureException(Type type) {
5081                 this.type = type;
5082             }
5083 
5084             public Type type() {
5085                 return type;
5086             }
5087 
5088             @Override
5089             public Throwable fillInStackTrace() {
5090                 // This is an internal exception; the stack trace is irrelevant.
5091                 return this;
5092             }
5093         }
5094 
5095         private final Types types;
5096 
5097         protected abstract void append(char ch);
5098         protected abstract void append(byte[] ba);
5099         protected abstract void append(Name name);
5100         protected void classReference(ClassSymbol c) { /* by default: no-op */ }
5101 
5102         protected SignatureGenerator(Types types) {
5103             this.types = types;
5104         }
5105 
5106         protected void reportIllegalSignature(Type t) {
5107             throw new InvalidSignatureException(t);
5108         }
5109 
5110         /**
5111          * Assemble signature of given type in string buffer.
5112          */
5113         public void assembleSig(Type type) {
5114             switch (type.getTag()) {
5115                 case BYTE:
5116                     append('B');
5117                     break;
5118                 case SHORT:
5119                     append('S');
5120                     break;
5121                 case CHAR:
5122                     append('C');
5123                     break;
5124                 case INT:
5125                     append('I');
5126                     break;
5127                 case LONG:
5128                     append('J');
5129                     break;
5130                 case FLOAT:
5131                     append('F');
5132                     break;
5133                 case DOUBLE:
5134                     append('D');
5135                     break;
5136                 case BOOLEAN:
5137                     append('Z');
5138                     break;
5139                 case VOID:
5140                     append('V');
5141                     break;
5142                 case CLASS:
5143                     if (type.isCompound()) {
5144                         reportIllegalSignature(type);
5145                     }
5146                     append('L');
5147                     assembleClassSig(type);
5148                     append(';');
5149                     break;
5150                 case ARRAY:
5151                     ArrayType at = (ArrayType) type;
5152                     append('[');
5153                     assembleSig(at.elemtype);
5154                     break;
5155                 case METHOD:
5156                     MethodType mt = (MethodType) type;
5157                     append('(');
5158                     assembleSig(mt.argtypes);
5159                     append(')');
5160                     assembleSig(mt.restype);
5161                     if (hasTypeVar(mt.thrown)) {
5162                         for (List<Type> l = mt.thrown; l.nonEmpty(); l = l.tail) {
5163                             append('^');
5164                             assembleSig(l.head);
5165                         }
5166                     }
5167                     break;
5168                 case WILDCARD: {
5169                     Type.WildcardType ta = (Type.WildcardType) type;
5170                     switch (ta.kind) {
5171                         case SUPER:
5172                             append('-');
5173                             assembleSig(ta.type);
5174                             break;
5175                         case EXTENDS:
5176                             append('+');
5177                             assembleSig(ta.type);
5178                             break;
5179                         case UNBOUND:
5180                             append('*');
5181                             break;
5182                         default:
5183                             throw new AssertionError(ta.kind);
5184                     }
5185                     break;
5186                 }
5187                 case TYPEVAR:
5188                     if (((TypeVar)type).isCaptured()) {
5189                         reportIllegalSignature(type);
5190                     }
5191                     append('T');
5192                     append(type.tsym.name);
5193                     append(';');
5194                     break;
5195                 case FORALL:
5196                     Type.ForAll ft = (Type.ForAll) type;
5197                     assembleParamsSig(ft.tvars);
5198                     assembleSig(ft.qtype);
5199                     break;
5200                 default:
5201                     throw new AssertionError("typeSig " + type.getTag());
5202             }
5203         }
5204 
5205         public boolean hasTypeVar(List<Type> l) {
5206             while (l.nonEmpty()) {
5207                 if (l.head.hasTag(TypeTag.TYPEVAR)) {
5208                     return true;
5209                 }
5210                 l = l.tail;
5211             }
5212             return false;
5213         }
5214 
5215         public void assembleClassSig(Type type) {
5216             ClassType ct = (ClassType) type;
5217             ClassSymbol c = (ClassSymbol) ct.tsym;
5218             classReference(c);
5219             Type outer = ct.getEnclosingType();
5220             if (outer.allparams().nonEmpty()) {
5221                 boolean rawOuter =
5222                         c.owner.kind == MTH || // either a local class
5223                         c.name == types.names.empty; // or anonymous
5224                 assembleClassSig(rawOuter
5225                         ? types.erasure(outer)
5226                         : outer);
5227                 append(rawOuter ? '$' : '.');
5228                 Assert.check(c.flatname.startsWith(c.owner.enclClass().flatname));
5229                 append(rawOuter
5230                         ? c.flatname.subName(c.owner.enclClass().flatname.length() + 1)
5231                         : c.name);
5232             } else {
5233                 append(externalize(c.flatname));
5234             }
5235             if (ct.getTypeArguments().nonEmpty()) {
5236                 append('<');
5237                 assembleSig(ct.getTypeArguments());
5238                 append('>');
5239             }
5240         }
5241 
5242         public void assembleParamsSig(List<Type> typarams) {
5243             append('<');
5244             for (List<Type> ts = typarams; ts.nonEmpty(); ts = ts.tail) {
5245                 Type.TypeVar tvar = (Type.TypeVar) ts.head;
5246                 append(tvar.tsym.name);
5247                 List<Type> bounds = types.getBounds(tvar);
5248                 if ((bounds.head.tsym.flags() & INTERFACE) != 0) {
5249                     append(':');
5250                 }
5251                 for (List<Type> l = bounds; l.nonEmpty(); l = l.tail) {
5252                     append(':');
5253                     assembleSig(l.head);
5254                 }
5255             }
5256             append('>');
5257         }
5258 
5259         public void assembleSig(List<Type> types) {
5260             for (List<Type> ts = types; ts.nonEmpty(); ts = ts.tail) {
5261                 assembleSig(ts.head);
5262             }
5263         }
5264     }
5265 
5266     public Type constantType(LoadableConstant c) {
5267         switch (c.poolTag()) {
5268             case ClassFile.CONSTANT_Class:
5269                 return syms.classType;
5270             case ClassFile.CONSTANT_String:
5271                 return syms.stringType;
5272             case ClassFile.CONSTANT_Integer:
5273                 return syms.intType;
5274             case ClassFile.CONSTANT_Float:
5275                 return syms.floatType;
5276             case ClassFile.CONSTANT_Long:
5277                 return syms.longType;
5278             case ClassFile.CONSTANT_Double:
5279                 return syms.doubleType;
5280             case ClassFile.CONSTANT_MethodHandle:
5281                 return syms.methodHandleType;
5282             case ClassFile.CONSTANT_MethodType:
5283                 return syms.methodTypeType;
5284             case ClassFile.CONSTANT_Dynamic:
5285                 return ((DynamicVarSymbol)c).type;
5286             default:
5287                 throw new AssertionError("Not a loadable constant: " + c.poolTag());
5288         }
5289     }
5290     // </editor-fold>
5291 
5292     public void newRound() {
5293         descCache._map.clear();
5294         isDerivedRawCache.clear();
5295         implCache._map.clear();
5296         membersCache._map.clear();
5297         closureCache.clear();
5298     }
5299 }