1 /*
   2  * Copyright (c) 1999, 2021, 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 //todo: one might eliminate uninits.andSets when monotonic
  27 
  28 package com.sun.tools.javac.comp;
  29 
  30 import java.util.HashMap;
  31 import java.util.HashSet;
  32 import java.util.Set;
  33 import java.util.stream.StreamSupport;
  34 
  35 import com.sun.source.tree.LambdaExpressionTree.BodyKind;
  36 import com.sun.tools.javac.code.*;
  37 import com.sun.tools.javac.code.Scope.WriteableScope;
  38 import com.sun.tools.javac.code.Source.Feature;
  39 import com.sun.tools.javac.resources.CompilerProperties.Errors;
  40 import com.sun.tools.javac.resources.CompilerProperties.Warnings;
  41 import com.sun.tools.javac.tree.*;
  42 import com.sun.tools.javac.tree.TreeInfo.PatternPrimaryType;
  43 import com.sun.tools.javac.util.*;
  44 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
  45 import com.sun.tools.javac.util.JCDiagnostic.Error;
  46 import com.sun.tools.javac.util.JCDiagnostic.Warning;
  47 
  48 import com.sun.tools.javac.code.Symbol.*;
  49 import com.sun.tools.javac.tree.JCTree.*;
  50 
  51 import static com.sun.tools.javac.code.Flags.*;
  52 import static com.sun.tools.javac.code.Flags.BLOCK;
  53 import static com.sun.tools.javac.code.Kinds.Kind.*;
  54 import com.sun.tools.javac.code.Type.TypeVar;
  55 import static com.sun.tools.javac.code.TypeTag.BOOLEAN;
  56 import static com.sun.tools.javac.code.TypeTag.VOID;
  57 import com.sun.tools.javac.resources.CompilerProperties.Fragments;
  58 import static com.sun.tools.javac.tree.JCTree.Tag.*;
  59 import com.sun.tools.javac.util.JCDiagnostic.Fragment;
  60 
  61 /** This pass implements dataflow analysis for Java programs though
  62  *  different AST visitor steps. Liveness analysis (see AliveAnalyzer) checks that
  63  *  every statement is reachable. Exception analysis (see FlowAnalyzer) ensures that
  64  *  every checked exception that is thrown is declared or caught.  Definite assignment analysis
  65  *  (see AssignAnalyzer) ensures that each variable is assigned when used.  Definite
  66  *  unassignment analysis (see AssignAnalyzer) in ensures that no final variable
  67  *  is assigned more than once. Finally, local variable capture analysis (see CaptureAnalyzer)
  68  *  determines that local variables accessed within the scope of an inner class/lambda
  69  *  are either final or effectively-final.
  70  *
  71  *  <p>The JLS has a number of problems in the
  72  *  specification of these flow analysis problems. This implementation
  73  *  attempts to address those issues.
  74  *
  75  *  <p>First, there is no accommodation for a finally clause that cannot
  76  *  complete normally. For liveness analysis, an intervening finally
  77  *  clause can cause a break, continue, or return not to reach its
  78  *  target.  For exception analysis, an intervening finally clause can
  79  *  cause any exception to be "caught".  For DA/DU analysis, the finally
  80  *  clause can prevent a transfer of control from propagating DA/DU
  81  *  state to the target.  In addition, code in the finally clause can
  82  *  affect the DA/DU status of variables.
  83  *
  84  *  <p>For try statements, we introduce the idea of a variable being
  85  *  definitely unassigned "everywhere" in a block.  A variable V is
  86  *  "unassigned everywhere" in a block iff it is unassigned at the
  87  *  beginning of the block and there is no reachable assignment to V
  88  *  in the block.  An assignment V=e is reachable iff V is not DA
  89  *  after e.  Then we can say that V is DU at the beginning of the
  90  *  catch block iff V is DU everywhere in the try block.  Similarly, V
  91  *  is DU at the beginning of the finally block iff V is DU everywhere
  92  *  in the try block and in every catch block.  Specifically, the
  93  *  following bullet is added to 16.2.2
  94  *  <pre>
  95  *      V is <em>unassigned everywhere</em> in a block if it is
  96  *      unassigned before the block and there is no reachable
  97  *      assignment to V within the block.
  98  *  </pre>
  99  *  <p>In 16.2.15, the third bullet (and all of its sub-bullets) for all
 100  *  try blocks is changed to
 101  *  <pre>
 102  *      V is definitely unassigned before a catch block iff V is
 103  *      definitely unassigned everywhere in the try block.
 104  *  </pre>
 105  *  <p>The last bullet (and all of its sub-bullets) for try blocks that
 106  *  have a finally block is changed to
 107  *  <pre>
 108  *      V is definitely unassigned before the finally block iff
 109  *      V is definitely unassigned everywhere in the try block
 110  *      and everywhere in each catch block of the try statement.
 111  *  </pre>
 112  *  <p>In addition,
 113  *  <pre>
 114  *      V is definitely assigned at the end of a constructor iff
 115  *      V is definitely assigned after the block that is the body
 116  *      of the constructor and V is definitely assigned at every
 117  *      return that can return from the constructor.
 118  *  </pre>
 119  *  <p>In addition, each continue statement with the loop as its target
 120  *  is treated as a jump to the end of the loop body, and "intervening"
 121  *  finally clauses are treated as follows: V is DA "due to the
 122  *  continue" iff V is DA before the continue statement or V is DA at
 123  *  the end of any intervening finally block.  V is DU "due to the
 124  *  continue" iff any intervening finally cannot complete normally or V
 125  *  is DU at the end of every intervening finally block.  This "due to
 126  *  the continue" concept is then used in the spec for the loops.
 127  *
 128  *  <p>Similarly, break statements must consider intervening finally
 129  *  blocks.  For liveness analysis, a break statement for which any
 130  *  intervening finally cannot complete normally is not considered to
 131  *  cause the target statement to be able to complete normally. Then
 132  *  we say V is DA "due to the break" iff V is DA before the break or
 133  *  V is DA at the end of any intervening finally block.  V is DU "due
 134  *  to the break" iff any intervening finally cannot complete normally
 135  *  or V is DU at the break and at the end of every intervening
 136  *  finally block.  (I suspect this latter condition can be
 137  *  simplified.)  This "due to the break" is then used in the spec for
 138  *  all statements that can be "broken".
 139  *
 140  *  <p>The return statement is treated similarly.  V is DA "due to a
 141  *  return statement" iff V is DA before the return statement or V is
 142  *  DA at the end of any intervening finally block.  Note that we
 143  *  don't have to worry about the return expression because this
 144  *  concept is only used for constructors.
 145  *
 146  *  <p>There is no spec in the JLS for when a variable is definitely
 147  *  assigned at the end of a constructor, which is needed for final
 148  *  fields (8.3.1.2).  We implement the rule that V is DA at the end
 149  *  of the constructor iff it is DA and the end of the body of the
 150  *  constructor and V is DA "due to" every return of the constructor.
 151  *
 152  *  <p>Intervening finally blocks similarly affect exception analysis.  An
 153  *  intervening finally that cannot complete normally allows us to ignore
 154  *  an otherwise uncaught exception.
 155  *
 156  *  <p>To implement the semantics of intervening finally clauses, all
 157  *  nonlocal transfers (break, continue, return, throw, method call that
 158  *  can throw a checked exception, and a constructor invocation that can
 159  *  thrown a checked exception) are recorded in a queue, and removed
 160  *  from the queue when we complete processing the target of the
 161  *  nonlocal transfer.  This allows us to modify the queue in accordance
 162  *  with the above rules when we encounter a finally clause.  The only
 163  *  exception to this [no pun intended] is that checked exceptions that
 164  *  are known to be caught or declared to be caught in the enclosing
 165  *  method are not recorded in the queue, but instead are recorded in a
 166  *  global variable "{@code Set<Type> thrown}" that records the type of all
 167  *  exceptions that can be thrown.
 168  *
 169  *  <p>Other minor issues the treatment of members of other classes
 170  *  (always considered DA except that within an anonymous class
 171  *  constructor, where DA status from the enclosing scope is
 172  *  preserved), treatment of the case expression (V is DA before the
 173  *  case expression iff V is DA after the switch expression),
 174  *  treatment of variables declared in a switch block (the implied
 175  *  DA/DU status after the switch expression is DU and not DA for
 176  *  variables defined in a switch block), the treatment of boolean ?:
 177  *  expressions (The JLS rules only handle b and c non-boolean; the
 178  *  new rule is that if b and c are boolean valued, then V is
 179  *  (un)assigned after a?b:c when true/false iff V is (un)assigned
 180  *  after b when true/false and V is (un)assigned after c when
 181  *  true/false).
 182  *
 183  *  <p>There is the remaining question of what syntactic forms constitute a
 184  *  reference to a variable.  It is conventional to allow this.x on the
 185  *  left-hand-side to initialize a final instance field named x, yet
 186  *  this.x isn't considered a "use" when appearing on a right-hand-side
 187  *  in most implementations.  Should parentheses affect what is
 188  *  considered a variable reference?  The simplest rule would be to
 189  *  allow unqualified forms only, parentheses optional, and phase out
 190  *  support for assigning to a final field via this.x.
 191  *
 192  *  <p><b>This is NOT part of any supported API.
 193  *  If you write code that depends on this, you do so at your own risk.
 194  *  This code and its internal interfaces are subject to change or
 195  *  deletion without notice.</b>
 196  */
 197 public class Flow {
 198     protected static final Context.Key<Flow> flowKey = new Context.Key<>();
 199 
 200     private final Names names;
 201     private final Log log;
 202     private final Symtab syms;
 203     private final Types types;
 204     private final Check chk;
 205     private       TreeMaker make;
 206     private final Resolve rs;
 207     private final JCDiagnostic.Factory diags;
 208     private Env<AttrContext> attrEnv;
 209     private       Lint lint;
 210     private final boolean allowEffectivelyFinalInInnerClasses;
 211 
 212     public static Flow instance(Context context) {
 213         Flow instance = context.get(flowKey);
 214         if (instance == null)
 215             instance = new Flow(context);
 216         return instance;
 217     }
 218 
 219     public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
 220         new AliveAnalyzer().analyzeTree(env, make);
 221         new AssignAnalyzer().analyzeTree(env, make);
 222         new FlowAnalyzer().analyzeTree(env, make);
 223         new CaptureAnalyzer().analyzeTree(env, make);
 224     }
 225 
 226     public void analyzeLambda(Env<AttrContext> env, JCLambda that, TreeMaker make, boolean speculative) {
 227         Log.DiagnosticHandler diagHandler = null;
 228         //we need to disable diagnostics temporarily; the problem is that if
 229         //a lambda expression contains e.g. an unreachable statement, an error
 230         //message will be reported and will cause compilation to skip the flow analysis
 231         //step - if we suppress diagnostics, we won't stop at Attr for flow-analysis
 232         //related errors, which will allow for more errors to be detected
 233         if (!speculative) {
 234             diagHandler = new Log.DiscardDiagnosticHandler(log);
 235         }
 236         try {
 237             new LambdaAliveAnalyzer().analyzeTree(env, that, make);
 238         } finally {
 239             if (!speculative) {
 240                 log.popDiagnosticHandler(diagHandler);
 241             }
 242         }
 243     }
 244 
 245     public List<Type> analyzeLambdaThrownTypes(final Env<AttrContext> env,
 246             JCLambda that, TreeMaker make) {
 247         //we need to disable diagnostics temporarily; the problem is that if
 248         //a lambda expression contains e.g. an unreachable statement, an error
 249         //message will be reported and will cause compilation to skip the flow analysis
 250         //step - if we suppress diagnostics, we won't stop at Attr for flow-analysis
 251         //related errors, which will allow for more errors to be detected
 252         Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
 253         try {
 254             new LambdaAssignAnalyzer(env).analyzeTree(env, that, make);
 255             LambdaFlowAnalyzer flowAnalyzer = new LambdaFlowAnalyzer();
 256             flowAnalyzer.analyzeTree(env, that, make);
 257             return flowAnalyzer.inferredThrownTypes;
 258         } finally {
 259             log.popDiagnosticHandler(diagHandler);
 260         }
 261     }
 262 
 263     public boolean aliveAfter(Env<AttrContext> env, JCTree that, TreeMaker make) {
 264         //we need to disable diagnostics temporarily; the problem is that if
 265         //"that" contains e.g. an unreachable statement, an error
 266         //message will be reported and will cause compilation to skip the flow analysis
 267         //step - if we suppress diagnostics, we won't stop at Attr for flow-analysis
 268         //related errors, which will allow for more errors to be detected
 269         Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
 270         try {
 271             SnippetAliveAnalyzer analyzer = new SnippetAliveAnalyzer();
 272 
 273             analyzer.analyzeTree(env, that, make);
 274             return analyzer.isAlive();
 275         } finally {
 276             log.popDiagnosticHandler(diagHandler);
 277         }
 278     }
 279 
 280     public boolean breaksOutOf(Env<AttrContext> env, JCTree loop, JCTree body, TreeMaker make) {
 281         //we need to disable diagnostics temporarily; the problem is that if
 282         //"that" contains e.g. an unreachable statement, an error
 283         //message will be reported and will cause compilation to skip the flow analysis
 284         //step - if we suppress diagnostics, we won't stop at Attr for flow-analysis
 285         //related errors, which will allow for more errors to be detected
 286         Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
 287         try {
 288             SnippetBreakAnalyzer analyzer = new SnippetBreakAnalyzer();
 289 
 290             analyzer.analyzeTree(env, body, make);
 291             return analyzer.breaksOut();
 292         } finally {
 293             log.popDiagnosticHandler(diagHandler);
 294         }
 295     }
 296 
 297     /**
 298      * Definite assignment scan mode
 299      */
 300     enum FlowKind {
 301         /**
 302          * This is the normal DA/DU analysis mode
 303          */
 304         NORMAL("var.might.already.be.assigned", false),
 305         /**
 306          * This is the speculative DA/DU analysis mode used to speculatively
 307          * derive assertions within loop bodies
 308          */
 309         SPECULATIVE_LOOP("var.might.be.assigned.in.loop", true);
 310 
 311         final String errKey;
 312         final boolean isFinal;
 313 
 314         FlowKind(String errKey, boolean isFinal) {
 315             this.errKey = errKey;
 316             this.isFinal = isFinal;
 317         }
 318 
 319         boolean isFinal() {
 320             return isFinal;
 321         }
 322     }
 323 
 324     protected Flow(Context context) {
 325         context.put(flowKey, this);
 326         names = Names.instance(context);
 327         log = Log.instance(context);
 328         syms = Symtab.instance(context);
 329         types = Types.instance(context);
 330         chk = Check.instance(context);
 331         lint = Lint.instance(context);
 332         rs = Resolve.instance(context);
 333         diags = JCDiagnostic.Factory.instance(context);
 334         Source source = Source.instance(context);
 335         allowEffectivelyFinalInInnerClasses = Feature.EFFECTIVELY_FINAL_IN_INNER_CLASSES.allowedInSource(source);
 336     }
 337 
 338     /**
 339      * Base visitor class for all visitors implementing dataflow analysis logic.
 340      * This class define the shared logic for handling jumps (break/continue statements).
 341      */
 342     abstract static class BaseAnalyzer extends TreeScanner {
 343 
 344         enum JumpKind {
 345             BREAK(JCTree.Tag.BREAK) {
 346                 @Override
 347                 JCTree getTarget(JCTree tree) {
 348                     return ((JCBreak)tree).target;
 349                 }
 350             },
 351             CONTINUE(JCTree.Tag.CONTINUE) {
 352                 @Override
 353                 JCTree getTarget(JCTree tree) {
 354                     return ((JCContinue)tree).target;
 355                 }
 356             },
 357             YIELD(JCTree.Tag.YIELD) {
 358                 @Override
 359                 JCTree getTarget(JCTree tree) {
 360                     return ((JCYield)tree).target;
 361                 }
 362             };
 363 
 364             final JCTree.Tag treeTag;
 365 
 366             private JumpKind(Tag treeTag) {
 367                 this.treeTag = treeTag;
 368             }
 369 
 370             abstract JCTree getTarget(JCTree tree);
 371         }
 372 
 373         /** The currently pending exits that go from current inner blocks
 374          *  to an enclosing block, in source order.
 375          */
 376         ListBuffer<PendingExit> pendingExits;
 377 
 378         /** A pending exit.  These are the statements return, break, and
 379          *  continue.  In addition, exception-throwing expressions or
 380          *  statements are put here when not known to be caught.  This
 381          *  will typically result in an error unless it is within a
 382          *  try-finally whose finally block cannot complete normally.
 383          */
 384         static class PendingExit {
 385             JCTree tree;
 386 
 387             PendingExit(JCTree tree) {
 388                 this.tree = tree;
 389             }
 390 
 391             void resolveJump() {
 392                 //do nothing
 393             }
 394         }
 395 
 396         abstract void markDead();
 397 
 398         /** Record an outward transfer of control. */
 399         void recordExit(PendingExit pe) {
 400             pendingExits.append(pe);
 401             markDead();
 402         }
 403 
 404         /** Resolve all jumps of this statement. */
 405         private Liveness resolveJump(JCTree tree,
 406                          ListBuffer<PendingExit> oldPendingExits,
 407                          JumpKind jk) {
 408             boolean resolved = false;
 409             List<PendingExit> exits = pendingExits.toList();
 410             pendingExits = oldPendingExits;
 411             for (; exits.nonEmpty(); exits = exits.tail) {
 412                 PendingExit exit = exits.head;
 413                 if (exit.tree.hasTag(jk.treeTag) &&
 414                         jk.getTarget(exit.tree) == tree) {
 415                     exit.resolveJump();
 416                     resolved = true;
 417                 } else {
 418                     pendingExits.append(exit);
 419                 }
 420             }
 421             return Liveness.from(resolved);
 422         }
 423 
 424         /** Resolve all continues of this statement. */
 425         Liveness resolveContinues(JCTree tree) {
 426             return resolveJump(tree, new ListBuffer<PendingExit>(), JumpKind.CONTINUE);
 427         }
 428 
 429         /** Resolve all breaks of this statement. */
 430         Liveness resolveBreaks(JCTree tree, ListBuffer<PendingExit> oldPendingExits) {
 431             return resolveJump(tree, oldPendingExits, JumpKind.BREAK);
 432         }
 433 
 434         /** Resolve all yields of this statement. */
 435         Liveness resolveYields(JCTree tree, ListBuffer<PendingExit> oldPendingExits) {
 436             return resolveJump(tree, oldPendingExits, JumpKind.YIELD);
 437         }
 438 
 439         @Override
 440         public void scan(JCTree tree) {
 441             if (tree != null && (
 442                     tree.type == null ||
 443                     tree.type != Type.stuckType)) {
 444                 super.scan(tree);
 445             }
 446         }
 447 
 448         public void visitPackageDef(JCPackageDecl tree) {
 449             // Do nothing for PackageDecl
 450         }
 451 
 452         protected void scanSyntheticBreak(TreeMaker make, JCTree swtch) {
 453             if (swtch.hasTag(SWITCH_EXPRESSION)) {
 454                 JCYield brk = make.at(Position.NOPOS).Yield(null);
 455                 brk.target = swtch;
 456                 scan(brk);
 457             } else {
 458                 JCBreak brk = make.at(Position.NOPOS).Break(null);
 459                 brk.target = swtch;
 460                 scan(brk);
 461             }
 462         }
 463     }
 464 
 465     /**
 466      * This pass implements the first step of the dataflow analysis, namely
 467      * the liveness analysis check. This checks that every statement is reachable.
 468      * The output of this analysis pass are used by other analyzers. This analyzer
 469      * sets the 'finallyCanCompleteNormally' field in the JCTry class.
 470      */
 471     class AliveAnalyzer extends BaseAnalyzer {
 472 
 473         /** A flag that indicates whether the last statement could
 474          *  complete normally.
 475          */
 476         private Liveness alive;
 477 
 478         @Override
 479         void markDead() {
 480             alive = Liveness.DEAD;
 481         }
 482 
 483     /*************************************************************************
 484      * Visitor methods for statements and definitions
 485      *************************************************************************/
 486 
 487         /** Analyze a definition.
 488          */
 489         void scanDef(JCTree tree) {
 490             scanStat(tree);
 491             if (tree != null && tree.hasTag(JCTree.Tag.BLOCK) && alive == Liveness.DEAD) {
 492                 log.error(tree.pos(),
 493                           Errors.InitializerMustBeAbleToCompleteNormally);
 494             }
 495         }
 496 
 497         /** Analyze a statement. Check that statement is reachable.
 498          */
 499         void scanStat(JCTree tree) {
 500             if (alive == Liveness.DEAD && tree != null) {
 501                 log.error(tree.pos(), Errors.UnreachableStmt);
 502                 if (!tree.hasTag(SKIP)) alive = Liveness.RECOVERY;
 503             }
 504             scan(tree);
 505         }
 506 
 507         /** Analyze list of statements.
 508          */
 509         void scanStats(List<? extends JCStatement> trees) {
 510             if (trees != null)
 511                 for (List<? extends JCStatement> l = trees; l.nonEmpty(); l = l.tail)
 512                     scanStat(l.head);
 513         }
 514 
 515         /* ------------ Visitor methods for various sorts of trees -------------*/
 516 
 517         public void visitClassDef(JCClassDecl tree) {
 518             if (tree.sym == null) return;
 519             Liveness alivePrev = alive;
 520             ListBuffer<PendingExit> pendingExitsPrev = pendingExits;
 521             Lint lintPrev = lint;
 522 
 523             pendingExits = new ListBuffer<>();
 524             lint = lint.augment(tree.sym);
 525 
 526             try {
 527                 // process all the static initializers
 528                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
 529                     if (!l.head.hasTag(METHODDEF) &&
 530                         (TreeInfo.flags(l.head) & STATIC) != 0) {
 531                         scanDef(l.head);
 532                         clearPendingExits(false);
 533                     }
 534                 }
 535 
 536                 // process all the instance initializers
 537                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
 538                     if (!l.head.hasTag(METHODDEF) &&
 539                         (TreeInfo.flags(l.head) & STATIC) == 0) {
 540                         scanDef(l.head);
 541                         clearPendingExits(false);
 542                     }
 543                 }
 544 
 545                 // process all the methods
 546                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
 547                     if (l.head.hasTag(METHODDEF)) {
 548                         scan(l.head);
 549                     }
 550                 }
 551             } finally {
 552                 pendingExits = pendingExitsPrev;
 553                 alive = alivePrev;
 554                 lint = lintPrev;
 555             }
 556         }
 557 
 558         public void visitMethodDef(JCMethodDecl tree) {
 559             if (tree.body == null) return;
 560             Lint lintPrev = lint;
 561 
 562             lint = lint.augment(tree.sym);
 563 
 564             Assert.check(pendingExits.isEmpty());
 565 
 566             try {
 567                 alive = Liveness.ALIVE;
 568                 scanStat(tree.body);
 569                 tree.completesNormally = alive != Liveness.DEAD;
 570 
 571                 if (alive == Liveness.ALIVE && !tree.sym.type.getReturnType().hasTag(VOID))
 572                     log.error(TreeInfo.diagEndPos(tree.body), Errors.MissingRetStmt);
 573 
 574                 clearPendingExits(true);
 575             } finally {
 576                 lint = lintPrev;
 577             }
 578         }
 579 
 580         private void clearPendingExits(boolean inMethod) {
 581             List<PendingExit> exits = pendingExits.toList();
 582             pendingExits = new ListBuffer<>();
 583             while (exits.nonEmpty()) {
 584                 PendingExit exit = exits.head;
 585                 exits = exits.tail;
 586                 Assert.check((inMethod && exit.tree.hasTag(RETURN)) ||
 587                                 log.hasErrorOn(exit.tree.pos()));
 588             }
 589         }
 590 
 591         public void visitVarDef(JCVariableDecl tree) {
 592             if (tree.init != null) {
 593                 Lint lintPrev = lint;
 594                 lint = lint.augment(tree.sym);
 595                 try{
 596                     scan(tree.init);
 597                 } finally {
 598                     lint = lintPrev;
 599                 }
 600             }
 601         }
 602 
 603         public void visitBlock(JCBlock tree) {
 604             scanStats(tree.stats);
 605         }
 606 
 607         public void visitDoLoop(JCDoWhileLoop tree) {
 608             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 609             pendingExits = new ListBuffer<>();
 610             scanStat(tree.body);
 611             alive = alive.or(resolveContinues(tree));
 612             scan(tree.cond);
 613             alive = alive.and(!tree.cond.type.isTrue());
 614             alive = alive.or(resolveBreaks(tree, prevPendingExits));
 615         }
 616 
 617         public void visitWhileLoop(JCWhileLoop tree) {
 618             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 619             pendingExits = new ListBuffer<>();
 620             scan(tree.cond);
 621             alive = Liveness.from(!tree.cond.type.isFalse());
 622             scanStat(tree.body);
 623             alive = alive.or(resolveContinues(tree));
 624             alive = resolveBreaks(tree, prevPendingExits).or(
 625                 !tree.cond.type.isTrue());
 626         }
 627 
 628         public void visitForLoop(JCForLoop tree) {
 629             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 630             scanStats(tree.init);
 631             pendingExits = new ListBuffer<>();
 632             if (tree.cond != null) {
 633                 scan(tree.cond);
 634                 alive = Liveness.from(!tree.cond.type.isFalse());
 635             } else {
 636                 alive = Liveness.ALIVE;
 637             }
 638             scanStat(tree.body);
 639             alive = alive.or(resolveContinues(tree));
 640             scan(tree.step);
 641             alive = resolveBreaks(tree, prevPendingExits).or(
 642                 tree.cond != null && !tree.cond.type.isTrue());
 643         }
 644 
 645         public void visitForeachLoop(JCEnhancedForLoop tree) {
 646             visitVarDef(tree.var);
 647             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 648             scan(tree.expr);
 649             pendingExits = new ListBuffer<>();
 650             scanStat(tree.body);
 651             alive = alive.or(resolveContinues(tree));
 652             resolveBreaks(tree, prevPendingExits);
 653             alive = Liveness.ALIVE;
 654         }
 655 
 656         public void visitLabelled(JCLabeledStatement tree) {
 657             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 658             pendingExits = new ListBuffer<>();
 659             scanStat(tree.body);
 660             alive = alive.or(resolveBreaks(tree, prevPendingExits));
 661         }
 662 
 663         public void visitSwitch(JCSwitch tree) {
 664             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 665             pendingExits = new ListBuffer<>();
 666             scan(tree.selector);
 667             boolean exhaustiveSwitch = TreeInfo.expectedExhaustive(tree);
 668             Set<Symbol> constants = exhaustiveSwitch ? new HashSet<>() : null;
 669             for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
 670                 alive = Liveness.ALIVE;
 671                 JCCase c = l.head;
 672                 for (JCCaseLabel pat : c.labels) {
 673                     scan(pat);
 674                     handleConstantCaseLabel(constants, pat);
 675                 }
 676                 scanStats(c.stats);
 677                 if (alive != Liveness.DEAD && c.caseKind == JCCase.RULE) {
 678                     scanSyntheticBreak(make, tree);
 679                     alive = Liveness.DEAD;
 680                 }
 681                 // Warn about fall-through if lint switch fallthrough enabled.
 682                 if (alive == Liveness.ALIVE &&
 683                     lint.isEnabled(Lint.LintCategory.FALLTHROUGH) &&
 684                     c.stats.nonEmpty() && l.tail.nonEmpty())
 685                     log.warning(Lint.LintCategory.FALLTHROUGH,
 686                                 l.tail.head.pos(),
 687                                 Warnings.PossibleFallThroughIntoCase);
 688             }
 689             tree.isExhaustive = tree.hasTotalPattern ||
 690                                 TreeInfo.isErrorEnumSwitch(tree.selector, tree.cases);
 691             if (exhaustiveSwitch) {
 692                 tree.isExhaustive |= isExhaustive(tree.selector.pos(), tree.selector.type, constants);
 693                 if (!tree.isExhaustive) {
 694                     log.error(tree, Errors.NotExhaustiveStatement);
 695                 }
 696             }
 697             if (!tree.hasTotalPattern) {
 698                 alive = Liveness.ALIVE;
 699             }
 700             alive = alive.or(resolveBreaks(tree, prevPendingExits));
 701         }
 702 
 703         @Override
 704         public void visitSwitchExpression(JCSwitchExpression tree) {
 705             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 706             pendingExits = new ListBuffer<>();
 707             scan(tree.selector);
 708             Set<Symbol> constants = new HashSet<>();
 709             Liveness prevAlive = alive;
 710             for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
 711                 alive = Liveness.ALIVE;
 712                 JCCase c = l.head;
 713                 for (JCCaseLabel pat : c.labels) {
 714                     scan(pat);
 715                     handleConstantCaseLabel(constants, pat);
 716                 }
 717                 scanStats(c.stats);
 718                 if (alive == Liveness.ALIVE) {
 719                     if (c.caseKind == JCCase.RULE) {
 720                         log.error(TreeInfo.diagEndPos(c.body),
 721                                   Errors.RuleCompletesNormally);
 722                     } else if (l.tail.isEmpty()) {
 723                         log.error(TreeInfo.diagEndPos(tree),
 724                                   Errors.SwitchExpressionCompletesNormally);
 725                     }
 726                 }
 727             }
 728             tree.isExhaustive = tree.hasTotalPattern ||
 729                                 TreeInfo.isErrorEnumSwitch(tree.selector, tree.cases) ||
 730                                 isExhaustive(tree.selector.pos(), tree.selector.type, constants);
 731             if (!tree.isExhaustive) {
 732                 log.error(tree, Errors.NotExhaustive);
 733             }
 734             alive = prevAlive;
 735             alive = alive.or(resolveYields(tree, prevPendingExits));
 736         }
 737 
 738         private void handleConstantCaseLabel(Set<Symbol> constants, JCCaseLabel pat) {
 739             if (constants != null) {
 740                 if (pat.isExpression()) {
 741                     JCExpression expr = (JCExpression) pat;
 742                     if (expr.hasTag(IDENT) && ((JCIdent) expr).sym.isEnum())
 743                         constants.add(((JCIdent) expr).sym);
 744                 } else if (pat.isPattern()) {
 745                     PatternPrimaryType patternType = TreeInfo.primaryPatternType((JCPattern) pat);
 746 
 747                     if (patternType.unconditional()) {
 748                         constants.add(patternType.type().tsym);
 749                     }
 750                 }
 751             }
 752         }
 753 
 754         private void transitiveCovers(DiagnosticPosition pos, Type seltype, Set<Symbol> covered) {
 755             List<Symbol> todo = List.from(covered);
 756             while (todo.nonEmpty()) {
 757                 Symbol sym = todo.head;
 758                 todo = todo.tail;
 759                 switch (sym.kind) {
 760                     case VAR -> {
 761                         Iterable<Symbol> constants = sym.owner
 762                                                         .members()
 763                                                         .getSymbols(s -> s.isEnum() &&
 764                                                                          s.kind == VAR);
 765                         boolean hasAll = StreamSupport.stream(constants.spliterator(), false)
 766                                                       .allMatch(covered::contains);
 767 
 768                         if (hasAll && covered.add(sym.owner)) {
 769                             todo = todo.prepend(sym.owner);
 770                         }
 771                     }
 772 
 773                     case TYP -> {
 774                         for (Type sup : types.directSupertypes(sym.type)) {
 775                             if (sup.tsym.kind == TYP) {
 776                                 if (isTransitivelyCovered(pos, seltype, sup.tsym, covered) &&
 777                                     covered.add(sup.tsym)) {
 778                                     todo = todo.prepend(sup.tsym);
 779                                 }
 780                             }
 781                         }
 782                     }
 783                 }
 784             }
 785         }
 786 
 787         private boolean isTransitivelyCovered(DiagnosticPosition pos, Type seltype,
 788                                               Symbol sealed, Set<Symbol> covered) {
 789             try {
 790                 if (covered.stream().anyMatch(c -> sealed.isSubClass(c, types)))
 791                     return true;
 792                 if (sealed.kind == TYP && sealed.isAbstract() && sealed.isSealed()) {
 793                     return ((ClassSymbol) sealed).permitted
 794                                                  .stream()
 795                                                  .filter(s -> {
 796                                                      return types.isCastable(seltype, s.type/*, types.noWarnings*/);
 797                                                  })
 798                                                  .allMatch(s -> isTransitivelyCovered(pos, seltype, s, covered));
 799                 }
 800                 return false;
 801             } catch (CompletionFailure cf) {
 802                 chk.completionError(pos, cf);
 803                 return true;
 804             }
 805         }
 806 
 807         private boolean isExhaustive(DiagnosticPosition pos, Type seltype, Set<Symbol> covered) {
 808             transitiveCovers(pos, seltype, covered);
 809             return switch (seltype.getTag()) {
 810                 case CLASS -> {
 811                     if (seltype.isCompound()) {
 812                         if (seltype.isIntersection()) {
 813                             yield ((Type.IntersectionClassType) seltype).getComponents()
 814                                                                         .stream()
 815                                                                         .anyMatch(t -> isExhaustive(pos, t, covered));
 816                         }
 817                         yield false;
 818                     }
 819                     yield covered.contains(seltype.tsym);
 820                 }
 821                 case TYPEVAR -> isExhaustive(pos, ((TypeVar) seltype).getUpperBound(), covered);
 822                 default -> false;
 823             };
 824         }
 825 
 826         public void visitTry(JCTry tree) {
 827             ListBuffer<PendingExit> prevPendingExits = pendingExits;
 828             pendingExits = new ListBuffer<>();
 829             for (JCTree resource : tree.resources) {
 830                 if (resource instanceof JCVariableDecl variableDecl) {
 831                     visitVarDef(variableDecl);
 832                 } else if (resource instanceof JCExpression expression) {
 833                     scan(expression);
 834                 } else {
 835                     throw new AssertionError(tree);  // parser error
 836                 }
 837             }
 838 
 839             scanStat(tree.body);
 840             Liveness aliveEnd = alive;
 841 
 842             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
 843                 alive = Liveness.ALIVE;
 844                 JCVariableDecl param = l.head.param;
 845                 scan(param);
 846                 scanStat(l.head.body);
 847                 aliveEnd = aliveEnd.or(alive);
 848             }
 849             if (tree.finalizer != null) {
 850                 ListBuffer<PendingExit> exits = pendingExits;
 851                 pendingExits = prevPendingExits;
 852                 alive = Liveness.ALIVE;
 853                 scanStat(tree.finalizer);
 854                 tree.finallyCanCompleteNormally = alive != Liveness.DEAD;
 855                 if (alive == Liveness.DEAD) {
 856                     if (lint.isEnabled(Lint.LintCategory.FINALLY)) {
 857                         log.warning(Lint.LintCategory.FINALLY,
 858                                 TreeInfo.diagEndPos(tree.finalizer),
 859                                 Warnings.FinallyCannotComplete);
 860                     }
 861                 } else {
 862                     while (exits.nonEmpty()) {
 863                         pendingExits.append(exits.next());
 864                     }
 865                     alive = aliveEnd;
 866                 }
 867             } else {
 868                 alive = aliveEnd;
 869                 ListBuffer<PendingExit> exits = pendingExits;
 870                 pendingExits = prevPendingExits;
 871                 while (exits.nonEmpty()) pendingExits.append(exits.next());
 872             }
 873         }
 874 
 875         @Override
 876         public void visitIf(JCIf tree) {
 877             scan(tree.cond);
 878             scanStat(tree.thenpart);
 879             if (tree.elsepart != null) {
 880                 Liveness aliveAfterThen = alive;
 881                 alive = Liveness.ALIVE;
 882                 scanStat(tree.elsepart);
 883                 alive = alive.or(aliveAfterThen);
 884             } else {
 885                 alive = Liveness.ALIVE;
 886             }
 887         }
 888 
 889         public void visitBreak(JCBreak tree) {
 890             recordExit(new PendingExit(tree));
 891         }
 892 
 893         @Override
 894         public void visitYield(JCYield tree) {
 895             scan(tree.value);
 896             recordExit(new PendingExit(tree));
 897         }
 898 
 899         public void visitContinue(JCContinue tree) {
 900             recordExit(new PendingExit(tree));
 901         }
 902 
 903         public void visitReturn(JCReturn tree) {
 904             scan(tree.expr);
 905             recordExit(new PendingExit(tree));
 906         }
 907 
 908         public void visitThrow(JCThrow tree) {
 909             scan(tree.expr);
 910             markDead();
 911         }
 912 
 913         public void visitApply(JCMethodInvocation tree) {
 914             scan(tree.meth);
 915             scan(tree.args);
 916         }
 917 
 918         public void visitNewClass(JCNewClass tree) {
 919             scan(tree.encl);
 920             scan(tree.args);
 921             if (tree.def != null) {
 922                 scan(tree.def);
 923             }
 924         }
 925 
 926         @Override
 927         public void visitLambda(JCLambda tree) {
 928             if (tree.type != null &&
 929                     tree.type.isErroneous()) {
 930                 return;
 931             }
 932 
 933             ListBuffer<PendingExit> prevPending = pendingExits;
 934             Liveness prevAlive = alive;
 935             try {
 936                 pendingExits = new ListBuffer<>();
 937                 alive = Liveness.ALIVE;
 938                 scanStat(tree.body);
 939                 tree.canCompleteNormally = alive != Liveness.DEAD;
 940             }
 941             finally {
 942                 pendingExits = prevPending;
 943                 alive = prevAlive;
 944             }
 945         }
 946 
 947         public void visitModuleDef(JCModuleDecl tree) {
 948             // Do nothing for modules
 949         }
 950 
 951     /**************************************************************************
 952      * main method
 953      *************************************************************************/
 954 
 955         /** Perform definite assignment/unassignment analysis on a tree.
 956          */
 957         public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
 958             analyzeTree(env, env.tree, make);
 959         }
 960         public void analyzeTree(Env<AttrContext> env, JCTree tree, TreeMaker make) {
 961             try {
 962                 attrEnv = env;
 963                 Flow.this.make = make;
 964                 pendingExits = new ListBuffer<>();
 965                 alive = Liveness.ALIVE;
 966                 scan(tree);
 967             } finally {
 968                 pendingExits = null;
 969                 Flow.this.make = null;
 970             }
 971         }
 972     }
 973 
 974     /**
 975      * This pass implements the second step of the dataflow analysis, namely
 976      * the exception analysis. This is to ensure that every checked exception that is
 977      * thrown is declared or caught. The analyzer uses some info that has been set by
 978      * the liveliness analyzer.
 979      */
 980     class FlowAnalyzer extends BaseAnalyzer {
 981 
 982         /** A flag that indicates whether the last statement could
 983          *  complete normally.
 984          */
 985         HashMap<Symbol, List<Type>> preciseRethrowTypes;
 986 
 987         /** The current class being defined.
 988          */
 989         JCClassDecl classDef;
 990 
 991         /** The list of possibly thrown declarable exceptions.
 992          */
 993         List<Type> thrown;
 994 
 995         /** The list of exceptions that are either caught or declared to be
 996          *  thrown.
 997          */
 998         List<Type> caught;
 999 
1000         class ThrownPendingExit extends BaseAnalyzer.PendingExit {
1001 
1002             Type thrown;
1003 
1004             ThrownPendingExit(JCTree tree, Type thrown) {
1005                 super(tree);
1006                 this.thrown = thrown;
1007             }
1008         }
1009 
1010         @Override
1011         void markDead() {
1012             //do nothing
1013         }
1014 
1015         /*-------------------- Exceptions ----------------------*/
1016 
1017         /** Complain that pending exceptions are not caught.
1018          */
1019         void errorUncaught() {
1020             for (PendingExit exit = pendingExits.next();
1021                  exit != null;
1022                  exit = pendingExits.next()) {
1023                 if (exit instanceof ThrownPendingExit thrownExit) {
1024                     if (classDef != null &&
1025                         classDef.pos == exit.tree.pos) {
1026                         log.error(exit.tree.pos(),
1027                                   Errors.UnreportedExceptionDefaultConstructor(thrownExit.thrown));
1028                     } else if (exit.tree.hasTag(VARDEF) &&
1029                             ((JCVariableDecl)exit.tree).sym.isResourceVariable()) {
1030                         log.error(exit.tree.pos(),
1031                                   Errors.UnreportedExceptionImplicitClose(thrownExit.thrown,
1032                                                                           ((JCVariableDecl)exit.tree).sym.name));
1033                     } else {
1034                         log.error(exit.tree.pos(),
1035                                   Errors.UnreportedExceptionNeedToCatchOrThrow(thrownExit.thrown));
1036                     }
1037                 } else {
1038                     Assert.check(log.hasErrorOn(exit.tree.pos()));
1039                 }
1040             }
1041         }
1042 
1043         /** Record that exception is potentially thrown and check that it
1044          *  is caught.
1045          */
1046         void markThrown(JCTree tree, Type exc) {
1047             if (!chk.isUnchecked(tree.pos(), exc)) {
1048                 if (!chk.isHandled(exc, caught)) {
1049                     pendingExits.append(new ThrownPendingExit(tree, exc));
1050                 }
1051                 thrown = chk.incl(exc, thrown);
1052             }
1053         }
1054 
1055     /*************************************************************************
1056      * Visitor methods for statements and definitions
1057      *************************************************************************/
1058 
1059         /* ------------ Visitor methods for various sorts of trees -------------*/
1060 
1061         public void visitClassDef(JCClassDecl tree) {
1062             if (tree.sym == null) return;
1063 
1064             JCClassDecl classDefPrev = classDef;
1065             List<Type> thrownPrev = thrown;
1066             List<Type> caughtPrev = caught;
1067             ListBuffer<PendingExit> pendingExitsPrev = pendingExits;
1068             Lint lintPrev = lint;
1069             boolean anonymousClass = tree.name == names.empty;
1070             pendingExits = new ListBuffer<>();
1071             if (!anonymousClass) {
1072                 caught = List.nil();
1073             }
1074             classDef = tree;
1075             thrown = List.nil();
1076             lint = lint.augment(tree.sym);
1077 
1078             try {
1079                 // process all the static initializers
1080                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
1081                     if (!l.head.hasTag(METHODDEF) &&
1082                         (TreeInfo.flags(l.head) & STATIC) != 0) {
1083                         scan(l.head);
1084                         errorUncaught();
1085                     }
1086                 }
1087 
1088                 // add intersection of all thrown clauses of initial constructors
1089                 // to set of caught exceptions, unless class is anonymous.
1090                 if (!anonymousClass) {
1091                     boolean firstConstructor = true;
1092                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
1093                         if (TreeInfo.isInitialConstructor(l.head)) {
1094                             List<Type> mthrown =
1095                                 ((JCMethodDecl) l.head).sym.type.getThrownTypes();
1096                             if (firstConstructor) {
1097                                 caught = mthrown;
1098                                 firstConstructor = false;
1099                             } else {
1100                                 caught = chk.intersect(mthrown, caught);
1101                             }
1102                         }
1103                     }
1104                 }
1105 
1106                 // process all the instance initializers
1107                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
1108                     if (!l.head.hasTag(METHODDEF) &&
1109                         (TreeInfo.flags(l.head) & STATIC) == 0) {
1110                         scan(l.head);
1111                         errorUncaught();
1112                     }
1113                 }
1114 
1115                 // in an anonymous class, add the set of thrown exceptions to
1116                 // the throws clause of the synthetic constructor and propagate
1117                 // outwards.
1118                 // Changing the throws clause on the fly is okay here because
1119                 // the anonymous constructor can't be invoked anywhere else,
1120                 // and its type hasn't been cached.
1121                 if (anonymousClass) {
1122                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
1123                         if (TreeInfo.isConstructor(l.head)) {
1124                             JCMethodDecl mdef = (JCMethodDecl)l.head;
1125                             scan(mdef);
1126                             mdef.thrown = make.Types(thrown);
1127                             mdef.sym.type = types.createMethodTypeWithThrown(mdef.sym.type, thrown);
1128                         }
1129                     }
1130                     thrownPrev = chk.union(thrown, thrownPrev);
1131                 }
1132 
1133                 // process all the methods
1134                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
1135                     if (anonymousClass && TreeInfo.isConstructor(l.head))
1136                         continue; // there can never be an uncaught exception.
1137                     if (l.head.hasTag(METHODDEF)) {
1138                         scan(l.head);
1139                         errorUncaught();
1140                     }
1141                 }
1142 
1143                 thrown = thrownPrev;
1144             } finally {
1145                 pendingExits = pendingExitsPrev;
1146                 caught = caughtPrev;
1147                 classDef = classDefPrev;
1148                 lint = lintPrev;
1149             }
1150         }
1151 
1152         public void visitMethodDef(JCMethodDecl tree) {
1153             if (tree.body == null) return;
1154 
1155             List<Type> caughtPrev = caught;
1156             List<Type> mthrown = tree.sym.type.getThrownTypes();
1157             Lint lintPrev = lint;
1158 
1159             lint = lint.augment(tree.sym);
1160 
1161             Assert.check(pendingExits.isEmpty());
1162 
1163             try {
1164                 for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
1165                     JCVariableDecl def = l.head;
1166                     scan(def);
1167                 }
1168                 if (TreeInfo.isInitialConstructor(tree))
1169                     caught = chk.union(caught, mthrown);
1170                 else if ((tree.sym.flags() & (BLOCK | STATIC)) != BLOCK)
1171                     caught = mthrown;
1172                 // else we are in an instance initializer block;
1173                 // leave caught unchanged.
1174 
1175                 scan(tree.body);
1176 
1177                 List<PendingExit> exits = pendingExits.toList();
1178                 pendingExits = new ListBuffer<>();
1179                 while (exits.nonEmpty()) {
1180                     PendingExit exit = exits.head;
1181                     exits = exits.tail;
1182                     if (!(exit instanceof ThrownPendingExit)) {
1183                         Assert.check(exit.tree.hasTag(RETURN) ||
1184                                          log.hasErrorOn(exit.tree.pos()));
1185                     } else {
1186                         // uncaught throws will be reported later
1187                         pendingExits.append(exit);
1188                     }
1189                 }
1190             } finally {
1191                 caught = caughtPrev;
1192                 lint = lintPrev;
1193             }
1194         }
1195 
1196         public void visitVarDef(JCVariableDecl tree) {
1197             if (tree.init != null) {
1198                 Lint lintPrev = lint;
1199                 lint = lint.augment(tree.sym);
1200                 try{
1201                     scan(tree.init);
1202                 } finally {
1203                     lint = lintPrev;
1204                 }
1205             }
1206         }
1207 
1208         public void visitBlock(JCBlock tree) {
1209             scan(tree.stats);
1210         }
1211 
1212         public void visitDoLoop(JCDoWhileLoop tree) {
1213             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1214             pendingExits = new ListBuffer<>();
1215             scan(tree.body);
1216             resolveContinues(tree);
1217             scan(tree.cond);
1218             resolveBreaks(tree, prevPendingExits);
1219         }
1220 
1221         public void visitWhileLoop(JCWhileLoop tree) {
1222             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1223             pendingExits = new ListBuffer<>();
1224             scan(tree.cond);
1225             scan(tree.body);
1226             resolveContinues(tree);
1227             resolveBreaks(tree, prevPendingExits);
1228         }
1229 
1230         public void visitForLoop(JCForLoop tree) {
1231             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1232             scan(tree.init);
1233             pendingExits = new ListBuffer<>();
1234             if (tree.cond != null) {
1235                 scan(tree.cond);
1236             }
1237             scan(tree.body);
1238             resolveContinues(tree);
1239             scan(tree.step);
1240             resolveBreaks(tree, prevPendingExits);
1241         }
1242 
1243         public void visitForeachLoop(JCEnhancedForLoop tree) {
1244             visitVarDef(tree.var);
1245             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1246             scan(tree.expr);
1247             pendingExits = new ListBuffer<>();
1248             scan(tree.body);
1249             resolveContinues(tree);
1250             resolveBreaks(tree, prevPendingExits);
1251         }
1252 
1253         public void visitLabelled(JCLabeledStatement tree) {
1254             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1255             pendingExits = new ListBuffer<>();
1256             scan(tree.body);
1257             resolveBreaks(tree, prevPendingExits);
1258         }
1259 
1260         public void visitSwitch(JCSwitch tree) {
1261             handleSwitch(tree, tree.selector, tree.cases);
1262         }
1263 
1264         @Override
1265         public void visitSwitchExpression(JCSwitchExpression tree) {
1266             handleSwitch(tree, tree.selector, tree.cases);
1267         }
1268 
1269         private void handleSwitch(JCTree tree, JCExpression selector, List<JCCase> cases) {
1270             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1271             pendingExits = new ListBuffer<>();
1272             scan(selector);
1273             for (List<JCCase> l = cases; l.nonEmpty(); l = l.tail) {
1274                 JCCase c = l.head;
1275                 scan(c.labels);
1276                 scan(c.stats);
1277             }
1278             if (tree.hasTag(SWITCH_EXPRESSION)) {
1279                 resolveYields(tree, prevPendingExits);
1280             } else {
1281                 resolveBreaks(tree, prevPendingExits);
1282             }
1283         }
1284 
1285         public void visitTry(JCTry tree) {
1286             List<Type> caughtPrev = caught;
1287             List<Type> thrownPrev = thrown;
1288             thrown = List.nil();
1289             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
1290                 List<JCExpression> subClauses = TreeInfo.isMultiCatch(l.head) ?
1291                         ((JCTypeUnion)l.head.param.vartype).alternatives :
1292                         List.of(l.head.param.vartype);
1293                 for (JCExpression ct : subClauses) {
1294                     caught = chk.incl(ct.type, caught);
1295                 }
1296             }
1297 
1298             ListBuffer<PendingExit> prevPendingExits = pendingExits;
1299             pendingExits = new ListBuffer<>();
1300             for (JCTree resource : tree.resources) {
1301                 if (resource instanceof JCVariableDecl variableDecl) {
1302                     visitVarDef(variableDecl);
1303                 } else if (resource instanceof JCExpression expression) {
1304                     scan(expression);
1305                 } else {
1306                     throw new AssertionError(tree);  // parser error
1307                 }
1308             }
1309             for (JCTree resource : tree.resources) {
1310                 List<Type> closeableSupertypes = resource.type.isCompound() ?
1311                     types.interfaces(resource.type).prepend(types.supertype(resource.type)) :
1312                     List.of(resource.type);
1313                 for (Type sup : closeableSupertypes) {
1314                     if (types.asSuper(sup, syms.autoCloseableType.tsym) != null) {
1315                         Symbol closeMethod = rs.resolveQualifiedMethod(tree,
1316                                 attrEnv,
1317                                 types.skipTypeVars(sup, false),
1318                                 names.close,
1319                                 List.nil(),
1320                                 List.nil());
1321                         Type mt = types.memberType(resource.type, closeMethod);
1322                         if (closeMethod.kind == MTH) {
1323                             for (Type t : mt.getThrownTypes()) {
1324                                 markThrown(resource, t);
1325                             }
1326                         }
1327                     }
1328                 }
1329             }
1330             scan(tree.body);
1331             List<Type> thrownInTry = chk.union(thrown, List.of(syms.runtimeExceptionType, syms.errorType));
1332             thrown = thrownPrev;
1333             caught = caughtPrev;
1334 
1335             List<Type> caughtInTry = List.nil();
1336             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
1337                 JCVariableDecl param = l.head.param;
1338                 List<JCExpression> subClauses = TreeInfo.isMultiCatch(l.head) ?
1339                         ((JCTypeUnion)l.head.param.vartype).alternatives :
1340                         List.of(l.head.param.vartype);
1341                 List<Type> ctypes = List.nil();
1342                 List<Type> rethrownTypes = chk.diff(thrownInTry, caughtInTry);
1343                 for (JCExpression ct : subClauses) {
1344                     Type exc = ct.type;
1345                     if (exc != syms.unknownType) {
1346                         ctypes = ctypes.append(exc);
1347                         if (types.isSameType(exc, syms.objectType))
1348                             continue;
1349                         var pos = subClauses.size() > 1 ? ct.pos() : l.head.pos();
1350                         checkCaughtType(pos, exc, thrownInTry, caughtInTry);
1351                         caughtInTry = chk.incl(exc, caughtInTry);
1352                     }
1353                 }
1354                 scan(param);
1355                 preciseRethrowTypes.put(param.sym, chk.intersect(ctypes, rethrownTypes));
1356                 scan(l.head.body);
1357                 preciseRethrowTypes.remove(param.sym);
1358             }
1359             if (tree.finalizer != null) {
1360                 List<Type> savedThrown = thrown;
1361                 thrown = List.nil();
1362                 ListBuffer<PendingExit> exits = pendingExits;
1363                 pendingExits = prevPendingExits;
1364                 scan(tree.finalizer);
1365                 if (!tree.finallyCanCompleteNormally) {
1366                     // discard exits and exceptions from try and finally
1367                     thrown = chk.union(thrown, thrownPrev);
1368                 } else {
1369                     thrown = chk.union(thrown, chk.diff(thrownInTry, caughtInTry));
1370                     thrown = chk.union(thrown, savedThrown);
1371                     // FIX: this doesn't preserve source order of exits in catch
1372                     // versus finally!
1373                     while (exits.nonEmpty()) {
1374                         pendingExits.append(exits.next());
1375                     }
1376                 }
1377             } else {
1378                 thrown = chk.union(thrown, chk.diff(thrownInTry, caughtInTry));
1379                 ListBuffer<PendingExit> exits = pendingExits;
1380                 pendingExits = prevPendingExits;
1381                 while (exits.nonEmpty()) pendingExits.append(exits.next());
1382             }
1383         }
1384 
1385         @Override
1386         public void visitIf(JCIf tree) {
1387             scan(tree.cond);
1388             scan(tree.thenpart);
1389             if (tree.elsepart != null) {
1390                 scan(tree.elsepart);
1391             }
1392         }
1393 
1394         void checkCaughtType(DiagnosticPosition pos, Type exc, List<Type> thrownInTry, List<Type> caughtInTry) {
1395             if (chk.subset(exc, caughtInTry)) {
1396                 log.error(pos, Errors.ExceptAlreadyCaught(exc));
1397             } else if (!chk.isUnchecked(pos, exc) &&
1398                     !isExceptionOrThrowable(exc) &&
1399                     !chk.intersects(exc, thrownInTry)) {
1400                 log.error(pos, Errors.ExceptNeverThrownInTry(exc));
1401             } else {
1402                 List<Type> catchableThrownTypes = chk.intersect(List.of(exc), thrownInTry);
1403                 // 'catchableThrownTypes' cannot possibly be empty - if 'exc' was an
1404                 // unchecked exception, the result list would not be empty, as the augmented
1405                 // thrown set includes { RuntimeException, Error }; if 'exc' was a checked
1406                 // exception, that would have been covered in the branch above
1407                 if (chk.diff(catchableThrownTypes, caughtInTry).isEmpty() &&
1408                         !isExceptionOrThrowable(exc)) {
1409                     Warning key = catchableThrownTypes.length() == 1 ?
1410                             Warnings.UnreachableCatch(catchableThrownTypes) :
1411                             Warnings.UnreachableCatch1(catchableThrownTypes);
1412                     log.warning(pos, key);
1413                 }
1414             }
1415         }
1416         //where
1417             private boolean isExceptionOrThrowable(Type exc) {
1418                 return exc.tsym == syms.throwableType.tsym ||
1419                     exc.tsym == syms.exceptionType.tsym;
1420             }
1421 
1422         public void visitBreak(JCBreak tree) {
1423             recordExit(new PendingExit(tree));
1424         }
1425 
1426         public void visitYield(JCYield tree) {
1427             scan(tree.value);
1428             recordExit(new PendingExit(tree));
1429         }
1430 
1431         public void visitContinue(JCContinue tree) {
1432             recordExit(new PendingExit(tree));
1433         }
1434 
1435         public void visitReturn(JCReturn tree) {
1436             scan(tree.expr);
1437             recordExit(new PendingExit(tree));
1438         }
1439 
1440         public void visitThrow(JCThrow tree) {
1441             scan(tree.expr);
1442             Symbol sym = TreeInfo.symbol(tree.expr);
1443             if (sym != null &&
1444                 sym.kind == VAR &&
1445                 (sym.flags() & (FINAL | EFFECTIVELY_FINAL)) != 0 &&
1446                 preciseRethrowTypes.get(sym) != null) {
1447                 for (Type t : preciseRethrowTypes.get(sym)) {
1448                     markThrown(tree, t);
1449                 }
1450             }
1451             else {
1452                 markThrown(tree, tree.expr.type);
1453             }
1454             markDead();
1455         }
1456 
1457         public void visitApply(JCMethodInvocation tree) {
1458             scan(tree.meth);
1459             scan(tree.args);
1460             for (List<Type> l = tree.meth.type.getThrownTypes(); l.nonEmpty(); l = l.tail)
1461                 markThrown(tree, l.head);
1462         }
1463 
1464         public void visitNewClass(JCNewClass tree) {
1465             scan(tree.encl);
1466             scan(tree.args);
1467            // scan(tree.def);
1468             for (List<Type> l = tree.constructorType.getThrownTypes();
1469                  l.nonEmpty();
1470                  l = l.tail) {
1471                 markThrown(tree, l.head);
1472             }
1473             List<Type> caughtPrev = caught;
1474             try {
1475                 // If the new class expression defines an anonymous class,
1476                 // analysis of the anonymous constructor may encounter thrown
1477                 // types which are unsubstituted type variables.
1478                 // However, since the constructor's actual thrown types have
1479                 // already been marked as thrown, it is safe to simply include
1480                 // each of the constructor's formal thrown types in the set of
1481                 // 'caught/declared to be thrown' types, for the duration of
1482                 // the class def analysis.
1483                 if (tree.def != null)
1484                     for (List<Type> l = tree.constructor.type.getThrownTypes();
1485                          l.nonEmpty();
1486                          l = l.tail) {
1487                         caught = chk.incl(l.head, caught);
1488                     }
1489                 scan(tree.def);
1490             }
1491             finally {
1492                 caught = caughtPrev;
1493             }
1494         }
1495 
1496         @Override
1497         public void visitLambda(JCLambda tree) {
1498             if (tree.type != null &&
1499                     tree.type.isErroneous()) {
1500                 return;
1501             }
1502             List<Type> prevCaught = caught;
1503             List<Type> prevThrown = thrown;
1504             ListBuffer<PendingExit> prevPending = pendingExits;
1505             try {
1506                 pendingExits = new ListBuffer<>();
1507                 caught = tree.getDescriptorType(types).getThrownTypes();
1508                 thrown = List.nil();
1509                 scan(tree.body);
1510                 List<PendingExit> exits = pendingExits.toList();
1511                 pendingExits = new ListBuffer<>();
1512                 while (exits.nonEmpty()) {
1513                     PendingExit exit = exits.head;
1514                     exits = exits.tail;
1515                     if (!(exit instanceof ThrownPendingExit)) {
1516                         Assert.check(exit.tree.hasTag(RETURN) ||
1517                                         log.hasErrorOn(exit.tree.pos()));
1518                     } else {
1519                         // uncaught throws will be reported later
1520                         pendingExits.append(exit);
1521                     }
1522                 }
1523 
1524                 errorUncaught();
1525             } finally {
1526                 pendingExits = prevPending;
1527                 caught = prevCaught;
1528                 thrown = prevThrown;
1529             }
1530         }
1531 
1532         public void visitModuleDef(JCModuleDecl tree) {
1533             // Do nothing for modules
1534         }
1535 
1536     /**************************************************************************
1537      * main method
1538      *************************************************************************/
1539 
1540         /** Perform definite assignment/unassignment analysis on a tree.
1541          */
1542         public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
1543             analyzeTree(env, env.tree, make);
1544         }
1545         public void analyzeTree(Env<AttrContext> env, JCTree tree, TreeMaker make) {
1546             try {
1547                 attrEnv = env;
1548                 Flow.this.make = make;
1549                 pendingExits = new ListBuffer<>();
1550                 preciseRethrowTypes = new HashMap<>();
1551                 this.thrown = this.caught = null;
1552                 this.classDef = null;
1553                 scan(tree);
1554             } finally {
1555                 pendingExits = null;
1556                 Flow.this.make = null;
1557                 this.thrown = this.caught = null;
1558                 this.classDef = null;
1559             }
1560         }
1561     }
1562 
1563     /**
1564      * Specialized pass that performs reachability analysis on a lambda
1565      */
1566     class LambdaAliveAnalyzer extends AliveAnalyzer {
1567 
1568         boolean inLambda;
1569 
1570         @Override
1571         public void visitReturn(JCReturn tree) {
1572             //ignore lambda return expression (which might not even be attributed)
1573             recordExit(new PendingExit(tree));
1574         }
1575 
1576         @Override
1577         public void visitLambda(JCLambda tree) {
1578             if (inLambda || tree.getBodyKind() == BodyKind.EXPRESSION) {
1579                 return;
1580             }
1581             inLambda = true;
1582             try {
1583                 super.visitLambda(tree);
1584             } finally {
1585                 inLambda = false;
1586             }
1587         }
1588 
1589         @Override
1590         public void visitClassDef(JCClassDecl tree) {
1591             //skip
1592         }
1593     }
1594 
1595     /**
1596      * Determine if alive after the given tree.
1597      */
1598     class SnippetAliveAnalyzer extends AliveAnalyzer {
1599         @Override
1600         public void visitClassDef(JCClassDecl tree) {
1601             //skip
1602         }
1603         @Override
1604         public void visitLambda(JCLambda tree) {
1605             //skip
1606         }
1607         public boolean isAlive() {
1608             return super.alive != Liveness.DEAD;
1609         }
1610     }
1611 
1612     class SnippetBreakAnalyzer extends AliveAnalyzer {
1613         private final Set<JCTree> seenTrees = new HashSet<>();
1614         private boolean breaksOut;
1615 
1616         public SnippetBreakAnalyzer() {
1617         }
1618 
1619         @Override
1620         public void visitLabelled(JCTree.JCLabeledStatement tree) {
1621             seenTrees.add(tree);
1622             super.visitLabelled(tree);
1623         }
1624 
1625         @Override
1626         public void visitWhileLoop(JCTree.JCWhileLoop tree) {
1627             seenTrees.add(tree);
1628             super.visitWhileLoop(tree);
1629         }
1630 
1631         @Override
1632         public void visitForLoop(JCTree.JCForLoop tree) {
1633             seenTrees.add(tree);
1634             super.visitForLoop(tree);
1635         }
1636 
1637         @Override
1638         public void visitForeachLoop(JCTree.JCEnhancedForLoop tree) {
1639             seenTrees.add(tree);
1640             super.visitForeachLoop(tree);
1641         }
1642 
1643         @Override
1644         public void visitDoLoop(JCTree.JCDoWhileLoop tree) {
1645             seenTrees.add(tree);
1646             super.visitDoLoop(tree);
1647         }
1648 
1649         @Override
1650         public void visitBreak(JCBreak tree) {
1651             breaksOut |= (super.alive == Liveness.ALIVE &&
1652                           !seenTrees.contains(tree.target));
1653             super.visitBreak(tree);
1654         }
1655 
1656         public boolean breaksOut() {
1657             return breaksOut;
1658         }
1659     }
1660 
1661     /**
1662      * Specialized pass that performs DA/DU on a lambda
1663      */
1664     class LambdaAssignAnalyzer extends AssignAnalyzer {
1665         WriteableScope enclosedSymbols;
1666         boolean inLambda;
1667 
1668         LambdaAssignAnalyzer(Env<AttrContext> env) {
1669             enclosedSymbols = WriteableScope.create(env.enclClass.sym);
1670         }
1671 
1672         @Override
1673         public void visitLambda(JCLambda tree) {
1674             if (inLambda) {
1675                 return;
1676             }
1677             inLambda = true;
1678             try {
1679                 super.visitLambda(tree);
1680             } finally {
1681                 inLambda = false;
1682             }
1683         }
1684 
1685         @Override
1686         public void visitVarDef(JCVariableDecl tree) {
1687             enclosedSymbols.enter(tree.sym);
1688             super.visitVarDef(tree);
1689         }
1690         @Override
1691         protected boolean trackable(VarSymbol sym) {
1692             return enclosedSymbols.includes(sym) &&
1693                    sym.owner.kind == MTH;
1694         }
1695 
1696         @Override
1697         public void visitClassDef(JCClassDecl tree) {
1698             //skip
1699         }
1700     }
1701 
1702     /**
1703      * Specialized pass that performs inference of thrown types for lambdas.
1704      */
1705     class LambdaFlowAnalyzer extends FlowAnalyzer {
1706         List<Type> inferredThrownTypes;
1707         boolean inLambda;
1708         @Override
1709         public void visitLambda(JCLambda tree) {
1710             if ((tree.type != null &&
1711                     tree.type.isErroneous()) || inLambda) {
1712                 return;
1713             }
1714             List<Type> prevCaught = caught;
1715             List<Type> prevThrown = thrown;
1716             ListBuffer<PendingExit> prevPending = pendingExits;
1717             inLambda = true;
1718             try {
1719                 pendingExits = new ListBuffer<>();
1720                 caught = List.of(syms.throwableType);
1721                 thrown = List.nil();
1722                 scan(tree.body);
1723                 inferredThrownTypes = thrown;
1724             } finally {
1725                 pendingExits = prevPending;
1726                 caught = prevCaught;
1727                 thrown = prevThrown;
1728                 inLambda = false;
1729             }
1730         }
1731         @Override
1732         public void visitClassDef(JCClassDecl tree) {
1733             //skip
1734         }
1735     }
1736 
1737     /**
1738      * This pass implements (i) definite assignment analysis, which ensures that
1739      * each variable is assigned when used and (ii) definite unassignment analysis,
1740      * which ensures that no final variable is assigned more than once. This visitor
1741      * depends on the results of the liveliness analyzer. This pass is also used to mark
1742      * effectively-final local variables/parameters.
1743      */
1744 
1745     public class AssignAnalyzer extends BaseAnalyzer {
1746 
1747         /** The set of definitely assigned variables.
1748          */
1749         final Bits inits;
1750 
1751         /** The set of definitely unassigned variables.
1752          */
1753         final Bits uninits;
1754 
1755         /** The set of variables that are definitely unassigned everywhere
1756          *  in current try block. This variable is maintained lazily; it is
1757          *  updated only when something gets removed from uninits,
1758          *  typically by being assigned in reachable code.  To obtain the
1759          *  correct set of variables which are definitely unassigned
1760          *  anywhere in current try block, intersect uninitsTry and
1761          *  uninits.
1762          */
1763         final Bits uninitsTry;
1764 
1765         /** When analyzing a condition, inits and uninits are null.
1766          *  Instead we have:
1767          */
1768         final Bits initsWhenTrue;
1769         final Bits initsWhenFalse;
1770         final Bits uninitsWhenTrue;
1771         final Bits uninitsWhenFalse;
1772 
1773         /** A mapping from addresses to variable symbols.
1774          */
1775         protected JCVariableDecl[] vardecls;
1776 
1777         /** The current class being defined.
1778          */
1779         JCClassDecl classDef;
1780 
1781         /** The first variable sequence number in this class definition.
1782          */
1783         int firstadr;
1784 
1785         /** The next available variable sequence number.
1786          */
1787         protected int nextadr;
1788 
1789         /** The first variable sequence number in a block that can return.
1790          */
1791         protected int returnadr;
1792 
1793         /** The list of unreferenced automatic resources.
1794          */
1795         WriteableScope unrefdResources;
1796 
1797         /** Modified when processing a loop body the second time for DU analysis. */
1798         FlowKind flowKind = FlowKind.NORMAL;
1799 
1800         /** The starting position of the analyzed tree */
1801         int startPos;
1802 
1803         public class AssignPendingExit extends BaseAnalyzer.PendingExit {
1804 
1805             final Bits inits;
1806             final Bits uninits;
1807             final Bits exit_inits = new Bits(true);
1808             final Bits exit_uninits = new Bits(true);
1809 
1810             public AssignPendingExit(JCTree tree, final Bits inits, final Bits uninits) {
1811                 super(tree);
1812                 this.inits = inits;
1813                 this.uninits = uninits;
1814                 this.exit_inits.assign(inits);
1815                 this.exit_uninits.assign(uninits);
1816             }
1817 
1818             @Override
1819             public void resolveJump() {
1820                 inits.andSet(exit_inits);
1821                 uninits.andSet(exit_uninits);
1822             }
1823         }
1824 
1825         public AssignAnalyzer() {
1826             this.inits = new Bits();
1827             uninits = new Bits();
1828             uninitsTry = new Bits();
1829             initsWhenTrue = new Bits(true);
1830             initsWhenFalse = new Bits(true);
1831             uninitsWhenTrue = new Bits(true);
1832             uninitsWhenFalse = new Bits(true);
1833         }
1834 
1835         private boolean isInitialConstructor = false;
1836 
1837         @Override
1838         protected void markDead() {
1839             if (!isInitialConstructor) {
1840                 inits.inclRange(returnadr, nextadr);
1841             } else {
1842                 for (int address = returnadr; address < nextadr; address++) {
1843                     if (!(isFinalUninitializedStaticField(vardecls[address].sym))) {
1844                         inits.incl(address);
1845                     }
1846                 }
1847             }
1848             uninits.inclRange(returnadr, nextadr);
1849         }
1850 
1851         /*-------------- Processing variables ----------------------*/
1852 
1853         /** Do we need to track init/uninit state of this symbol?
1854          *  I.e. is symbol either a local or a blank final variable?
1855          */
1856         protected boolean trackable(VarSymbol sym) {
1857             return
1858                 sym.pos >= startPos &&
1859                 ((sym.owner.kind == MTH || sym.owner.kind == VAR ||
1860                 isFinalUninitializedField(sym)));
1861         }
1862 
1863         boolean isFinalUninitializedField(VarSymbol sym) {
1864             return sym.owner.kind == TYP &&
1865                    ((sym.flags() & (FINAL | HASINIT | PARAMETER)) == FINAL &&
1866                    classDef.sym.isEnclosedBy((ClassSymbol)sym.owner));
1867         }
1868 
1869         boolean isFinalUninitializedStaticField(VarSymbol sym) {
1870             return isFinalUninitializedField(sym) && sym.isStatic();
1871         }
1872 
1873         /** Initialize new trackable variable by setting its address field
1874          *  to the next available sequence number and entering it under that
1875          *  index into the vars array.
1876          */
1877         void newVar(JCVariableDecl varDecl) {
1878             VarSymbol sym = varDecl.sym;
1879             vardecls = ArrayUtils.ensureCapacity(vardecls, nextadr);
1880             if ((sym.flags() & FINAL) == 0) {
1881                 sym.flags_field |= EFFECTIVELY_FINAL;
1882             }
1883             sym.adr = nextadr;
1884             vardecls[nextadr] = varDecl;
1885             inits.excl(nextadr);
1886             uninits.incl(nextadr);
1887             nextadr++;
1888         }
1889 
1890         /** Record an initialization of a trackable variable.
1891          */
1892         void letInit(DiagnosticPosition pos, VarSymbol sym) {
1893             if (sym.adr >= firstadr && trackable(sym)) {
1894                 if ((sym.flags() & EFFECTIVELY_FINAL) != 0) {
1895                     if (!uninits.isMember(sym.adr)) {
1896                         //assignment targeting an effectively final variable
1897                         //makes the variable lose its status of effectively final
1898                         //if the variable is _not_ definitively unassigned
1899                         sym.flags_field &= ~EFFECTIVELY_FINAL;
1900                     } else {
1901                         uninit(sym);
1902                     }
1903                 }
1904                 else if ((sym.flags() & FINAL) != 0) {
1905                     if ((sym.flags() & PARAMETER) != 0) {
1906                         if ((sym.flags() & UNION) != 0) { //multi-catch parameter
1907                             log.error(pos, Errors.MulticatchParameterMayNotBeAssigned(sym));
1908                         }
1909                         else {
1910                             log.error(pos,
1911                                       Errors.FinalParameterMayNotBeAssigned(sym));
1912                         }
1913                     } else if (!uninits.isMember(sym.adr)) {
1914                         log.error(pos, diags.errorKey(flowKind.errKey, sym));
1915                     } else {
1916                         uninit(sym);
1917                     }
1918                 }
1919                 inits.incl(sym.adr);
1920             } else if ((sym.flags() & FINAL) != 0) {
1921                 log.error(pos, Errors.VarMightAlreadyBeAssigned(sym));
1922             }
1923         }
1924         //where
1925             void uninit(VarSymbol sym) {
1926                 if (!inits.isMember(sym.adr)) {
1927                     // reachable assignment
1928                     uninits.excl(sym.adr);
1929                     uninitsTry.excl(sym.adr);
1930                 } else {
1931                     //log.rawWarning(pos, "unreachable assignment");//DEBUG
1932                     uninits.excl(sym.adr);
1933                 }
1934             }
1935 
1936         /** If tree is either a simple name or of the form this.name or
1937          *  C.this.name, and tree represents a trackable variable,
1938          *  record an initialization of the variable.
1939          */
1940         void letInit(JCTree tree) {
1941             tree = TreeInfo.skipParens(tree);
1942             if (tree.hasTag(IDENT) || tree.hasTag(SELECT)) {
1943                 Symbol sym = TreeInfo.symbol(tree);
1944                 if (sym.kind == VAR) {
1945                     letInit(tree.pos(), (VarSymbol)sym);
1946                 }
1947             }
1948         }
1949 
1950         /** Check that trackable variable is initialized.
1951          */
1952         void checkInit(DiagnosticPosition pos, VarSymbol sym) {
1953             checkInit(pos, sym, Errors.VarMightNotHaveBeenInitialized(sym));
1954         }
1955 
1956         void checkInit(DiagnosticPosition pos, VarSymbol sym, Error errkey) {
1957             if ((sym.adr >= firstadr || sym.owner.kind != TYP) &&
1958                 trackable(sym) &&
1959                 !inits.isMember(sym.adr) &&
1960                 (sym.flags_field & CLASH) == 0) {
1961                     log.error(pos, errkey);
1962                 inits.incl(sym.adr);
1963             }
1964         }
1965 
1966         /** Utility method to reset several Bits instances.
1967          */
1968         private void resetBits(Bits... bits) {
1969             for (Bits b : bits) {
1970                 b.reset();
1971             }
1972         }
1973 
1974         /** Split (duplicate) inits/uninits into WhenTrue/WhenFalse sets
1975          */
1976         void split(boolean setToNull) {
1977             initsWhenFalse.assign(inits);
1978             uninitsWhenFalse.assign(uninits);
1979             initsWhenTrue.assign(inits);
1980             uninitsWhenTrue.assign(uninits);
1981             if (setToNull) {
1982                 resetBits(inits, uninits);
1983             }
1984         }
1985 
1986         /** Merge (intersect) inits/uninits from WhenTrue/WhenFalse sets.
1987          */
1988         protected void merge() {
1989             inits.assign(initsWhenFalse.andSet(initsWhenTrue));
1990             uninits.assign(uninitsWhenFalse.andSet(uninitsWhenTrue));
1991         }
1992 
1993     /* ************************************************************************
1994      * Visitor methods for statements and definitions
1995      *************************************************************************/
1996 
1997         /** Analyze an expression. Make sure to set (un)inits rather than
1998          *  (un)initsWhenTrue(WhenFalse) on exit.
1999          */
2000         void scanExpr(JCTree tree) {
2001             if (tree != null) {
2002                 scan(tree);
2003                 if (inits.isReset()) {
2004                     merge();
2005                 }
2006             }
2007         }
2008 
2009         /** Analyze a list of expressions.
2010          */
2011         void scanExprs(List<? extends JCExpression> trees) {
2012             if (trees != null)
2013                 for (List<? extends JCExpression> l = trees; l.nonEmpty(); l = l.tail)
2014                     scanExpr(l.head);
2015         }
2016 
2017         /** Analyze a condition. Make sure to set (un)initsWhenTrue(WhenFalse)
2018          *  rather than (un)inits on exit.
2019          */
2020         void scanCond(JCTree tree) {
2021             if (tree.type.isFalse()) {
2022                 if (inits.isReset()) merge();
2023                 initsWhenTrue.assign(inits);
2024                 initsWhenTrue.inclRange(firstadr, nextadr);
2025                 uninitsWhenTrue.assign(uninits);
2026                 uninitsWhenTrue.inclRange(firstadr, nextadr);
2027                 initsWhenFalse.assign(inits);
2028                 uninitsWhenFalse.assign(uninits);
2029             } else if (tree.type.isTrue()) {
2030                 if (inits.isReset()) merge();
2031                 initsWhenFalse.assign(inits);
2032                 initsWhenFalse.inclRange(firstadr, nextadr);
2033                 uninitsWhenFalse.assign(uninits);
2034                 uninitsWhenFalse.inclRange(firstadr, nextadr);
2035                 initsWhenTrue.assign(inits);
2036                 uninitsWhenTrue.assign(uninits);
2037             } else {
2038                 scan(tree);
2039                 if (!inits.isReset())
2040                     split(tree.type != syms.unknownType);
2041             }
2042             if (tree.type != syms.unknownType) {
2043                 resetBits(inits, uninits);
2044             }
2045         }
2046 
2047         /* ------------ Visitor methods for various sorts of trees -------------*/
2048 
2049         public void visitClassDef(JCClassDecl tree) {
2050             if (tree.sym == null) {
2051                 return;
2052             }
2053 
2054             Lint lintPrev = lint;
2055             lint = lint.augment(tree.sym);
2056             try {
2057                 if (tree.sym == null) {
2058                     return;
2059                 }
2060 
2061                 JCClassDecl classDefPrev = classDef;
2062                 int firstadrPrev = firstadr;
2063                 int nextadrPrev = nextadr;
2064                 ListBuffer<PendingExit> pendingExitsPrev = pendingExits;
2065 
2066                 pendingExits = new ListBuffer<>();
2067                 if (tree.name != names.empty) {
2068                     firstadr = nextadr;
2069                 }
2070                 classDef = tree;
2071                 try {
2072                     // define all the static fields
2073                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
2074                         if (l.head.hasTag(VARDEF)) {
2075                             JCVariableDecl def = (JCVariableDecl)l.head;
2076                             if ((def.mods.flags & STATIC) != 0) {
2077                                 VarSymbol sym = def.sym;
2078                                 if (trackable(sym)) {
2079                                     newVar(def);
2080                                 }
2081                             }
2082                         }
2083                     }
2084 
2085                     // process all the static initializers
2086                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
2087                         if (!l.head.hasTag(METHODDEF) &&
2088                             (TreeInfo.flags(l.head) & STATIC) != 0) {
2089                             scan(l.head);
2090                             clearPendingExits(false);
2091                         }
2092                     }
2093 
2094                     // define all the instance fields
2095                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
2096                         if (l.head.hasTag(VARDEF)) {
2097                             JCVariableDecl def = (JCVariableDecl)l.head;
2098                             if ((def.mods.flags & STATIC) == 0) {
2099                                 VarSymbol sym = def.sym;
2100                                 if (trackable(sym)) {
2101                                     newVar(def);
2102                                 }
2103                             }
2104                         }
2105                     }
2106 
2107                     // process all the instance initializers
2108                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
2109                         if (!l.head.hasTag(METHODDEF) &&
2110                             (TreeInfo.flags(l.head) & STATIC) == 0) {
2111                             scan(l.head);
2112                             clearPendingExits(false);
2113                         }
2114                     }
2115 
2116                     // process all the methods
2117                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
2118                         if (l.head.hasTag(METHODDEF)) {
2119                             scan(l.head);
2120                         }
2121                     }
2122                 } finally {
2123                     pendingExits = pendingExitsPrev;
2124                     nextadr = nextadrPrev;
2125                     firstadr = firstadrPrev;
2126                     classDef = classDefPrev;
2127                 }
2128             } finally {
2129                 lint = lintPrev;
2130             }
2131         }
2132 
2133         public void visitMethodDef(JCMethodDecl tree) {
2134             if (tree.body == null) {
2135                 return;
2136             }
2137 
2138             /*  MemberEnter can generate synthetic methods ignore them
2139              */
2140             if ((tree.sym.flags() & SYNTHETIC) != 0) {
2141                 return;
2142             }
2143 
2144             Lint lintPrev = lint;
2145             lint = lint.augment(tree.sym);
2146             try {
2147                 if (tree.body == null) {
2148                     return;
2149                 }
2150                 /*  Ignore synthetic methods, except for translated lambda methods.
2151                  */
2152                 if ((tree.sym.flags() & (SYNTHETIC | LAMBDA_METHOD)) == SYNTHETIC) {
2153                     return;
2154                 }
2155 
2156                 final Bits initsPrev = new Bits(inits);
2157                 final Bits uninitsPrev = new Bits(uninits);
2158                 int nextadrPrev = nextadr;
2159                 int firstadrPrev = firstadr;
2160                 int returnadrPrev = returnadr;
2161 
2162                 Assert.check(pendingExits.isEmpty());
2163                 boolean lastInitialConstructor = isInitialConstructor;
2164                 try {
2165                     isInitialConstructor = TreeInfo.isInitialConstructor(tree);
2166 
2167                     if (!isInitialConstructor) {
2168                         firstadr = nextadr;
2169                     }
2170                     for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
2171                         JCVariableDecl def = l.head;
2172                         scan(def);
2173                         Assert.check((def.sym.flags() & PARAMETER) != 0, "Method parameter without PARAMETER flag");
2174                         /*  If we are executing the code from Gen, then there can be
2175                          *  synthetic or mandated variables, ignore them.
2176                          */
2177                         initParam(def);
2178                     }
2179                     // else we are in an instance initializer block;
2180                     // leave caught unchanged.
2181                     scan(tree.body);
2182 
2183                     boolean isCompactConstructor = (tree.sym.flags() & Flags.COMPACT_RECORD_CONSTRUCTOR) != 0;
2184                     if (isInitialConstructor) {
2185                         boolean isSynthesized = (tree.sym.flags() &
2186                                                  GENERATEDCONSTR) != 0;
2187                         for (int i = firstadr; i < nextadr; i++) {
2188                             JCVariableDecl vardecl = vardecls[i];
2189                             VarSymbol var = vardecl.sym;
2190                             if (var.owner == classDef.sym) {
2191                                 // choose the diagnostic position based on whether
2192                                 // the ctor is default(synthesized) or not
2193                                 if (isSynthesized && !isCompactConstructor) {
2194                                     checkInit(TreeInfo.diagnosticPositionFor(var, vardecl),
2195                                             var, Errors.VarNotInitializedInDefaultConstructor(var));
2196                                 } else if (isCompactConstructor) {
2197                                     boolean isInstanceRecordField = var.enclClass().isRecord() &&
2198                                             (var.flags_field & (Flags.PRIVATE | Flags.FINAL | Flags.GENERATED_MEMBER | Flags.RECORD)) != 0 &&
2199                                             !var.isStatic() &&
2200                                             var.owner.kind == TYP;
2201                                     if (isInstanceRecordField) {
2202                                         boolean notInitialized = !inits.isMember(var.adr);
2203                                         if (notInitialized && uninits.isMember(var.adr) && tree.completesNormally) {
2204                                         /*  this way we indicate Lower that it should generate an initialization for this field
2205                                          *  in the compact constructor
2206                                          */
2207                                             var.flags_field |= UNINITIALIZED_FIELD;
2208                                         } else {
2209                                             checkInit(TreeInfo.diagEndPos(tree.body), var);
2210                                         }
2211                                     } else {
2212                                         checkInit(TreeInfo.diagnosticPositionFor(var, vardecl), var);
2213                                     }
2214                                 } else {
2215                                     checkInit(TreeInfo.diagEndPos(tree.body), var);
2216                                 }
2217                             }
2218                         }
2219                     }
2220                     clearPendingExits(true);
2221                 } finally {
2222                     inits.assign(initsPrev);
2223                     uninits.assign(uninitsPrev);
2224                     nextadr = nextadrPrev;
2225                     firstadr = firstadrPrev;
2226                     returnadr = returnadrPrev;
2227                     isInitialConstructor = lastInitialConstructor;
2228                 }
2229             } finally {
2230                 lint = lintPrev;
2231             }
2232         }
2233 
2234         private void clearPendingExits(boolean inMethod) {
2235             List<PendingExit> exits = pendingExits.toList();
2236             pendingExits = new ListBuffer<>();
2237             while (exits.nonEmpty()) {
2238                 PendingExit exit = exits.head;
2239                 exits = exits.tail;
2240                 Assert.check((inMethod && exit.tree.hasTag(RETURN)) ||
2241                                  log.hasErrorOn(exit.tree.pos()),
2242                              exit.tree);
2243                 if (inMethod && isInitialConstructor) {
2244                     Assert.check(exit instanceof AssignPendingExit);
2245                     inits.assign(((AssignPendingExit) exit).exit_inits);
2246                     for (int i = firstadr; i < nextadr; i++) {
2247                         checkInit(exit.tree.pos(), vardecls[i].sym);
2248                     }
2249                 }
2250             }
2251         }
2252         protected void initParam(JCVariableDecl def) {
2253             inits.incl(def.sym.adr);
2254             uninits.excl(def.sym.adr);
2255         }
2256 
2257         public void visitVarDef(JCVariableDecl tree) {
2258             Lint lintPrev = lint;
2259             lint = lint.augment(tree.sym);
2260             try{
2261                 boolean track = trackable(tree.sym);
2262                 if (track && (tree.sym.owner.kind == MTH || tree.sym.owner.kind == VAR)) {
2263                     newVar(tree);
2264                 }
2265                 if (tree.init != null) {
2266                     scanExpr(tree.init);
2267                     if (track) {
2268                         letInit(tree.pos(), tree.sym);
2269                     }
2270                 }
2271             } finally {
2272                 lint = lintPrev;
2273             }
2274         }
2275 
2276         public void visitBlock(JCBlock tree) {
2277             int nextadrPrev = nextadr;
2278             scan(tree.stats);
2279             nextadr = nextadrPrev;
2280         }
2281 
2282         public void visitDoLoop(JCDoWhileLoop tree) {
2283             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2284             FlowKind prevFlowKind = flowKind;
2285             flowKind = FlowKind.NORMAL;
2286             final Bits initsSkip = new Bits(true);
2287             final Bits uninitsSkip = new Bits(true);
2288             pendingExits = new ListBuffer<>();
2289             int prevErrors = log.nerrors;
2290             do {
2291                 final Bits uninitsEntry = new Bits(uninits);
2292                 uninitsEntry.excludeFrom(nextadr);
2293                 scan(tree.body);
2294                 resolveContinues(tree);
2295                 scanCond(tree.cond);
2296                 if (!flowKind.isFinal()) {
2297                     initsSkip.assign(initsWhenFalse);
2298                     uninitsSkip.assign(uninitsWhenFalse);
2299                 }
2300                 if (log.nerrors !=  prevErrors ||
2301                     flowKind.isFinal() ||
2302                     new Bits(uninitsEntry).diffSet(uninitsWhenTrue).nextBit(firstadr)==-1)
2303                     break;
2304                 inits.assign(initsWhenTrue);
2305                 uninits.assign(uninitsEntry.andSet(uninitsWhenTrue));
2306                 flowKind = FlowKind.SPECULATIVE_LOOP;
2307             } while (true);
2308             flowKind = prevFlowKind;
2309             inits.assign(initsSkip);
2310             uninits.assign(uninitsSkip);
2311             resolveBreaks(tree, prevPendingExits);
2312         }
2313 
2314         public void visitWhileLoop(JCWhileLoop tree) {
2315             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2316             FlowKind prevFlowKind = flowKind;
2317             flowKind = FlowKind.NORMAL;
2318             final Bits initsSkip = new Bits(true);
2319             final Bits uninitsSkip = new Bits(true);
2320             pendingExits = new ListBuffer<>();
2321             int prevErrors = log.nerrors;
2322             final Bits uninitsEntry = new Bits(uninits);
2323             uninitsEntry.excludeFrom(nextadr);
2324             do {
2325                 scanCond(tree.cond);
2326                 if (!flowKind.isFinal()) {
2327                     initsSkip.assign(initsWhenFalse) ;
2328                     uninitsSkip.assign(uninitsWhenFalse);
2329                 }
2330                 inits.assign(initsWhenTrue);
2331                 uninits.assign(uninitsWhenTrue);
2332                 scan(tree.body);
2333                 resolveContinues(tree);
2334                 if (log.nerrors != prevErrors ||
2335                     flowKind.isFinal() ||
2336                     new Bits(uninitsEntry).diffSet(uninits).nextBit(firstadr) == -1) {
2337                     break;
2338                 }
2339                 uninits.assign(uninitsEntry.andSet(uninits));
2340                 flowKind = FlowKind.SPECULATIVE_LOOP;
2341             } while (true);
2342             flowKind = prevFlowKind;
2343             //a variable is DA/DU after the while statement, if it's DA/DU assuming the
2344             //branch is not taken AND if it's DA/DU before any break statement
2345             inits.assign(initsSkip);
2346             uninits.assign(uninitsSkip);
2347             resolveBreaks(tree, prevPendingExits);
2348         }
2349 
2350         public void visitForLoop(JCForLoop tree) {
2351             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2352             FlowKind prevFlowKind = flowKind;
2353             flowKind = FlowKind.NORMAL;
2354             int nextadrPrev = nextadr;
2355             scan(tree.init);
2356             final Bits initsSkip = new Bits(true);
2357             final Bits uninitsSkip = new Bits(true);
2358             pendingExits = new ListBuffer<>();
2359             int prevErrors = log.nerrors;
2360             do {
2361                 final Bits uninitsEntry = new Bits(uninits);
2362                 uninitsEntry.excludeFrom(nextadr);
2363                 if (tree.cond != null) {
2364                     scanCond(tree.cond);
2365                     if (!flowKind.isFinal()) {
2366                         initsSkip.assign(initsWhenFalse);
2367                         uninitsSkip.assign(uninitsWhenFalse);
2368                     }
2369                     inits.assign(initsWhenTrue);
2370                     uninits.assign(uninitsWhenTrue);
2371                 } else if (!flowKind.isFinal()) {
2372                     initsSkip.assign(inits);
2373                     initsSkip.inclRange(firstadr, nextadr);
2374                     uninitsSkip.assign(uninits);
2375                     uninitsSkip.inclRange(firstadr, nextadr);
2376                 }
2377                 scan(tree.body);
2378                 resolveContinues(tree);
2379                 scan(tree.step);
2380                 if (log.nerrors != prevErrors ||
2381                     flowKind.isFinal() ||
2382                     new Bits(uninitsEntry).diffSet(uninits).nextBit(firstadr) == -1)
2383                     break;
2384                 uninits.assign(uninitsEntry.andSet(uninits));
2385                 flowKind = FlowKind.SPECULATIVE_LOOP;
2386             } while (true);
2387             flowKind = prevFlowKind;
2388             //a variable is DA/DU after a for loop, if it's DA/DU assuming the
2389             //branch is not taken AND if it's DA/DU before any break statement
2390             inits.assign(initsSkip);
2391             uninits.assign(uninitsSkip);
2392             resolveBreaks(tree, prevPendingExits);
2393             nextadr = nextadrPrev;
2394         }
2395 
2396         public void visitForeachLoop(JCEnhancedForLoop tree) {
2397             visitVarDef(tree.var);
2398 
2399             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2400             FlowKind prevFlowKind = flowKind;
2401             flowKind = FlowKind.NORMAL;
2402             int nextadrPrev = nextadr;
2403             scan(tree.expr);
2404             final Bits initsStart = new Bits(inits);
2405             final Bits uninitsStart = new Bits(uninits);
2406 
2407             letInit(tree.pos(), tree.var.sym);
2408             pendingExits = new ListBuffer<>();
2409             int prevErrors = log.nerrors;
2410             do {
2411                 final Bits uninitsEntry = new Bits(uninits);
2412                 uninitsEntry.excludeFrom(nextadr);
2413                 scan(tree.body);
2414                 resolveContinues(tree);
2415                 if (log.nerrors != prevErrors ||
2416                     flowKind.isFinal() ||
2417                     new Bits(uninitsEntry).diffSet(uninits).nextBit(firstadr) == -1)
2418                     break;
2419                 uninits.assign(uninitsEntry.andSet(uninits));
2420                 flowKind = FlowKind.SPECULATIVE_LOOP;
2421             } while (true);
2422             flowKind = prevFlowKind;
2423             inits.assign(initsStart);
2424             uninits.assign(uninitsStart.andSet(uninits));
2425             resolveBreaks(tree, prevPendingExits);
2426             nextadr = nextadrPrev;
2427         }
2428 
2429         public void visitLabelled(JCLabeledStatement tree) {
2430             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2431             pendingExits = new ListBuffer<>();
2432             scan(tree.body);
2433             resolveBreaks(tree, prevPendingExits);
2434         }
2435 
2436         public void visitSwitch(JCSwitch tree) {
2437             handleSwitch(tree, tree.selector, tree.cases, tree.isExhaustive);
2438         }
2439 
2440         public void visitSwitchExpression(JCSwitchExpression tree) {
2441             handleSwitch(tree, tree.selector, tree.cases, tree.isExhaustive);
2442         }
2443 
2444         private void handleSwitch(JCTree tree, JCExpression selector,
2445                                   List<JCCase> cases, boolean isExhaustive) {
2446             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2447             pendingExits = new ListBuffer<>();
2448             int nextadrPrev = nextadr;
2449             scanExpr(selector);
2450             final Bits initsSwitch = new Bits(inits);
2451             final Bits uninitsSwitch = new Bits(uninits);
2452             for (List<JCCase> l = cases; l.nonEmpty(); l = l.tail) {
2453                 inits.assign(initsSwitch);
2454                 uninits.assign(uninits.andSet(uninitsSwitch));
2455                 JCCase c = l.head;
2456                 for (JCCaseLabel pat : c.labels) {
2457                     scan(pat);
2458                     if (inits.isReset()) {
2459                         inits.assign(initsWhenTrue);
2460                         uninits.assign(uninitsWhenTrue);
2461                     }
2462                 }
2463                 if (l.head.stats.isEmpty() &&
2464                     l.tail.nonEmpty() &&
2465                     l.tail.head.labels.size() == 1 &&
2466                     l.tail.head.labels.head.isExpression() &&
2467                     TreeInfo.isNull(l.tail.head.labels.head)) {
2468                     //handling:
2469                     //case Integer i:
2470                     //case null:
2471                     //joining these two cases together - processing Integer i pattern,
2472                     //but statements from case null:
2473                     l = l.tail;
2474                     c = l.head;
2475                 }
2476                 scan(c.stats);
2477                 if (c.completesNormally && c.caseKind == JCCase.RULE) {
2478                     scanSyntheticBreak(make, tree);
2479                 }
2480                 addVars(c.stats, initsSwitch, uninitsSwitch);
2481                 // Warn about fall-through if lint switch fallthrough enabled.
2482             }
2483             if (!isExhaustive) {
2484                 if (tree.hasTag(SWITCH_EXPRESSION)) {
2485                     markDead();
2486                 } else if (tree.hasTag(SWITCH) && !TreeInfo.expectedExhaustive((JCSwitch) tree)) {
2487                     inits.assign(initsSwitch);
2488                     uninits.assign(uninits.andSet(uninitsSwitch));
2489                 }
2490             }
2491             if (tree.hasTag(SWITCH_EXPRESSION)) {
2492                 resolveYields(tree, prevPendingExits);
2493             } else {
2494                 resolveBreaks(tree, prevPendingExits);
2495             }
2496             nextadr = nextadrPrev;
2497         }
2498         // where
2499             /** Add any variables defined in stats to inits and uninits. */
2500             private void addVars(List<JCStatement> stats, final Bits inits,
2501                                         final Bits uninits) {
2502                 for (;stats.nonEmpty(); stats = stats.tail) {
2503                     JCTree stat = stats.head;
2504                     if (stat.hasTag(VARDEF)) {
2505                         int adr = ((JCVariableDecl) stat).sym.adr;
2506                         inits.excl(adr);
2507                         uninits.incl(adr);
2508                     }
2509                 }
2510             }
2511 
2512         public void visitTry(JCTry tree) {
2513             ListBuffer<JCVariableDecl> resourceVarDecls = new ListBuffer<>();
2514             final Bits uninitsTryPrev = new Bits(uninitsTry);
2515             ListBuffer<PendingExit> prevPendingExits = pendingExits;
2516             pendingExits = new ListBuffer<>();
2517             final Bits initsTry = new Bits(inits);
2518             uninitsTry.assign(uninits);
2519             for (JCTree resource : tree.resources) {
2520                 if (resource instanceof JCVariableDecl variableDecl) {
2521                     visitVarDef(variableDecl);
2522                     unrefdResources.enter(variableDecl.sym);
2523                     resourceVarDecls.append(variableDecl);
2524                 } else if (resource instanceof JCExpression expression) {
2525                     scanExpr(expression);
2526                 } else {
2527                     throw new AssertionError(tree);  // parser error
2528                 }
2529             }
2530             scan(tree.body);
2531             uninitsTry.andSet(uninits);
2532             final Bits initsEnd = new Bits(inits);
2533             final Bits uninitsEnd = new Bits(uninits);
2534             int nextadrCatch = nextadr;
2535 
2536             if (!resourceVarDecls.isEmpty() &&
2537                     lint.isEnabled(Lint.LintCategory.TRY)) {
2538                 for (JCVariableDecl resVar : resourceVarDecls) {
2539                     if (unrefdResources.includes(resVar.sym)) {
2540                         log.warning(Lint.LintCategory.TRY, resVar.pos(),
2541                                     Warnings.TryResourceNotReferenced(resVar.sym));
2542                         unrefdResources.remove(resVar.sym);
2543                     }
2544                 }
2545             }
2546 
2547             /*  The analysis of each catch should be independent.
2548              *  Each one should have the same initial values of inits and
2549              *  uninits.
2550              */
2551             final Bits initsCatchPrev = new Bits(initsTry);
2552             final Bits uninitsCatchPrev = new Bits(uninitsTry);
2553 
2554             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
2555                 JCVariableDecl param = l.head.param;
2556                 inits.assign(initsCatchPrev);
2557                 uninits.assign(uninitsCatchPrev);
2558                 scan(param);
2559                 /* If this is a TWR and we are executing the code from Gen,
2560                  * then there can be synthetic variables, ignore them.
2561                  */
2562                 initParam(param);
2563                 scan(l.head.body);
2564                 initsEnd.andSet(inits);
2565                 uninitsEnd.andSet(uninits);
2566                 nextadr = nextadrCatch;
2567             }
2568             if (tree.finalizer != null) {
2569                 inits.assign(initsTry);
2570                 uninits.assign(uninitsTry);
2571                 ListBuffer<PendingExit> exits = pendingExits;
2572                 pendingExits = prevPendingExits;
2573                 scan(tree.finalizer);
2574                 if (!tree.finallyCanCompleteNormally) {
2575                     // discard exits and exceptions from try and finally
2576                 } else {
2577                     uninits.andSet(uninitsEnd);
2578                     // FIX: this doesn't preserve source order of exits in catch
2579                     // versus finally!
2580                     while (exits.nonEmpty()) {
2581                         PendingExit exit = exits.next();
2582                         if (exit instanceof AssignPendingExit assignPendingExit) {
2583                             assignPendingExit.exit_inits.orSet(inits);
2584                             assignPendingExit.exit_uninits.andSet(uninits);
2585                         }
2586                         pendingExits.append(exit);
2587                     }
2588                     inits.orSet(initsEnd);
2589                 }
2590             } else {
2591                 inits.assign(initsEnd);
2592                 uninits.assign(uninitsEnd);
2593                 ListBuffer<PendingExit> exits = pendingExits;
2594                 pendingExits = prevPendingExits;
2595                 while (exits.nonEmpty()) pendingExits.append(exits.next());
2596             }
2597             uninitsTry.andSet(uninitsTryPrev).andSet(uninits);
2598         }
2599 
2600         public void visitConditional(JCConditional tree) {
2601             scanCond(tree.cond);
2602             final Bits initsBeforeElse = new Bits(initsWhenFalse);
2603             final Bits uninitsBeforeElse = new Bits(uninitsWhenFalse);
2604             inits.assign(initsWhenTrue);
2605             uninits.assign(uninitsWhenTrue);
2606             if (tree.truepart.type.hasTag(BOOLEAN) &&
2607                 tree.falsepart.type.hasTag(BOOLEAN)) {
2608                 // if b and c are boolean valued, then
2609                 // v is (un)assigned after a?b:c when true iff
2610                 //    v is (un)assigned after b when true and
2611                 //    v is (un)assigned after c when true
2612                 scanCond(tree.truepart);
2613                 final Bits initsAfterThenWhenTrue = new Bits(initsWhenTrue);
2614                 final Bits initsAfterThenWhenFalse = new Bits(initsWhenFalse);
2615                 final Bits uninitsAfterThenWhenTrue = new Bits(uninitsWhenTrue);
2616                 final Bits uninitsAfterThenWhenFalse = new Bits(uninitsWhenFalse);
2617                 inits.assign(initsBeforeElse);
2618                 uninits.assign(uninitsBeforeElse);
2619                 scanCond(tree.falsepart);
2620                 initsWhenTrue.andSet(initsAfterThenWhenTrue);
2621                 initsWhenFalse.andSet(initsAfterThenWhenFalse);
2622                 uninitsWhenTrue.andSet(uninitsAfterThenWhenTrue);
2623                 uninitsWhenFalse.andSet(uninitsAfterThenWhenFalse);
2624             } else {
2625                 scanExpr(tree.truepart);
2626                 final Bits initsAfterThen = new Bits(inits);
2627                 final Bits uninitsAfterThen = new Bits(uninits);
2628                 inits.assign(initsBeforeElse);
2629                 uninits.assign(uninitsBeforeElse);
2630                 scanExpr(tree.falsepart);
2631                 inits.andSet(initsAfterThen);
2632                 uninits.andSet(uninitsAfterThen);
2633             }
2634         }
2635 
2636         public void visitIf(JCIf tree) {
2637             scanCond(tree.cond);
2638             final Bits initsBeforeElse = new Bits(initsWhenFalse);
2639             final Bits uninitsBeforeElse = new Bits(uninitsWhenFalse);
2640             inits.assign(initsWhenTrue);
2641             uninits.assign(uninitsWhenTrue);
2642             scan(tree.thenpart);
2643             if (tree.elsepart != null) {
2644                 final Bits initsAfterThen = new Bits(inits);
2645                 final Bits uninitsAfterThen = new Bits(uninits);
2646                 inits.assign(initsBeforeElse);
2647                 uninits.assign(uninitsBeforeElse);
2648                 scan(tree.elsepart);
2649                 inits.andSet(initsAfterThen);
2650                 uninits.andSet(uninitsAfterThen);
2651             } else {
2652                 inits.andSet(initsBeforeElse);
2653                 uninits.andSet(uninitsBeforeElse);
2654             }
2655         }
2656 
2657         @Override
2658         public void visitBreak(JCBreak tree) {
2659             recordExit(new AssignPendingExit(tree, inits, uninits));
2660         }
2661 
2662         @Override
2663         public void visitYield(JCYield tree) {
2664             JCSwitchExpression expr = (JCSwitchExpression) tree.target;
2665             if (expr != null && expr.type.hasTag(BOOLEAN)) {
2666                 scanCond(tree.value);
2667                 Bits initsAfterBreakWhenTrue = new Bits(initsWhenTrue);
2668                 Bits initsAfterBreakWhenFalse = new Bits(initsWhenFalse);
2669                 Bits uninitsAfterBreakWhenTrue = new Bits(uninitsWhenTrue);
2670                 Bits uninitsAfterBreakWhenFalse = new Bits(uninitsWhenFalse);
2671                 PendingExit exit = new PendingExit(tree) {
2672                     @Override
2673                     void resolveJump() {
2674                         if (!inits.isReset()) {
2675                             split(true);
2676                         }
2677                         initsWhenTrue.andSet(initsAfterBreakWhenTrue);
2678                         initsWhenFalse.andSet(initsAfterBreakWhenFalse);
2679                         uninitsWhenTrue.andSet(uninitsAfterBreakWhenTrue);
2680                         uninitsWhenFalse.andSet(uninitsAfterBreakWhenFalse);
2681                     }
2682                 };
2683                 merge();
2684                 recordExit(exit);
2685                 return ;
2686             } else {
2687                 scanExpr(tree.value);
2688                 recordExit(new AssignPendingExit(tree, inits, uninits));
2689             }
2690         }
2691 
2692         @Override
2693         public void visitContinue(JCContinue tree) {
2694             recordExit(new AssignPendingExit(tree, inits, uninits));
2695         }
2696 
2697         @Override
2698         public void visitReturn(JCReturn tree) {
2699             scanExpr(tree.expr);
2700             recordExit(new AssignPendingExit(tree, inits, uninits));
2701         }
2702 
2703         public void visitThrow(JCThrow tree) {
2704             scanExpr(tree.expr);
2705             markDead();
2706         }
2707 
2708         public void visitApply(JCMethodInvocation tree) {
2709             scanExpr(tree.meth);
2710             scanExprs(tree.args);
2711         }
2712 
2713         public void visitNewClass(JCNewClass tree) {
2714             scanExpr(tree.encl);
2715             scanExprs(tree.args);
2716             scan(tree.def);
2717         }
2718 
2719         @Override
2720         public void visitLambda(JCLambda tree) {
2721             final Bits prevUninits = new Bits(uninits);
2722             final Bits prevInits = new Bits(inits);
2723             int returnadrPrev = returnadr;
2724             int nextadrPrev = nextadr;
2725             ListBuffer<PendingExit> prevPending = pendingExits;
2726             try {
2727                 returnadr = nextadr;
2728                 pendingExits = new ListBuffer<>();
2729                 for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
2730                     JCVariableDecl def = l.head;
2731                     scan(def);
2732                     inits.incl(def.sym.adr);
2733                     uninits.excl(def.sym.adr);
2734                 }
2735                 if (tree.getBodyKind() == JCLambda.BodyKind.EXPRESSION) {
2736                     scanExpr(tree.body);
2737                 } else {
2738                     scan(tree.body);
2739                 }
2740             }
2741             finally {
2742                 returnadr = returnadrPrev;
2743                 uninits.assign(prevUninits);
2744                 inits.assign(prevInits);
2745                 pendingExits = prevPending;
2746                 nextadr = nextadrPrev;
2747             }
2748         }
2749 
2750         public void visitNewArray(JCNewArray tree) {
2751             scanExprs(tree.dims);
2752             scanExprs(tree.elems);
2753         }
2754 
2755         public void visitAssert(JCAssert tree) {
2756             final Bits initsExit = new Bits(inits);
2757             final Bits uninitsExit = new Bits(uninits);
2758             scanCond(tree.cond);
2759             uninitsExit.andSet(uninitsWhenTrue);
2760             if (tree.detail != null) {
2761                 inits.assign(initsWhenFalse);
2762                 uninits.assign(uninitsWhenFalse);
2763                 scanExpr(tree.detail);
2764             }
2765             inits.assign(initsExit);
2766             uninits.assign(uninitsExit);
2767         }
2768 
2769         public void visitAssign(JCAssign tree) {
2770             if (!TreeInfo.isIdentOrThisDotIdent(tree.lhs))
2771                 scanExpr(tree.lhs);
2772             scanExpr(tree.rhs);
2773             letInit(tree.lhs);
2774         }
2775 
2776         // check fields accessed through this.<field> are definitely
2777         // assigned before reading their value
2778         public void visitSelect(JCFieldAccess tree) {
2779             super.visitSelect(tree);
2780             if (TreeInfo.isThisQualifier(tree.selected) &&
2781                 tree.sym.kind == VAR) {
2782                 checkInit(tree.pos(), (VarSymbol)tree.sym);
2783             }
2784         }
2785 
2786         public void visitAssignop(JCAssignOp tree) {
2787             scanExpr(tree.lhs);
2788             scanExpr(tree.rhs);
2789             letInit(tree.lhs);
2790         }
2791 
2792         public void visitUnary(JCUnary tree) {
2793             switch (tree.getTag()) {
2794             case NOT:
2795                 scanCond(tree.arg);
2796                 final Bits t = new Bits(initsWhenFalse);
2797                 initsWhenFalse.assign(initsWhenTrue);
2798                 initsWhenTrue.assign(t);
2799                 t.assign(uninitsWhenFalse);
2800                 uninitsWhenFalse.assign(uninitsWhenTrue);
2801                 uninitsWhenTrue.assign(t);
2802                 break;
2803             case PREINC: case POSTINC:
2804             case PREDEC: case POSTDEC:
2805                 scanExpr(tree.arg);
2806                 letInit(tree.arg);
2807                 break;
2808             default:
2809                 scanExpr(tree.arg);
2810             }
2811         }
2812 
2813         public void visitBinary(JCBinary tree) {
2814             switch (tree.getTag()) {
2815             case AND:
2816                 scanCond(tree.lhs);
2817                 final Bits initsWhenFalseLeft = new Bits(initsWhenFalse);
2818                 final Bits uninitsWhenFalseLeft = new Bits(uninitsWhenFalse);
2819                 inits.assign(initsWhenTrue);
2820                 uninits.assign(uninitsWhenTrue);
2821                 scanCond(tree.rhs);
2822                 initsWhenFalse.andSet(initsWhenFalseLeft);
2823                 uninitsWhenFalse.andSet(uninitsWhenFalseLeft);
2824                 break;
2825             case OR:
2826                 scanCond(tree.lhs);
2827                 final Bits initsWhenTrueLeft = new Bits(initsWhenTrue);
2828                 final Bits uninitsWhenTrueLeft = new Bits(uninitsWhenTrue);
2829                 inits.assign(initsWhenFalse);
2830                 uninits.assign(uninitsWhenFalse);
2831                 scanCond(tree.rhs);
2832                 initsWhenTrue.andSet(initsWhenTrueLeft);
2833                 uninitsWhenTrue.andSet(uninitsWhenTrueLeft);
2834                 break;
2835             default:
2836                 scanExpr(tree.lhs);
2837                 scanExpr(tree.rhs);
2838             }
2839         }
2840 
2841         public void visitIdent(JCIdent tree) {
2842             if (tree.sym.kind == VAR) {
2843                 checkInit(tree.pos(), (VarSymbol)tree.sym);
2844                 referenced(tree.sym);
2845             }
2846         }
2847 
2848         @Override
2849         public void visitBindingPattern(JCBindingPattern tree) {
2850             super.visitBindingPattern(tree);
2851             initParam(tree.var);
2852         }
2853 
2854         void referenced(Symbol sym) {
2855             unrefdResources.remove(sym);
2856         }
2857 
2858         public void visitAnnotatedType(JCAnnotatedType tree) {
2859             // annotations don't get scanned
2860             tree.underlyingType.accept(this);
2861         }
2862 
2863         public void visitModuleDef(JCModuleDecl tree) {
2864             // Do nothing for modules
2865         }
2866 
2867     /**************************************************************************
2868      * main method
2869      *************************************************************************/
2870 
2871         /** Perform definite assignment/unassignment analysis on a tree.
2872          */
2873         public void analyzeTree(Env<?> env, TreeMaker make) {
2874             analyzeTree(env, env.tree, make);
2875          }
2876 
2877         public void analyzeTree(Env<?> env, JCTree tree, TreeMaker make) {
2878             try {
2879                 startPos = tree.pos().getStartPosition();
2880 
2881                 if (vardecls == null)
2882                     vardecls = new JCVariableDecl[32];
2883                 else
2884                     for (int i=0; i<vardecls.length; i++)
2885                         vardecls[i] = null;
2886                 firstadr = 0;
2887                 nextadr = 0;
2888                 Flow.this.make = make;
2889                 pendingExits = new ListBuffer<>();
2890                 this.classDef = null;
2891                 unrefdResources = WriteableScope.create(env.enclClass.sym);
2892                 scan(tree);
2893             } finally {
2894                 // note that recursive invocations of this method fail hard
2895                 startPos = -1;
2896                 resetBits(inits, uninits, uninitsTry, initsWhenTrue,
2897                         initsWhenFalse, uninitsWhenTrue, uninitsWhenFalse);
2898                 if (vardecls != null) {
2899                     for (int i=0; i<vardecls.length; i++)
2900                         vardecls[i] = null;
2901                 }
2902                 firstadr = 0;
2903                 nextadr = 0;
2904                 Flow.this.make = null;
2905                 pendingExits = null;
2906                 this.classDef = null;
2907                 unrefdResources = null;
2908             }
2909         }
2910     }
2911 
2912     /**
2913      * This pass implements the last step of the dataflow analysis, namely
2914      * the effectively-final analysis check. This checks that every local variable
2915      * reference from a lambda body/local inner class is either final or effectively final.
2916      * Additional this also checks that every variable that is used as an operand to
2917      * try-with-resources is final or effectively final.
2918      * As effectively final variables are marked as such during DA/DU, this pass must run after
2919      * AssignAnalyzer.
2920      */
2921     class CaptureAnalyzer extends BaseAnalyzer {
2922 
2923         JCTree currentTree; //local class or lambda
2924 
2925         @Override
2926         void markDead() {
2927             //do nothing
2928         }
2929 
2930         @SuppressWarnings("fallthrough")
2931         void checkEffectivelyFinal(DiagnosticPosition pos, VarSymbol sym) {
2932             if (currentTree != null &&
2933                     sym.owner.kind == MTH &&
2934                     sym.pos < currentTree.getStartPosition()) {
2935                 switch (currentTree.getTag()) {
2936                     case CLASSDEF:
2937                         if (!allowEffectivelyFinalInInnerClasses) {
2938                             if ((sym.flags() & FINAL) == 0) {
2939                                 reportInnerClsNeedsFinalError(pos, sym);
2940                             }
2941                             break;
2942                         }
2943                     case GUARDPATTERN:
2944                     case LAMBDA:
2945                         if ((sym.flags() & (EFFECTIVELY_FINAL | FINAL)) == 0) {
2946                            reportEffectivelyFinalError(pos, sym);
2947                         }
2948                 }
2949             }
2950         }
2951 
2952         @SuppressWarnings("fallthrough")
2953         void letInit(JCTree tree) {
2954             tree = TreeInfo.skipParens(tree);
2955             if (tree.hasTag(IDENT) || tree.hasTag(SELECT)) {
2956                 Symbol sym = TreeInfo.symbol(tree);
2957                 if (currentTree != null &&
2958                         sym.kind == VAR &&
2959                         sym.owner.kind == MTH &&
2960                         ((VarSymbol)sym).pos < currentTree.getStartPosition()) {
2961                     switch (currentTree.getTag()) {
2962                         case CLASSDEF:
2963                             if (!allowEffectivelyFinalInInnerClasses) {
2964                                 reportInnerClsNeedsFinalError(tree, sym);
2965                                 break;
2966                             }
2967                         case GUARDPATTERN:
2968                         case LAMBDA:
2969                             reportEffectivelyFinalError(tree, sym);
2970                     }
2971                 }
2972             }
2973         }
2974 
2975         void reportEffectivelyFinalError(DiagnosticPosition pos, Symbol sym) {
2976             Fragment subKey = switch (currentTree.getTag()) {
2977                 case LAMBDA -> Fragments.Lambda;
2978                 case GUARDPATTERN -> Fragments.Guard;
2979                 case CLASSDEF -> Fragments.InnerCls;
2980                 default -> throw new AssertionError("Unexpected tree kind: " + currentTree.getTag());
2981             };
2982             log.error(pos, Errors.CantRefNonEffectivelyFinalVar(sym, diags.fragment(subKey)));
2983         }
2984 
2985         void reportInnerClsNeedsFinalError(DiagnosticPosition pos, Symbol sym) {
2986             log.error(pos,
2987                       Errors.LocalVarAccessedFromIclsNeedsFinal(sym));
2988         }
2989 
2990     /*************************************************************************
2991      * Visitor methods for statements and definitions
2992      *************************************************************************/
2993 
2994         /* ------------ Visitor methods for various sorts of trees -------------*/
2995 
2996         public void visitClassDef(JCClassDecl tree) {
2997             JCTree prevTree = currentTree;
2998             try {
2999                 currentTree = tree.sym.isDirectlyOrIndirectlyLocal() ? tree : null;
3000                 super.visitClassDef(tree);
3001             } finally {
3002                 currentTree = prevTree;
3003             }
3004         }
3005 
3006         @Override
3007         public void visitLambda(JCLambda tree) {
3008             JCTree prevTree = currentTree;
3009             try {
3010                 currentTree = tree;
3011                 super.visitLambda(tree);
3012             } finally {
3013                 currentTree = prevTree;
3014             }
3015         }
3016 
3017         @Override
3018         public void visitGuardPattern(JCGuardPattern tree) {
3019             scan(tree.patt);
3020             JCTree prevTree = currentTree;
3021             try {
3022                 currentTree = tree;
3023                 scan(tree.expr);
3024             } finally {
3025                 currentTree = prevTree;
3026             }
3027         }
3028 
3029         @Override
3030         public void visitIdent(JCIdent tree) {
3031             if (tree.sym.kind == VAR) {
3032                 checkEffectivelyFinal(tree, (VarSymbol)tree.sym);
3033             }
3034         }
3035 
3036         public void visitAssign(JCAssign tree) {
3037             JCTree lhs = TreeInfo.skipParens(tree.lhs);
3038             if (!(lhs instanceof JCIdent)) {
3039                 scan(lhs);
3040             }
3041             scan(tree.rhs);
3042             letInit(lhs);
3043         }
3044 
3045         public void visitAssignop(JCAssignOp tree) {
3046             scan(tree.lhs);
3047             scan(tree.rhs);
3048             letInit(tree.lhs);
3049         }
3050 
3051         public void visitUnary(JCUnary tree) {
3052             switch (tree.getTag()) {
3053                 case PREINC: case POSTINC:
3054                 case PREDEC: case POSTDEC:
3055                     scan(tree.arg);
3056                     letInit(tree.arg);
3057                     break;
3058                 default:
3059                     scan(tree.arg);
3060             }
3061         }
3062 
3063         public void visitTry(JCTry tree) {
3064             for (JCTree resource : tree.resources) {
3065                 if (!resource.hasTag(VARDEF)) {
3066                     Symbol var = TreeInfo.symbol(resource);
3067                     if (var != null && (var.flags() & (FINAL | EFFECTIVELY_FINAL)) == 0) {
3068                         log.error(resource.pos(), Errors.TryWithResourcesExprEffectivelyFinalVar(var));
3069                     }
3070                 }
3071             }
3072             super.visitTry(tree);
3073         }
3074 
3075         @Override
3076         public void visitYield(JCYield tree) {
3077             scan(tree.value);
3078         }
3079 
3080         public void visitModuleDef(JCModuleDecl tree) {
3081             // Do nothing for modules
3082         }
3083 
3084     /**************************************************************************
3085      * main method
3086      *************************************************************************/
3087 
3088         /** Perform definite assignment/unassignment analysis on a tree.
3089          */
3090         public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
3091             analyzeTree(env, env.tree, make);
3092         }
3093         public void analyzeTree(Env<AttrContext> env, JCTree tree, TreeMaker make) {
3094             try {
3095                 attrEnv = env;
3096                 Flow.this.make = make;
3097                 pendingExits = new ListBuffer<>();
3098                 scan(tree);
3099             } finally {
3100                 pendingExits = null;
3101                 Flow.this.make = null;
3102             }
3103         }
3104     }
3105 
3106     enum Liveness {
3107         ALIVE {
3108             @Override
3109             public Liveness or(Liveness other) {
3110                 return this;
3111             }
3112             @Override
3113             public Liveness and(Liveness other) {
3114                 return other;
3115             }
3116         },
3117         DEAD {
3118             @Override
3119             public Liveness or(Liveness other) {
3120                 return other;
3121             }
3122             @Override
3123             public Liveness and(Liveness other) {
3124                 return this;
3125             }
3126         },
3127         RECOVERY {
3128             @Override
3129             public Liveness or(Liveness other) {
3130                 if (other == ALIVE) {
3131                     return ALIVE;
3132                 } else {
3133                     return this;
3134                 }
3135             }
3136             @Override
3137             public Liveness and(Liveness other) {
3138                 if (other == DEAD) {
3139                     return DEAD;
3140                 } else {
3141                     return this;
3142                 }
3143             }
3144         };
3145 
3146         public abstract Liveness or(Liveness other);
3147         public abstract Liveness and(Liveness other);
3148         public Liveness or(boolean value) {
3149             return or(from(value));
3150         }
3151         public Liveness and(boolean value) {
3152             return and(from(value));
3153         }
3154         public static Liveness from(boolean value) {
3155             return value ? ALIVE : DEAD;
3156         }
3157     }
3158 
3159 }