[Switch Expressions] Use control flow analysis rather than structural…

… analysis of syntax tree, to flag switch rule blocks that complete normally. (#3456)

* Fixes #3455

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ASTNode.java

@@ -224,7 +224,7 @@ public abstract class ASTNode implements TypeConstants, TypeIds {
 	public static final int IsUsefulEmptyStatement = Bit1;
 
 	// for block and method declaration
-	public static final int SwitchRuleBlock = Bit1;
+	public static final int BlockShouldEndDead = Bit1;
 	public static final int UndocumentedEmptyBlock = Bit4;
 	public static final int OverridingMethodWithSupercall = Bit5;
 	public static final int CanBeStatic = Bit9;   // used to flag a method that can be declared static

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Block.java

@@ -74,10 +74,16 @@ public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, Fl
 			}
 		}
 	}
-	if ((this.bits & ASTNode.SwitchRuleBlock) != 0) { // switch rule blocks don't fall through
+	if ((this.bits & ASTNode.BlockShouldEndDead) != 0) { // switch rule blocks don't fall through
 		if (flowInfo != FlowInfo.DEAD_END) {
-			flowContext.recordBreakFrom(flowInfo);
-			return FlowInfo.DEAD_END;
+			if (flowContext.associatedNode instanceof SwitchExpression) { // ... demand that for expression switch ...
+				currentScope.problemReporter().switchExpressionBlockCompletesNormally(this);
+			} else { // ... enforce that for statement switch, by having the code generator inject an automagic break ...
+				flowContext.recordBreakFrom(flowInfo);
+				return FlowInfo.DEAD_END;
+			}
+		} else {
+			this.bits &= ~ASTNode.BlockShouldEndDead; // Already dead-ends; nothing special needed from code generator
 		}
 	}
 	return flowInfo;
@@ -182,17 +188,4 @@ public boolean completesByContinue() {
 	int length = this.statements == null ? 0 : this.statements.length;
 	return length > 0 && this.statements[length - 1].completesByContinue();
 }
-
-@Override
-public boolean canCompleteNormally() {
-	int length = this.statements == null ? 0 : this.statements.length;
-	return length == 0 || this.statements[length - 1].canCompleteNormally();
-}
-
-@Override
-public boolean continueCompletes() {
-	int length = this.statements == null ? 0 : this.statements.length;
-	return length > 0 && this.statements[length - 1].continueCompletes();
-}
-
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/BreakStatement.java

@@ -109,9 +109,4 @@ public void traverse(ASTVisitor visitor, BlockScope blockscope) {
 public boolean doesNotCompleteNormally() {
 	return true;
 }
-
-@Override
-public boolean canCompleteNormally() {
-	return false;
-}
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ContinueStatement.java

@@ -118,14 +118,4 @@ public boolean doesNotCompleteNormally() {
 public boolean completesByContinue() {
 	return true;
 }
-
-@Override
-public boolean canCompleteNormally() {
-	return false;
-}
-
-@Override
-public boolean continueCompletes() {
-	return true;
-}
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/DoStatement.java

@@ -273,28 +273,4 @@ public boolean doesNotCompleteNormally() {
 public boolean completesByContinue() {
 	return this.action.continuesAtOuterLabel();
 }
-
-@Override
-public boolean canCompleteNormally() {
-	Constant cst = this.condition.constant;
-	boolean isConditionTrue = cst == null || cst != Constant.NotAConstant && cst.booleanValue() == true;
-	cst = this.condition.optimizedBooleanConstant();
-	boolean isConditionOptimizedTrue = cst == null ? true : cst != Constant.NotAConstant && cst.booleanValue() == true;
-
-	if (!(isConditionTrue || isConditionOptimizedTrue)) {
-		if (this.action == null || this.action.canCompleteNormally())
-			return true;
-		if (this.action != null && this.action.continueCompletes())
-			return true;
-	}
-	if (this.action != null && this.action.breaksOut(null))
-		return true;
-
-	return false;
-}
-@Override
-public boolean continueCompletes() {
-	return this.action.continuesAtOuterLabel();
-}
-
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ForStatement.java

@@ -489,23 +489,4 @@ public boolean doesNotCompleteNormally() {
 	public boolean completesByContinue() {
 		return this.action.continuesAtOuterLabel();
 	}
-	@Override
-	public boolean canCompleteNormally() {
-		Constant cst = this.condition == null ? null : this.condition.constant;
-		boolean isConditionTrue = cst == null || cst != Constant.NotAConstant && cst.booleanValue() == true;
-		cst = this.condition == null ? null : this.condition.optimizedBooleanConstant();
-		boolean isConditionOptimizedTrue = cst == null ? true : cst != Constant.NotAConstant && cst.booleanValue() == true;
-
-		if (!(isConditionTrue || isConditionOptimizedTrue))
-			return true;
-		if (this.action != null && this.action.breaksOut(null))
-			return true;
-		return false;
-	}
-
-	@Override
-	public boolean continueCompletes() {
-		return this.action.continuesAtOuterLabel();
-	}
-
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ForeachStatement.java

@@ -688,10 +688,4 @@ public void traverse(
 	public boolean doesNotCompleteNormally() {
 		return false; // may not be entered at all.
 	}
-
-	@Override
-	public boolean canCompleteNormally() {
-		return true;
-	}
-
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/IfStatement.java

@@ -340,14 +340,4 @@ public boolean doesNotCompleteNormally() {
 public boolean completesByContinue() {
 	return this.thenStatement != null && this.thenStatement.completesByContinue() || this.elseStatement != null && this.elseStatement.completesByContinue();
 }
-@Override
-public boolean canCompleteNormally() {
-	return ((this.thenStatement == null || this.thenStatement.canCompleteNormally()) ||
-		(this.elseStatement == null || this.elseStatement.canCompleteNormally()));
-}
-@Override
-public boolean continueCompletes() {
-	return this.thenStatement != null && this.thenStatement.continueCompletes() ||
-			this.elseStatement != null && this.elseStatement.continueCompletes();
-}
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/LabeledStatement.java

@@ -165,17 +165,4 @@ public boolean doesNotCompleteNormally() {
 	public boolean completesByContinue() {
 		return this.statement instanceof ContinueStatement; // NOT this.statement.continuesAtOuterLabel
 	}
-
-	@Override
-	public boolean canCompleteNormally() {
-		if (this.statement.canCompleteNormally())
-			return true;
-		return this.statement.breaksOut(this.label);
-	}
-
-	@Override
-	public boolean continueCompletes() {
-		return this.statement instanceof ContinueStatement; // NOT this.statement.continuesAtOuterLabel
-	}
-
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ReturnStatement.java

@@ -217,13 +217,8 @@ public boolean doesNotCompleteNormally() {
 	return true;
 }
 
-@Override
-public boolean canCompleteNormally() {
-	return false;
-}
-
 /**
- * Retrun statement code generation
+ * Return statement code generation
  *
  *   generate the finallyInvocationSequence.
  *

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Statement.java

@@ -104,23 +104,6 @@ public boolean completesByContinue() {
 	return false;
 }
 
-/**
- * Switch Expression analysis: *Assuming* this is reachable, analyze if this completes normally
- *  i.e control flow can reach the textually next statement, as per JLS 14 Sec 14.22
- *  For blocks, we don't perform intra-reachability analysis.
- *  Note: delinking this from a similar (opposite) {@link #doesNotCompleteNormally()} since that was
- *  coded for a specific purpose of Lambda Shape Analysis.
- */
-public boolean canCompleteNormally() {
-	return true;
-}
-/**
- * The equivalent function of completesByContinue - implements both the rules concerning continue with
- * and without a label.
- */
-public boolean continueCompletes() {
-	return false;
-}
 	public static final int NOT_COMPLAINED = 0;
 	public static final int COMPLAINED_FAKE_REACHABLE = 1;
 	public static final int COMPLAINED_UNREACHABLE = 2;

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/SwitchExpression.java

@@ -376,16 +376,6 @@ private TypeBinding resolveAsType(TypeBinding switchType) {
 	@Override
 	public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
 		flowInfo = super.analyseCode(currentScope, flowContext, flowInfo);
-		if ((this.switchBits & LabeledRules) != 0) { // 15.28.1
-			for (Statement stmt : this.statements) {
-				if (stmt instanceof Block && stmt.canCompleteNormally())
-					currentScope.problemReporter().switchExpressionBlockCompletesNormally(stmt);
-			}
-		} else {
-			Statement ultimateStmt = this.statements[this.statements.length - 1]; // length guaranteed > 0
-			if (ultimateStmt.canCompleteNormally())
-				currentScope.problemReporter().switchExpressionBlockCompletesNormally(ultimateStmt);
-		}
 
 		if (currentScope.compilerOptions().enableSyntacticNullAnalysisForFields)
 			flowContext.expireNullCheckedFieldInfo(); // wipe information that was meant only for this result expression:

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/SwitchStatement.java

@@ -105,6 +105,7 @@ public static record SingletonBootstrap(String id, char[] selector, char[] signa
 	public final static int Exhaustive = ASTNode.Bit3;
 	public final static int QualifiedEnum = ASTNode.Bit4;
 	public final static int LabeledBlockStatementGroup = ASTNode.Bit5;
+	public final static int BarricadeInjectedDefault = ASTNode.Bit6;
 
 	// for switch on strings
 	private static final char[] SecretSelectorVariableName = " selector".toCharArray(); //$NON-NLS-1$
@@ -438,6 +439,12 @@ else if ((statement.bits & ASTNode.DocumentedFallthrough) == 0) // the case is n
 					}
 				}
 			}
+			if (caseInits != FlowInfo.DEAD_END) {
+				if (isTrulyExpression())
+					currentScope.problemReporter().switchExpressionBlockCompletesNormally(this.statements[this.statements.length - 1]);
+				if (this.defaultCase == null)
+					this.switchBits |= BarricadeInjectedDefault;
+			}
 
 			final TypeBinding resolvedTypeBinding = this.expression.resolvedType;
 			if (resolvedTypeBinding.isEnum() && !needPatternDispatchCopy()) {
@@ -607,7 +614,7 @@ public String toString() {
 							defaultCaseLabel.place(); // branch label gets placed by generateCode below.
 					}
 				    statement.generateCode(this.scope, codeStream);
-				    if ((this.switchBits & LabeledRules) != 0 && statement instanceof Block && statement.canCompleteNormally())
+				    if (statement instanceof Block block && (block.bits & BlockShouldEndDead) != 0)
 						codeStream.goto_(this.breakLabel);
 				}
 			}
@@ -759,7 +766,7 @@ public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 							codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.preSwitchInitStateIndex);
 					}
 					statement.generateCode(this.scope, codeStream);
-					if ((this.switchBits & LabeledRules) != 0 && statement instanceof Block && statement.canCompleteNormally())
+					if (statement instanceof Block block && (block.bits & BlockShouldEndDead) != 0)
 						codeStream.goto_(this.breakLabel);
 				}
 			}
@@ -782,7 +789,7 @@ public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 				 */
 				if (this.scope.compilerOptions().complianceLevel >= ClassFileConstants.JDK19) {
 					// since 19 we have MatchException for this
-					if (this.statements.length > 0 && this.statements[this.statements.length - 1].canCompleteNormally())
+					if ((this.switchBits & BarricadeInjectedDefault) != 0)
 						codeStream.goto_(this.breakLabel); // hop, skip and jump over match exception throw.
 					defaultLabel.place();
 					codeStream.newJavaLangMatchException();
@@ -1355,55 +1362,6 @@ public boolean completesByContinue() {
 		return false;
 	}
 
-	@Override
-	public boolean canCompleteNormally() {
-		if (this.statements == null || this.statements.length == 0)
-			return true;
-		if ((this.switchBits & LabeledRules) == 0) { // switch labeled statement group
-			if (this.statements[this.statements.length - 1].canCompleteNormally())
-				return true; // last statement as well as last switch label after blocks if exists.
-			if (this.totalPattern == null && this.defaultCase == null)
-				return true;
-			for (Statement statement : this.statements) {
-				if (statement.breaksOut(null))
-					return true;
-			}
-		} else {
-			// switch block consists of switch rules
-			for (Statement stmt : this.statements) {
-				if (stmt instanceof CaseStatement)
-					continue; // skip case
-				if (this.totalPattern == null && this.defaultCase == null)
-					return true;
-				if (stmt instanceof Expression)
-					return true;
-				if (stmt.canCompleteNormally())
-					return true;
-				if (stmt instanceof YieldStatement && ((YieldStatement) stmt).isImplicit) // note: artificially introduced
-					return true;
-				if (stmt instanceof Block) {
-					Block block = (Block) stmt;
-					if (block.canCompleteNormally())
-						return true;
-					if (block.breaksOut(null))
-						return true;
-				}
-			}
-		}
-		return false;
-	}
-
-	@Override
-	public boolean continueCompletes() {
-		if (this.statements == null || this.statements.length == 0)
-			return false;
-		for (Statement statement : this.statements) {
-			if (statement.continueCompletes())
-				return true;
-		}
-		return false;
-	}
-
 	@Override
 	public StringBuilder printExpression(int indent, StringBuilder output) {
 		return printStatement(indent, output);

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/SynchronizedStatement.java

@@ -248,14 +248,4 @@ public boolean doesNotCompleteNormally() {
 public boolean completesByContinue() {
 	return this.block.completesByContinue();
 }
-
-@Override
-public boolean canCompleteNormally() {
-	return this.block.canCompleteNormally();
-}
-
-@Override
-public boolean continueCompletes() {
-	return this.block.continueCompletes();
-}
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ThrowStatement.java

@@ -99,10 +99,4 @@ public void traverse(ASTVisitor visitor, BlockScope blockScope) {
 public boolean doesNotCompleteNormally() {
 	return true;
 }
-
-@Override
-public boolean canCompleteNormally() {
-	return false;
-}
-
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TryStatement.java

@@ -1270,34 +1270,4 @@ public boolean completesByContinue() {
 	}
 	return this.finallyBlock != null && this.finallyBlock.completesByContinue();
 }
-@Override
-public boolean canCompleteNormally() {
-	if (this.tryBlock.canCompleteNormally()) {
-		return (this.finallyBlock != null) ? this.finallyBlock.canCompleteNormally() : true;
-	}
-	if (this.catchBlocks != null) {
-		for (Block catchBlock : this.catchBlocks) {
-			if (catchBlock.canCompleteNormally()) {
-				return (this.finallyBlock != null) ? this.finallyBlock.canCompleteNormally() : true;
-			}
-		}
-	}
-	return false;
-}
-@Override
-public boolean continueCompletes() {
-	if (this.tryBlock.continueCompletes()) {
-		return (this.finallyBlock == null) ? true :
-			this.finallyBlock.canCompleteNormally() || this.finallyBlock.continueCompletes();
-	}
-	if (this.catchBlocks != null) {
-		for (Block catchBlock : this.catchBlocks) {
-			if (catchBlock.continueCompletes()) {
-				return (this.finallyBlock == null) ? true :
-					this.finallyBlock.canCompleteNormally() || this.finallyBlock.continueCompletes();
-			}
-		}
-	}
-	return this.finallyBlock != null && this.finallyBlock.continueCompletes();
-}
 }