* Exclude unnamed pattern bindings from scope, flow analysis and code

generation

* Fixes #2020

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

@@ -90,7 +90,8 @@ public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, Fl
 	}
 	if (this.initialization == null) {
 		if (this.binding != null && this.binding.isPatternVariable())
-			this.bits |= FirstAssignmentToLocal;
+			if (!this.binding.declaration.isUnnamed(currentScope))
+				this.bits |= FirstAssignmentToLocal;
 		return flowInfo;
 	}
 	this.initialization.checkNPEbyUnboxing(currentScope, flowContext, flowInfo);

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

@@ -64,6 +64,10 @@ public void setEnclosingPattern(RecordPattern enclosingPattern) {
 		this.enclosingPattern = enclosingPattern;
 	}
 
+	public boolean isUnnamed() {
+		return false;
+	}
+
 	/**
 	 * Implement the rules in the spec under 14.11.1.1 Exhaustive Switch Blocks
 	 *

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

@@ -237,12 +237,13 @@ original record instance as receiver - leaving the stack drained.
 					p.accessorMethod.returnType.erasure()))
 				codeStream.checkcast(p.accessorMethod.returnType); // lastComponent ? [C] : [R, C]
 			if (p instanceof RecordPattern || !p.isTotalTypeNode) {
-				codeStream.dup(); // lastComponent ? [C, C] : [R, C, C]
-				codeStream.instance_of(p.resolvedType); // lastComponent ? [C, boolean] : [R, C, boolean]
+				if (!p.isUnnamed())
+					codeStream.dup(); // lastComponent ? named ? ([C, C] : [R, C, C]) : ([C] : [R, C])
+				codeStream.instance_of(p.resolvedType); // lastComponent ? named ? ([C, boolean] : [R, C, boolean]) : ([boolean] : [R, boolean])
 				BranchLabel target = falseLabel != null ? falseLabel : new BranchLabel(codeStream);
 				BranchLabel innerTruthLabel = new BranchLabel(codeStream);
-				codeStream.ifne(innerTruthLabel); // lastComponent ? [C] : [R, C]
-				int pops = 1; // Not going to store into the component pattern binding, so need to pop, the duped value.
+				codeStream.ifne(innerTruthLabel); // lastComponent ? named ? ([C] : [R, C]) : ([] : [R])
+				int pops = p.isUnnamed() ? 0 : 1; // Not going to store into the component pattern binding, so need to pop, the duped value.
 				Pattern current = p;
 				RecordPattern outer = this;
 				while (outer != null) {

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

@@ -40,14 +40,26 @@ public TypePattern(LocalDeclaration local) {
 		this.local = local;
 	}
 
+	public static TypePattern createTypePattern(LocalDeclaration lokal) {
+		if (lokal.name.length == 1 && lokal.name[0] == '_') {
+			return new TypePattern(lokal) {
+				@Override
+				public boolean isUnnamed() {
+					return true;
+				}
+			};
+		}
+		return new TypePattern(lokal);
+	}
+
 	@Override
 	public TypeReference getType() {
 		return this.local.type;
 	}
 
 	@Override
 	public LocalVariableBinding[] bindingsWhenTrue() {
-		return this.local.binding == null ? NO_VARIABLES : new LocalVariableBinding[] { this.local.binding };
+		return this.isUnnamed() || this.local.binding == null ? NO_VARIABLES : new LocalVariableBinding[] { this.local.binding };
 	}
 
 	@Override
@@ -62,6 +74,10 @@ public boolean checkUnsafeCast(Scope scope, TypeBinding castType, TypeBinding ex
 	public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
 		flowInfo = this.local.analyseCode(currentScope, flowContext, flowInfo);
 		FlowInfo patternInfo = flowInfo.copy();
+
+		if (this.isUnnamed())
+			return patternInfo; // exclude anonymous blokes from flow analysis.
+
 		patternInfo.markAsDefinitelyAssigned(this.local.binding);
 		if (!this.isTotalTypeNode) {
 			// non-total type patterns create a nonnull local:
@@ -80,10 +96,23 @@ public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, Fl
 
 	@Override
 	public void generateOptimizedBoolean(BlockScope currentScope, CodeStream codeStream, BranchLabel trueLabel, BranchLabel falseLabel) {
-		if (!this.isTotalTypeNode) {
-			codeStream.checkcast(this.local.binding.type);
+		if (isUnnamed()) {
+			if (this.isTotalTypeNode) {
+				switch (this.local.binding.type.id) {
+					case T_long :
+					case T_double :
+						codeStream.pop2();
+						break;
+					default :
+						codeStream.pop();
+				}
+			} // else we don't value on stack.
+		} else {
+			if (!this.isTotalTypeNode) {
+				codeStream.checkcast(this.local.binding.type);
+			}
+			this.local.generateCode(currentScope, codeStream);
 		}
-		this.local.generateCode(currentScope, codeStream);
 	}
 
 	@Override

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/lookup/BlockScope.java

@@ -146,20 +146,21 @@ public final void addLocalVariable(LocalVariableBinding binding) {
 		return;
 	}
 	checkAndSetModifiersForVariable(binding);
-	// insert local in scope
-	if (this.localIndex == this.locals.length)
-		System.arraycopy(
-			this.locals,
-			0,
-			(this.locals = new LocalVariableBinding[this.localIndex * 2]),
-			0,
-			this.localIndex);
-	this.locals[this.localIndex++] = binding;
+	// insert local in scope, skipping unnamed pattern variables.
+	if (!binding.isPatternVariable() || !binding.declaration.isUnnamed(this)) {
+		if (this.localIndex == this.locals.length)
+			System.arraycopy(
+				this.locals,
+				0,
+				(this.locals = new LocalVariableBinding[this.localIndex * 2]),
+				0,
+				this.localIndex);
+		this.locals[this.localIndex++] = binding;
+		binding.id = outerMostMethodScope().analysisIndex++; // share the outermost method scope analysisIndex
+	}
 
 	// update local variable binding
 	binding.declaringScope = this;
-	binding.id = outerMostMethodScope().analysisIndex++;
-	// share the outermost method scope analysisIndex
 }
 
 public void addSubscope(Scope childScope) {

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/parser/Parser.java

@@ -10357,7 +10357,7 @@ protected void consumeTypePattern() {
 	type.annotations = null;
 	local.type = type;
 
-	TypePattern aTypePattern = new TypePattern(local);
+	TypePattern aTypePattern = TypePattern.createTypePattern(local);
 	aTypePattern.sourceStart = this.intStack[this.intPtr--];
 	local.modifiers =  this.intStack[this.intPtr--];
 	local.declarationSourceStart = type.sourceStart;
@@ -10379,7 +10379,7 @@ protected void consumeUnnamedPattern() {
 	this.identifierPtr--;
 	this.identifierLengthPtr--;
 
-	TypePattern aUnnamedPattern = new TypePattern(local);
+	TypePattern aUnnamedPattern = TypePattern.createTypePattern(local);
 	aUnnamedPattern.sourceStart = local.sourceStart;
 	aUnnamedPattern.sourceEnd = local.sourceEnd;