Support parsing and generating unnamed variables and patterns

Doesn't include support for lists of patterns in case labels, that will be handled in a future PR. Signed-off-by: David Thompson <[email protected]>
datho7561 · Jan 18, 2024 · 4929232 · 4929232
1 parent a8d8033
commit 4929232
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Showing 57 changed files with 3,138 additions and 2,147 deletions.
diff --git a/org.eclipse.jdt.core.compiler.batch/grammar/java.g b/org.eclipse.jdt.core.compiler.batch/grammar/java.g
@@ -124,6 +124,7 @@ $Terminals
 	BeginCaseElement
 	RestrictedIdentifierWhen
 	BeginRecordPattern
+	UNDERSCORE
 
 --    BodyMarker
 
@@ -181,6 +182,7 @@ $Alias
 	'...'  ::= ELLIPSIS
 	'@308' ::= AT308
 	'@308...' ::= AT308DOTDOTDOT
+	'_' ::= UNDERSCORE
 
 $Start
 	Goal
@@ -835,6 +837,8 @@ RestoreDiet ::= $empty
 VariableDeclaratorId ::= 'Identifier' Dimsopt
 /:$readableName VariableDeclaratorId:/
 /:$recovery_template Identifier:/
+VariableDeclaratorId ::= '_'
+/.$putCase consumeUnnamedVariable(); $break ./
 
 VariableInitializer -> Expression
 VariableInitializer -> ArrayInitializer
@@ -1263,6 +1267,10 @@ Pattern -> RecordPattern
 TypePattern ::= Modifiersopt Type 'Identifier'
 /.$putCase consumeTypePattern(); $break ./
 /:$readableName TypePattern:/
+TypePattern ::= Modifiersopt Type '_'
+/.$putCase consumeTypePattern(); $break ./
+/:$readableName TypePattern:/
+/:$compliance 21:/
 
 -----------------------------------------------
 -- 16 feature : end of instanceof pattern matching
@@ -1272,26 +1280,30 @@ TypePattern ::= Modifiersopt Type 'Identifier'
 -- 20 preview feature : record patterns
 -----------------------------------------------
 
-RecordPattern ::= Modifiersopt ReferenceType PushLPAREN PatternListopt PushRPAREN
+RecordPattern ::= Modifiersopt ReferenceType PushLPAREN ComponentPatternListopt PushRPAREN
 /.$putCase consumeRecordPattern(); $break ./
 /:$readableName RecordPattern:/
 /:$compliance 20:/
 
-PatternListopt ::=  $empty
+ComponentPatternListopt ::=  $empty
 /.$putCase consumePatternListopt(); $break ./
-/:$readableName PatternListopt:/
+/:$readableName ComponentPatternListopt:/
 /:$compliance 20:/
 
-PatternListopt -> PatternList
+ComponentPatternListopt -> ComponentPatternList
 /:$readableName PatternListopt:/
 /:$compliance 20:/
 
-PatternList -> Pattern
-PatternList ::= PatternList ',' Pattern
+ComponentPatternList -> ComponentPattern
+ComponentPatternList ::= ComponentPatternList ',' ComponentPattern
 /.$putCase consumePatternList();  $break ./
-/:$readableName PatternList:/
+/:$readableName ComponentPatternList:/
 /:$compliance 20:/
 
+ComponentPattern -> Pattern
+ComponentPattern -> UnnamedPattern
+/:$compliance 21:/
+
 -----------------------------------------------
 -- 20 preview feature : end of record patterns
 -----------------------------------------------
@@ -1323,6 +1335,11 @@ StringTemplateExpression ::= Primary '.' TemplateArgument
 -- 21 preview feature : end of String templates
 -----------------------------------------------
 
+UnnamedPattern ::= '_'
+/.$putCase consumeUnnamedPattern(); $break ./
+/:$readableName UnnamedPattern:/
+/:$compliance 21:/
+
 ConstantDeclaration -> FieldDeclaration
 /:$readableName ConstantDeclaration:/
 
@@ -1898,6 +1915,11 @@ NestedLambda ::= $empty
 /.$putCase consumeNestedLambda(); $break ./
 /:$readableName NestedLambda:/
 
+LambdaParameters ::= '_' NestedLambda
+/.$putCase consumeTypeElidedLambdaParameter(false); $break ./
+/:$readableName TypeElidedUnnamedFormalParameter:/
+/:$compliance 21:/
+
 LambdaParameters ::= Identifier NestedLambda
 /.$putCase consumeTypeElidedLambdaParameter(false); $break ./
 /:$readableName TypeElidedFormalParameter:/
@@ -1931,6 +1953,11 @@ TypeElidedFormalParameter ::= Modifiersopt Identifier
 /:$readableName TypeElidedFormalParameter:/
 /:$compliance 1.8:/
 
+TypeElidedFormalParameter ::= '_'
+/.$putCase consumeBracketedTypeElidedUnderscoreLambdaParameter(); $break ./
+/:$readableName TypeElidedFormalParameter:/
+/:$compliance 21:/
+
 -- A lambda body of the form x is really '{' return x; '}'
 LambdaBody -> ElidedLeftBraceAndReturn Expression ElidedSemicolonAndRightBrace
 LambdaBody -> Block
@@ -2515,11 +2542,11 @@ EnhancedForStatementNoShortIf ::= EnhancedForStatementHeader StatementNoShortIf
 /.$putCase consumeEnhancedForStatement(); $break ./
 /:$readableName EnhancedForStatementNoShortIf:/
 
-EnhancedForStatementHeaderInit ::= 'for' '(' Type PushModifiers Identifier Dimsopt
+EnhancedForStatementHeaderInit ::= 'for' '(' Type PushModifiers VariableDeclaratorId
 /.$putCase consumeEnhancedForStatementHeaderInit(false); $break ./
 /:$readableName EnhancedForStatementHeaderInit:/
 
-EnhancedForStatementHeaderInit ::= 'for' '(' Modifiers Type PushRealModifiers Identifier Dimsopt
+EnhancedForStatementHeaderInit ::= 'for' '(' Modifiers Type PushRealModifiers VariableDeclaratorId
 /.$putCase consumeEnhancedForStatementHeaderInit(true); $break ./
 /:$readableName EnhancedForStatementHeaderInit:/
 
@@ -3203,6 +3230,7 @@ AT308DOTDOTDOT ::= '@'
 ELLIPSIS ::=    '...'    
 ARROW ::= '->'
 COLON_COLON ::= '::'
+UNDERSCORE ::= '_'
 
 $end
 -- need a carriage return after the $end
diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/core/compiler/IProblem.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/core/compiler/IProblem.java
@@ -2581,4 +2581,15 @@ public interface IProblem {
 	 * @since 3.35
 	 */
 	int SyntheticAccessorNotEnclosingMethod = MethodRelated + 1990;
+
+	/**
+	 * @since 3.37
+	 * @noreference preview feature
+	 */
+	int UnderscoreCannotBeUsedHere = PreviewRelated + 2000;
+	/**
+	 * @since 3.37
+	 * @noreference preview feature
+	 */
+	int UnnamedVariableMustHaveInitializer = PreviewRelated + 2001;
 }
diff --git a/...compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/AbstractVariableDeclaration.java b/...compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/AbstractVariableDeclaration.java
@@ -16,6 +16,7 @@
  *******************************************************************************/
 package org.eclipse.jdt.internal.compiler.ast;
 
+import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
 import org.eclipse.jdt.internal.compiler.flow.FlowContext;
 import org.eclipse.jdt.internal.compiler.flow.FlowInfo;
 import org.eclipse.jdt.internal.compiler.lookup.BlockScope;
@@ -144,4 +145,15 @@ public void setDepth(int depth) {
 	public void setFieldIndex(int depth) {
 		// do nothing by default
 	}
+
+	/**
+	 * Returns true if this variable is an unnamed variable (_) and false otherwise.
+	 *
+	 * @param scope used to determine source level
+	 */
+	public boolean isUnnamed(BlockScope scope) {
+		return ((this.name.length == 1 && this.name[0] == '_') || ("\\u005F".equals(this.name.toString()))) //$NON-NLS-1$
+				&& scope.compilerOptions().sourceLevel >= ClassFileConstants.JDK21
+				&& scope.compilerOptions().enablePreviewFeatures;
+	}
 }
diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Argument.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Argument.java
@@ -116,19 +116,25 @@ private Annotation[] getCorrespondingRecordComponentAnnotationsIfApplicable(Abst
 		return null;
 	}
 	public TypeBinding bind(MethodScope scope, TypeBinding typeBinding, boolean used) {
+		if (this.isUnnamed(scope) && !scope.isLambdaScope()) {
+			scope.problemReporter().illegalUseOfUnderscoreAsAnIdentifier(this.sourceStart, this.sourceEnd, scope.compilerOptions().sourceLevel > ClassFileConstants.JDK1_8, true);
+		}
+
 		TypeBinding newTypeBinding = createBinding(scope, typeBinding); // basically a no-op if createBinding() was called before
 
 		// record the resolved type into the type reference
 		Binding existingVariable = scope.getBinding(this.name, Binding.VARIABLE, this, false /*do not resolve hidden field*/);
 		if (existingVariable != null && existingVariable.isValidBinding()){
 			final boolean localExists = existingVariable instanceof LocalVariableBinding;
 			if (localExists && this.hiddenVariableDepth == 0) {
-				if ((this.bits & ASTNode.ShadowsOuterLocal) != 0 && scope.isLambdaSubscope()) {
-					scope.problemReporter().lambdaRedeclaresArgument(this);
-				} else if (scope.referenceContext instanceof CompactConstructorDeclaration) {
-					// skip error reporting - hidden params - already reported in record components
-				} else {
-					scope.problemReporter().redefineArgument(this);
+				if (!this.isUnnamed(scope)) {
+					if ((this.bits & ASTNode.ShadowsOuterLocal) != 0 && scope.isLambdaSubscope()) {
+						scope.problemReporter().lambdaRedeclaresArgument(this);
+					} else if (scope.referenceContext instanceof CompactConstructorDeclaration) {
+						// skip error reporting - hidden params - already reported in record components
+					} else {
+						scope.problemReporter().redefineArgument(this);
+					}
 				}
 			} else {
 				boolean isSpecialArgument = false;
@@ -234,7 +240,7 @@ public TypeBinding resolveForCatch(BlockScope scope) {
 			}
 		}
 		Binding existingVariable = scope.getBinding(this.name, Binding.VARIABLE, this, false /*do not resolve hidden field*/);
-		if (existingVariable != null && existingVariable.isValidBinding()){
+		if (existingVariable != null && existingVariable.isValidBinding() && !isUnnamed(scope)) {
 			if (existingVariable instanceof LocalVariableBinding && this.hiddenVariableDepth == 0) {
 				scope.problemReporter().redefineArgument(this);
 			} else {

diff --git a/...e.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/FieldDeclaration.java b/...e.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/FieldDeclaration.java
@@ -207,6 +207,10 @@ public StringBuilder printStatement(int indent, StringBuilder output) {
 }
 
 public void resolve(MethodScope initializationScope) {
+	if (this.isUnnamed(initializationScope)) {
+		initializationScope.problemReporter().illegalUseOfUnderscoreAsAnIdentifier(this.sourceStart, this.sourceEnd, initializationScope.compilerOptions().sourceLevel > ClassFileConstants.JDK1_8, true);
+	}
+
 	// the two <constant = Constant.NotAConstant> could be regrouped into
 	// a single line but it is clearer to have two lines while the reason of their
 	// existence is not at all the same. See comment for the second one.

diff --git a/...e.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/LocalDeclaration.java b/...e.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/LocalDeclaration.java
@@ -47,12 +47,24 @@
 import java.util.Set;
 
 import org.eclipse.jdt.internal.compiler.ASTVisitor;
-import org.eclipse.jdt.internal.compiler.impl.*;
 import org.eclipse.jdt.internal.compiler.ast.TypeReference.AnnotationCollector;
 import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
-import org.eclipse.jdt.internal.compiler.codegen.*;
-import org.eclipse.jdt.internal.compiler.flow.*;
-import org.eclipse.jdt.internal.compiler.lookup.*;
+import org.eclipse.jdt.internal.compiler.codegen.AnnotationContext;
+import org.eclipse.jdt.internal.compiler.codegen.CodeStream;
+import org.eclipse.jdt.internal.compiler.flow.FlowContext;
+import org.eclipse.jdt.internal.compiler.flow.FlowInfo;
+import org.eclipse.jdt.internal.compiler.impl.CompilerOptions;
+import org.eclipse.jdt.internal.compiler.impl.Constant;
+import org.eclipse.jdt.internal.compiler.lookup.ArrayBinding;
+import org.eclipse.jdt.internal.compiler.lookup.Binding;
+import org.eclipse.jdt.internal.compiler.lookup.BlockScope;
+import org.eclipse.jdt.internal.compiler.lookup.ExtraCompilerModifiers;
+import org.eclipse.jdt.internal.compiler.lookup.LocalVariableBinding;
+import org.eclipse.jdt.internal.compiler.lookup.Scope;
+import org.eclipse.jdt.internal.compiler.lookup.TagBits;
+import org.eclipse.jdt.internal.compiler.lookup.TypeBinding;
+import org.eclipse.jdt.internal.compiler.lookup.TypeBindingVisitor;
+import org.eclipse.jdt.internal.compiler.lookup.TypeVariableBinding;
 import org.eclipse.jdt.internal.compiler.parser.RecoveryScanner;
 
 public class LocalDeclaration extends AbstractVariableDeclaration {
@@ -139,7 +151,6 @@ public void checkModifiers() {
 	 */
 	@Override
 	public void generateCode(BlockScope currentScope, CodeStream codeStream) {
-
 		// even if not reachable, variable must be added to visible if allocated (28298)
 		if (this.binding.resolvedPosition != -1) {
 			codeStream.addVisibleLocalVariable(this.binding);
@@ -260,10 +271,13 @@ private static Expression findPolyExpression(Expression e) {
 	public void resolve(BlockScope scope) {
 		resolve(scope, false);
 	}
-	public void resolve(BlockScope scope, boolean isPatternVariable) {
-		// prescan NNBD
+	public void resolve(BlockScope scope, boolean isPatternVariable) {		// prescan NNBD
 		handleNonNullByDefault(scope, this.annotations, this);
 
+		if (!isPatternVariable && (this.bits & ASTNode.IsForeachElementVariable) == 0 && this.initialization == null && this.isUnnamed(scope)) {
+			scope.problemReporter().unnamedVariableMustHaveInitializer(this);
+		}
+
 		TypeBinding variableType = null;
 		boolean variableTypeInferenceError = false;
 		boolean isTypeNameVar = isTypeNameVar(scope);
@@ -301,7 +315,7 @@ public void resolve(BlockScope scope, boolean isPatternVariable) {
 		}
 
 		Binding existingVariable = scope.getBinding(this.name, Binding.VARIABLE, this, false /*do not resolve hidden field*/);
-		if (existingVariable != null && existingVariable.isValidBinding()){
+		if (existingVariable != null && existingVariable.isValidBinding() && !this.isUnnamed(scope)) {
 			boolean localExists = existingVariable instanceof LocalVariableBinding;
 			if (localExists && (this.bits & ASTNode.ShadowsOuterLocal) != 0 && scope.isLambdaSubscope() && this.hiddenVariableDepth == 0) {
 				scope.problemReporter().lambdaRedeclaresLocal(this);
@@ -484,7 +498,9 @@ public void traverse(ASTVisitor visitor, BlockScope scope) {
 				for (int i = 0; i < annotationsLength; i++)
 					this.annotations[i].traverse(visitor, scope);
 			}
-			this.type.traverse(visitor, scope);
+			if (this.type != null) {
+				this.type.traverse(visitor, scope);
+			}
 			if (this.initialization != null)
 				this.initialization.traverse(visitor, scope);
 		}

diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Pattern.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Pattern.java
@@ -39,6 +39,9 @@ public abstract class Pattern extends Expression {
 
 	public int nestingLevel = 0;
 
+	// denotes index of this pattern in the parent record pattern, or -1 for patterns whose parent is not a record pattern
+	public int index = -1;
+
 	@Override
 	public boolean containsPatternVariable() {
 		class PatternVariablesVisitor extends ASTVisitor {
@@ -48,7 +51,7 @@ class PatternVariablesVisitor extends ASTVisitor {
 			@Override
 			public boolean visit(TypePattern typePattern, BlockScope blockScope) {
 				 this.hasPatternVar = typePattern.local != null;
-				 this.typeElidedVar |= typePattern.getType().isTypeNameVar(blockScope);
+				 this.typeElidedVar |= typePattern.getType() == null || typePattern.getType().isTypeNameVar(blockScope);
 				 return !(this.hasPatternVar && this.typeElidedVar);
 			}
  		}

diff --git a/...ipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/RecordPattern.java b/...ipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/RecordPattern.java
@@ -197,7 +197,7 @@ private void setAccessorsPlusInfuseInferredType(BlockScope scope) {
 					continue;
 				TypePattern tp = (TypePattern) p;
 				RecordComponentBinding componentBinding = components[i];
-				if (p.getType().isTypeNameVar(scope)) {
+				if (p.getType() == null || p.getType().isTypeNameVar(scope)) {
 					infuseInferredType(scope, tp, componentBinding);
 					if (tp.local.binding != null) // rewrite with the inferred type
 						tp.local.binding.type = componentBinding.type;
@@ -227,14 +227,26 @@ private boolean shouldInitiateRecordTypeInference() {
 		return this.resolvedType != null && this.resolvedType.isRawType();
 	}
 	private void infuseInferredType(Scope currentScope, TypePattern tp, RecordComponentBinding componentBinding) {
-		SingleTypeReference ref = new SingleTypeReference(tp.local.type.getTypeName()[0],
-				tp.local.type.sourceStart,
-				tp.local.type.sourceEnd) {
-			@Override
-			public TypeBinding resolveType(BlockScope scope, boolean checkBounds) {
-				return componentBinding.type;
-			}
-		};
+		SingleTypeReference ref;
+		if (tp.local.type == null) {
+			ref = new SingleTypeReference("var".toCharArray(), //$NON-NLS-1$
+					tp.local.sourceStart,
+					tp.local.sourceEnd) {
+				@Override
+				public TypeBinding resolveType(BlockScope scope, boolean checkBounds) {
+					return componentBinding.type;
+				}
+			};
+		} else {
+			ref = new SingleTypeReference(tp.local.type.getTypeName()[0],
+					tp.local.type.sourceStart,
+					tp.local.type.sourceEnd) {
+				@Override
+				public TypeBinding resolveType(BlockScope scope, boolean checkBounds) {
+					return componentBinding.type;
+				}
+			};
+		}
 		tp.local.type = ref;
 		if (componentBinding.type != null && (componentBinding.tagBits & TagBits.HasMissingType) != 0) {
 			currentScope.problemReporter().invalidType(ref, componentBinding.type);

diff --git a/...clipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java b/...clipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java
@@ -38,7 +38,6 @@ public class TypePattern extends Pattern {
 
 	public LocalDeclaration local;
 	Expression expression;
-	public int index = -1; // denoting position
 
 	public TypePattern(LocalDeclaration local) {
 		this.local = local;
@@ -54,7 +53,7 @@ public void collectPatternVariablesToScope(LocalVariableBinding[] variables, Blo
 		if (this.resolvedType == null) {
 			this.resolveType(scope);
 		}
-		if (this.local != null && this.local.binding != null) {
+		if (this.local != null && this.local.binding != null && !this.local.isUnnamed(scope)) {
 			LocalVariableBinding binding = this.local.binding;
 			if (variables != null) {
 				for (LocalVariableBinding variable : variables) {

diff --git a/...lipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/impl/JavaFeature.java b/...lipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/impl/JavaFeature.java
@@ -66,7 +66,7 @@ public enum JavaFeature {
 			new char[][] {},
 			false),
 	UNNAMMED_PATTERNS_AND_VARS(ClassFileConstants.JDK21,
-			Messages.bind(Messages.unnammed_patterns_and_vars),
+			Messages.bind(Messages.unnamed_patterns_and_vars),
 			new char[][] {},
 			true),
 	UNNAMMED_CLASSES_AND_INSTANCE_MAIN_METHODS(ClassFileConstants.JDK21,

diff --git a/...ipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/lookup/BlockScope.java b/...ipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/lookup/BlockScope.java
@@ -288,7 +288,8 @@ void computeLocalVariablePositions(int ilocal, int initOffset, CodeStream codeSt
 			// do not report fake used variable
 			if (local.useFlag == LocalVariableBinding.UNUSED
 				&& (local.declaration != null) // unused (and non secret) local
-				&& ((local.declaration.bits & ASTNode.IsLocalDeclarationReachable) != 0)) { // declaration is reachable
+				&& ((local.declaration.bits & ASTNode.IsLocalDeclarationReachable) != 0) // declaration is reachable
+				&& !local.declaration.isUnnamed(local.declaringScope)) {
 
 				if (local.isCatchParameter()) {
 					problemReporter().unusedExceptionParameter(local.declaration); // report unused catch arguments