/// <summary> /// Lower a foreach loop that will enumerate a collection using an enumerator. /// /// E e = ((C)(x)).GetEnumerator() /// try { /// while (e.MoveNext()) { /// V v = (V)(T)e.Current; /// // body /// } /// } /// finally { /// // clean up e /// } /// </summary> private BoundStatement RewriteEnumeratorForEachStatement(BoundForEachStatement node) { ForEachStatementSyntax forEachSyntax = (ForEachStatementSyntax)node.Syntax; ForEachEnumeratorInfo enumeratorInfo = node.EnumeratorInfoOpt; Debug.Assert(enumeratorInfo != null); BoundExpression collectionExpression = GetUnconvertedCollectionExpression(node); BoundExpression rewrittenExpression = (BoundExpression)Visit(collectionExpression); BoundStatement rewrittenBody = (BoundStatement)Visit(node.Body); TypeSymbol enumeratorType = enumeratorInfo.GetEnumeratorMethod.ReturnType; TypeSymbol elementType = enumeratorInfo.ElementType; // E e LocalSymbol enumeratorVar = new TempLocalSymbol(enumeratorType, RefKind.None, this.containingMethod); // Reference to e. BoundLocal boundEnumeratorVar = MakeBoundLocal(forEachSyntax, enumeratorVar, enumeratorType); // ((C)(x)).GetEnumerator() or (x).GetEnumerator(); BoundExpression enumeratorVarInitValue = SynthesizeCall(forEachSyntax, rewrittenExpression, enumeratorInfo.GetEnumeratorMethod, enumeratorInfo.CollectionConversion, enumeratorInfo.CollectionType); // E e = ((C)(x)).GetEnumerator(); BoundStatement enumeratorVarDecl = MakeLocalDeclaration(forEachSyntax, enumeratorVar, enumeratorVarInitValue); AddForEachExpressionSequencePoint(forEachSyntax, ref enumeratorVarDecl); // V v LocalSymbol iterationVar = node.IterationVariable; //(V)(T)e.Current BoundExpression iterationVarAssignValue = SynthesizeConversion( syntax: forEachSyntax, operand: SynthesizeConversion( syntax: forEachSyntax, operand: BoundCall.Synthesized( syntax: forEachSyntax, receiverOpt: boundEnumeratorVar, method: enumeratorInfo.CurrentPropertyGetter), conversion: enumeratorInfo.CurrentConversion, type: elementType), conversion: node.ElementConversion, type: iterationVar.Type); // V v = (V)(T)e.Current; BoundStatement iterationVarDecl = MakeLocalDeclaration(forEachSyntax, iterationVar, iterationVarAssignValue); AddForEachIterationVariableSequencePoint(forEachSyntax, ref iterationVarDecl); // while (e.MoveNext()) { // V v = (V)(T)e.Current; // /* node.Body */ // } BoundStatement whileLoop = RewriteWhileStatement( syntax: forEachSyntax, rewrittenCondition: BoundCall.Synthesized( syntax: forEachSyntax, receiverOpt: boundEnumeratorVar, method: enumeratorInfo.MoveNextMethod), conditionSequencePointSpan: forEachSyntax.InKeyword.Span, rewrittenBody: new BoundBlock(rewrittenBody.Syntax, statements: ReadOnlyArray <BoundStatement> .CreateFrom(iterationVarDecl, rewrittenBody), localsOpt: ReadOnlyArray <LocalSymbol> .CreateFrom(iterationVar)), breakLabel: node.BreakLabel, continueLabel: node.ContinueLabel, hasErrors: false); BoundStatement result; if (enumeratorInfo.DisposeMethodOpt != null) { BoundBlock finallyBlockOpt; var idisposableTypeSymbol = enumeratorInfo.DisposeMethodOpt.ContainingType; var conversions = new TypeConversions(this.containingMethod.ContainingAssembly.CorLibrary); if (conversions.ClassifyImplicitConversion(enumeratorType, idisposableTypeSymbol).IsImplicit) { Debug.Assert(enumeratorInfo.DisposeMethodOpt != null); Conversion receiverConversion = enumeratorType.IsStructType() ? Conversion.Boxing : Conversion.ImplicitReference; // ((IDisposable)e).Dispose(); or e.Dispose(); BoundStatement disposeCall = new BoundExpressionStatement(forEachSyntax, expression: SynthesizeCall(forEachSyntax, boundEnumeratorVar, enumeratorInfo.DisposeMethodOpt, receiverConversion, idisposableTypeSymbol)); BoundStatement disposeStmt; if (enumeratorType.IsValueType) { // No way for the struct to be nullable and disposable. Debug.Assert(((TypeSymbol)enumeratorType.OriginalDefinition).SpecialType != SpecialType.System_Nullable_T); // For non-nullable structs, no null check is required. disposeStmt = disposeCall; } else { // NB: cast to object missing from spec. Needed to ignore user-defined operators and box type parameters. // if ((object)e != null) ((IDisposable)e).Dispose(); disposeStmt = RewriteIfStatement( syntax: forEachSyntax, rewrittenCondition: new BoundBinaryOperator(forEachSyntax, operatorKind: BinaryOperatorKind.NotEqual, left: SynthesizeConversion( syntax: forEachSyntax, operand: boundEnumeratorVar, conversion: enumeratorInfo.EnumeratorConversion, type: this.compilation.GetSpecialType(SpecialType.System_Object)), right: new BoundLiteral(forEachSyntax, constantValueOpt: ConstantValue.Null, type: null), constantValueOpt: null, methodOpt: null, resultKind: LookupResultKind.Viable, type: this.compilation.GetSpecialType(SpecialType.System_Boolean)), rewrittenConsequence: disposeCall, rewrittenAlternativeOpt: null, hasErrors: false); } finallyBlockOpt = new BoundBlock(forEachSyntax, localsOpt: ReadOnlyArray <LocalSymbol> .Null, statements: ReadOnlyArray <BoundStatement> .CreateFrom(disposeStmt)); } else { Debug.Assert(!enumeratorType.IsSealed); // IDisposable d LocalSymbol disposableVar = new TempLocalSymbol(idisposableTypeSymbol, RefKind.None, this.containingMethod); // Reference to d. BoundLocal boundDisposableVar = MakeBoundLocal(forEachSyntax, disposableVar, idisposableTypeSymbol); BoundTypeExpression boundIDisposableTypeExpr = new BoundTypeExpression(forEachSyntax, type: idisposableTypeSymbol); // e as IDisposable BoundExpression disposableVarInitValue = new BoundAsOperator(forEachSyntax, operand: boundEnumeratorVar, targetType: boundIDisposableTypeExpr, conversion: Conversion.ExplicitReference, // Explicit so the emitter won't optimize it away. type: idisposableTypeSymbol); // IDisposable d = e as IDisposable; BoundStatement disposableVarDecl = MakeLocalDeclaration(forEachSyntax, disposableVar, disposableVarInitValue); // if (d != null) d.Dispose(); BoundStatement ifStmt = RewriteIfStatement( syntax: forEachSyntax, rewrittenCondition: new BoundBinaryOperator(forEachSyntax, operatorKind: BinaryOperatorKind.NotEqual, // reference equality left: boundDisposableVar, right: new BoundLiteral(forEachSyntax, constantValueOpt: ConstantValue.Null, type: null), constantValueOpt: null, methodOpt: null, resultKind: LookupResultKind.Viable, type: this.compilation.GetSpecialType(SpecialType.System_Boolean)), rewrittenConsequence: new BoundExpressionStatement(forEachSyntax, expression: BoundCall.Synthesized( syntax: forEachSyntax, receiverOpt: boundDisposableVar, method: enumeratorInfo.DisposeMethodOpt)), rewrittenAlternativeOpt: null, hasErrors: false); // IDisposable d = e as IDisposable; // if (d != null) d.Dispose(); finallyBlockOpt = new BoundBlock(forEachSyntax, localsOpt: ReadOnlyArray <LocalSymbol> .CreateFrom(disposableVar), statements: ReadOnlyArray <BoundStatement> .CreateFrom(disposableVarDecl, ifStmt)); } // try { // while (e.MoveNext()) { // V v = (V)(T)e.Current; // /* loop body */ // } // } // finally { // /* dispose of e */ // } BoundStatement tryFinally = new BoundTryStatement(forEachSyntax, tryBlock: new BoundBlock(forEachSyntax, localsOpt: ReadOnlyArray <LocalSymbol> .Empty, statements: ReadOnlyArray <BoundStatement> .CreateFrom(whileLoop)), catchBlocks: ReadOnlyArray <BoundCatchBlock> .Empty, finallyBlockOpt: finallyBlockOpt); // E e = ((C)(x)).GetEnumerator(); // try { // /* as above */ result = new BoundBlock( syntax: forEachSyntax, localsOpt: ReadOnlyArray <LocalSymbol> .CreateFrom(enumeratorVar), statements: ReadOnlyArray <BoundStatement> .CreateFrom(enumeratorVarDecl, tryFinally)); } else { // E e = ((C)(x)).GetEnumerator(); // while (e.MoveNext()) { // V v = (V)(T)e.Current; // /* loop body */ // } result = new BoundBlock( syntax: forEachSyntax, localsOpt: ReadOnlyArray <LocalSymbol> .CreateFrom(enumeratorVar), statements: ReadOnlyArray <BoundStatement> .CreateFrom(enumeratorVarDecl, whileLoop)); } AddForEachKeywordSequencePoint(forEachSyntax, ref result); return(result); }
/// <summary> /// Lower a foreach loop that will enumerate a collection using an enumerator. /// /// E e = ((C)(x)).GetEnumerator() /// try { /// while (e.MoveNext()) { /// V v = (V)(T)e.Current; /// // body /// } /// } /// finally { /// // clean up e /// } /// </summary> private BoundStatement RewriteEnumeratorForEachStatement(BoundForEachStatement node) { ForEachStatementSyntax forEachSyntax = (ForEachStatementSyntax)node.Syntax; ForEachEnumeratorInfo enumeratorInfo = node.EnumeratorInfoOpt; Debug.Assert(enumeratorInfo != null); BoundExpression collectionExpression = GetUnconvertedCollectionExpression(node); BoundExpression rewrittenExpression = (BoundExpression)Visit(collectionExpression); BoundStatement rewrittenBody = (BoundStatement)Visit(node.Body); TypeSymbol enumeratorType = enumeratorInfo.GetEnumeratorMethod.ReturnType; TypeSymbol elementType = enumeratorInfo.ElementType; // E e LocalSymbol enumeratorVar = new TempLocalSymbol(enumeratorType, RefKind.None, this.containingMethod); // Reference to e. BoundLocal boundEnumeratorVar = MakeBoundLocal(forEachSyntax, enumeratorVar, enumeratorType); // ((C)(x)).GetEnumerator() or (x).GetEnumerator(); BoundExpression enumeratorVarInitValue = SynthesizeCall(forEachSyntax, rewrittenExpression, enumeratorInfo.GetEnumeratorMethod, enumeratorInfo.CollectionConversion, enumeratorInfo.CollectionType); // E e = ((C)(x)).GetEnumerator(); BoundStatement enumeratorVarDecl = MakeLocalDeclaration(forEachSyntax, enumeratorVar, enumeratorVarInitValue); AddForEachExpressionSequencePoint(forEachSyntax, ref enumeratorVarDecl); // V v LocalSymbol iterationVar = node.IterationVariable; //(V)(T)e.Current BoundExpression iterationVarAssignValue = SynthesizeConversion( syntax: forEachSyntax, operand: SynthesizeConversion( syntax: forEachSyntax, operand: BoundCall.Synthesized( syntax: forEachSyntax, receiverOpt: boundEnumeratorVar, method: enumeratorInfo.CurrentPropertyGetter), conversion: enumeratorInfo.CurrentConversion, type: elementType), conversion: node.ElementConversion, type: iterationVar.Type); // V v = (V)(T)e.Current; BoundStatement iterationVarDecl = MakeLocalDeclaration(forEachSyntax, iterationVar, iterationVarAssignValue); AddForEachIterationVariableSequencePoint(forEachSyntax, ref iterationVarDecl); // while (e.MoveNext()) { // V v = (V)(T)e.Current; // /* node.Body */ // } BoundStatement whileLoop = RewriteWhileStatement( syntax: forEachSyntax, rewrittenCondition: BoundCall.Synthesized( syntax: forEachSyntax, receiverOpt: boundEnumeratorVar, method: enumeratorInfo.MoveNextMethod), conditionSequencePointSpan: forEachSyntax.InKeyword.Span, rewrittenBody: new BoundBlock(rewrittenBody.Syntax, statements: ReadOnlyArray<BoundStatement>.CreateFrom(iterationVarDecl, rewrittenBody), localsOpt: ReadOnlyArray<LocalSymbol>.CreateFrom(iterationVar)), breakLabel: node.BreakLabel, continueLabel: node.ContinueLabel, hasErrors: false); BoundStatement result; if (enumeratorInfo.DisposeMethodOpt != null) { BoundBlock finallyBlockOpt; var idisposableTypeSymbol = enumeratorInfo.DisposeMethodOpt.ContainingType; var conversions = new TypeConversions(this.containingMethod.ContainingAssembly.CorLibrary); if (conversions.ClassifyImplicitConversion(enumeratorType, idisposableTypeSymbol).IsImplicit) { Debug.Assert(enumeratorInfo.DisposeMethodOpt != null); Conversion receiverConversion = enumeratorType.IsStructType() ? Conversion.Boxing : Conversion.ImplicitReference; // ((IDisposable)e).Dispose(); or e.Dispose(); BoundStatement disposeCall = new BoundExpressionStatement(forEachSyntax, expression: SynthesizeCall(forEachSyntax, boundEnumeratorVar, enumeratorInfo.DisposeMethodOpt, receiverConversion, idisposableTypeSymbol)); BoundStatement disposeStmt; if (enumeratorType.IsValueType) { // No way for the struct to be nullable and disposable. Debug.Assert(((TypeSymbol)enumeratorType.OriginalDefinition).SpecialType != SpecialType.System_Nullable_T); // For non-nullable structs, no null check is required. disposeStmt = disposeCall; } else { // NB: cast to object missing from spec. Needed to ignore user-defined operators and box type parameters. // if ((object)e != null) ((IDisposable)e).Dispose(); disposeStmt = RewriteIfStatement( syntax: forEachSyntax, rewrittenCondition: new BoundBinaryOperator(forEachSyntax, operatorKind: BinaryOperatorKind.NotEqual, left: SynthesizeConversion( syntax: forEachSyntax, operand: boundEnumeratorVar, conversion: enumeratorInfo.EnumeratorConversion, type: this.compilation.GetSpecialType(SpecialType.System_Object)), right: new BoundLiteral(forEachSyntax, constantValueOpt: ConstantValue.Null, type: null), constantValueOpt: null, methodOpt: null, resultKind: LookupResultKind.Viable, type: this.compilation.GetSpecialType(SpecialType.System_Boolean)), rewrittenConsequence: disposeCall, rewrittenAlternativeOpt: null, hasErrors: false); } finallyBlockOpt = new BoundBlock(forEachSyntax, localsOpt: ReadOnlyArray<LocalSymbol>.Null, statements: ReadOnlyArray<BoundStatement>.CreateFrom(disposeStmt)); } else { Debug.Assert(!enumeratorType.IsSealed); // IDisposable d LocalSymbol disposableVar = new TempLocalSymbol(idisposableTypeSymbol, RefKind.None, this.containingMethod); // Reference to d. BoundLocal boundDisposableVar = MakeBoundLocal(forEachSyntax, disposableVar, idisposableTypeSymbol); BoundTypeExpression boundIDisposableTypeExpr = new BoundTypeExpression(forEachSyntax, type: idisposableTypeSymbol); // e as IDisposable BoundExpression disposableVarInitValue = new BoundAsOperator(forEachSyntax, operand: boundEnumeratorVar, targetType: boundIDisposableTypeExpr, conversion: Conversion.ExplicitReference, // Explicit so the emitter won't optimize it away. type: idisposableTypeSymbol); // IDisposable d = e as IDisposable; BoundStatement disposableVarDecl = MakeLocalDeclaration(forEachSyntax, disposableVar, disposableVarInitValue); // if (d != null) d.Dispose(); BoundStatement ifStmt = RewriteIfStatement( syntax: forEachSyntax, rewrittenCondition: new BoundBinaryOperator(forEachSyntax, operatorKind: BinaryOperatorKind.NotEqual, // reference equality left: boundDisposableVar, right: new BoundLiteral(forEachSyntax, constantValueOpt: ConstantValue.Null, type: null), constantValueOpt: null, methodOpt: null, resultKind: LookupResultKind.Viable, type: this.compilation.GetSpecialType(SpecialType.System_Boolean)), rewrittenConsequence: new BoundExpressionStatement(forEachSyntax, expression: BoundCall.Synthesized( syntax: forEachSyntax, receiverOpt: boundDisposableVar, method: enumeratorInfo.DisposeMethodOpt)), rewrittenAlternativeOpt: null, hasErrors: false); // IDisposable d = e as IDisposable; // if (d != null) d.Dispose(); finallyBlockOpt = new BoundBlock(forEachSyntax, localsOpt: ReadOnlyArray<LocalSymbol>.CreateFrom(disposableVar), statements: ReadOnlyArray<BoundStatement>.CreateFrom(disposableVarDecl, ifStmt)); } // try { // while (e.MoveNext()) { // V v = (V)(T)e.Current; // /* loop body */ // } // } // finally { // /* dispose of e */ // } BoundStatement tryFinally = new BoundTryStatement(forEachSyntax, tryBlock: new BoundBlock(forEachSyntax, localsOpt: ReadOnlyArray<LocalSymbol>.Empty, statements: ReadOnlyArray<BoundStatement>.CreateFrom(whileLoop)), catchBlocks: ReadOnlyArray<BoundCatchBlock>.Empty, finallyBlockOpt: finallyBlockOpt); // E e = ((C)(x)).GetEnumerator(); // try { // /* as above */ result = new BoundBlock( syntax: forEachSyntax, localsOpt: ReadOnlyArray<LocalSymbol>.CreateFrom(enumeratorVar), statements: ReadOnlyArray<BoundStatement>.CreateFrom(enumeratorVarDecl, tryFinally)); } else { // E e = ((C)(x)).GetEnumerator(); // while (e.MoveNext()) { // V v = (V)(T)e.Current; // /* loop body */ // } result = new BoundBlock( syntax: forEachSyntax, localsOpt: ReadOnlyArray<LocalSymbol>.CreateFrom(enumeratorVar), statements: ReadOnlyArray<BoundStatement>.CreateFrom(enumeratorVarDecl, whileLoop)); } AddForEachKeywordSequencePoint(forEachSyntax, ref result); return result; }