Merge pull request dotnet#20199 from sharwell/faster-use-var

Optimize fast path for "Use 'var'" code style
yetangye · Jun 19, 2017 · 94ca919 · 94ca919
2 parents 6cd6215 + d401b19
commit 94ca919
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Showing 3 changed files with 61 additions and 9 deletions.
diff --git a/src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpTypeStyleDiagnosticAnalyzerBase.cs b/src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpTypeStyleDiagnosticAnalyzerBase.cs
@@ -83,8 +83,13 @@ private void HandleVariableDeclaration(SyntaxNodeAnalysisContext context)
                 var declaration = (ForEachStatementSyntax)declarationStatement;
                 declaredType = declaration.Type;
 
-                state = State.Generate(declarationStatement, semanticModel, optionSet, isVariableDeclarationContext: false, cancellationToken: cancellationToken);
-                shouldAnalyze = IsStylePreferred(semanticModel, optionSet, state, cancellationToken);
+                shouldAnalyze = ShouldAnalyzeForEachStatement(declaration, semanticModel, cancellationToken);
+
+                if (shouldAnalyze)
+                {
+                    state = State.Generate(declarationStatement, semanticModel, optionSet, isVariableDeclarationContext: false, cancellationToken: cancellationToken);
+                    shouldAnalyze = IsStylePreferred(semanticModel, optionSet, state, cancellationToken);
+                }
             }
             else
             {
@@ -107,7 +112,7 @@ private void HandleVariableDeclaration(SyntaxNodeAnalysisContext context)
         private Diagnostic CreateDiagnostic(DiagnosticDescriptor descriptor, SyntaxNode declaration, TextSpan diagnosticSpan) =>
             Diagnostic.Create(descriptor, declaration.SyntaxTree.GetLocation(diagnosticSpan));
 
-        private bool ShouldAnalyzeVariableDeclaration(VariableDeclarationSyntax variableDeclaration, SemanticModel semanticModel, CancellationToken cancellationToken)
+        protected virtual bool ShouldAnalyzeVariableDeclaration(VariableDeclarationSyntax variableDeclaration, SemanticModel semanticModel, CancellationToken cancellationToken)
         {
             // implict type is applicable only for local variables and
             // such declarations cannot have multiple declarators and
@@ -121,5 +126,8 @@ private bool ShouldAnalyzeVariableDeclaration(VariableDeclarationSyntax variable
                    variableDeclaration.Variables.Count == 1 &&
                    variableDeclaration.Variables.Single().Initializer.IsKind(SyntaxKind.EqualsValueClause);
         }
+
+        protected virtual bool ShouldAnalyzeForEachStatement(ForEachStatementSyntax forEachStatement, SemanticModel semanticModel, CancellationToken cancellationToken)
+            => true;
     }
 }
diff --git a/...Features/CSharp/Portable/Diagnostics/Analyzers/CSharpUseExplicitTypeDiagnosticAnalyzer.cs b/...Features/CSharp/Portable/Diagnostics/Analyzers/CSharpUseExplicitTypeDiagnosticAnalyzer.cs
@@ -28,6 +28,30 @@ public CSharpUseExplicitTypeDiagnosticAnalyzer()
         {
         }
 
+        protected override bool ShouldAnalyzeVariableDeclaration(VariableDeclarationSyntax variableDeclaration, SemanticModel semanticModel, CancellationToken cancellationToken)
+        {
+            if (!variableDeclaration.Type.IsVar)
+            {
+                // If the type is not 'var', this analyze has no work to do
+                return false;
+            }
+
+            // The base analyzer may impose further limitations
+            return base.ShouldAnalyzeVariableDeclaration(variableDeclaration, semanticModel, cancellationToken);
+        }
+
+        protected override bool ShouldAnalyzeForEachStatement(ForEachStatementSyntax forEachStatement, SemanticModel semanticModel, CancellationToken cancellationToken)
+        {
+            if (!forEachStatement.Type.IsVar)
+            {
+                // If the type is not 'var', this analyze has no work to do
+                return false;
+            }
+
+            // The base analyzer may impose further limitations
+            return base.ShouldAnalyzeForEachStatement(forEachStatement, semanticModel, cancellationToken);
+        }
+
         protected override bool IsStylePreferred(SemanticModel semanticModel, OptionSet optionSet, State state, CancellationToken cancellationToken)
         {
             var stylePreferences = state.TypeStylePreference;

diff --git a/...Features/CSharp/Portable/Diagnostics/Analyzers/CSharpUseImplicitTypeDiagnosticAnalyzer.cs b/...Features/CSharp/Portable/Diagnostics/Analyzers/CSharpUseImplicitTypeDiagnosticAnalyzer.cs
@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System.Diagnostics;
 using System.Linq;
 using System.Threading;
 using Microsoft.CodeAnalysis;
@@ -29,6 +30,30 @@ public CSharpUseImplicitTypeDiagnosticAnalyzer()
         {
         }
 
+        protected override bool ShouldAnalyzeVariableDeclaration(VariableDeclarationSyntax variableDeclaration, SemanticModel semanticModel, CancellationToken cancellationToken)
+        {
+            if (variableDeclaration.Type.IsVar)
+            {
+                // If the type is already 'var', this analyze has no work to do
+                return false;
+            }
+
+            // The base analyzer may impose further limitations
+            return base.ShouldAnalyzeVariableDeclaration(variableDeclaration, semanticModel, cancellationToken);
+        }
+
+        protected override bool ShouldAnalyzeForEachStatement(ForEachStatementSyntax forEachStatement, SemanticModel semanticModel, CancellationToken cancellationToken)
+        {
+            if (forEachStatement.Type.IsVar)
+            {
+                // If the type is already 'var', this analyze has no work to do
+                return false;
+            }
+
+            // The base analyzer may impose further limitations
+            return base.ShouldAnalyzeForEachStatement(forEachStatement, semanticModel, cancellationToken);
+        }
+
         protected override bool IsStylePreferred(SemanticModel semanticModel, OptionSet optionSet, State state, CancellationToken cancellationToken)
         {
             var stylePreferences = state.TypeStylePreference;
@@ -56,12 +81,7 @@ protected override bool IsStylePreferred(SemanticModel semanticModel, OptionSet
 
         protected override bool TryAnalyzeVariableDeclaration(TypeSyntax typeName, SemanticModel semanticModel, OptionSet optionSet, CancellationToken cancellationToken, out TextSpan issueSpan)
         {
-            // If it is already var, return.
-            if (typeName.IsTypeInferred(semanticModel))
-            {
-                issueSpan = default(TextSpan);
-                return false;
-            }
+            Debug.Assert(!typeName.IsVar, "'var' special case should have prevented analysis of this variable.");
 
             var candidateReplacementNode = SyntaxFactory.IdentifierName("var");
             var candidateIssueSpan = typeName.Span;