Merge pull request #49 from edespong/Issue42_Interpolation

Warn if value type is used in string interpolation
microsoft · Jul 10, 2018 · 9afb157 · 9afb157
2 parents 2c2aada + 8bf702a
commit 9afb157
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diff --git a/ClrHeapAllocationsAnalyzer.Test/TypeConversionAllocationAnalyzerTests.cs b/ClrHeapAllocationsAnalyzer.Test/TypeConversionAllocationAnalyzerTests.cs
@@ -476,6 +476,27 @@ public static implicit operator string(AStruct astruct)
             Assert.AreEqual(0, info1.Allocations.Count);
         }
 
+        [TestMethod]
+        public void TypeConversionAllocation_InterpolatedStringWithInt_BoxingWarning() {
+            var sampleProgram = @"string s = $""{1}"";";
+
+            var analyser = new TypeConversionAllocationAnalyzer();
+            var info = ProcessCode(analyser, sampleProgram, ImmutableArray.Create(SyntaxKind.Interpolation));
+
+            Assert.AreEqual(1, info.Allocations.Count);
+            AssertEx.ContainsDiagnostic(info.Allocations, id: TypeConversionAllocationAnalyzer.ValueTypeToReferenceTypeConversionRule.Id, line: 1, character: 15);
+        }
+
+        [TestMethod]
+        public void TypeConversionAllocation_InterpolatedStringWithString_NoWarning() {
+            var sampleProgram = @"string s = $""{1.ToString()}"";";
+
+            var analyser = new TypeConversionAllocationAnalyzer();
+            var info = ProcessCode(analyser, sampleProgram, ImmutableArray.Create(SyntaxKind.Interpolation));
+
+            Assert.AreEqual(0, info.Allocations.Count);
+        }
+
         [TestMethod]
         public void TypeConversionAllocation_DelegateAssignmentToReadonly_DoNotWarn()
         {

diff --git a/ClrHeapAllocationsAnalyzer/TypeConversionAllocationAnalyzer.cs b/ClrHeapAllocationsAnalyzer/TypeConversionAllocationAnalyzer.cs
@@ -37,6 +37,7 @@ public override void Initialize(AnalysisContext context)
                 SyntaxKind.ConditionalExpression,
                 SyntaxKind.ForEachStatement,
                 SyntaxKind.EqualsValueClause,
+                SyntaxKind.Interpolation,
                 SyntaxKind.Argument,
                 SyntaxKind.ArrowExpressionClause
             };
@@ -97,6 +98,12 @@ private static void AnalyzeNode(SyntaxNodeAnalysisContext context)
                 return;
             }
 
+            // string a = $"{1}";
+            if (node is InterpolationSyntax) {
+                InterpolationCheck(node, semanticModel, reportDiagnostic, filePath, cancellationToken);
+                return;
+            }
+
             // var f = (object)
             if (node is CastExpressionSyntax)
             {
@@ -173,6 +180,16 @@ private static void BinaryExpressionCheck(SyntaxNode node, SemanticModel semanti
             }
         }
 
+        private static void InterpolationCheck(SyntaxNode node, SemanticModel semanticModel, Action<Diagnostic> reportDiagnostic, string filePath, CancellationToken cancellationToken)
+        {
+            var interpolation = node as InterpolationSyntax;
+            var typeInfo = semanticModel.GetTypeInfo(interpolation.Expression, cancellationToken);
+            if (typeInfo.Type?.IsValueType == true) {
+                reportDiagnostic(Diagnostic.Create(ValueTypeToReferenceTypeConversionRule, interpolation.Expression.GetLocation(), EmptyMessageArgs));
+                HeapAllocationAnalyzerEventSource.Logger.BoxingAllocation(filePath);
+            }
+        }
+
         private static void CastExpressionCheck(SyntaxNode node, SemanticModel semanticModel, Action<Diagnostic> reportDiagnostic, string filePath, CancellationToken cancellationToken)
         {
             var castExpression = node as CastExpressionSyntax;