Handle default expression value properly in Value content analysis

Fixes #6164

Author: mavasani

src/Utilities/Compiler/Extensions/ITypeSymbolExtensions.cs

@@ -294,6 +294,11 @@ public static bool IsAttribute(this ITypeSymbol symbol)
         public static bool HasValueCopySemantics(this ITypeSymbol typeSymbol)
             => typeSymbol.IsValueType || typeSymbol.SpecialType == SpecialType.System_String;
 
+        public static bool HasReferenceTypeSemantics([NotNullWhen(returnValue: true)] this ITypeSymbol? typeSymbol)
+            => typeSymbol.IsReferenceTypeOrNullableValueType() ||
+               typeSymbol?.IsRefLikeType == true ||
+               typeSymbol is ITypeParameterSymbol typeParameter && !typeParameter.IsValueType;
+
         public static bool IsNonNullableValueType([NotNullWhen(returnValue: true)] this ITypeSymbol? typeSymbol)
             => typeSymbol != null && typeSymbol.IsValueType && typeSymbol.OriginalDefinition.SpecialType != SpecialType.System_Nullable_T;
 

src/Utilities/FlowAnalysis/FlowAnalysis/Analysis/PointsToAnalysis/PointsToAnalysis.cs

@@ -90,9 +90,7 @@ private PointsToAnalysis(PointsToAnalysisDomain analysisDomain, PointsToDataFlow
         }
 
         internal static bool ShouldBeTracked([NotNullWhen(returnValue: true)] ITypeSymbol? typeSymbol, Func<ITypeSymbol?, bool> isDisposable)
-            => typeSymbol.IsReferenceTypeOrNullableValueType() ||
-               typeSymbol?.IsRefLikeType == true ||
-               typeSymbol is ITypeParameterSymbol typeParameter && !typeParameter.IsValueType ||
+            => typeSymbol.HasReferenceTypeSemantics() ||
                isDisposable(typeSymbol);
 
         internal static bool ShouldBeTracked(AnalysisEntity analysisEntity, PointsToAnalysisKind pointsToAnalysisKind, Func<ITypeSymbol?, bool> isDisposable)

src/Utilities/FlowAnalysis/FlowAnalysis/Analysis/ValueContentAnalysis/ValueContentAnalysis.ValueContentDataFlowOperationVisitor.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using Analyzer.Utilities.Extensions;
 using Microsoft.CodeAnalysis.FlowAnalysis.DataFlow.CopyAnalysis;
 using Microsoft.CodeAnalysis.Operations;
 
@@ -62,7 +63,7 @@ protected override ValueContentAbstractValue GetAbstractValue(AnalysisEntity ana
                 => CurrentAnalysisData.TryGetValue(analysisEntity, out var value) ? value : ValueDomain.UnknownOrMayBeValue;
 
             protected override ValueContentAbstractValue GetAbstractDefaultValue(ITypeSymbol? type)
-                => type != null ?
+                => type != null && !type.HasReferenceTypeSemantics() ?
                    ValueContentAbstractValue.DoesNotContainLiteralOrNonLiteralState :
                    ValueContentAbstractValue.ContainsNullLiteralState;