C#: Avoid typerefs for constructed types.

calumgrant · hvitved · commit 7628caa2db66 · 2020-09-02T10:52:04.000+02:00
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs
@@ -29,7 +29,8 @@ public override void Populate(TextWriter trapFile)
                 return;
             }
 
-            trapFile.typeref_type((NamedTypeRef)TypeRef, this);
+            if (UsesTypeRef)
+                trapFile.typeref_type((NamedTypeRef)TypeRef, this);
 
             if (symbol.IsGenericType)
             {
@@ -148,7 +149,14 @@ class NamedTypeFactory : ICachedEntityFactory<INamedTypeSymbol, NamedType>
             public NamedType Create(Context cx, INamedTypeSymbol init) => new NamedType(cx, init);
         }
 
-        public override Type TypeRef => NamedTypeRef.Create(Context, symbol);
+        // Do not create typerefs of constructed generics as they are always in the current trap file, and there is a possibility
+        // that a generic could make the typedef ambiguous which leads to performance problems in QL.
+        // Create typerefs for constructed error types in case they are fully defined elsewhere.
+        // We cannot use `!this.NeedsPopulation` because this would not be stable as it would depend on
+        // the assembly that was being extracted at the time.
+        bool UsesTypeRef => symbol.TypeKind == TypeKind.Error || SymbolEqualityComparer.Default.Equals(symbol.OriginalDefinition, symbol);
+
+        public override Type TypeRef => UsesTypeRef ? (Type)NamedTypeRef.Create(Context, symbol) : this;
     }
 
     class NamedTypeRef : Type<INamedTypeSymbol>

Original file line number	Diff line number	Diff line change
`@@ -29,7 +29,8 @@ public override void Populate(TextWriter trapFile)`
`29`	`29`	`return;`
`30`	`30`	`}`
`31`	`31`
`32`		`- trapFile.typeref_type((NamedTypeRef)TypeRef, this);`
	`32`	`+ if (UsesTypeRef)`
	`33`	`+ trapFile.typeref_type((NamedTypeRef)TypeRef, this);`
`33`	`34`
`34`	`35`	`if (symbol.IsGenericType)`
`35`	`36`	`{`
`@@ -148,7 +149,14 @@ class NamedTypeFactory : ICachedEntityFactory<INamedTypeSymbol, NamedType>`
`148`	`149`	`public NamedType Create(Context cx, INamedTypeSymbol init) => new NamedType(cx, init);`
`149`	`150`	`}`
`150`	`151`
`151`		`- public override Type TypeRef => NamedTypeRef.Create(Context, symbol);`
	`152`	`+ // Do not create typerefs of constructed generics as they are always in the current trap file, and there is a possibility`
	`153`	`+ // that a generic could make the typedef ambiguous which leads to performance problems in QL.`
	`154`	`+ // Create typerefs for constructed error types in case they are fully defined elsewhere.`
	`155`	+ // We cannot use `!this.NeedsPopulation` because this would not be stable as it would depend on
	`156`	`+ // the assembly that was being extracted at the time.`
	`157`	`+ bool UsesTypeRef => symbol.TypeKind == TypeKind.Error \|\| SymbolEqualityComparer.Default.Equals(symbol.OriginalDefinition, symbol);`
	`158`	`+`
	`159`	`+ public override Type TypeRef => UsesTypeRef ? (Type)NamedTypeRef.Create(Context, symbol) : this;`
`152`	`160`	`}`
`153`	`161`
`154`	`162`	`class NamedTypeRef : Type<INamedTypeSymbol>`