C#: Add regression test and fix for type mentions of type parameter constraints.

Author: calumgrant

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/TypeParameter.cs

@@ -38,14 +38,12 @@ public override void Populate()
                     Context.Compilation.GetTypeByMetadataName(valueTypeName) :
                     Context.Compilation.ObjectType;
 
-            var constraintTypes = new List<Type>();
             foreach (var abase in symbol.ConstraintTypes)
             {
                 if (abase.TypeKind != TypeKind.Interface)
                     baseType = abase;
                 var t = Create(Context, abase);
                 Context.Emit(Tuples.specific_type_parameter_constraints(constraints, t.TypeRef));
-                constraintTypes.Add(t);
             }
 
             Context.Emit(Tuples.types(this, Semmle.Extraction.Kinds.TypeKind.TYPE_PARAMETER, symbol.Name));
@@ -67,12 +65,15 @@ public override void Populate()
                 clauses = clauses.Concat(declSyntaxReferences.OfType<ClassDeclarationSyntax>().SelectMany(c => c.ConstraintClauses));
                 clauses = clauses.Concat(declSyntaxReferences.OfType<InterfaceDeclarationSyntax>().SelectMany(c => c.ConstraintClauses));
                 clauses = clauses.Concat(declSyntaxReferences.OfType<StructDeclarationSyntax>().SelectMany(c => c.ConstraintClauses));
-                int i = 0;
-                foreach (var clause in clauses.Where(c => c.Name.ToString() == symbol.Name))
+                foreach (var clause in clauses.Where(c => c.Name.Identifier.Text == symbol.Name))
                 {
                     TypeMention.Create(Context, clause.Name, this, this);
                     foreach (var constraint in clause.Constraints.OfType<TypeConstraintSyntax>())
-                        TypeMention.Create(Context, constraint.Type, this, constraintTypes[i++]);
+                    {
+                        var ti = Context.Model(constraint).GetTypeInfo(constraint.Type);
+                        var target = Type.Create(Context, ti.Type);
+                        TypeMention.Create(Context, constraint.Type, this, target);
+                    }
                 }
             }
         }

csharp/ql/test/library-tests/regressions/Program.cs

@@ -139,4 +139,12 @@ class LocalVariableTags
     };
 }
 
+partial class C1<T> where T: DynamicType
+{
+}
+
+partial class C1<T> where T: DynamicType
+{
+}
+
 // semmle-extractor-options: /r:System.Dynamic.Runtime.dll

csharp/ql/test/library-tests/regressions/TypeMentions.expected

@@ -64,3 +64,7 @@
 | Program.cs:135:33:135:38 | String |
 | Program.cs:135:41:135:46 | Object |
 | Program.cs:137:10:137:15 | Object |
+| Program.cs:142:27:142:27 | T |
+| Program.cs:142:30:142:40 | DynamicType |
+| Program.cs:146:27:146:27 | T |
+| Program.cs:146:30:146:40 | DynamicType |