Sema: Banish GenericTypeParamType from the constraint system

Author: slavapestov

lib/Sema/Constraint.cpp

@@ -48,7 +48,7 @@ Constraint::Constraint(ConstraintKind kind, ArrayRef<Constraint *> constraints,
 }
 
 static bool isAdmissibleType(Type type) {
-  return !type->hasUnboundGenericType();
+  return !type->hasUnboundGenericType() && !type->hasTypeParameter();
 }
 
 Constraint::Constraint(ConstraintKind Kind, Type First, Type Second,

lib/Sema/TypeOfReference.cpp

@@ -72,6 +72,14 @@ Type ConstraintSystem::openUnboundGenericType(GenericTypeDecl *decl,
       if (found == subs.end())
         continue;
 
+      // When a nominal type is declared in generic local context (which is
+      // not actually valid anyway), the context substitution map will map
+      // the outer generic parameters to themselves. Skip such entries to
+      // avoid introducing constraints that contain type parameters into
+      // the solver.
+      if (found->second->hasTypeParameter())
+        continue;
+
       addConstraint(ConstraintKind::Bind, pair.second, found->second,
                     locator);
     }