AST: Tweak LookUpConformanceInSubstitutionMap

Author: slavapestov

lib/AST/TypeSubstitution.cpp

@@ -220,10 +220,6 @@ operator()(CanType dependentType, Type conformingReplacementType,
 ProtocolConformanceRef LookUpConformanceInSubstitutionMap::
 operator()(CanType dependentType, Type conformingReplacementType,
            ProtocolDecl *conformedProtocol) const {
-  auto result = Subs.lookupConformance(dependentType, conformedProtocol);
-  if (!result.isInvalid())
-    return result;
-
   // Lookup conformances for archetypes that conform concretely
   // via a superclass.
   if (auto archetypeType = conformingReplacementType->getAs<ArchetypeType>()) {
@@ -232,10 +228,15 @@ operator()(CanType dependentType, Type conformingReplacementType,
         /*allowMissing=*/true);
   }
 
+  auto result = Subs.lookupConformance(dependentType, conformedProtocol);
+  if (!result.isInvalid())
+    return result;
+
   // Otherwise, the original type might be fixed to a concrete type in
   // the substitution map's input generic signature.
   if (auto genericSig = Subs.getGenericSignature()) {
-    if (genericSig->isConcreteType(dependentType)) {
+    if (genericSig->isValidTypeParameter(dependentType) &&
+        genericSig->isConcreteType(dependentType)) {
       return conformedProtocol->getModuleContext()->lookupConformance(
           conformingReplacementType, conformedProtocol,
           /*allowMissing=*/true);