Fix getRequirementsWithInverses()

Author: slavapestov

lib/AST/GenericSignature.cpp

@@ -1259,8 +1259,9 @@ void GenericSignatureImpl::getRequirementsWithInverses(
 
   // Record the absence of conformances to invertible protocols.
   for (auto gp : getGenericParams()) {
-    // Any generic parameter with a superclass bound could not have an inverse.
-    if (getSuperclassBound(gp))
+    // Any generic parameter with a superclass bound or concrete type does not
+    // have an inverse.
+    if (getSuperclassBound(gp) || getConcreteType(gp))
       continue;
 
     for (auto ip : InvertibleProtocolSet::full()) {