AST: Don't allow SuperclassDeclRequest on deserialized protocol

Author: slavapestov

lib/AST/NameLookup.cpp

@@ -3219,16 +3219,8 @@ SuperclassDeclRequest::evaluate(Evaluator &evaluator,
   // Protocols may get their superclass bound from a `where Self : Superclass`
   // clause.
   if (auto *proto = dyn_cast<ProtocolDecl>(subject)) {
-    // If the protocol came from a serialized module, compute the superclass via
-    // its generic signature.
-    if (proto->wasDeserialized()) {
-      auto superTy = proto->getGenericSignature()
-          ->getSuperclassBound(proto->getSelfInterfaceType());
-      if (superTy)
-        return superTy->getClassOrBoundGenericClass();
-    }
+    assert(!proto->wasDeserialized());
 
-    // Otherwise check the where clause.
     auto selfBounds = getSelfBoundsFromWhereClause(proto);
     for (auto inheritedNominal : selfBounds.decls)
       if (auto classDecl = dyn_cast<ClassDecl>(inheritedNominal))