RequirementMachine: Do a better job of filtering out invalid superclass and concrete type requirements

In the long run it doesn't really matter if we leave them in there, but for now
matching the GenericSignatureBuilder's behavior makes the tests pass with
-requirement-machine-inferred-signatures=verify.

Author: slavapestov

lib/AST/RequirementMachine/RequirementMachineRequests.cpp

@@ -123,21 +123,41 @@ RequirementMachine::buildRequirementsFromRules(
         return;
 
       case Symbol::Kind::Superclass: {
-        // For compatibility with the old GenericSignatureBuilder, drop requirements
-        // containing ErrorTypes.
+        // Requirements containing unresolved name symbols originate from
+        // invalid code and should not appear in the generic signature.
+        for (auto term : prop->getSubstitutions()) {
+          if (term.containsUnresolvedSymbols())
+            return;
+        }
+
+        // Requirements containing error types originate from invalid code
+        // and should not appear in the generic signature.
+        if (prop->getConcreteType()->hasError())
+          return;
+
         auto superclassType = Map.getTypeFromSubstitutionSchema(
                                 prop->getConcreteType(),
                                 prop->getSubstitutions(),
                                 genericParams, MutableTerm());
-        if (superclassType->hasError())
-          return;
 
         reqs.emplace_back(RequirementKind::Superclass,
                           subjectType, superclassType);
         return;
       }
 
       case Symbol::Kind::ConcreteType: {
+        // Requirements containing unresolved name symbols originate from
+        // invalid code and should not appear in the generic signature.
+        for (auto term : prop->getSubstitutions()) {
+          if (term.containsUnresolvedSymbols())
+            return;
+        }
+
+        // Requirements containing error types originate from invalid code
+        // and should not appear in the generic signature.
+        if (prop->getConcreteType()->hasError())
+          return;
+
         auto concreteType = Map.getTypeFromSubstitutionSchema(
                                 prop->getConcreteType(),
                                 prop->getSubstitutions(),