[TypeCheck] Bad Self GTPTs from invalid protocols shouldn't crash.

lib/Sema/GenericTypeResolver.h

@@ -166,8 +166,11 @@ public:
 /// This should only be used when resolving/validating where clauses in
 /// protocols.
 class ProtocolRequirementTypeResolver : public GenericTypeResolver {
+  ProtocolDecl *Proto;
+
 public:
-  explicit ProtocolRequirementTypeResolver() {}
+  explicit ProtocolRequirementTypeResolver(ProtocolDecl *proto)
+      : Proto(proto) {}
 
   virtual Type resolveGenericTypeParamType(GenericTypeParamType *gp);
 

lib/Sema/TypeCheckDecl.cpp

@@ -4348,7 +4348,7 @@ public:
           if (auto whereClause = assocType->getTrailingWhereClause()) {
             DeclContext *lookupDC = assocType->getDeclContext();
 
-            ProtocolRequirementTypeResolver resolver;
+            ProtocolRequirementTypeResolver resolver(PD);
             TypeResolutionOptions options;
 
             for (auto &req : whereClause->getRequirements()) {

lib/Sema/TypeCheckGeneric.cpp

@@ -130,7 +130,7 @@ void GenericTypeToArchetypeResolver::recordParamType(ParamDecl *decl, Type type)
 
 Type ProtocolRequirementTypeResolver::resolveGenericTypeParamType(
     GenericTypeParamType *gp) {
-  assert(gp->getDepth() == 0 && gp->getIndex() == 0 &&
+  assert(gp->isEqual(Proto->getSelfInterfaceType()) &&
          "found non-Self-shaped GTPT when resolving protocol requirement");
   return gp;
 }
@@ -143,6 +143,7 @@ Type ProtocolRequirementTypeResolver::resolveDependentMemberType(
 
 Type ProtocolRequirementTypeResolver::resolveSelfAssociatedType(
     Type selfTy, AssociatedTypeDecl *assocType) {
+  assert(selfTy->isEqual(Proto->getSelfInterfaceType()));
   return assocType->getDeclaredInterfaceType();
 }