AST: Allow ProtocolConformanceRef::getAssociatedType() with invalid conformance

Author: slavapestov

lib/AST/ProtocolConformanceRef.cpp

@@ -198,28 +198,40 @@ Type ProtocolConformanceRef::getAssociatedType(Type conformingType,
                                                Type assocType) const {
   if (isPack()) {
     auto *pack = getPack();
-    assert(conformingType->isEqual(pack->getType()));
+    ASSERT(conformingType->isEqual(pack->getType()));
     return pack->getAssociatedType(assocType);
   }
 
-  assert(!isConcrete() || getConcrete()->getType()->isEqual(conformingType));
-
   auto type = assocType->getCanonicalType();
-  auto proto = getRequirement();
 
   // Fast path for generic parameters.
-  if (isa<GenericTypeParamType>(type)) {
-    assert(type->isEqual(proto->getSelfInterfaceType()) &&
+  if (auto paramTy = dyn_cast<GenericTypeParamType>(type)) {
+    ASSERT(paramTy->getDepth() == 0 && paramTy->getIndex() == 0 &&
            "type parameter in protocol was not Self");
     return conformingType;
   }
 
-  // Fast path for dependent member types on 'Self' of our associated types.
-  auto memberType = cast<DependentMemberType>(type);
-  if (memberType.getBase()->isEqual(proto->getSelfInterfaceType()) &&
-      memberType->getAssocType()->getProtocol() == proto &&
-      isConcrete())
-    return getConcrete()->getTypeWitness(memberType->getAssocType());
+  if (isInvalid())
+    return ErrorType::get(assocType->getASTContext());
+
+  auto proto = getRequirement();
+
+  if (isConcrete()) {
+    if (auto selfType = conformingType->getAs<DynamicSelfType>())
+      conformingType = selfType->getSelfType();
+    ASSERT(getConcrete()->getType()->isEqual(conformingType));
+
+    // Fast path for dependent member types on 'Self' of our associated types.
+    auto memberType = cast<DependentMemberType>(type);
+    if (memberType.getBase()->isEqual(proto->getSelfInterfaceType()) &&
+        memberType->getAssocType()->getProtocol() == proto) {
+      auto witnessType = getConcrete()->getTypeWitness(
+          memberType->getAssocType());
+      if (!witnessType)
+        return ErrorType::get(assocType->getASTContext());
+      return witnessType;
+    }
+  }
 
   // General case: consult the substitution map.
   auto substMap =