[NFC] Always use syntactic information in ExtendedNominalRequest.

Since we started saving the nominal in the .swiftmodule, changing the other
call-sites in ClangImporter to save the value means that we can rely on
the typeRepr being non-null except when the syntax tree was ill-formed.

Author: varungandhi-apple

lib/AST/NameLookup.cpp

@@ -2123,18 +2123,14 @@ SuperclassDeclRequest::evaluate(Evaluator &evaluator,
 llvm::Expected<NominalTypeDecl *>
 ExtendedNominalRequest::evaluate(Evaluator &evaluator,
                                  ExtensionDecl *ext) const {
-  DirectlyReferencedTypeDecls referenced;
-  ASTContext &ctx = ext->getASTContext();
+  auto typeRepr = ext->getExtendedTypeRepr();
+  if (!typeRepr)
+    // We must've seen 'extension { ... }' during parsing.
+    return nullptr;
 
-  // Prefer syntactic information when we have it.
-  if (auto typeRepr = ext->getExtendedTypeRepr()) {
-    referenced = directReferencesForTypeRepr(evaluator, ctx, typeRepr, ext);
-  } else if (auto type = ext->getExtendedType()) {
-    // Fall back to semantic types.
-    // FIXME: In the long run, we shouldn't need this. Non-syntactic results
-    // should be cached.
-    referenced = directReferencesForType(type);
-  }
+  ASTContext &ctx = ext->getASTContext();
+  DirectlyReferencedTypeDecls referenced =
+    directReferencesForTypeRepr(evaluator, ctx, typeRepr, ext);
 
   // Resolve those type declarations to nominal type declarations.
   SmallVector<ModuleDecl *, 2> modulesFound;

lib/ClangImporter/ImportDecl.cpp

@@ -30,6 +30,7 @@
 #include "swift/AST/GenericSignature.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/NameLookup.h"
+#include "swift/AST/NameLookupRequests.h"
 #include "swift/AST/ParameterList.h"
 #include "swift/AST/Pattern.h"
 #include "swift/AST/PrettyStackTrace.h"
@@ -4546,10 +4547,10 @@ namespace {
                       Impl.SwiftContext, loc,
                       nullptr,
                       { }, dc, nullptr, decl);
-      Impl.SwiftContext
-          .evaluator
-          .cacheOutput(ExtendedTypeRequest{result},
-                       objcClass->getDeclaredType());
+      Impl.SwiftContext.evaluator.cacheOutput(ExtendedTypeRequest{result},
+                                              objcClass->getDeclaredType());
+      Impl.SwiftContext.evaluator.cacheOutput(ExtendedNominalRequest{result},
+                                              objcClass);
 
       // Determine the type and generic args of the extension.
       if (objcClass->getGenericParams()) {
@@ -8127,6 +8128,8 @@ ClangImporter::Implementation::importDeclContextOf(
                                    getClangModuleForDecl(decl), nullptr);
   SwiftContext.evaluator.cacheOutput(ExtendedTypeRequest{ext},
                                      nominal->getDeclaredType());
+  SwiftContext.evaluator.cacheOutput(ExtendedNominalRequest{ext},
+                                     std::move(nominal));
   ext->setValidationToChecked();
   ext->setMemberLoader(this, reinterpret_cast<uintptr_t>(declSubmodule));