[AST] NFC: Clarify when extension type repr wouldn't be available

Author: xedin

include/swift/AST/Decl.h

@@ -1315,6 +1315,9 @@ class ExtensionDecl final : public GenericContext, public Decl,
   bool alreadyBoundToNominal() const { return NextExtension.getInt(); }
 
   /// Retrieve the extended type definition as written in the source, if it exists.
+  ///
+  /// Repr would not be available if the extension was been loaded
+  /// from a serialized module.
   TypeRepr *getExtendedTypeRepr() const { return ExtendedTypeRepr; }
 
   /// Retrieve the set of protocols that this type inherits (i.e,

lib/Sema/CSDiagnostics.cpp

@@ -7435,7 +7435,7 @@ bool InvalidMemberRefOnProtocolMetatype::diagnoseAsError() {
   } else if (auto nameRepr = extension->getExtendedTypeRepr()) {
     // Type repr is not always available so we need to be defensive
     // about its presence and validity.
-    if (nameRepr->isInvalid()))
+    if (nameRepr->isInvalid())
       return true;
 
     if (auto noteLoc = nameRepr->getEndLoc()) {