[clangd] AddUsing: Fix a crash on ElaboratedTypes without NestedNameSpecfiiers.

Differential Revision: https://reviews.llvm.org/D92579

clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp

@@ -274,6 +274,8 @@ bool AddUsing::prepare(const Selection &Inputs) {
   } else if (auto *T = Node->ASTNode.get<TypeLoc>()) {
     if (auto E = T->getAs<ElaboratedTypeLoc>()) {
       QualifierToRemove = E.getQualifierLoc();
+      if (!QualifierToRemove)
+        return false;
 
       auto SpelledTokens =
           TB.spelledForExpanded(TB.expandedTokens(E.getSourceRange()));

clang-tools-extra/clangd/unittests/TweakTests.cpp

@@ -2523,6 +2523,9 @@ public:
   // Do not offer code action on typo-corrections.
   EXPECT_UNAVAILABLE(Header + "/*error-ok*/c^c C;");
 
+  // NestedNameSpecifier, but no namespace.
+  EXPECT_UNAVAILABLE(Header + "class Foo {}; class F^oo foo;");
+
   // Check that we do not trigger in header files.
   FileName = "test.h";
   ExtraArgs.push_back("-xc++-header"); // .h file is treated a C by default.