[clangd] Fix an assertion violation in rename.

[hokein]

Summary

NamedDecl::getName() asserts the name must be an identifier.

[sammccall]

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

949

This case seems a little *too* special: you might consider -(int) foo:(int)x; or so to make it clearer why this isn't an ordinary name.

I'd also make the comment a bit more specific: "Token is an identifier, but declaration name isn't a simple identifier".

[hokein]

address comment.

clang-tools-extra/clangd/refactor/Rename.cpp

if (locateMacroAt(*IdentifierToken, AST.getPreprocessor()))
     return makeError(ReasonToReject::UnsupportedSymbol);
 
   auto DeclsUnderCursor = locateDeclAt(AST, IdentifierToken->location());
   if (DeclsUnderCursor.empty())
     return makeError(ReasonToReject::NoSymbolFound);
   if (DeclsUnderCursor.size() > 1)
     return makeError(ReasonToReject::AmbiguousSymbol);
   const auto &RenameDecl = **DeclsUnderCursor.begin();
-  if (RenameDecl.getName() == RInputs.NewName)
+  const auto *ID = RenameDecl.getIdentifier();
+  if (!ID)
+    return makeError(ReasonToReject::UnsupportedSymbol);
+  if (ID->getName() == RInputs.NewName)
     return makeError(ReasonToReject::SameName);
   auto Invalid = checkName(RenameDecl, RInputs.NewName);
   if (Invalid)
     return makeError(*Invalid);
 
   auto Reject = renameable(RenameDecl, RInputs.MainFilePath, RInputs.Index,
                            Opts.AllowCrossFile);
   if (Reject)

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

Case Cases[] = {
          namespace std {
          inline namespace __u {
          class str^ing {};
          }
          }
        )cpp",
        "not a supported kind", !HeaderFile, Index},
 
+      {R"cpp(// disallow rename on non-normal identifiers.
+         @interface Foo {}
+         -(int) fo^o:(int)x; // Token is an identifier, but declaration name isn't a simple identifier.
+         @end
+       )cpp",
+       "not a supported kind", HeaderFile, Index},
+
       {R"cpp(
          void foo(int);
          void foo(char);
          template <typename T> void f(T t) {
            fo^o(t);
          })cpp",
        "multiple symbols", !HeaderFile, nullptr /*no index*/},