[clangd] Fix crash in AddUsing tweak due to non-identifier DeclName

[hokein]

thanks for tracking it down.

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

214

nit:

if (const auto* II = D->getDecl()->getIdentifier()) {
    ...
  Name = II->getName();
}

[adamcz]

Addressed review comment

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

if (Node->ASTNode.get<NestedNameSpecifierLoc>()) {
       }
     }
     break;
   }
   if (Node == nullptr)
     return false;
 
   if (auto *D = Node->ASTNode.get<DeclRefExpr>()) {
+    if (auto *II = D->getDecl()->getIdentifier()) {
       QualifierToRemove = D->getQualifierLoc();
-    Name = D->getDecl()->getName();
+      Name = II->getName();
+    }
   } else if (auto *T = Node->ASTNode.get<TypeLoc>()) {
     if (auto E = T->getAs<ElaboratedTypeLoc>()) {
       if (auto *BaseTypeIdentifier =
               E.getType().getUnqualifiedType().getBaseTypeIdentifier()) {
         Name = BaseTypeIdentifier->getName();
         QualifierToRemove = E.getQualifierLoc();
       }
     }

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

 template<typename TT> class tt {};
 namespace two {
 enum ee {};
 void ff() {}
 class cc {
 public:
   struct st {};
   static void mm() {}
+  cc operator|(const cc& x) const { return x; }
 };
 }
 })cpp";
 
   EXPECT_AVAILABLE(Header + "void fun() { o^n^e^:^:^t^w^o^:^:^f^f(); }");
   EXPECT_AVAILABLE(Header + "void fun() { o^n^e^::^o^o(); }");
   EXPECT_AVAILABLE(Header + "void fun() { o^n^e^:^:^t^w^o^:^:^e^e E; }");
   EXPECT_AVAILABLE(Header + "void fun() { o^n^e^:^:^t^w^o:^:^c^c C; }");
   EXPECT_UNAVAILABLE(Header +
                      "void fun() { o^n^e^:^:^t^w^o^:^:^c^c^:^:^m^m(); }");
   EXPECT_UNAVAILABLE(Header +
                      "void fun() { o^n^e^:^:^t^w^o^:^:^c^c^:^:^s^t inst; }");
   EXPECT_UNAVAILABLE(Header +
                      "void fun() { o^n^e^:^:^t^w^o^:^:^c^c^:^:^s^t inst; }");
   EXPECT_UNAVAILABLE(Header + "void fun() { N^S(c^c) inst; }");
   // This used to crash. Ideally we would support this case, but for now we just
   // test that we don't crash.
   EXPECT_UNAVAILABLE(Header +
                      "template<typename TT> using foo = one::tt<T^T>;");
+  // Test that we don't crash or misbehave on unnamed DeclRefExpr.
+  EXPECT_UNAVAILABLE(Header +
+                     "void fun() { one::two::cc() ^| one::two::cc(); }");
 
   // 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.
   EXPECT_UNAVAILABLE(Header + "void fun() { one::two::f^f(); }");
   FileName = "test.hpp";
   EXPECT_UNAVAILABLE(Header + "void fun() { one::two::f^f(); }");
 }