[clangd] AddUsing: Fix support for template specializations.

[adamcz]

Summary

Before this change, we would add "using std::vector<int>" instead of
just "using std::vector;", which would not even compile.

Fixes https://github.com/clangd/clangd/issues/904

[kadircet]

thanks!

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

284

nit: NameRange.setEnd(T.getTemplateNameLoc()).

[adamcz]

Thanks Kadir!

[adamcz]

review comments

[kadircet]

(oops, i didn't notice i wasn't the reviewer :D)

[usaxena95]

No worries. Thanks for taking a look :)

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

if (auto *II = D->getDecl()->getIdentifier()) {
       MustInsertAfterLoc = D->getDecl()->getBeginLoc();
     }
   } 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()));
+      auto NameRange = E.getSourceRange();
+      if (auto T = E.getNamedTypeLoc().getAs<TemplateSpecializationTypeLoc>()) {
+        // Remove the template arguments from the name.
+        NameRange.setEnd(T.getLAngleLoc().getLocWithOffset(-1));
+      }
+
+      auto SpelledTokens = TB.spelledForExpanded(TB.expandedTokens(NameRange));
       if (!SpelledTokens)
         return false;
       auto SpelledRange = syntax::Token::range(SM, SpelledTokens->front(),
                                                SpelledTokens->back());
       Name = SpelledRange.text(SM);
 
       std::string QualifierToRemoveStr = getNNSLAsString(
           QualifierToRemove, Inputs.AST->getASTContext().getPrintingPolicy());

clang-tools-extra/clangd/unittests/tweaks/AddUsingTests.cpp

 #include "test.hpp"
 using one::two::ee::ee_one;
 one::t^wo::cc c;
 )cpp",
              R"cpp(
 #include "test.hpp"
 using one::two::cc;using one::two::ee::ee_one;
 cc c;
+)cpp"},
+            // Template (like std::vector).
+            {R"cpp(
+#include "test.hpp"
+one::v^ec<int> foo;
+)cpp",
+             R"cpp(
+#include "test.hpp"
+using one::vec;
+
+vec<int> foo;
 )cpp"}};
   llvm::StringMap<std::string> EditedFiles;
   for (const auto &Case : Cases) {
     for (const auto &SubCase : expandCases(Case.TestSource)) {
       ExtraFiles["test.hpp"] = R"cpp(
 namespace one {
 void oo() {}
 namespace two {
 enum ee {ee_one};
 void ff() {}
 class cc {
 public:
   struct st { struct nested {}; };
   static void mm() {}
 };
 }
 using uu = two::cc;
+template<typename T> struct vec {};
 })cpp";
       EXPECT_EQ(apply(SubCase, &EditedFiles), Case.ExpectedSource);
     }
   }
 }
 
 } // namespace
 } // namespace clangd
 } // namespace clang