[clangd] Fix add-using tweak on declrefs with template arguments

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

if (auto *T = Node->ASTNode.get<TypeLoc>()) {
         continue;
       }
     }
     break;
   }
   if (Node == nullptr)
     return false;
 
+  // Closed range for the fully qualified name as spelled in source code.
   SourceRange SpelledNameRange;
   if (auto *D = Node->ASTNode.get<DeclRefExpr>()) {
     if (D->getDecl()->getIdentifier()) {
       QualifierToRemove = D->getQualifierLoc();
+      // Use the name range rather than expr, as the latter can contain template
+      // arguments in the range.
       SpelledNameRange = D->getSourceRange();
+      // Remove the template arguments from the name, as they shouldn't be
+      // spelled in the using declaration.
+      if (auto AngleLoc = D->getLAngleLoc(); AngleLoc.isValid())
+        SpelledNameRange.setEnd(AngleLoc.getLocWithOffset(-1));
       MustInsertAfterLoc = D->getDecl()->getBeginLoc();
     }
   } else if (auto *T = Node->ASTNode.get<TypeLoc>()) {
     if (auto E = T->getAs<ElaboratedTypeLoc>()) {
       QualifierToRemove = E.getQualifierLoc();
 
       SpelledNameRange = E.getSourceRange();
       if (auto T = E.getNamedTypeLoc().getAs<TemplateSpecializationTypeLoc>()) {

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

 // error-ok
 #include "test.hpp"
 using one::two::ee_one;
 
 void foo() {
   switch(one::two::ee{}) { case ee_one:break; }
 }
 )cpp"},
+      {R"cpp(
+#include "test.hpp"
+void foo() {
+  one::f^unc_temp<int>();
+})cpp",
+       R"cpp(
+#include "test.hpp"
+using one::func_temp;
+
+void foo() {
+  func_temp<int>();
+})cpp"},
+      {R"cpp(
+#include "test.hpp"
+void foo() {
+  one::va^r_temp<int>;
+})cpp",
+       R"cpp(
+#include "test.hpp"
+using one::var_temp;
+
+void foo() {
+  var_temp<int>;
+})cpp"},
   };
   llvm::StringMap<std::string> EditedFiles;
   for (const auto &Case : Cases) {
     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 {};
+template <typename T> void func_temp();
+template <typename T> T var_temp();
 })cpp";
     // Typo correction is disabled in msvc-compatibility mode.
     ExtraArgs.push_back("-fno-ms-compatibility");
     EXPECT_EQ(apply(Case.TestSource, &EditedFiles), Case.ExpectedSource);
   }
 }
 
 } // namespace
 } // namespace clangd
 } // namespace clang