[clangd] Handle variable templates consistently with class templates in code completion (#85740)

The option --function-arg-placeholders=0 results in placeholders being
omitted for class template argument lists. This patch extends the same
treatment to variable template argument lists.

Fixes clangd/clangd#1976

Author: HighCommander4

clang-tools-extra/clangd/CodeComplete.cpp

@@ -619,7 +619,8 @@ struct CodeCompletionBuilder {
     }
     // 'CompletionItemKind::Interface' matches template type aliases.
     if (Completion.Kind == CompletionItemKind::Interface ||
-        Completion.Kind == CompletionItemKind::Class) {
+        Completion.Kind == CompletionItemKind::Class ||
+        Completion.Kind == CompletionItemKind::Variable) {
       if (Snippet->front() != '<')
         return *Snippet; // Not an arg snippet?
 

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

@@ -2648,12 +2648,15 @@ TEST(CompletionTest, CompletionFunctionArgsDisabled) {
       class foo_class{};
       template <class T>
       using foo_alias = T**;
+      template <class T>
+      T foo_var = T{};
       void f() { foo_^ })cpp",
         {}, Opts);
     EXPECT_THAT(
         Results.Completions,
         UnorderedElementsAre(AllOf(named("foo_class"), snippetSuffix("<$0>")),
-                             AllOf(named("foo_alias"), snippetSuffix("<$0>"))));
+                             AllOf(named("foo_alias"), snippetSuffix("<$0>")),
+                             AllOf(named("foo_var"), snippetSuffix("<$0>"))));
   }
   {
     auto Results = completions(