[clangd] Unify macro matching in code completion for AST and Index based macros

[kadircet]

Summary

fixes https://github.com/clangd/clangd/issues/489

[hokein]

clang-tools-extra/clangd/CodeComplete.cpp

1619–1620

this comment seems stale, macros are not sema-only now.

[kadircet]

• Drop the comment

clang-tools-extra/clangd/CodeComplete.cpp

mergeResults(const std::vector<CodeCompletionResult> &SemaResults,
     TopN<ScoredBundle, ScoredBundleGreater> Top(
         Opts.Limit == 0 ? std::numeric_limits<size_t>::max() : Opts.Limit);
     for (auto &Bundle : Bundles)
       addCandidate(Top, std::move(Bundle));
     return std::move(Top).items();
   }
 
   llvm::Optional<float> fuzzyScore(const CompletionCandidate &C) {
     // Macros can be very spammy, so we only support prefix completion.
-    // We won't end up with underfull index results, as macros are sema-only.
-    if (C.SemaResult && C.SemaResult->Kind == CodeCompletionResult::RK_Macro &&
+    if (((C.SemaResult &&
+          C.SemaResult->Kind == CodeCompletionResult::RK_Macro) ||
+         (C.IndexResult &&
+          C.IndexResult->SymInfo.Kind == index::SymbolKind::Macro)) &&
         !C.Name.startswith_lower(Filter->pattern()))
       return None;
     return Filter->match(C.Name);
   }
 
   // Scores a candidate and adds it to the TopN structure.
   void addCandidate(TopN<ScoredBundle, ScoredBundleGreater> &Candidates,
                     CompletionCandidate::Bundle Bundle) {

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

struct S {
       int Qux;
     };
   )cpp";
 
   // Only items matching the fuzzy query are returned.
   EXPECT_THAT(completions(Body + "int main() { S().Foba^ }").Completions,
               AllOf(Has("FooBar"), Has("FooBaz"), Not(Has("Qux"))));
 
-  // Macros require  prefix match.
-  EXPECT_THAT(completions(Body + "int main() { C^ }").Completions,
-              AllOf(Has("Car"), Not(Has("MotorCar"))));
+  // Macros require prefix match, either from index or AST.
+  Symbol Sym = var("MotorCarIndex");
+  Sym.SymInfo.Kind = index::SymbolKind::Macro;
+  EXPECT_THAT(
+      completions(Body + "int main() { C^ }", {Sym}).Completions,
+      AllOf(Has("Car"), Not(Has("MotorCar")), Not(Has("MotorCarIndex"))));
+  EXPECT_THAT(completions(Body + "int main() { M^ }", {Sym}).Completions,
+              AllOf(Has("MotorCar"), Has("MotorCarIndex")));
 }
 
 void testAfterDotCompletion(clangd::CodeCompleteOptions Opts) {
   auto Results = completions(
       R"cpp(
       int global_var;
 
       int global_func();