[clangd] Don't attach FixIt to the source code in macro.

[hokein]

Summary

We are less certain it is the correct fix. Also, clang doesn't apply FixIt to
the source code in macro.

[ilya-biryukov]

LGTM. Thanks!

clangd/Diagnostics.cpp

void StoreDiags::HandleDiagnostic(DiagnosticsEngine::Level DiagLevel,
   auto AddFix = [&](bool SyntheticMessage) -> bool {
     assert(!Info.getFixItHints().empty() &&
            "diagnostic does not have attached fix-its");
     if (!InsideMainFile)
       return false;
 
     llvm::SmallVector<TextEdit, 1> Edits;
     for (auto &FixIt : Info.getFixItHints()) {
+      // Follow clang's behavior, don't apply FixIt to the code in macros,
+      // we are less certain it is the right fix.
+      if (FixIt.RemoveRange.getBegin().isMacroID() ||
+          FixIt.RemoveRange.getEnd().isMacroID())
+        return false;
       if (!isInsideMainFile(FixIt.RemoveRange.getBegin(),
                             Info.getSourceManager()))
         return false;
       Edits.push_back(toTextEdit(FixIt, Info.getSourceManager(), *LangOpts));
     }
 
     llvm::SmallString<64> Message;
     // If requested and possible, create a message like "change 'foo' to 'bar'".

unittests/clangd/DiagnosticsTests.cpp

EXPECT_THAT(TestTU::withCode(Test.code()).build().getDiagnostics(),
               ElementsAre(Diag(Test.range("foo"),
                                "cannot initialize return object of type "
                                "'int *' with an rvalue of type 'int'"),
                           Diag(Test.range("bar"),
                                "cannot initialize return object of type "
                                "'int *' with an rvalue of type 'int'")));
 }
 
+TEST(DiagnosticsTest, NoFixItInMacro) {
+  Annotations Test(R"cpp(
+    #define Define(name) void name() {}
+
+    [[Define]](main)
+  )cpp");
+  auto TU = TestTU::withCode(Test.code());
+  EXPECT_THAT(TU.build().getDiagnostics(),
+              ElementsAre(AllOf(Diag(Test.range(), "'main' must return 'int'"),
+                                Not(WithFix(_)))));
+}
+
 TEST(DiagnosticsTest, ToLSP) {
   clangd::Diag D;
   D.Message = "something terrible happened";
   D.Range = {pos(1, 2), pos(3, 4)};
   D.InsideMainFile = true;
   D.Severity = DiagnosticsEngine::Error;
   D.File = "foo/bar/main.cpp";