[clangd] Use the "macro" semantic token for pre-defined identifiers

[ckandeler]

Summary

This matches user expectations.

[sammccall]

Yeah, this seems reasonable to me.
Wonder if we can support this in hover too!

[sammccall]

clang-tools-extra/clangd/SemanticHighlighting.cpp

546

actually, would HighlightingKind::LocalVariable be more appropriate?

The standard calls this a "The function-local predefined variable".

Admittedly I have a tendency to think of it as macro-like by analogy with __LINE__ etc but this model is observably wrong: it breaks down with templates and in other ways.

[ckandeler]

clang-tools-extra/clangd/SemanticHighlighting.cpp

546

Hm, yes, I was not aware it was specified explicitly as a local variable. Will change.

[ckandeler]

Use variable instead of macro.

[sammccall]

(thanks, still LG)

[ckandeler]

Thanks for the review. Can you please merge it?

[sammccall]

Sure thing!

Also sent D132135 to support hover.

[ckandeler]

By the way: How do I change the commit message when using arc? It seems to ignore all subsequent changes other than in the code itself, and now the patch is in the repo with a misleading commit message.

[sammccall]

In D131175#3732163, @ckandeler wrote:

By the way: How do I change the commit message when using arc? It seems to ignore all subsequent changes other than in the code itself, and now the patch is in the repo with a misleading commit message.

Yeah that's unfortunate and I do it myself all the time :-(

When I remember, my workflow is to amend the commit message locally with git, and then arc diff --verbatim will push this into the phab description (in addition to the usual snapshotting behavior).
But often I forget and edit it in phab, and I don't know of a command to pull those edits down into my git repo.

[ilya-biryukov]

In D131175#3732379, @sammccall wrote:

But often I forget and edit it in phab, and I don't know of a command to pull those edits down into my git repo.

I ended up always doing this for landing changes:

$ git switch main
$ git pull --ff-only
$ arc patch --nobranch D123456
$ git push origin main

That way I get the latest description from phabricator and also the reviewed-by tags.
And I basically ignore what the commit messages says on my branch while it's WIP, phab is source of truth after the initial change.

clang-tools-extra/clangd/SemanticHighlighting.cpp

public:
 
   bool TraverseConstructorInitializer(CXXCtorInitializer *Init) {
     if (Init->isMemberInitializer())
       if (auto *Member = Init->getMember())
         highlightMutableReferenceArgument(Member->getType(), Init->getInit());
     return Base::TraverseConstructorInitializer(Init);
   }
 
+  bool VisitPredefinedExpr(PredefinedExpr *E) {
+    H.addToken(E->getLocation(), HighlightingKind::LocalVariable)
+        .addModifier(HighlightingModifier::Static)
+        .addModifier(HighlightingModifier::Readonly)
+        .addModifier(HighlightingModifier::FunctionScope);
+    return true;
+  }
+
   bool VisitCallExpr(CallExpr *E) {
     // Highlighting parameters passed by non-const reference does not really
     // make sense for literals...
     if (isa<UserDefinedLiteral>(E))
       return true;
 
     // FIXME: consider highlighting parameters of some other overloaded
     // operators as well

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

)cpp",
         void $Function_decl[[Foo]](int $Parameter_decl[[x]]);
         template <typename $TemplateParameter_decl[[T]]>
         void $Function_decl[[Bar]]($TemplateParameter[[T]] $Parameter_decl[[x]]) {
             $Function_deprecated[[Foo]]($Parameter[[x]]); 
             $Function_deprecated[[Foo]]($Parameter[[x]]); 
             $Function_deprecated[[Foo]]($Parameter[[x]]); 
         }
       )cpp",
+      // Predefined identifiers
+      R"cpp(
+        void $Function_decl[[Foo]]() {
+            const char *$LocalVariable_decl_readonly[[s]] = $LocalVariable_readonly_static[[__func__]];
+        }
+      )cpp",
       // Explicit template specialization
       R"cpp(
         struct $Class_decl[[Base]]{};
         template <typename $TemplateParameter_decl[[T]]>
         struct $Class_decl[[S]] : public $Class[[Base]] {};
         template <> 
         struct $Class_decl[[S]]<void> : public $Class[[Base]] {};