[clangd] Skip implicit nodes when traversing for highlightings

[ilya-biryukov]

Summary

Implicit code adds corner cases to handle and does not provide any value
as those nodes cannot be mapped back to source text.

[ilya-biryukov]

Ah, sorry, that's actually the default... So we are already doing this.

clang-tools-extra/clangd/SemanticHighlighting.cpp

class HighlightingTokenCollector
   std::vector<HighlightingToken> Tokens;
   ASTContext &Ctx;
   const SourceManager &SM;
 
 public:
   HighlightingTokenCollector(ParsedAST &AST)
       : Ctx(AST.getASTContext()), SM(AST.getSourceManager()) {}
 
+  // Only highlight nodes that map to source code, skip implicitly generated
+  // code.
+  bool shouldVisitImplicitCode() const { return false; }
+
   std::vector<HighlightingToken> collectTokens() {
     Tokens.clear();
     TraverseAST(Ctx);
     return Tokens;
   }
 
   bool VisitNamespaceAliasDecl(NamespaceAliasDecl *NAD) {
     // The target namespace of an alias can not be found in any other way.