Identify if a file is a system header by its path

Author: Jinjie-Huang

clang/lib/Lex/HeaderSearch.cpp

@@ -887,8 +887,8 @@ void HeaderSearch::DiagnoseHeaderShadowing(
     ArrayRef<std::pair<OptionalFileEntryRef, DirectoryEntryRef>> Includers,
     bool isAngled, int IncluderLoopIndex, ConstSearchDirIterator MainLoopIt) {
 
-  if (Diags.isIgnored(diag::warn_header_shadowing, IncludeLoc) || isAngled ||
-      DiagnosedShadowing)
+  if (Diags.isIgnored(diag::warn_header_shadowing, IncludeLoc) ||
+      DiagnosedShadowing || (getFileInfo(*FE).DirInfo != SrcMgr::C_User))
     return;
 
   DiagnosedShadowing = true;