[clang] [Clang][Preprocessor] Unify header-name lookahead for import and include (PR #191004)

[Yihan Wang via cfe-commits]

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@@ -1356,32 +1356,32 @@ bool Preprocessor::HandleModuleContextualKeyword(Token &Result) {
   llvm::SaveAndRestore<bool> SavedParsingPreprocessorDirective(
       CurPPLexer->ParsingPreprocessorDirective, true);
 
-  // The next token may be an angled string literal after import keyword.
-  llvm::SaveAndRestore<bool> SavedParsingFilemame(
-      CurPPLexer->ParsingFilename,
-      Result.getIdentifierInfo()->isImportKeyword());
-
-  std::optional<Token> NextTok = peekNextPPToken();
-  if (!NextTok)
-    return false;
-
-  if (NextTok->is(tok::raw_identifier))
-    LookUpIdentifierInfo(*NextTok);
-
-  if (Result.getIdentifierInfo()->isImportKeyword()) {
-    if (NextTok->isOneOf(tok::identifier, tok::less, tok::colon,
-                         tok::header_name)) {
-      Result.setKind(tok::kw_import);
-      ModuleImportLoc = Result.getLocation();
-      return true;
+  if (II->isModuleKeyword()) {
+    if (auto NextTok = peekNextPPToken()) {
----------------
yronglin wrote:

I recall the original PR used peek here because we wanted a lightweight approach, as peek only incurs one lex overhead, while using lex + `Enter Token` might incur additional mem alloc overhead. And after `HandleModuleContextualKeyword`, `HandleDirective` requires CurPPLexer is available, but `EnterToken` will change the current lexer to a TokenLexer.

https://github.com/llvm/llvm-project/pull/191004