[clang] [Clang] prevent assertion in __has_embed parameter recovery at end-of-directive (PR #175104)

[Oleksandr T. via cfe-commits]

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@@ -3686,14 +3686,14 @@ Preprocessor::LexEmbedParameters(Token &CurTok, bool ForHasEmbed) {
           std::pair<tok::TokenKind, SourceLocation> Matches) {
         Diag(CurTok, diag::err_expected) << Expected;
         Diag(Matches.second, diag::note_matching) << Matches.first;
-        if (CurTok.isNot(EndTokenKind))
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a-tarasyuk wrote:

@shafik Thanks for the feedback. `LexEmbedParameters` is shared by `#embed` and `__has_embed(...)`, so `EndTokenKind` is still required to terminate normal parsing appropriately. 

This change only affects error recovery. `DiscardUntilEndOfDirective` is specifically intended to skip the remainder of the directive line, so once `CurTok` is already `tok::eod`, there is nothing left to discard, and the context-specific expected end token (e.g., `tok::r_paren` for `__has_embed`) is no longer relevant.

The added tests cover this behavior. Other scenarios appear to be handled by the existing `embed___has_embed_parsing_errors` tests; if there are additional edge cases to cover, please let me know.

https://github.com/llvm/llvm-project/pull/175104