[PATCH] D138861: [Clang] Implement CWG2640 Allow more characters in an n-char sequence

Wed Nov 30 06:41:34 PST 2022

aaron.ballman accepted this revision as: aaron.ballman.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM with a request for a comment, but please give @tahonermann a chance to look at the review before landing.

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Comment at: clang/lib/Lex/Lexer.cpp:3379

-  if (LooseMatch)
+  if (LooseMatch && Diagnose)
     Res = LooseMatch->CodePoint;
----------------
cor3ntin wrote:
> aaron.ballman wrote:
> > Why do we only want to do this if we're diagnosing?
> The scenario we want to avoid:
> 
> There is a tentative parse of a token,  no diagnostic is emitted.
> The token gets cached and contains the loose match.
> Then that cached token gets reused, and because it is well formed, we never get to emit a diagnostic for a loose match.
> Only returning a Loose Match when a diagnostic ensure we always emit the diag once
> Note that previously we would always emit a diag, but doing so caused the diag to be emitted twice for macros (once when parsing the directive and once more when substituting.
Ahhh okay, that makes sense. I think it'd help to add a comment here to explain that because it's a bit subtle.

Repository:
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  https://reviews.llvm.org/D138861/new/

https://reviews.llvm.org/D138861