[clang] Diagnose potential size confusion with VLA params [contd.] (PR #181550)

[Yeoul Na via cfe-commits]

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@@ -1114,7 +1114,8 @@ def VexingParse : DiagGroup<"vexing-parse">;
 def VLAUseStaticAssert : DiagGroup<"vla-extension-static-assert">;
 def VLACxxExtension : DiagGroup<"vla-cxx-extension", [VLAUseStaticAssert]>;
 def VLAExtension : DiagGroup<"vla-extension", [VLACxxExtension]>;
-def VLA : DiagGroup<"vla", [VLAExtension]>;
+def VLASizeConfusion : DiagGroup<"vla-potential-size-confusion">;
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rapidsna wrote:

> > @AaronBallman Would you have any concerns narrowing this PR to focus just on the array size issue, so we can move forward with it?
> 
> I think it's fine to focus on array size in function parameters at the moment, 

Sounds great, thank you!

> but I think there's two different (but related) diagnostics depending on whether `-fexperimental-late-parse-attributes` is enabled or not. Did my example above help clarify?

Yes, that makes sense — thanks for the clarification!

To clarify my earlier point: `-fexperimental-late-parse-attributes` is intended to change parsing behavior within attributes (as the flag name suggests), not array sizes — and the same applies to `-fbounds-safety`. The reason these dialects are relevant to this PR, however, is that what we learn here may inform decisions about them down the road — for example, whether this name lookup behavior remains experimental and gets superseded by whatever approach array sizes end up taking, or whether it evolves into something more broadly applicable to the core language.

https://github.com/llvm/llvm-project/pull/181550