[PATCH] D52400: Improve -Wshadow warnings with enumerators

[Stephan Bergmann via Phabricator via cfe-commits]

sberg added a comment.

In https://reviews.llvm.org/D52400#1266341, @aaron.ballman wrote:

> In https://reviews.llvm.org/D52400#1266307, @sberg wrote:
>
> >
>


[...]

> Then again, this is a case where you don't get any error but you do get a silent behavioral ambiguity without the current enumerator shadow diagnostic:
> 
>   struct S1;
>   struct S2;
>   struct S3 {
>     void S1();
>     enum { S2 };
>   
>     void f(decltype(S2) s);
>   };
> 
> 
> So there are cases where this behavior can be somewhat useful.

but decltype(S2) is a syntax error when S2 names a struct type, no?

>> (ran into such a new -Wshadow while compiling LibreOffice)
> 
> Was it a frequent/annoying occurrence?

there was less than 20 cases overall. about half were "good" warnings about clashing enumerators from different non-scoped enums. the others were "unhelpful" ones about clashes with class names, two of them in stable interface code that cant be changed (so would need ugly #pragma clang warning decorations), one of them even about entities in unrelated include files, so whether a warning is emitted depends on the order in which the files happen to get included in a TU

(and in any case, "declaration shadows a variable" sounds wrong when the shadowed entity is a class type. thats why I thought something is not quite right with this new code yet)


https://reviews.llvm.org/D52400