[PATCH] D60573: [Sema] ADL: Associated namespaces for class types and enumeration types (CWG 1691)

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

In D60573#1463641 <https://reviews.llvm.org/D60573#1463641>, @riccibruno wrote:

> In D60573#1463569 <https://reviews.llvm.org/D60573#1463569>, @rjmccall wrote:
>
> > Hmm.  Does this never impact code that's just using a locally-defined type within its scope?  I guess if ADL is involved, unqualified lookup must have reached the scope of the innermost namespace, and so it would be searching that namespace anyway.
> >
> > In that case, I think I'm mollified that the source-compatibility risk is low and we should just unconditionally apply the new rule.  LGTM.
>
>
> I am not sure about what you mean. It is certainly possible to construct a piece of C++11 code which breaks with this patch.


Yes, but these examples are contrived, so it's easy to rationalize that the source impact is low.  The typical use-pattern of a local type is that you only use it locally, so the most important question would be whether it is possible to change the semantics of, say,

  void test() {
    struct A { ... };
    foo(A{});
  }

But I think the answer is "no", for the reasons I explained.


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