Quuxplusone added inline comments.
================
Comment at:
test/CXX/basic/basic.lookup/basic.lookup.argdep/p2-associated-namespaces-classes.cpp:304
+ static_assert(f(g3) == 4, ""); // FIXME: Also well-formed from the
union rule.
+ // expected-error@-1 {{use of
undeclared}}
+ }
----------------
I see how `g3` matches the example in CWG997
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#997
However, I don't see how CWG997's resolution actually affected this example in
the slightest. The wording inserted for CWG997 was, "Additionally, if the
aforementioned set of overloaded functions is named with a template-id, its
associated classes and namespaces are those of its type template-arguments and
its template template-arguments." That makes e.g.
f(g3<N::S>)
consider `N::f`, because `N::S` is a "type template-argument" of the
template-id `g3<N::S>` which names the set of overloaded functions. But it
doesn't do anything at all to `f(g3)` because `g3` is not a template-id and
doesn't have any template-arguments.
This piece of ADL is implemented only by GCC (not EDG, Clang, or MSVC), and
personally I would very much like to keep it that way. We know there's no
real-world code that expects or relies on CWG997 — because such code would
never work in practice except on GCC. Let's keep it that way! As soon as you
implement a crazy arcane rule, such that code _could_ portably rely on it, code
_will start_ relying on it... and then we'll never be able to simplify the
language.
Case in point: the piece of ADL described in this blog post --
https://quuxplusone.github.io/blog/2019/04/09/adl-insanity-round-2/
As soon as the above-described arcane ADL rule was implemented in GCC and
Clang, Boost.Hana started relying on it; and now the rule is "locked in" to the
paper standard because there's real-world code relying on it.
Personally I'd like to _keep_ real-world code from relying on CWG997, until
someone figures out what CWG was thinking when they added it.
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D60570/new/
https://reviews.llvm.org/D60570
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