ilya-biryukov added a comment.
Should access checks should happen in the context where `concept` is written or
where it's used? Is there a standard wording around it?
If access-checking should happen where concept is defined, having a hard error
seems fine because of the wording you quoted:
> If the substitution of template arguments into a requirement would always
> result in a substitution failure, the program is ill-formed; no diagnostic
> required.
The program is ill-formed and we show the diagnostic even though it's not
required.
I poked around and found an interesting case where GCC seems to be doing the
wrong thing:
template <class> struct B;
class A {
static void f();
friend struct B<short>;
};
template <class T> struct B {
static constexpr int index() requires requires{ A::f(); } {
return 1;
}
static constexpr int index() {
return 2;
}
};
static_assert(B<short>::index() == 1); // GCC picks 1, MSVC picks 1.
static_assert(B<int>::index() == 2); // GCC (incorrectly?) picks 1, MSVC
picks 2!
Is this related to this change? Could we add a test that validates Clang is
doing the right thing?
================
Comment at: clang/lib/Parse/ParseExprCXX.cpp:3510
Actions, Sema::ExpressionEvaluationContext::Unevaluated);
+ Sema::ContextRAII SaveContext(Actions, Actions.CurContext);
----------------
Could you explain how this changes behaviour and how it leads to fixing the
issue?
I'm sure there is quite a bit of thought and debugging behind this one-line
change, but it's not evident by just looking at it how it solves the issue.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D140876/new/
https://reviews.llvm.org/D140876
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