https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95910
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ppalka at gcc dot gnu.org
--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Thanks for the report.
The const-qualified transform_view::begin() member has as its constraints
constexpr _Iterator<true>
begin() const
requires range<const _Vp>
&& regular_invocable<const _Fp&, range_reference_t<const _Vp>>.
So as part of overload resolution of the implicit call to
'transform_view::begin', we end up evaluating 'is_invocable_v<lambda, const
int&>'. But because the lambda's return type is omitted and because evaluation
of 'is_invocable_v' requires knowing the return type, we have to instantiate
the body of the lambda in order to deduce its return type. And instantiation
leads to a hard error from the failed static_assert.
So noe workaround here is to give the lambda an explicit return type.
