https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101091
--- Comment #1 from Jakub Gałecki ---
Consider the following example: https://godbolt.org/z/YYzqWaM9G
#include
#include
#include
void copy_drop_n1(const std::vector& src, std::vector& dest,
std::size_t n) { // size_t - narrowing conversion
std::ranges::copy(src | std::views::drop(n), begin(dest) + n);
}
void copy_drop_n2(const std::vector& src, std::vector& dest,
std::ptrdiff_t n) { // ptrdiff_t
std::ranges::copy(src | std::views::drop(n), begin(dest) + n);
}
As per the standard [range.take.overview]:
The name views::take denotes a range adaptor object ([range.adaptor.object]).
Let E and F be expressions, let T be remove_cvref_t, and let D
be range_difference_t. If decltype((F)) does not model
convertible_to, views::take(E, F) is ill-formed. Otherwise, the
expression views::take(E, F) is expression-equivalent to [...]
The example above should therefore compile for size_t as well as ptrdiff_t,
since size_t is convertible to ptrdiff_t. This is a regression from libstdc++
version 10.x, where both functions compile.
