https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115296
Bug ID: 115296
Summary: CTAD fails
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tiagomacarios at gmail dot com
Target Milestone: ---
The following code compiles fine with clang and msvc, but fails with gcc.
https://godbolt.org/z/e4dP7rzar
```
#include <span>
template <typename T>
using array_view = std::span<T>;
void fun(std::span<int> s) {
[[maybe_unused]] auto _1 = std::span{s};
[[maybe_unused]] auto _2 = array_view{s};
}
```
Error:
```
In file included from <source>:1:
/opt/compiler-explorer/gcc-trunk-20240530/include/c++/15.0.0/span: In function
'void fun(std::span<int>)':
/opt/compiler-explorer/gcc-trunk-20240530/include/c++/15.0.0/span:450:5: error:
size '18446744073709551615' of array exceeds maximum object size
'9223372036854775807'
450 | span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>;
| ^~~~
/opt/compiler-explorer/gcc-trunk-20240530/include/c++/15.0.0/span:450:10:
error: size '18446744073709551615' of array exceeds maximum object size
'9223372036854775807'
450 | span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>;
| ^~~~~~~~~~~~~~~~~~~~~~
<source>:8:44: error: class template argument deduction failed:
8 | [[maybe_unused]] auto _2 = array_view{s};
| ^
<source>:8:44: error: call of overloaded 'span(std::span<int>&)' is ambiguous
/opt/compiler-explorer/gcc-trunk-20240530/include/c++/15.0.0/span:464:5: note:
candidate: 'std::span(_Range&&)-> span<typename
remove_reference<ranges::range_reference_t<_Range&> >::type> requires
__is_deducible (array_view, std::span<typename
std::remove_reference<decltype(*(declval<decltype(std::ranges::__access::__begin((declval<_Container&>)()))&>)())>::type,
18446744073709551615>) [with _Range = span<int>&; typename
remove_reference<ranges::range_reference_t<_Range&> >::type = int;
ranges::range_reference_t<_Range&> = int&]'
464 | span(_Range &&)
| ^~~~
/opt/compiler-explorer/gcc-trunk-20240530/include/c++/15.0.0/span:54:11: note:
candidate: 'span(std::span<_Type, 18446744073709551615>)-> std::span<_Type,
18446744073709551615> [with T = int]'
54 | class span;
| ^~~~
/opt/compiler-explorer/gcc-trunk-20240530/include/c++/15.0.0/span:225:7: note:
candidate: 'span(const std::span<_Type, 18446744073709551615>&)->
std::span<_Type, 18446744073709551615> [with T = int]'
225 | span(const span&) noexcept = default;
| ^~~~
Compiler returned: 1
```
