[libcxx-commits] [libcxx] [libc++][ranges] LWG4096: `views::iota(views::iota(0))` should be rejected (PR #152855)

[A. Jiang via libcxx-commits]

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@@ -374,10 +375,11 @@ namespace views {
 namespace __iota {
 struct __fn {
   template <class _Start>
+    requires(requires(_Start __s) { ranges::iota_view<decay_t<_Start>>(std::forward<_Start>(__s)); })
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frederick-vs-ja wrote:

I think we should do choose one of the following approaches:
- exactly using `decltype(ranges::iota_view<decay_t<_Start>>(std::forward<_Start>(__start)))` to achieve expression-equivalency, or
- using `requires` and deduced return type (plain `auto` for this `operator()`).

In either case, we should use `noexcept(noexcept(ranges::iota_view<decay_t<_Start>>(std::forward<_Start>(__start))))` for consistency.

(However, it is currently always equivalent to `noexcept(false)`. No change requested for exception specification strengthening.)

https://github.com/llvm/llvm-project/pull/152855