f72b3e1c07
Adds explanation why `is_constructible` evaluates to false. This reapplies as-is e476f968bc8e438a0435d10934f148de570db8eb. This was reverted in 16d5db71b3c38f21aa17783a8758f947dca5883f because of a test failure in libc++. The test failure in libc++ is interesting in that, in the absence of nested diagnostics a bunch of diagnostics are emitted as error instead of notes, which we cannot silence with `-verify-ignore-unexpected`. The fix here is to prevent the diagnostics to be emitted in the first place. However this is clearly not ideal and we should make sure to deploy a better solution in the clang 22 time frame, in the lines of https://discourse.llvm.org/t/rfc-add-a-new-text-diagnostics-format-that-supports-nested-diagnostics/87641/12 Fixes #150601 --------- Co-authored-by: Shamshura Egor <164661612+egorshamshura@users.noreply.github.com>