[PATCH] c++: make __is_constructible work with paren-init of aggrs [PR94149]

[Jonathan Wakely]

On 09/04/20 17:00 -0400, Marek Polacek wrote:
>In C++20 this is well-formed:
>
>  using T = int[2];
>  T t(1, 2);
>
>which means that std::is_constructible_v<int[2], int, int> should be true.
>But constructible_expr immediately returned the error_mark_node when it
>saw a list with more than one element.  To give accurate results in
>C++20, we have to try initializing the aggregate from a parenthesized list of
>values.
>
>To not repeat the same mistake as in c++/93790, if there's only one
>element, I'm trying {} only when () didn't succeed.  is_constructible5.C
>verifies this.
>
>Jon, in paren-init24.C std::is_nothrow_constructible_v doesn't work,
>I'm getting
> error: invalid 'static_cast' from type 'int' to type 'int [1]'
>and
> error: functional cast to array type 'int [2]'
>
>Are these the issues you had in mind when we spoke earlier today?

Here's the library change needed to uncomment the FIXMEs in
paren-init24.C

Bootstrapped and tested on powerpc64le-linux, I plan to commit this
to master today.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: patch.txt
Type: text/x-patch
Size: 5819 bytes
Desc: not available
URL: <https://gcc.gnu.org/pipermail/libstdc++/attachments/20200421/b6117a6a/attachment.bin>