Fixed support for allocators with explicit copy constructors

[joaquintides]

Fixes #204

[cppalliance-bot]

An automated preview of the documentation is available at https://234.unordered.prtest2.cppalliance.org/libs/unordered/doc/html/unordered.html

[pdimov]

Interesting. Are such allocators conforming? The latest allocator requirement table seems to say so; was it always such, or is this a recent change?

[pdimov]

(Apart from those philosophical questions, I don't see anything wrong with the change.)

[joaquintides]

Interesting. Are such allocators conforming? The latest allocator requirement table seems to say so; was it always such, or is this a recent change?

I don't know for sure. If you refer to the A a(b) clause, with b being a rebound type from A, this seems to have been that way since ever; I couldn't find anything else explicitly allowing implicit convertibility.

[pdimov]

Seems intentional because the same type entries explicitly mandate A a2 = a; to also work.

[pdimov]

Looks like C++03 only had the X a(b); requirement, C++11 added the X a1(a); requirement, and C++14 added X a1 = a;.

This seems a bit accidental to me.

[joaquintides]

This seems a bit accidental to me.

Probably. If I recall correctly, though, Chris commented this issue actually hit a real user, so it doesn't hurt to have it fixed.

[pdimov]

Yeah, I know, I was just wondering whether such allocators are allowed.