Re: [boost] [type_traits] Big changes in develop

Subject: Re: [boost] [type_traits] Big changes in develop
From: Peter Dimov (lists_at_[hidden])
Date: 2015-05-28 13:46:25

> I'm not at the PR point yet, need to clean up the implementation and check 
> against the existing tests (which are pretty slim by the way) first.

Interesting. The standard appears to mandate std::common_type<char, 
char>::type to be char&&. Do we want this behavior?

I see that our decltype implementation uses decay<> on the result, but that 
doesn't seem to be what the standard says:

"Let C denote the type, if any, of an unevaluated conditional expression 
(5.16) whose first operand is an arbitrary value of type bool, whose second 
operand is an xvalue of type T1, and whose third operand is an xvalue of 
type T2."

This is in the latest C++17 draft.

Using decay<> on the result throws away reference information, doesn't it? 
Base&, Derived& -> Base instead of Base&.