[phobos] [D-Programming-Language/phobos] 005775: Allow Variant.visit to support const types.

[GitHub via phobos]

  Branch: refs/heads/master
  Home:   https://github.com/D-Programming-Language/phobos
  Commit: 0057756b28f78664cc184eac100dc975e3fdc625
      https://github.com/D-Programming-Language/phobos/commit/0057756b28f78664cc184eac100dc975e3fdc625
  Author: Ryan Roden-Corrent <ryan at rcorre.net>
  Date:   2015-08-11 (Tue, 11 Aug 2015)

  Changed paths:
    M std/variant.d

  Log Message:
  -----------
  Allow Variant.visit to support const types.

Assuming that Foo.depth and Bar.depth are both const (e.g. both are just int
members), the following should compile:
-----
    int depth(in FooBar fb) {
  return fb.visit!((Foo foo) => foo.depth,
                   (Bar bar) => bar.depth);
    }
-----

However, it was failing with:
std/variant.d(2246): Error: cannot implicitly convert expression (variant.peek())
of type const(Foo)* to Foo*
std/variant.d(2246): Error: cannot implicitly convert expression (variant.peek())
of type const(Bar)* to Bar*

This patch changes an explicit `T*` declaration to an `auto` declaration so
const types can be visited.


  Commit: 82b98200953d38978aab70b567f0658f606bd520
      https://github.com/D-Programming-Language/phobos/commit/82b98200953d38978aab70b567f0658f606bd520
  Author: Dmitry Olshansky <dmitry.olsh at gmail.com>
  Date:   2015-08-23 (Sun, 23 Aug 2015)

  Changed paths:
    M std/variant.d

  Log Message:
  -----------
  Merge pull request #3549 from rcorre/variant-visit-inout-fix

Allow Variant.visit to support const types.


Compare: https://github.com/D-Programming-Language/phobos/compare/354778b43009...82b98200953d