Added description to EnumMember documentation to get name of value

[Zevenberge]

Explicitly stated that the enum name can be retrieved with __traits. There was a unittest for this, but it was not stated in the documentation.
I've added an example to generate a switch-statement with static foreach. Furthermore, I removed the generate example from the documentation, as (in my eyes) it is basically a duplicate of the square root example.

Suggestions for improvement are appreciated.

[dlang-bot]

Thanks for your pull request and interest in making D better, @Zevenberge! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the annotated coverage diff directly on GitHub with CodeCov's browser extension
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + phobos#7003"

[wilzbach]

You already have the name, otherwise case wouldn't work.

[Zevenberge]

As far as I know, we don't: https://run.dlang.io/is/FGGmOH
EnumMembers returns an AliasSeq of values. E.g. members[i].stringof returns cast(FooEnum)0. I might be missing something as I'm no thorough expert.

On the other hand, if we can make it such that we can return the name more easily, then that has my preference as well. But I think that will be a breaking change, as members with the same value are no longer unique.

[Zevenberge]

Apparently std.conv: to!string also works to retrieve the member as a string in this example. (It makes me wonder why there is a unittest for the identifier, but that is out of scope for improving the documentation.)

[Zevenberge]

import std.conv;
enum Enum {foo = 0, bar = 1, baz = 0}
static foreach(i, member; EnumMembers!Enum)
{
	pragma(msg, to!string(member) ~ " " ~ __traits(identifier, EnumMembers!Enum[i]));
}

prints

foo foo
bar bar
foo baz

[thewilsonator]

grep -nr '[[:blank:]]$' etc std ; test $? -eq 1
--
  | Enforce whitespace before opening parenthesis
  | grep -nrE "\<(for\|foreach\|foreach_reverse\|if\|while\|switch\|catch\|version)\(" $(find etc std -name '*.d') ; test $? -eq 1
  | std/traits.d:4203:    s: final switch(var)
  | std/traits.d:4206:        static foreach(i; 0 .. members.length)
  | posix.mak:562: recipe for target 'style_lint' failed

[Zevenberge]

Alright, this documentation should fit the implementation (and clarifies the difference between __traits and to!string).