cmp: package name collides with de facto stdlib 'go-cmp'

[bitfield]

I missed the memo where constraints was renamed to cmp, but if I'd seen it, I would have pointed out that this name collides with an extremely widely-used package, go-cmp/cmp. As in, for example:

if !cmp.Equal(want, got) {
  t.Error(cmp.Diff(want, got))
}

Sure, the stdlib is privileged: it can name packages whatever it wants, and it's for third-party package authors to change their names to avoid collisions. But, in this case, go-cmp was there first, and it's so commonly used I'd say it's part of the de facto stdlib.

I'd like to see a cmp package in Go, and I'd like it to have the functionality of go-cmp (I think this has been proposed). Until then, I think it would be wise to keep this part of the namespace open.

[robpike]

The naming decision was discussed and made in the original proposal: #59488. And as discussed at length in many places, package names have no uniqueness requirement, and it's easy to provide a distinct name in the import if there is a collision.

Note too that existing code will be unaffected because no existing code uses the new package.

This is truly not a problem.

[seankhliao]

as mentioned above, it was raised multiple times in the original proposal and addressed in #59488 (comment)