On Wed, Jan 6, 2021 at 11:39 PM Amit Saha <amitsaha...@gmail.com> wrote:
> Is it fair to say then that any user-defined type here is acceptable as a
> key?
>
No. You can create a user-defined type out of *any* type T, by just writing
`type X T`. In particular, you can write `type X func()` and get an
incomparable user-defined type.
I highly recommend sticking to the recommendation from the docs: Use `type
ctxKey struct{}` as a key type and `ctxKey{}` as the key - it's comparable
and the only value equal to `ctxKey{}` is `ctxKey{}`, which gives exactly
the desirable semantics. And as it's zero-sized, it also doesn't occur any
allocation (at least with gc, all zero-sized objects have the same
address). You could also use `[0]int` or similar, but `struct{}` is very
common for use-cases like this.
>
>
> >>
> >> Thanks,
> >> Amit.
> >>
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> .
>
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