proposal: spec: allow convert ~[]interface{~byte|~rune} to string

[leaxoy]

Proposal Details

Currently we have generics, but can't convert byte or rune slice to string. https://go.dev/play/p/QIBgNfzHYFY

Let's support it.

[adonovan]

To be more specific: today it is possible to apply the string(.) conversion to:

• a byte or rune;
• a []byte or []rune;
• a type variable constrained to be []byte or []rune; but not
• a type variable constrained to be a slice of elements constrained to byte or rune.

See https://go.dev/play/p/wrnZwb0pGfz

@griesemer @ianlancetaylor

[earthboundkid]

This does not compile:

func x[E byte, S ~[]E](s S) string {
	return string(s)
}

But this does:

func x[S ~[]byte](s S) string {
	return string(s)
}

I think that should be considered a bug since the only difference is naming E.

[griesemer]

@carlmjohnson This is not a bug, but it's still unfortunate. Related: #63940 . Generics are hard.

[ianlancetaylor]

Closing in favor of #70128, which addresses the general issue.