cmd/compile: embedding comparable is not considered in calculating type sets

[zigo101]

What version of Go are you using (go version)?

$ go version
go version go1.18rc1 linux/amd64

What did you do?

package main

func main() {
	foo("Abc")
	foo([]byte{}) // compiles okay, but should not
}

type C interface {
	comparable
	[]byte | string
}
	
func foo[T C](x T) {}

What did you expect to see?

Fails to compile.

What did you see instead?

Compiles okay.

[ianlancetaylor]

CC @griesemer @findleyr

[griesemer]

Briefly looked at this. It appears we're forgetting to consider the "comparable" field in typesets under some circumstances. Appears like a trivial oversight, as the actual type set computations are ok. Will fix tomorrow.

[griesemer]

Quick update: fix is pending but given that we're so short before the release, I'll spend some time adding more tests; this shouldn't have slipped. CL probably later today or tomorrow.

[gopherbot]

Change https://go.dev/cl/390025 mentions this issue: types2: correctly include comparable in type set intersection

[gopherbot]

Change https://go.dev/cl/390419 mentions this issue: [release-branch.go1.18] go/types, types2: correctly include comparable in type set intersection