The following code type-checks, but probably shouldn't.

package p

import "fmt"

type C[T any] interface {
	m(T)
	n(T)
}

type Interface interface {
	m(int)
	n(string)
}

func F[T any](t C[T]) {
	switch t.(type) {
	case Interface:
		fmt.Println("here")
	}
}

func main() {
	F[int](nil)
}

(note that there is no instantiation of C that has different argument types for m and n). The reason for this is that the MissingMethod API (used internally for interface assertions) unifies individual methods separately, not the entire method set.

Discovered while looking into #50658.

CC @griesemer