The program below currently prints FAIL interface conversion: interface is nil, not main.I and exits with failure when built with cmd/compile. I think this is incorrect, as there's no type assertion in the user code.

I believe the correct behavior is the method call p.M() should raise a "nil pointer dereference" panic, and so the test program should quietly exit with success.

This isn't a spec compliance issue per se, as the Go spec doesn't mandate any particular panic messages. But it is inconsistent with the documentation for package runtime.

package main

import (
	"fmt"
	"strings"
)

type I interface{ M() }

func F[P I](p P) { p.M() }

func main() {
	defer func() {
		err := recover()
		if err, ok := err.(error); ok && strings.Contains(err.Error(), "nil pointer dereference") {
			return
		}
		fmt.Println("FAIL", err)
	}()

	F[I](nil)
}

Marking for Go 1.19, because I doubt this affects any real users.

/cc @griesemer @ianlancetaylor @randall77