The Go spec says "For an operand x of pointer type *T, the pointer indirection *x denotes the variable of type T pointed to by x. If x is nil, an attempt to evaluate *x will cause a run-time panic."

This program correctly panics with cmd/compile, but does not with gccgo 8.0.0:

package main

func main() {
	var p *struct{}
	*p = *p
}

/cc @ianlancetaylor