cmd/compile: spurious error for use of struct field with undefined type

[rsc]

Go 1.19 (and tip):

package p

var x struct{ f *NotAType }
var _ = x.f == nil

var y *NotAType
var _ = y == nil

./prog.go:3:18: undefined: NotAType
./prog.go:4:16: invalid operation: x.f == nil (operator == not defined on untyped nil)
./prog.go:6:8: undefined: NotAType

The second error, on line 4, should not be printed.
Note that there is no second error involving y.
Something about the struct field is confusing the matter.

https://go.dev/play/p/UQP8ZveEPVh

[gopherbot]

Change https://go.dev/cl/423234 mentions this issue: cmd/compile: skip doing comparison for invalid types

[gopherbot]

Change https://go.dev/cl/424054 mentions this issue: go/types, types2: skip comparison for operands with invalid types