On Wed, Mar 16, 2022 at 3:25 PM Alex Besogonov <alex.besogo...@gmail.com>
wrote:
> Note that in your case, the dynamic value of that interface *is not nil*.
> It's a struct value. Structs can not be nil.
>
> Incorrect. Go language allows coercing a struct with an embedded pointer
> to an interface. Spec:
> "If S contains an embedded field *T, the method sets of S and *S both
> include promoted methods with receiver T or *T."
>
Consider this code:
interface Fooable { Foo() }
type T struct {}
func (*T) Foo() {}
type S struct { *T }
func bar(f Fooable) { f.Foo() }
func baz() {
var s S
bar(s)
}
As far as I can tell, you seem to think that the call bar(s) is equivalent
to bar(s.T). In other words, what is passed to bar is an interface value
containing a copy of s.T. This is not correct.
What actually happens is equivalent to the compiler generating a method
var (s S) Foo() { s.T.Foo() }
so that S actually implements the interface Fooable. And the call bar(s)
passes to bar an interface value containing a copy of s itself.
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