In runtime internal, blank and non-blank interface types are represented
with different structures.
https://go101.org/article/value-part.html#interface-structure mentions this
a little.
On Tuesday, January 22, 2019 at 1:38:23 PM UTC-4, 徐建海 wrote:
>
> when i dig ingo value.go, i found that:
> func (v Value) Elem() Value {
> k := v.kind()
> switch k {
> case Interface:
> var eface interface{}
> if v.typ.NumMethod() == 0 {
> eface = *(*interface{})(v.ptr)
> } else {
> eface = (interface{})(*(*interface {
> M()
> })(v.ptr))
> }
> x := unpackEface(eface)
> if x.flag != 0 {
> x.flag |= v.flag.ro()
> }
> return x
> case Ptr:
> ptr := v.ptr
> if v.flag&flagIndir != 0 {
> ptr = *(*unsafe.Pointer)(ptr)
> }
> // The returned value's address is v's value.
> if ptr == nil {
> return Value{}
> }
> tt := (*ptrType)(unsafe.Pointer(v.typ))
> typ := tt.elem
> fl := v.flag&flagRO | flagIndir | flagAddr
> fl |= flag(typ.Kind())
> return Value{typ, ptr, fl}
> }
> panic(&ValueError{"reflect.Value.Elem", v.kind()})
> }
> I am curious about one piece of it:
> eface = (interface{})(*(*interface {
> M()
> })(v.ptr))
>
> the M() mean nothing? just show that v.ptr is not eface?
>
>
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