reflect: Anonymous fields and embedded fields

[nsf]

The type reflect.StructField has a field called "Anonymous". But frankly there
are no anonymous fields in Go, at least they are not what "reflect" thinks
they are. Reflect package puts "true" into that field on embedded fields,
which are not anonymous, because their name matches their type name. And real anonymous
fields:

type X struct {
    _ io.Reader
    _ io.Reader
}

are not marked as such. And that makes that particular case a source of terminology
confusion.

P.S. As a somewhat related note, it would be nice to be able to distinguish between a
user-defined method (that is written explicitly in the source code) and a automatically
generated method which was inherited from an embedded field. Should I create a separate
issue on that?

[cznic]

Comment 1:

Reflect is correct, see: http://golang.org/ref/spec#AnonymousField
IMO WorkingAsIntended

[nsf]

Comment 2:

In my opinion specification needs a fix for that too. Implicitly defined name doesn't
make a field anonymous.

[cznic]

Comment 3:

In `struct{ *t }` the (only) field is anonymous b/c it has no name (neither an implicit
name). Instead of a name the field is referenced to using the type name of the field.
Hence, anonymous field. (Name of the field !=== Name of the field's type)

[nsf]

Comment 4:

Makes sense, but then how do you call "_" fields? Blank fields? They really have no
name, because you can't normally reach them.
And you say that the field is anonymous b/c it has no name, yet, specification gives an
example of anonymous fields conflicting because of their names.
"The following declaration is illegal because field names must be unique in a struct
type:
struct {
    T     // conflicts with anonymous field *T and *P.T
    *T    // conflicts with anonymous field T and *P.T
    *P.T  // conflicts with anonymous field T and *T
}"
What we're talking about here is the definition of terminology confusion. :)

[cznic]

Comment 5:

In `struct{ _ t}` the (only) field _has_ a name: `_`. That name is non-binding:
http://golang.org/ref/spec#Blank_identifier

[ianlancetaylor]

Comment 6:

The intent is that Anonymous is true for embedded fields.  The name of a field declared
with a name of "_" is simply "_".  You can't refer to that field in a program, but that
doesn't mean it doesn't have a name.
I agree that it would be better to have a name other than Anonymous for embedded fields.
 But the Go 1 guarantee means that we can't change this, and it's not all that bad.  So
I think this is a documentation issue: we should provide better documentation for the
Anonymous field of reflect.StructField.

Labels changed: added priority-later, documentation, removed priority-triage.

Status changed to Accepted.

[rsc]

Comment 7:

This issue was closed by revision b396d11.

Status changed to Fixed.