Comment 1:

Labels changed: added release-none, repo-main.

Owner changed to @griesemer.

Status changed to Accepted.

Comment 2:

My thoughts on the options:
a) Do nothing: fine with me.
b) Change struct to expand: prefer not.
c) Change small interfaces to inline: very slighty positive.
Sometimes people write:
     if f, ok := x.(interface { Foo() }); ok {
             f.Foo()
     }
Which is always rewritten as:
    if f, ok := x.(interface {
        Foo()
    }); ok {
        f.Foo()
    }
Which means you end up writing:
    type fooer interface {
        Foo()
    }
    if f, ok := x.(fooer); ok {
        f.Foo()
    }

Comment 3:

C) is not an option, in the sense that we never shorten things this way.
The missing option is 
D) preserve single-line single-method interfaces
That is,
type T1 struct{ F }
type T2 interface { M() }
type T3 struct {
    F
}
type T4 interface {
    M()
}
T3 and T4 must be left alone no matter what. Today, T1 is left alone as well, but T2 is
changed.
I don't mind if we modify gofmt to allow T2 (but not to turn T4 into T2). I've run into
the example Brad gave too.
I'm also okay with leaving things alone. Robert should decide.

Comment 4:

I vote for preserving existing single line interfaces.

Comment 5:

Ditto.

This was fixed in Go 1.10

Thanks, closing.