spec: receiver-curried method expressions

[bradfitz]

We have method expressions of form Type.Method.

This is a wishlist bug for method expressions that curry the receiver, of form
receiver.Method.

type A struct {
   // ...
}

func (a *A) Foo(bar, baz int) {}

b := new(A)
foob := b.Foo  // foob is of type func(int, int)

[bradfitz]

Comment 1:

Owner changed to ---.

[robpike]

Comment 2:

Status changed to Accepted.

[rsc]

Comment 4:

Labels changed: added priority-someday, removed priority-low.

[gopherbot]

Comment 6 by cjmxp2009:

什么时候支持这个功能

[ianlancetaylor]

Comment 7:

There is no schedule or plan for this, it is just an idea.

[rsc]

Comment 8:

Labels changed: added go1.1maybe.

[rsc]

Comment 9:

Labels changed: added size-xl.

[bradfitz]

Comment 10:

Adding dependency on issue #4081.
And, adding to this bug the example I've given a few people now of when this is useful:
type T struct {
   once  sync.Once // guards setup of state
   state interface{}
}
func (t *T) initState() {
   t.state = ....
}
func (t *T) someMethod() {
   t.once.Do(t.initState)   // because Do requires type "func()"
   // use t.state
}
Currently we have to either do:
 t.once.Do(func() { t.initState() })
... which generates garbage each time, or give up on the zero value of T and instead
make a constructor:
func NewT() *T {
   t := new(T)
   t.initFunc = func() { t.initState }
   return t
}
func (t *T) someMethod() {
   t.once.Do(t.initFunc)
   ...
}

[rsc]

Comment 11:

Those are not the only choices:
type T struct {
    mu sync.Mutex
    state interface{}
}
func (t *T) someMethod() {
    t.mu.Lock()
    if t.state == nil {
        t.initState()
    }
    t.mu.Unlock()
    ...
}

[rsc]

Comment 12:

[The time for maybe has passed.]

Labels changed: removed go1.1maybe.

[rsc]

Comment 13:

Labels changed: added go1.1.

[rsc]

Comment 14:

This issue was closed by revision 6e15683.

Status changed to Fixed.