code review 708041: go spec: modification of defer statement

go spec: modification of defer statement

[gri, 2010-03-23 23:49:48]

Hello r, rsc, ken2, iant (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[gri, 2010-03-23 23:52:29]

PS: Changed "Specifically" to "For instance".
- Robert

On Tue, Mar 23, 2010 at 4:49 PM, <gri@golang.org> wrote:

> Reviewers: r, rsc, ken2, iant,
>
> Message:
> Hello r, rsc, ken2, iant (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change.
>
>
> Description:
> go spec: modification of defer statement
>
> Please review this at http://codereview.appspot.com/708041/show
>
> Affected files:
>  M doc/go_spec.html
>
>
> Index: doc/go_spec.html
> ===================================================================
> --- a/doc/go_spec.html
> +++ b/doc/go_spec.html
> @@ -4281,7 +4281,12 @@
>  function is not invoked.
>  Deferred function calls are executed in LIFO order
>  immediately before the surrounding function returns,
> -but after the return values, if any, have been evaluated.
> +after the return values, if any, have been evaluated, but before they
> +are returned to the caller. Specifically, if the deferred function is
> +a <a href="#Function_literals">function literal<a/> and the surrounding
> +function has <a href="#Function_types">named result parameters</a> that
> +are in scope within the literal, the deferred function may access the
> result
> +values returned by the surrounding function.
>  </p>
>
>  <pre>
> @@ -4292,6 +4297,14 @@
>  for i := 0; i &lt;= 3; i++ {
>        defer fmt.Print(i)
>  }
> +
> +// the result of f is 1
> +func f() (result int) {
> +       defer func() {
> +               result++
> +       }()
> +       return 0
> +}
>  </pre>
>
>  <h2 id="Built-in_functions">Built-in functions</h2>
>
>
>

[rsc, 2010-03-23 23:53:30]

> +are in scope within the literal, the deferred function may access the

s/access/& and modify/

> +// the result of f is 1
// f returns 1

[rsc, 2010-03-23 23:54:04]

LGTM

though add an implementation restriction at
the bottom of the spec saying that it's not
implemented yet in either 6g or gccgo.

[rsc, 2010-03-23 23:54:50]

also, delete

http://golang.org/doc/go_spec.html#Address_operators

A function result variable is not addressable.

[gri, 2010-03-23 23:58:53]

Hello r, rsc, ken2, iant (cc: golang-dev@googlegroups.com),

Please take another look.

[rsc1, 2010-03-24 00:00:17]

LGTM

http://codereview.appspot.com/708041/diff/13001/14001
File doc/go_spec.html (right):

http://codereview.appspot.com/708041/diff/13001/14001#newcode2999
doc/go_spec.html:2999: A function result variable is not addressable.
delete this line and next

[gri, 2010-03-24 00:00:25]

Hello r, rsc, ken2, iant (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2010-03-24 00:00:43]

LGTM

you can address the comments on the implementation restrictions in another CL if
you want

http://codereview.appspot.com/708041/diff/13001/14001
File doc/go_spec.html (right):

http://codereview.appspot.com/708041/diff/13001/14001#newcode4289
doc/go_spec.html:4289: the result values returned by the surrounding function.
s/returned/before they are &/

http://codereview.appspot.com/708041/diff/13001/14001#newcode4944
doc/go_spec.html:4944: <li><span class="alert">Method expressions are not
implemented.</span></li>
aren't these done?

http://codereview.appspot.com/708041/diff/13001/14001#newcode4945
doc/go_spec.html:4945: <li><span class="alert">The implementation of complex
numbers is incomplete.</span></li>
i think this can go now.

[rsc, 2010-03-24 00:02:48]

> http://codereview.appspot.com/708041/diff/13001/14001#newcode4944
> doc/go_spec.html:4944: <li><span class="alert">Method expressions are
> not implemented.</span></li>
> aren't these done?

6g has a bug in / incomplete code for method expressions when
T is an interface value, like io.Reader.Read.

[iant, 2010-03-24 00:06:39]

LGTM

[gri, 2010-03-24 00:30:17]

*** Submitted as http://code.google.com/p/go/source/detail?r=0d9f6cfa1a18 ***

go spec: modification of defer statement

R=r, rsc, ken2, iant
CC=golang-dev
http://codereview.appspot.com/708041