code review 6996053: spec: clarify language about unary operator &

spec: clarify language about unary operator &

A composite literal may be parenthesized when
used as operand for the unary operator &.

[gri, 2012-12-23 00:56:41]

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

I'd like you to review this change to
https://code.google.com/p/go

[rsc, 2012-12-23 01:45:07]

I think I'm missing something. Why is this exceptional?
& works on any parenthesized expression, and you can parenthesize any
composite literal when using it as an expression.

[gri, 2012-12-23 04:03:01]

In general we talk about the type of operands that are valid with an
operation, not the operands' syntax. In this case it's not the type
that is relevant but the syntactic structure ("composite literal").
Strictly speaking, syntactically, a parenthesized expression is not a
composite literal. Similarly, for go and defer statement, we care
about the syntactic structure of the argument (function call). There
we are explicit that it cannot be parenthesized. For the
unsafe.Offsetof built-in we are explicit as well: it may be
parenthesized.

Thus, I tried to be equally precise here.

I'm not feeling strongly about this - it was just a question that came
up when I implemented this check, and the spec was less clear here
then I thought it might be.

In the long run (past Go 1.1) we might want to have a brief
terminology paragraph somewhere, and then use the same terms
consistently (see also somewhat related issue 4532).

- gri


On Sat, Dec 22, 2012 at 5:45 PM, Russ Cox <rsc@golang.org> wrote:
> I think I'm missing something. Why is this exceptional?
> & works on any parenthesized expression, and you can parenthesize any
> composite literal when using it as an expression.

[rsc, 2013-01-02 22:41:47]

LGTM

[gri, 2013-01-03 02:11:55]

*** Submitted as https://code.google.com/p/go/source/detail?r=f0e7ba409b05 ***

spec: clarify language about unary operator &

A composite literal may be parenthesized when
used as operand for the unary operator &.

R=rsc, iant, r, ken
CC=golang-dev
https://codereview.appspot.com/6996053