code review 7625050: cmd/gc: accept ideal float as indices.

cmd/gc: accept ideal float as indices.

Fixes issue 4813.

[remyoudompheng, 2013-03-13 07:56:04]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[remyoudompheng, 2013-03-13 07:58:48]

https://codereview.appspot.com/7625050/diff/5001/src/cmd/gc/typecheck.c
File src/cmd/gc/typecheck.c (right):

https://codereview.appspot.com/7625050/diff/5001/src/cmd/gc/typecheck.c#newco...
src/cmd/gc/typecheck.c:296: defaultlit(np, types[TINT]);
If we don't want to accept 

a[1.0<<s + 2]

this will be changed in:

if(isconst(n))
    defaultlit(np, T);
else
    defaultlit(np, types[TINT]);

[DMorsing, 2013-03-13 12:44:22]

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c
File src/cmd/gc/typecheck.c (right):

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c#newc...
src/cmd/gc/typecheck.c:280: indexlit(Node **np)
Why is this function needed? Couldn't calls to this be replaced with
defaultlit(np, types[TINT]); ?

[rsc, 2013-03-15 04:03:02]

I echo Daniel's question about indexlit. Please add a comment explaining what
the goal is and why it differs from the simpler defaultlit call.

Otherwise seems fine.

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c
File src/cmd/gc/typecheck.c (right):

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c#newc...
src/cmd/gc/typecheck.c:878: if(n->right->op == OLITERAL) {
This should probably be if(isconst(n->right, CTINT)). Otherwise the mpgetfix
below is incorrect.

[remyoudompheng, 2013-03-20 21:23:30]

Hello golang-dev@googlegroups.com, daniel.morsing@gmail.com, rsc@golang.org (cc:
golang-dev@googlegroups.com),

Please take another look.

[remyoudompheng, 2013-03-20 21:34:36]

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c
File src/cmd/gc/typecheck.c (right):

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c#newc...
src/cmd/gc/typecheck.c:280: indexlit(Node **np)
On 2013/03/13 12:44:22, DMorsing wrote:
> Why is this function needed? Couldn't calls to this be replaced with
> defaultlit(np, types[TINT]); ?

To avoid unnecessary noise I chose to keep defaultlit(np, T) for string
constants, which matches the oold behaviour.

The code also has to make sure to reject 1.0<<s, until it becomes decided
otherwise.

https://codereview.appspot.com/7625050/diff/11001/src/cmd/gc/typecheck.c#newc...
src/cmd/gc/typecheck.c:878: if(n->right->op == OLITERAL) {
On 2013/03/15 04:03:02, rsc wrote:
> This should probably be if(isconst(n->right, CTINT)). Otherwise the mpgetfix
> below is incorrect.

Done. although I think the if above prevents bad const kinds from happening

[DMorsing, 2013-03-21 08:12:45]

LGTM

[rsc, 2013-03-21 20:02:29]

LGTM

[remyoudompheng, 2013-03-21 23:38:28]

*** Submitted as https://code.google.com/p/go/source/detail?r=7a6736903d57 ***

cmd/gc: accept ideal float as indices.

Fixes issue 4813.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://codereview.appspot.com/7625050