code review 194085: gc: improved syntax errors

gc: improved syntax errors

* example-based syntax errors (go.errors)

* enable bison's more specific errors
  and translate grammar token names into
  tokens like ++

* test cases

[rsc, 2010-01-26 19:42:23]

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

I'd like you to review this change.

[ken3, 2010-01-26 22:59:06]

LGTM

On 2010/01/26 19:42:23, rsc wrote:
> Hello ken2, r (cc: mailto:golang-dev@googlegroups.com),
> 
> I'd like you to review this change.

[r, 2010-01-27 02:12:19]

http://codereview.appspot.com/194085/diff/1001/1004
File src/cmd/gc/go.errors (right):

http://codereview.appspot.com/194085/diff/1001/1004#newcode45
src/cmd/gc/go.errors:45: "lower bound of slice expression is required",
i've never  liked error messages whose subject implies something is present that
is actually missing.  here, the sentence reads like you're complaining about the
lower bound but you're not, you're complaining about its absence. put another
way, until "required" you don't know what the subject is: lower bound of slice
expression is .... ?

missing lower bound in slice expression

the other messages are fine

http://codereview.appspot.com/194085/diff/1001/1006
File src/cmd/gc/lex.c (right):

http://codereview.appspot.com/194085/diff/1001/1006#newcode1520
src/cmd/gc/lex.c:1520: "LDEC",	"`--'",
why are there backquotes? they are not left quotes, and single quotes are not
right quotes.

http://codereview.appspot.com/194085/diff/1001/1006#newcode1543
src/cmd/gc/lex.c:1543: // turn 'x' into `x'.
why?

[rsc, 2010-01-27 02:15:55]

> src/cmd/gc/lex.c:1520: "LDEC",  "`--'",
> why are there backquotes? they are not left quotes, and single quotes
> are not right quotes.

would you prefer single quotes for both?
or unicode?

> src/cmd/gc/lex.c:1543: // turn 'x' into `x'.
> why?

i found it easier to read, but it's not essential.
i'm happy to do whatever.

russ

[r2, 2010-01-27 02:17:30]

On Jan 27, 2010, at 1:15 PM, Russ Cox wrote:

>> src/cmd/gc/lex.c:1520: "LDEC",  "`--'",
>> why are there backquotes? they are not left quotes, and single quotes
>> are not right quotes.
>
> would you prefer single quotes for both?
> or unicode?

either nothing (first choice) or double quotes.

>
>> src/cmd/gc/lex.c:1543: // turn 'x' into `x'.
>> why?
>
> i found it easier to read, but it's not essential.
> i'm happy to do whatever.

i've looked at them in several windows and they look wrong in all of  
them.

>
> russ

[rsc, 2010-01-27 04:42:59]

done (no quotes)

[rsc, 2010-01-27 04:43:29]

Hello ken2, r, ken3 (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2010-01-27 04:51:50]

LGTM

[rsc, 2010-01-27 07:13:29]

*** Submitted as http://code.google.com/p/go/source/detail?r=7427b07b5042 ***

gc: improved syntax errors

* example-based syntax errors (go.errors)

* enable bison's more specific errors
  and translate grammar token names into
  tokens like ++

* test cases

R=ken2, r, ken3
CC=golang-dev
http://codereview.appspot.com/194085