http://d.puremagic.com/issues/show_bug.cgi?id=5953

           Summary: Too many trailing commas are accepted
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid
          Severity: minor
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2011-05-07 16:28:09 PDT ---
Accepting an extra trailing comma is acceptable, but this looks excessive (this compiles and runs with no errors, DMD 2.053 beta):


void main() {
    auto a = [,,,,,,,,,,,,,,,,,,,,,,,,,,,,,];
    assert(a.length == 0);
}


As in Python I suggest to accept only one extra trailing comma:

>>> a = [1]
>>> a = [1,]
>>> a = [1,,]
  File "<stdin>", line 1
    a = [1,,]
           ^
SyntaxError: invalid syntax

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kennytm@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kennytm@gmail.com


--- Comment #1 from kennytm@gmail.com 2011-05-07 23:51:21 PDT ---
Please don't use Python to say a D syntax is invalid. Use the D spec or TDPL.

--------

In the D spec an array literal follows the rule:

ArrayLiteral:
    '[' ArgumentList ']'

ArgumentList:
    AssignExpression
        AssignExpression ','
    AssignExpression ',' ArgumentList

and an AssignExpression cannot be empty, so '[1,,]' should be rejected.

(BTW this rule doesn't handle '[]' at all.)

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--- Comment #2 from bearophile_hugs@eml.cc 2011-05-08 03:39:56 PDT ---
(In reply to comment #1)
> Please don't use Python to say a D syntax is invalid. Use the D spec or TDPL.

I feel free to show what's the design of other languages, if they are a good example.


> and an AssignExpression cannot be empty, so '[1,,]' should be rejected.

OK. So it's not a design problem, just an implementation issue.

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--- Comment #3 from kennytm@gmail.com 2011-05-08 04:40:20 PDT ---
(In reply to comment #2)
> (In reply to comment #1)
> > Please don't use Python to say a D syntax is invalid. Use the D spec or TDPL.
> 
> I feel free to show what's the design of other languages, if they are a good example.
> 

Yes, but with the 'accept-invalid' tag I think that you want to say [,,,,,,,,,,,,,,,,,,] is invalid because it is invalid in Python. Sorry for misinterpreting.

> 
> > and an AssignExpression cannot be empty, so '[1,,]' should be rejected.
> 
> OK. So it's not a design problem, just an implementation issue.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


--- Comment #6 from Walter Bright <bugzilla@digitalmars.com> 2011-08-31 00:36:53 PDT ---
https://github.com/D-Programming-Language/dmd/commit/ba4da917ed6b79fc896a21cec91a0de1a04128cb

https://github.com/D-Programming-Language/dmd/commit/fc0bbd3afba6e5f878fecc8a029f437b1df51e41

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