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digitalmars.D - UDAs grammar: <template_instance> valid?

reply Bruno Medeiros <bruno.do.medeiros+dng gmail.com> writes:
Someone opened an issue report for a bug in the DDT parser, it doesn't 
parse this:

template X(int Y){}

 X!3  // error here
void main(){}

And yet DMD accepts this code. Is this grammar supposed to be valid 
though? The grammar spec doesn't allow it, not that means much. I 
searched for an open grammar bug, but couldn't find one.


-- 
Bruno Medeiros
https://twitter.com/brunodomedeiros
Oct 29 2014
parent reply Kenji Hara via Digitalmars-d <digitalmars-d puremagic.com> writes:
2014-10-29 21:33 GMT+09:00 Bruno Medeiros via Digitalmars-d <
digitalmars-d puremagic.com>:


 Someone opened an issue report for a bug in the DDT parser, it doesn't
 parse this:

 template X(int Y){}

  X!3  // error here
 void main(){}

 And yet DMD accepts this code. Is this grammar supposed to be valid
 though? The grammar spec doesn't allow it, not that means much. I searched
 for an open grammar bug, but couldn't find one.



It is a grammar bug, because DMD parser intentionally accepts the syntax.

https://github.com/D-Programming-Language/dmd/blob/9d1d0245fda3107f01d2b1460c7bcc34188a751e/src/parse.c#L1003

StorageClass Parser::parseAttribute(Expressions **pudas)
{
    nextToken();
    Expressions *udas = NULL;
    StorageClass stc = 0;
    if (token.value == TOKidentifier)
    {
        if (token.ident == Id::property)
            ...
        else
        {
            // Allow identifier, template instantiation, or function call
<-----
            Expression *exp = parsePrimaryExp();
            if (token.value == TOKlparen)
            {
                Loc loc = token.loc;
                exp = new CallExp(loc, exp, parseArguments());
            }

            udas = new Expressions();
            udas->push(exp);
        }
    }

Kenji Hara
Oct 29 2014
parent Bruno Medeiros <bruno.do.medeiros+dng gmail.com> writes:
On 29/10/2014 13:21, Kenji Hara via Digitalmars-d wrote:

 2014-10-29 21:33 GMT+09:00 Bruno Medeiros via Digitalmars-d
 <digitalmars-d puremagic.com <mailto:digitalmars-d puremagic.com>>:

     Someone opened an issue report for a bug in the DDT parser, it
     doesn't parse this:

     template X(int Y){}

      X!3  // error here
     void main(){}

     And yet DMD accepts this code. Is this grammar supposed to be valid
     though? The grammar spec doesn't allow it, not that means much. I
     searched for an open grammar bug, but couldn't find one.


 It is a grammar bug, because DMD parser intentionally accepts the syntax.


Opened: https://issues.dlang.org/show_bug.cgi?id=13664


-- 
Bruno Medeiros
https://twitter.com/brunodomedeiros
Oct 29 2014