Make the varargs ellipsis a named node

[genotrance]

No information is provided about the ellipsis in the AST.

extern void eggx_gsetinitialparsegeometry( const char *, ... ) ;

AST is:

(translation_unit 1 1 64
 (declaration 1 1 64
  (storage_class_specifier 1 1 6)
  (primitive_type 1 8 4)
  (function_declarator 1 13 50
   (identifier 1 13 29)
   (parameter_list 1 42 21
    (parameter_declaration 1 44 12
     (type_qualifier 1 44 5)
     (primitive_type 1 50 4)
     (abstract_pointer_declarator 1 55 1)
    )
   )
  )
 )
)

[maxbrunsfeld]

The ... token is in there and you can access it, but it isn't named, so it doesn't show up in the printed tree. Maybe it should be given a name though.

[genotrance]

Can you provide some info on how to detect this in the tree? I see there's two extra unnamed nodes but not sure how to detect that it is ... Thanks.

Edit: never mind, figured this out.

[shi-yan]

I checked the code that handles variadic arguments, I think it is flawed and won't be simply fixed by giving ... a name:

    parameter_list: $ => seq(
      '(',
      commaSep(choice(
        $.parameter_declaration,
        $.optional_parameter_declaration,
        $.variadic_parameter_declaration,
        '...'
      )),
      ')'
    ),
...
    variadic_parameter_declaration: $ => seq(
      $._declaration_specifiers,
      field('declarator', choice(
        $.variadic_declarator,
        alias($.variadic_reference_declarator, $.reference_declarator)
      ))
    ),

    variadic_declarator: $ => seq(
      '...',
      optional($.identifier)
    ),

1. ... has to be the last token of a parameter_list. whereas the grammar allows it to be in front of other arguments:

commaSep(choice(
        $.parameter_declaration,
        $.optional_parameter_declaration,
        $.variadic_parameter_declaration,
        '...'
      )),

2. the last comma should be optional: https://en.cppreference.com/w/cpp/language/variadic_arguments , but the above would enforce it.

3. the current grammar requires _declaration_specifiers is in front of ...

    variadic_parameter_declaration: $ => seq(
      $._declaration_specifiers,
      field('declarator', choice(
        $.variadic_declarator,
        alias($.variadic_reference_declarator, $.reference_declarator)
      ))
    ),

this will result in char ... fmt being accepted, whereas char fmt... being rejected. it seems that the current grammar wants to handle parameter pack? (https://en.cppreference.com/w/cpp/language/parameter_pack)

4. also here,

    variadic_declarator: $ => seq(
      '...',
      optional($.identifier)
    ),

the ... token is defined as a prefix of an identifier, not a suffix? https://en.cppreference.com/w/cpp/language/variadic_arguments

some concrete examples:

tree-sitter-cpp:

void function(..., int a)
{}

accept

(translation_unit [0, 0] - [1, 2]
  (function_definition [0, 0] - [1, 2]
    type: (primitive_type [0, 0] - [0, 4])
    declarator: (function_declarator [0, 5] - [0, 25]
      declarator: (identifier [0, 5] - [0, 13])
      parameters: (parameter_list [0, 13] - [0, 25]
        (variadic_declarator [0, 14] - [0, 17])
        (parameter_declaration [0, 19] - [0, 24]
          type: (primitive_type [0, 19] - [0, 22])
          declarator: (identifier [0, 23] - [0, 24]))))
    body: (compound_statement [1, 0] - [1, 2])))

clang:

./test.cpp:1:6: error: variable has incomplete type 'void'
void function(..., int a)
     ^
./test.cpp:1:15: error: expected expression
void function(..., int a)
              ^
./test.cpp:1:24: error: expected '(' for function-style cast or type construction
void function(..., int a)
                   ~~~ ^
./test.cpp:1:26: error: expected ';' after top level declarator
void function(..., int a)
                         ^
                         ;
4 errors generated.

tree-sitter-cpp

void function(char ... a)
{}

accept

(translation_unit [0, 0] - [1, 2]
  (function_definition [0, 0] - [1, 2]
    type: (primitive_type [0, 0] - [0, 4])
    declarator: (function_declarator [0, 5] - [0, 25]
      declarator: (identifier [0, 5] - [0, 13])
      parameters: (parameter_list [0, 13] - [0, 25]
        (variadic_parameter_declaration [0, 14] - [0, 24]
          type: (primitive_type [0, 14] - [0, 18])
          declarator: (variadic_declarator [0, 19] - [0, 24]
            (identifier [0, 23] - [0, 24])))))
    body: (compound_statement [1, 0] - [1, 2])))

clang:

./test.cpp:1:20: error: type 'char' of function parameter pack does not contain any unexpanded parameter packs
void function(char ... a)
              ~~~~~^~~~~
1 error generated.

I think this should be labeled as bug