grammar.js

const C = require("tree-sitter-c/grammar")

const PREC = Object.assign(C.PREC, {
  LAMBDA: 18,
  NEW: C.PREC.CALL + 1,
  STRUCTURED_BINDING: -1,
})

module.exports = grammar(C, {
  name: 'cpp',

  extras: ($, original) => original.concat([
    $.doxygen
  ]),

  externals: $ => [
    $.raw_string_literal
  ],

  conflicts: ($, original) => original.concat([
    [$.template_function, $.template_type],
    [$.template_function, $.template_type, $._expression],
    [$.template_function, $._expression],
    [$.template_method, $.template_type, $.field_expression],
    [$.scoped_type_identifier, $.scoped_identifier],
    [$.scoped_type_identifier, $.scoped_field_identifier],
    [$.comma_expression, $.initializer_list],
    [$._expression, $._declarator],
    [$._expression, $.structured_binding_declarator],
    [$._expression, $._declarator, $._type_specifier],
    [$.parameter_list, $.argument_list],
    [$._type_specifier, $.call_expression],
    [$._declaration_specifiers, $.operator_cast_declaration, $.operator_cast_definition, $.constructor_or_destructor_definition],
	[$._declaration_specifiers, $.field_declaration, $.inline_method_definition, $.operator_cast_declaration, $.operator_cast_definition, $.constructor_or_destructor_definition, $.constructor_or_destructor_declaration],
    [$._declaration_specifiers, $._constructor_specifiers],
  ]),

  inline: ($, original) => original.concat([
    $._namespace_identifier,
  ]),

  rules: {
    _top_level_item: ($, original) => choice(
      original,
      $.namespace_definition,
      $.using_declaration,
      $.alias_declaration,
      $.static_assert_declaration,
      $.template_declaration,
      $.template_instantiation,
      alias($.constructor_or_destructor_definition, $.function_definition),
      alias($.operator_cast_definition, $.function_definition),
      alias($.operator_cast_declaration, $.declaration),
    ),

    // Types

    decltype: $ => seq(
      'decltype',
      '(',
      $._expression,
      ')',
    ),

    _type_specifier: $ => choice(
      $.struct_specifier,
      $.union_specifier,
      $.enum_specifier,
      $.class_specifier,
      $.sized_type_specifier,
      $.primitive_type,
      $.template_type,
      $.auto,
      $.dependent_type,
      $.decltype,
      prec.right(choice(
        $.scoped_type_identifier,
        $._type_identifier
      ))
    ),

    type_qualifier: ($, original) => choice(
      original,
      'mutable',
      'constexpr'
    ),

    // When used in a trailing return type, these specifiers can now occur immediately before
    // a compound statement. This introduces a shift/reduce conflict that needs to be resolved
    // with an associativity.
    class_specifier: $ => prec.right(seq(
      'class',
      repeat($._class_attribute),
      choice(
        field('name', $._class_name),
        seq(
          optional(field('name', $._class_name)),
          optional($.virtual_specifier),
          optional($.base_class_clause),
          field('body', $.field_declaration_list)
        )
      )
    )),

    union_specifier: $ => prec.right(seq(
      'union',
      repeat($._class_attribute),
      choice(
        field('name', $._class_name),
        seq(
          optional(field('name', $._class_name)),
          optional($.virtual_specifier),
          optional($.base_class_clause),
          field('body', $.field_declaration_list)
        )
      )
    )),

    struct_specifier: $ => prec.right(seq(
      'struct',
      repeat($._class_attribute),
      choice(
        field('name', $._class_name),
        seq(
          optional(field('name', $._class_name)),
          optional($.virtual_specifier),
          optional($.base_class_clause),
          field('body', $.field_declaration_list)
        )
      )
    )),

    _class_name: $ => prec.right(choice(
      $._type_identifier,
      $.scoped_type_identifier,
      $.template_type
    )),

    virtual_specifier: $ => choice(
      'final', // the only legal value here for classes
      'override' // legal for functions in addition to final, plus permutations.
    ),

    virtual_function_specifier: $ => choice(
      'virtual'
    ),
	
	_class_attribute: $ => prec.right(choice(
      $.alignas_specifier,
	  $.ms_declspec_modifier,
	  $.attribute
    )),
	
	alignas_specifier: $ => seq(
      'alignas',
	  '(',
	  choice($._expression, $._type_specifier, $.type_parameter_pack_expansion),
	  ')',
    ),

    explicit_function_specifier: $ => choice(
      'explicit',
      prec(PREC.CALL, seq(
        'explicit',
        '(',
        $._expression,
        ')'
      ))
    ),

    base_class_clause: $ => seq(
      ':',
      commaSep1(seq(
        optional(choice('public', 'private', 'protected')),
        $._class_name,
        optional('...')
      ))
    ),

    enum_specifier: $ => prec.right(seq(
      'enum',
      optional(choice('class', 'struct')),
      choice(
        seq(
          field('name', $._class_name),
          optional($._enum_base_clause),
          optional(field('body', $.enumerator_list))
        ),
        field('body', $.enumerator_list)
      )
    )),

    _enum_base_clause: $ => prec.right(seq(
      ':',
      field('base', choice($.scoped_type_identifier, $._type_identifier, $.sized_type_specifier))
    )),

    // The `auto` storage class is removed in C++0x in order to allow for the `auto` type.
    storage_class_specifier: ($, original) => choice(
      ...original.members.filter(member => member.value !== 'auto')
    ),

    auto: $ => 'auto',

    dependent_type: $ => prec.dynamic(-1, seq(
      'typename',
      $._type_specifier
    )),

    // Declarations

	_declaration_specifiers_list: $ => choice(
		$.storage_class_specifier,
        $.type_qualifier,
        $.attribute_specifier,
        $.ms_declspec_modifier,
		$.alignas_specifier,
		$.attribute
	),

    _declaration_specifiers: ($, original) => seq(
      repeat($._declaration_specifiers_list),
      field('type', $._type_specifier),
      repeat($._declaration_specifiers_list)
    ),

    template_declaration: $ => seq(
      'template',
      field('parameters', $.template_parameter_list),
      choice(
        $._empty_declaration,
        $.alias_declaration,
        $.declaration,
        $.template_declaration,
        $.function_definition,
        alias($.constructor_or_destructor_declaration, $.declaration),
        alias($.constructor_or_destructor_definition, $.function_definition),
        alias($.operator_cast_declaration, $.declaration),
        alias($.operator_cast_definition, $.function_definition),
      )
    ),

    template_instantiation: $ => seq(
      'template',
      optional($._declaration_specifiers),
      field('declarator', $._declarator),
      ';'
    ),

    template_parameter_list: $ => seq(
      '<',
      commaSep(choice(
        $.parameter_declaration,
        $.optional_parameter_declaration,
        $.type_parameter_declaration,
        $.variadic_parameter_declaration,
        $.variadic_type_parameter_declaration,
        $.optional_type_parameter_declaration,
        $.template_template_parameter_declaration
      )),
      alias(token(prec(1, '>')), '>')
    ),

    type_parameter_declaration: $ => prec(1, seq(
      choice('typename', 'class'),
      optional($._type_identifier)
    )),

    variadic_type_parameter_declaration: $ => prec(1, seq(
      choice('typename', 'class'),
      '...',
      optional($._type_identifier)
    )),

    optional_type_parameter_declaration: $ => seq(
      choice('typename', 'class'),
      optional(field('name', $._type_identifier)),
      '=',
      field('default_type', $._type_specifier)
    ),

    template_template_parameter_declaration: $ => seq(
      'template',
      field('parameters', $.template_parameter_list),
      choice(
        $.type_parameter_declaration,
        $.variadic_type_parameter_declaration,
        $.optional_type_parameter_declaration
      )
    ),

    parameter_list: $ => seq(
      '(',
      commaSep(choice(
        $.parameter_declaration,
        $.optional_parameter_declaration,
        $.variadic_parameter_declaration,
        '...'
      )),
      ')'
    ),

    optional_parameter_declaration: $ => seq(
      $._declaration_specifiers,
      field('declarator', optional($._declarator)),
      '=',
      field('default_value', $._expression)
    ),

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

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

    variadic_reference_declarator: $ => seq(
      choice('&&', '&'),
      $.variadic_declarator
    ),

    init_declarator: ($, original) => choice(
      original,
      seq(
        field('declarator', $._declarator),
        field('value', choice(
          $.argument_list,
          $.initializer_list
        ))
      )
    ),

    operator_cast: $ => prec(1, seq(
      optional(seq(
        field('namespace', optional(choice(
          $._namespace_identifier,
          $.template_type,
          $.scoped_namespace_identifier
        ))),
        '::',
      )),
      'operator',
      $._declaration_specifiers,
      field('declarator', $._abstract_declarator),
    )),

    // Avoid ambiguity between compound statement and initializer list in a construct like:
    //   A b {};
    compound_statement: ($, original) => prec(-1, original),

    field_initializer_list: $ => seq(
      ':',
      commaSep1($.field_initializer)
    ),

    field_initializer: $ => prec(1, seq(
      choice($._field_identifier, $.scoped_field_identifier),
      choice($.initializer_list, $.argument_list),
      optional('...')
    )),

    _field_declaration_list_item: ($, original) => seq(choice(
      original,
      $.template_declaration,
      alias($.inline_method_definition, $.function_definition),
      alias($.constructor_or_destructor_definition, $.function_definition),
      alias($.constructor_or_destructor_declaration, $.declaration),
      alias($.operator_cast_definition, $.function_definition),
      alias($.operator_cast_declaration, $.declaration),
      $.friend_declaration,
      $.access_specifier,
      $.alias_declaration,
      $.using_declaration,
      $.type_definition,
      $.static_assert_declaration
    ), repeat(';')),

    field_declaration: $ => seq(
	  optional(seq(repeat($._declaration_specifiers_list), $.virtual_function_specifier)),
      $._declaration_specifiers,
      commaSep(field('declarator', seq($._field_declarator, optional($.attribute_specifier)))),
      optional(choice(
		seq($.bitfield_clause, optional($.attribute_specifier)),
        field('default_value', $.initializer_list),
        seq('=', field('default_value', choice($._expression, $.initializer_list)))
      )),
      ';'
    ),

    inline_method_definition: $ => seq(
      optional(seq(repeat($._declaration_specifiers_list), $.virtual_function_specifier)),
      $._declaration_specifiers,
      field('declarator', $._field_declarator),
      choice(
        field('body', $.compound_statement), 
        $.default_method_clause,
        $.delete_method_clause
      )
    ),

    _constructor_specifiers: $ => repeat1(
      prec.right(choice(
        $._declaration_specifiers_list,
        $.virtual_function_specifier,
        $.explicit_function_specifier
      ))
    ),

    operator_cast_definition: $ => seq(
      optional($._constructor_specifiers),
      field('declarator', $.operator_cast),
      choice(
        field('body', $.compound_statement), 
        $.default_method_clause,
        $.delete_method_clause
      )
    ),

    operator_cast_declaration: $ => prec(1, seq(
      optional($._constructor_specifiers),
      field('declarator', $.operator_cast),
      optional(seq('=', field('default_value', $._expression))),
      ';'
    )),

    constructor_or_destructor_definition: $ => seq(
      optional($._constructor_specifiers),
      field('declarator', $.function_declarator),
      optional($.field_initializer_list),
      choice(
        field('body', $.compound_statement),
        $.default_method_clause,
        $.delete_method_clause
      )
    ),

    constructor_or_destructor_declaration: $ => seq(
      optional($._constructor_specifiers),
      field('declarator', $.function_declarator),
      ';'
    ),

    default_method_clause: $ => seq('=', 'default', ';'),
    delete_method_clause: $ => seq('=', 'delete', ';'),

    friend_declaration: $ => seq(
      'friend',
      choice(
        $.declaration,
        $.function_definition,
        seq(
          optional(choice(
            'class',
            'struct',
            'union'
          )),
          $._class_name, ';'
        )
      )
    ),

    access_specifier: $ => seq(
      choice(
        'public',
        'private',
        'protected'
      ),
      ':'
    ),

    _declarator: ($, original) => choice(
      original,
      $.reference_declarator,
      $.scoped_identifier,
      $.template_function,
      $.operator_name,
      $.destructor_name,
      $.structured_binding_declarator
    ),

    _field_declarator: ($, original) => choice(
      original,
      alias($.reference_field_declarator, $.reference_declarator),
      $.template_method,
      $.operator_name
    ),

    _abstract_declarator: ($, original) => choice(
      original,
      $.abstract_reference_declarator
    ),

    reference_declarator: $ => prec.dynamic(1, prec.right(seq(choice('&', '&&'), $._declarator))),
    reference_field_declarator: $ => prec.dynamic(1, prec.right(seq(choice('&', '&&'), $._field_declarator))),
    abstract_reference_declarator: $ => prec.right(seq(choice('&', '&&'), optional($._abstract_declarator))),

    structured_binding_declarator: $ => prec.dynamic(PREC.STRUCTURED_BINDING, seq(
      '[', commaSep1($.identifier), ']'
    )),

    function_declarator: ($, original) => prec.dynamic(1, seq(
      original,
      repeat(choice(
        $.type_qualifier,
        $.virtual_specifier,
        $.noexcept,
        $.throw_specifier,
        $.trailing_return_type
      ))
    )),

    function_field_declarator: ($, original) => prec.dynamic(1, seq(
      original,
      repeat(choice(
        $.type_qualifier,
        $.virtual_specifier,
        $.noexcept,
        $.throw_specifier,
        $.trailing_return_type
      ))
    )),

    abstract_function_declarator: ($, original) => prec.right(seq(
      original,
      repeat(choice(
        $.type_qualifier,
        $.noexcept,
        $.throw_specifier
      )),
      optional($.trailing_return_type)
    )),

    trailing_return_type: $ => prec.right(seq(
      '->',
      optional($.type_qualifier),
      $._type_specifier,
      optional($._abstract_declarator)
    )),

    noexcept: $ => prec.right(seq(
      'noexcept',
      optional(
        seq(
          '(',
          optional($._expression),
          ')',
        ),
      ),
    )),

    throw_specifier: $ => seq(
      'throw',
      seq(
        '(',
        commaSep($.type_descriptor),
        ')',
      )
    ),

    template_type: $ => seq(
      field('name', choice($._type_identifier, $.scoped_type_identifier)),
      field('arguments', $.template_argument_list)
    ),

    template_method: $ => seq(
      field('name', choice($._field_identifier, $.scoped_field_identifier)),
      field('arguments', $.template_argument_list)
    ),

    template_function: $ => seq(
      field('name', choice($.identifier, $.scoped_identifier)),
      field('arguments', $.template_argument_list)
    ),

    template_argument_list: $ => seq(
      '<',
      commaSep(choice(
        prec.dynamic(3, $.type_descriptor),
        prec.dynamic(2, alias($.type_parameter_pack_expansion, $.parameter_pack_expansion)),
        prec.dynamic(1, $._expression)
      )),
      alias(token(prec(1, '>')), '>')
    ),

    namespace_definition: $ => seq(
      'namespace',
      field('name', optional(
        choice(
          $.identifier,
          $.namespace_definition_name,
        ))),
      field('body', $.declaration_list)
    ),
  
    namespace_definition_name: $ => seq(
      choice(
        $.identifier,
        $.namespace_definition_name, 
      ),
      '::',
      optional('inline'),
      $.identifier,
    ),

    using_declaration: $ => seq(
      'using',
      optional('namespace'),
      choice(
        $.identifier,
        $.scoped_identifier
      ),
      ';'
    ),

    alias_declaration: $ => seq(
      'using',
      field('name', $._type_identifier),
      '=',
      field('type', $.type_descriptor),
      ';'
    ),

    static_assert_declaration: $ => seq(
      'static_assert',
      '(',
      field('condition', $._expression),
      optional(seq(
        ',',
        field('message', choice(
          $.string_literal,
          $.raw_string_literal,
          $.concatenated_string,
        ))
      )),
      ')',
      ';'
    ),

    // Statements

    _statement: ($, original) => choice(
      original,
      $.for_range_loop,
      $.try_statement,
      $.throw_statement,
    ),

    switch_statement: $ => seq(
      'switch',
      field('condition', $.condition_clause),
      field('body', $.compound_statement)
    ),

    while_statement: $ => seq(
      'while',
      field('condition', $.condition_clause),
      field('body', $._statement)
    ),

    if_statement: $ => prec.right(seq(
      'if',
      optional('constexpr'),
      field('condition', $.condition_clause),
      field('consequence', $._statement),
      optional(seq(
        'else',
        field('alternative', $._statement)
      ))
    )),

    condition_clause: $ => seq(
      '(',
      choice(
        seq(
          field('initializer', optional(choice(
            $.declaration,
            $.expression_statement
          ))),
          field('value', choice(
            $._expression,
            $.comma_expression
          )),
        ),
        field('value', alias($.condition_declaration, $.declaration))
      ),
      ')',
    ),

    condition_declaration: $ => seq(
      $._declaration_specifiers,
      field('declarator', $._declarator),
      choice(
        seq(
          '=',
          field('value', $._expression),
        ),
        field('value', $.initializer_list),
      )
    ),

    for_range_loop: $ => seq(
      'for',
      '(',
      $._declaration_specifiers,
      field('declarator', $._declarator),
      ':',
      field('right', choice(
        $._expression,
        $.initializer_list,
      )),
      ')',
      field('body', $._statement)
    ),

    return_statement: ($, original) => choice(
      original,
      seq('return', $.initializer_list, ';')
    ),

    throw_statement: $ => seq(
      'throw',
      optional($._expression),
      ';'
    ),

    try_statement: $ => seq(
      'try',
      field('body', $.compound_statement),
      repeat1($.catch_clause)
    ),

    catch_clause: $ => seq(
      'catch',
      field('parameters', $.parameter_list),
      field('body', $.compound_statement)
    ),

    attribute: $ => seq(
      '[[',
      commaSep1($._expression),
      ']]'
    ),

    // Expressions

    _expression: ($, original) => choice(
      original,
      $.template_function,
      $.scoped_identifier,
      $.new_expression,
      $.delete_expression,
      $.lambda_expression,
      $.parameter_pack_expansion,
      $.nullptr,
      $.this,
      $.raw_string_literal,
      $.alignof_expression
    ),

    call_expression: ($, original) => choice(original, seq(
      field('function', $.primitive_type),
      field('arguments', $.argument_list)
    )),

    new_expression: $ => prec.right(PREC.NEW, seq(
      optional('::'),
      'new',
      field('placement', optional($.argument_list)),
      field('type', $._type_specifier),
      field('declarator', optional($.new_declarator)),
      field('arguments', optional(choice(
        $.argument_list,
        $.initializer_list
      )))
    )),

    new_declarator: $ => prec.right(seq(
      '[',
      field('length', $._expression),
      ']',
      optional($.new_declarator)
    )),

    delete_expression: $ => seq(
      optional('::'),
      'delete',
      optional(seq('[', ']')),
      $._expression
    ),

    field_expression: ($, original) => choice(
      original,
      seq(
        prec(PREC.FIELD, seq(
          field('argument', $._expression),
          choice('.', '->')
        )),
        field('field', choice(
          $.destructor_name,
          $.template_method
        ))
      )
    ),

    lambda_expression: $ => seq(
      field('captures', $.lambda_capture_specifier),
      optional(field('declarator', $.abstract_function_declarator)),
      field('body', $.compound_statement)
    ),

    lambda_capture_specifier: $ => prec(PREC.LAMBDA, seq(
      '[',
      choice(
        $.lambda_default_capture,
        commaSep($._expression),
        seq(
          $.lambda_default_capture,
          ',', commaSep1($._expression)
        )
      ),
      ']'
    )),

    lambda_default_capture: $ => choice('=', '&'),

    parameter_pack_expansion: $ => prec(-1, seq(
      field('pattern', $._expression),
      '...'
    )),

    type_parameter_pack_expansion: $ => seq(
      field('pattern', $.type_descriptor),
      '...'
    ),

    sizeof_expression: ($, original) => choice(
      original,
      seq(
        'sizeof', '...',
        '(',
        field('value', $.identifier),
        ')'
      ),
    ),
	
	alignof_expression: $ => prec(PREC.SIZEOF, seq(
      'alignof',
      seq('(', field('type', $.type_descriptor), ')')
    )),

    argument_list: $ => seq(
      '(',
      commaSep(choice($._expression, $.initializer_list)),
      ')'
    ),

    destructor_name: $ => prec(1, seq('~', $.identifier)),

    compound_literal_expression: ($, original) => choice(
      original,
      seq(
        field('type', choice(
          $._type_identifier,
          $.template_type,
          $.scoped_type_identifier
        )),
        field('value', $.initializer_list)
      )
    ),

    scoped_field_identifier: $ => prec(1, seq(
      field('namespace', optional(choice(
        $._namespace_identifier,
        $.template_type,
        $.scoped_namespace_identifier
      ))),
      '::',
      field('name', choice(
        $._field_identifier,
        $.operator_name,
        $.destructor_name
      ))
    )),

    scoped_identifier: $ => prec(1, seq(
      field('namespace', optional(choice(
        $._namespace_identifier,
        $.template_type,
        $.scoped_namespace_identifier
      ))),
      '::',
	  optional('template'),
      field('name', choice(
        $.identifier,
        $.operator_name,
        $.destructor_name
      ))
    )),

    scoped_type_identifier: $ => prec(1, seq(
      field('namespace', optional(choice(
        $._namespace_identifier,
        $.template_type,
        $.scoped_namespace_identifier
      ))),
      '::',
	  optional('template'),
      field('name', $._type_identifier)
    )),

    scoped_namespace_identifier: $ => prec(2, seq(
      field('namespace', optional(choice(
        $._namespace_identifier,
        $.template_type,
        $.scoped_namespace_identifier
      ))),
      '::',
      field('name', $._namespace_identifier)
    )),

    _assignment_left_expression: ($, original) => choice(
      original,
      $.scoped_namespace_identifier,
    ),

    operator_name: $ => token(seq(
      'operator',
	  /[\t ]*/,
      choice(
        '+', '-', '*', '/', '%',
        '^', '&', '|', '~',
        '!', '=', '<', '>',
        '+=', '-=', '*=', '/=', '%=', '^=', '&=', '|=',
        '<<', '>>', '>>=', '<<=',
        '==', '!=', '<=', '>=',
        '&&', '||',
        '++', '--',
        ',',
        '->*',
        '->',
        '()', '[]',
        seq(choice('new', 'delete'),  /[\t ]*/, optional('[]')),
      )
    )),

    this: $ => 'this',
    nullptr: $ => 'nullptr',

    concatenated_string: $ => seq(
      choice($.raw_string_literal, $.string_literal),
      repeat1(choice($.raw_string_literal, $.string_literal))
    ),

    _namespace_identifier: $ => alias($.identifier, $.namespace_identifier),
	
	doxygen: $ => token(prec(1, choice(
      seq('///', /(\\(.|\r?\n)|[^\\\n])*/),
	  seq('/**',
        /[^*]*\*+([^/*][^*]*\*+)*/,
        '/'
	  )
    ))),
	
	comment: $ => token(choice(
      seq('//', /(\\(.|\r?\n)|[^\\\n])*/),
      seq(
        '/*',
        /[^*]*\*+([^/*][^*]*\*+)*/,
        '/'
      )
    )),
  }
});

function commaSep(rule) {
  return optional(commaSep1(rule));
}

function commaSep1(rule) {
  return seq(rule, repeat(seq(',', rule)));
}