improve switch match

[aspeddro]

This PR is a proposal to improve AST to switch_match

Currently, the exposed nodes in the tree are few. By exposing more nodes I can get better features like a better indentation.

Example:

switch n {
| 1 | 2 => Ok
| _ => Failed
}

Before:

(source_file [0, 0] - [5, 0]
  (expression_statement [0, 0] - [3, 1]
    (switch_expression [0, 0] - [3, 1]
      (value_identifier [0, 7] - [0, 8])
      (switch_match [1, 0] - [1, 13]
        (number [1, 2] - [1, 3])
        (number [1, 6] - [1, 7])
        (expression_statement [1, 11] - [1, 13]
          (variant [1, 11] - [1, 13]
            (variant_identifier [1, 11] - [1, 13]))))
      (switch_match [2, 0] - [2, 13]
        (value_identifier [2, 2] - [2, 3])
        (expression_statement [2, 7] - [2, 13]
          (variant [2, 7] - [2, 13]
            (variant_identifier [2, 7] - [2, 13])))))))

After:

(source_file [0, 0] - [5, 0]
  (expression_statement [0, 0] - [3, 1]
    (switch_expression [0, 0] - [3, 1]
      (value_identifier [0, 7] - [0, 8])
      (switch_match [1, 0] - [1, 13]
        pattern: (or_pattern [1, 2] - [1, 7]
          (number [1, 2] - [1, 3])
          (number [1, 6] - [1, 7]))
        body: (sequence_expression [1, 11] - [1, 13]
          (expression_statement [1, 11] - [1, 13]
            (variant [1, 11] - [1, 13]
              (variant_identifier [1, 11] - [1, 13])))))
      (switch_match [2, 0] - [2, 13]
        pattern: (value_identifier [2, 2] - [2, 3])
        body: (sequence_expression [2, 7] - [2, 13]
          (expression_statement [2, 7] - [2, 13]
            (variant [2, 7] - [2, 13]
              (variant_identifier [2, 7] - [2, 13]))))))))

Changes on grammar:

• Add or_pattern, range_pattern and exception_pattern
• Expose parenthesized_pattern
• Add two fields for swtich_match: pattern and body
• Remove the following rules: _switch_pattern, _switch_exception_pattern, _parenthesized_switch_pattern, _switch_value_pattern
• Rename rule switch_pattern_condition to guard

[aspeddro]

This match case is not valid, see Playground

The if or when condition cannot occur inside parenthesized_pattern.

[aspeddro]

This alias is so that the switch_match body has only one field.

[nkrkv]

Nice! Many thanks