Multiple return values not parsed correctly

[edkolev]

I've run into the following issue: multiples return values of functions are not always parsed correctly.

For example:

• the return values of func notOk() (int, map[int]int) are parsed incorrectly into

(parameter_list (
  (parameter_declaration ... 
     (array_type ...))    // incorrect - should have two parameter_declaration instead of one,
                          // no array_type expected, map_type expected

To reproduce:

• with Go code

func ok() ([]int, map[int]int) {
    return nil, nil
}

func notOk() (int, map[int]int) {
    return 0, nil
}

• inspect the tree, I use M-x treesit-explore-mode in emacs. The whole tree is pasted below. EDIT: below in a comment is the tree produced by tree-sitter parse ....

• the first function "ok" is as expected - ([]int, map[int]int) is parsed into one parameter_list with two parameter_declaration branches:

result:
   (parameter_list (
    (parameter_declaration
     type: (slice_type [ ] element: (type_identifier)))
    ,
    (parameter_declaration
     type: (map_type map [ key: (type_identifier) ] value: (type_identifier)))
))

• the second function "notOk" is not parsed as expected - (int, map[int]int) is parsed into one parameter_list with one parameter_declaration branches, I expect two parameter_declaration branches.

  result:
   (parameter_list (
    (parameter_declaration name: (identifier) name: , type: (identifier)
     (array_type [ length: (identifier) ] element: (type_identifier)))
    ))

---

Full tree:

(source_file
 (package_clause package (package_identifier))
 \n (comment)
 (function_declaration func name: (identifier)
  parameters: (parameter_list ( ))
  result:
   (parameter_list (
    (parameter_declaration
     type: (slice_type [ ] element: (type_identifier)))
    ,
    (parameter_declaration
     type: (map_type map [ key: (type_identifier) ] value: (type_identifier)))
    ))
  body:
   (block {
    (return_statement return
     (expression_list (nil) , (nil)))
    \n }))
 \n
 (function_declaration func name: (identifier)
  parameters: (parameter_list ( ))
  result:
   (parameter_list (
    (parameter_declaration name: (identifier) name: , type: (identifier)
     (array_type [ length: (identifier) ] element: (type_identifier)))
    ))
  body:
   (block {
    (return_statement return
     (expression_list (int_literal) , (nil)))
    \n }))
 \n)

[edkolev]

Here's a minimalistic example:

1. with input

func notOk() (int, map[int]int) {}

2. output by tree-sitter parse ...

(source_file [0, 0] - [1, 0]
  (function_declaration [0, 0] - [0, 34]
    name: (identifier [0, 5] - [0, 10])
    parameters: (parameter_list [0, 10] - [0, 12])
    result: (parameter_list [0, 13] - [0, 31]
      (parameter_declaration [0, 14] - [0, 30]
        name: (identifier [0, 14] - [0, 17])
        name: (identifier [0, 19] - [0, 22])
        type: (array_type [0, 22] - [0, 30]
          length: (identifier [0, 23] - [0, 26])
          element: (type_identifier [0, 27] - [0, 30]))))
    body: (block [0, 32] - [0, 34])))

3. you can see the "bad" array_type in the output

Attached is a screenshot of log.html