[ruby-core:103890] [Ruby master Bug#17869] `Ripper.sexp`'s S-expression when using endless method definition

Issue #17869 has been reported by koic (Koichi ITO).

----------------------------------------
Bug #17869: `Ripper.sexp`'s S-expression when using endless method definition
https://bugs.ruby-lang.org/issues/17869

* Author: koic (Koichi ITO)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.0dev (2021-05-17T10:51:51Z master ee611341c9) [x86_64-darwin19]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
## Summary

The result of `Ripper.sexp` differs between normal method definition and endless method definition.

### Normal method definition

```ruby
% ruby -rripper -e "pp Ripper.sexp('def m(a) foo end')"
[:program,
 [[:def,
   [:@ident, "m", [1, 4]],
   [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil, nil, nil, nil]],
   [:bodystmt, [[:vcall, [:@ident, "foo", [1, 9]]]], nil, nil, nil]]]]
```

### Endless method definition

```ruby
% ruby -rripper -e "pp Ripper.sexp('def m(a) = foo')"
[:program,
 [[:def,
   [:@ident, "m", [1, 4]],
   [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil, nil, nil, nil]],
   [:vcall, [:@ident, "foo", [1, 11]]]]]]
```

Endless method definition does not have `bodystmt`. Is it an expected behavior that these results differ?

This is reproduced in Ruby 3.1.0-dev and Ruby 3.0.1.

## Additional Information

Their results are the same when using `RubyVM::AbstractSyntaxTree.parse` and `ruby --dump=p`.

### `RubyVM::AbstractSyntaxTree.parse`

The following returns the same AST.

```console
% ruby -e "pp RubyVM::AbstractSyntaxTree.parse('def m(a) foo end')"
(SCOPE@1:0-1:16
 tbl: []
 args: nil
 body:
   (DEFN@1:0-1:16
    mid: :m
    body:
      (SCOPE@1:0-1:16
       tbl: [:a]
       args:
         (ARGS@1:6-1:7
          pre_num: 1
          pre_init: nil
          opt: nil
          first_post: nil
          post_num: 0
          post_init: nil
          rest: nil
          kw: nil
          kwrest: nil
          block: nil)
       body: (VCALL@1:9-1:12 :foo))))

% ruby -e "pp RubyVM::AbstractSyntaxTree.parse('def m(a) = foo')"
(SCOPE@1:0-1:14
 tbl: []
 args: nil
 body:
   (DEFN@1:0-1:14
    mid: :m
    body:
      (SCOPE@1:0-1:14
       tbl: [:a]
       args:
         (ARGS@1:6-1:7
          pre_num: 1
          pre_init: nil
          opt: nil
          first_post: nil
          post_num: 0
          post_init: nil
          rest: nil
          kw: nil
          kwrest: nil
          block: nil)
       body: (VCALL@1:11-1:14 :foo))))
```

### `ruby --dump=p`

The following returns the same parsetree.

```console
% ruby --dump=p -e 'def m(a) foo end'
###########################################################
## Do NOT use this node dump for any purpose other than #
## debug and research. ompatibility is not guaranteed. ##
###########################################################

# @ NODE_SCOPE (line: 1, location: (1,0)-(1,16))
# +- nd_tbl: (empty)
# +- nd_args:
# | (null node)
# +- nd_body:
# @ NODE_DEFN (line: 1, location: (1,0)-(1,16))*
# +- nd_mid: :m
# +- nd_defn:
# @ NODE_SCOPE (line: 1, location: (1,0)-(1,16))
# +- nd_tbl: :a
# +- nd_args:
# | @ NODE_ARGS (line: 1, location: (1,6)-(1,7))
# | +- nd_ainfo->pre_args_num: 1
# | +- nd_ainfo->pre_init:
# | | (null node)
# | +- nd_ainfo->post_args_num: 0
# | +- nd_ainfo->post_init:
# | | (null node)
# | +- nd_ainfo->first_post_arg: (null)
# | +- nd_ainfo->rest_arg: (null)
# | +- nd_ainfo->block_arg: (null)
# | +- nd_ainfo->opt_args:
# | | (null node)
# | +- nd_ainfo->kw_args:
# | | (null node)
# | +- nd_ainfo->kw_rest_arg:
# | (null node)
# +- nd_body:
# @ NODE_VCALL (line: 1, location: (1,9)-(1,12))*
# +- nd_mid: :foo

% ruby --dump=p -e 'def m(a) = foo'
###########################################################
## Do NOT use this node dump for any purpose other than  ##
## debug and research.  Compatibility is not guaranteed. ##
###########################################################

# @ NODE_SCOPE (line: 1, location: (1,0)-(1,14))
# +- nd_tbl: (empty)
# +- nd_args:
# |   (null node)
# +- nd_body:
#     @ NODE_DEFN (line: 1, location: (1,0)-(1,14))*
#     +- nd_mid: :m
#     +- nd_defn:
#         @ NODE_SCOPE (line: 1, location: (1,0)-(1,14))
#         +- nd_tbl: :a
#         +- nd_args:
#         |   @ NODE_ARGS (line: 1, location: (1,6)-(1,7))
#         |   +- nd_ainfo->pre_args_num: 1
#         |   +- nd_ainfo->pre_init:
#         |   |   (null node)
#         |   +- nd_ainfo->post_args_num: 0
#         |   +- nd_ainfo->post_init:
#         |   |   (null node)
#         |   +- nd_ainfo->first_post_arg: (null)
#         |   +- nd_ainfo->rest_arg: (null)
#         |   +- nd_ainfo->block_arg: (null)
#         |   +- nd_ainfo->opt_args:
#         |   |   (null node)
#         |   +- nd_ainfo->kw_args:
#         |   |   (null node)
#         |   +- nd_ainfo->kw_rest_arg:
#         |       (null node)
#         +- nd_body:
#             @ NODE_VCALL (line: 1, location: (1,11)-(1,14))
#             +- nd_mid: :foo
```

I noticed the issue because a 3rd party parser builds the same AST.

```ruby
% ruby-parse -e 'def m(a) = foo'
warning: parser/current is loading parser/ruby31, which recognizes
warning: 3.1.0-dev-compliant syntax, but you are running 3.1.0.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
(def :m
  (args
    (arg :a))
  (send nil :foo))

% ruby-parse -e 'def m(a) foo end'
warning: parser/current is loading parser/ruby31, which recognizes
warning: 3.1.0-dev-compliant syntax, but you are running 3.1.0.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
(def :m
  (args
    (arg :a))
  (send nil :foo))
```



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>