From: "tenderlovemaking (Aaron Patterson) via ruby-core" <ruby-core@...>
Date: 2024-04-30T21:51:23+00:00
Subject: [ruby-core:117741] [Ruby master Bug#20457] Final `return` is eliminated from the AST

Issue #20457 has been updated by tenderlovemaking (Aaron Patterson).


Eregon (Benoit Daloze) wrote in #note-2:
> I want to add for context that naturally Prism already provides this information (and much more) and has a much better API.
> Nobody should use `RubyVM::AbstractSyntaxTree`, as its documentation pretty much already says.

From what I understand, lrama intends to eventually provide the same AST that Prism does (or a superset).  As you say, people shouldn't use `RubyVM::AbstractSyntaxTree`, but if lrama (basically parse.y) intends on providing the same AST, then I think cases where Prism provides information that lrama doesn't should be considered a bug (and we should track it).

----------------------------------------
Bug #20457: Final `return` is eliminated from the AST
https://bugs.ruby-lang.org/issues/20457#change-108152

* Author: tenderlovemaking (Aaron Patterson)
* Status: Open
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
Given the following code:

```ruby
def foo
  a = 1
  return a
end
```

If you parse this with RubyVM::AbstractSyntaxTree, the AST will be missing the `return` node.  Of course the `return` node isn't necessary for compilation, but would be required for building an LSP for example.

Here's a full program to demonstrate:

```ruby
ast = RubyVM::AbstractSyntaxTree.parse DATA.read
pp ast

# Output is like this:
#
# (SCOPE@1:0-4:3
# tbl: []
# args: nil
# body:
#   (DEFN@1:0-4:3
#    mid: :foo
#    body:
#      (SCOPE@1:0-4:3
#       tbl: [:a]
#       args: (ARGS@1:7-1:7 pre_num: 0 pre_init: nil opt: nil first_post: nil post_num: 0 post_init: nil rest: nil kw: nil kwrest: nil block: nil)
#       body: (BLOCK@2:2-3:10 (LASGN@2:2-2:7 :a (INTEGER@2:6-2:7 1)) (LVAR@3:9-3:10 :a)))))

__END__
def foo
  a = 1
  return a
end
```

Btw, I'm happy to write failing tests for this type of stuff I'm just not sure where to put it! :)



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