From: "zverok (Victor Shepelev) via ruby-core" <ruby-core@...>
Date: 2023-02-01T07:59:54+00:00
Subject: [ruby-core:112165] [Ruby master Bug#19392] Endless method vs and/or

Issue #19392 has been updated by zverok (Victor Shepelev).


@nobu

> It depends on how you define "expressions".
> At least in Ruby's terms, any method definition can be an argument of other method calls.

Thank you, I am well aware of this. (I maintain [Ruby Changelog](https://rubyreferences.github.io/rubychanges/), including [detailed explanations](https://rubyreferences.github.io/rubychanges/3.0.html#improved-method-visibility-declaration) on how and why methods as expressions can be used.)

> To utilize this, def returns the ID since 2.3.

Since [2.1](https://rubyreferences.github.io/rubychanges/evolution.html#methods), actually :)

That's why I didn't say, "method definitions aren't expressions", I said, "method definitions aren't **any** expressions", meaning that while being _expressions_ indeed, they still behave differently in several important aspects from most the other expressions. 

One of those aspects is the creation of its own scope.
Endless methods do it without explicit ending sign (like, `}` or `end`). This makes "where the expression ends" an extremely sensitive question, which, I believe, shouldn't be brushed off easily.

----------------------------------------
Bug #19392: Endless method vs and/or
https://bugs.ruby-lang.org/issues/19392#change-101602

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.7: DONTNEED, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
[Discovered](https://twitter.com/lucianghinda/status/1617783952353406977) by Lucian Ghinda: 

```ruby
def test = puts("foo") and puts("bar")
# prints "bar" immediately
test
# prints "foo"
```

It seems that it is a parser error, right?..
```ruby
RubyVM::AbstractSyntaxTree.parse('def test = puts("foo") and puts("bar")')
#  => 
# (SCOPE@1:0-1:38                                                         
#  tbl: []                                                                
#  args: nil                                                              
#  body:                                                                  
#    (AND@1:0-1:38                                                        
#       (DEFN@1:0-1:22                                                    
#        mid: :test                                                       
#        body:                                                            
#          (SCOPE@1:0-1:22                                                
#           tbl: []                                                       
#           args:                                                         
#             (ARGS@1:0-1:8 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: (FCALL@1:11-1:22 :puts (LIST@1:16-1:21 (STR@1:16-1:21 "foo") nil))))
#       (FCALL@1:27-1:38 :puts (LIST@1:32-1:37 (STR@1:32-1:37 "bar") nil)))) 
```

E.g. it is parsed as 
```ruby
(def test = puts("foo")) and (puts("bar"))
```
...which is hardly intentional or have any practical use. The rightly parsed code in this case _can_ have practical use, like
```ruby
def write(data) = File.write(@filename, data) == data.size or raise "Something went wrong"
```



-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
 ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/