[ruby-core:101475] [Ruby master Bug#17398] SyntaxError in endless method

[ruby-core:101475] [Ruby master Bug#17398] SyntaxError in endless method

[zverok.offline]

Issue #17398 has been reported by zverok (Victor Shepelev).

----------------------------------------
Bug #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:101482] [Ruby master Bug#17398] SyntaxError in endless method

[mame]

Issue #17398 has been updated by mame (Yusuke Endoh).


The body of an endless method must be an expression (called "arg" in the syntax rules of parse.y). `puts("bar")` is an expression, but `puts "bar"` is a statement (called "command" in the syntax rules).

I think it could be a bit confusing, but I have no idea whether we can/should allow a statement as a body of an endless method.

----------------------------------------
Bug #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-89261

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:101495] [Ruby master Bug#17398] SyntaxError in endless method

[zverok.offline]

Issue #17398 has been updated by zverok (Victor Shepelev).


@mame Hmm, haven't thought about it from this perspective... Can you please explain a bit? As far as I can see, in, say, assignment context it behaves like an expression:

```ruby
result = puts 'foo'
# prints "foo", result = nil
```
I am just trying to describe the behavior in full for the next installment of my [changelog](https://rubyreferences.github.io/rubychanges/) and this aspect is quite confusing for me... Though, it is not endless-method specific, as far as I can see:

```ruby
y = sin x # OK
y = 1 + sin x
#           ^ unexpected local variable or method, expecting `do' or '{' or '('
```
What's the "rule of thumb" to understand this better?

----------------------------------------
Bug #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-89275

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:101496] [Ruby master Bug#17398] SyntaxError in endless method

[eregontp]

Issue #17398 has been updated by Eregon (Benoit Daloze).


Conceptually, according to the typical definition in computer science, both `puts("bar")` and `puts "bar"` are expressions (i.e., they return a value, and if it was some other method than `puts` it would also not always be `nil`).
It might be slightly less clear for e.g. `a = 42` (it's still an expression, it still returns a value), but I think `puts "bar"` is clear that it should be the same as `puts("bar")`, except for precedence.

So it's probably going to be very difficult to explain the actual condition, other than showing specific examples.

----------------------------------------
Bug #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-89276

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:101498] [Ruby master Bug#17398] SyntaxError in endless method

[halostatue]

Issue #17398 has been updated by austin (Austin Ziegler).


Eregon (Benoit Daloze) wrote in #note-3:
> So it's probably going to be very difficult to explain the actual condition, other than showing specific examples.

Endless methods definitions don’t support poetry mode?

----------------------------------------
Bug #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-89278

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:101503] [Ruby master Bug#17398] SyntaxError in endless method

[mame]

Issue #17398 has been updated by mame (Yusuke Endoh).


The following patch allows `def foo() = puts "bar"`. It brings no parser conflict.

https://gist.github.com/mame/0773bf3938e046e2b608de5fb2a826c8

However, it is not perfect. `private def foo() = puts "foo"` does not parse.
`private var = puts "bar"` is not allowed neither, so I have no idea how to allow this.

----------------------------------------
Bug #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-89283

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:103470] [Ruby master Feature#17398] SyntaxError in endless method

[matz]

Issue #17398 has been updated by matz (Yukihiro Matsumoto).

Backport deleted (2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN)
Tracker changed from Bug to Feature

Pros
* More intuitive / consistent / natural
Cons
* Duplicated syntax rules
* Even more complex syntax

If I were young, I would add @mame's patch. I did similar decisions many times in the past. But Ruby has been mature and complex, I now feel reluctant. Let us consider this idea for a while.

Matz.


----------------------------------------
Feature #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-91566

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.



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

[ruby-core:103510] [Ruby master Feature#17398] SyntaxError in endless method

[mame]

Issue #17398 has been updated by mame (Yusuke Endoh).

File allow-command-style-endless-method-def.patch added

I'm attaching an updated patch with a test.

----------------------------------------
Feature #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-91609

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.

---Files--------------------------------
allow-command-style-endless-method-def.patch (3.44 KB)


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

[ruby-core:103795] [Ruby master Feature#17398] SyntaxError in endless method

[matz]

Issue #17398 has been updated by matz (Yukihiro Matsumoto).


I have considered this issue for a while and concluded it should be merged to be consistent with the assignment statement.

Matz.


----------------------------------------
Feature #17398: SyntaxError in endless method
https://bugs.ruby-lang.org/issues/17398#change-91910

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
----------------------------------------
This works:
```ruby
def foo() = puts("bar")
```

This does not:
```ruby
def foo() = puts "bar"
#                ^ syntax error, unexpected string literal, expecting `do' or '{' or '('
```

Is this intentional or accidental? Not sure how it is reasoned.

---Files--------------------------------
allow-command-style-endless-method-def.patch (3.44 KB)


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