[ruby-core:123241] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[ruby-core:123241] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[kddnewton (Kevin Newton) via ruby-core]

Issue #21572 has been reported by kddnewton (Kevin Newton).

----------------------------------------
Feature #21572: Make illegal variable in alternation pattern a syntax error
https://bugs.ruby-lang.org/issues/21572

* Author: kddnewton (Kevin Newton)
* Status: Open
----------------------------------------
Currently when you have an illegal variable in an alternation pattern, you get a compile error, but no syntax error.

```ruby
case foo
in {a: } | Array
  "matched: #{a}"
end
```

yields

```
$ ruby -cv test.rb
ruby 3.5.0dev (2025-04-10T10:21:51Z master 756479324f) +PRISM [x86_64-linux]
Syntax OK
```

but

```
$ ruby test.rb
test.rb:2: illegal variable in alternative pattern (a)
test.rb: compile error (SyntaxError)
```

Looking at the compiler, since illegal jumps (like break, next, etc.) are now syntax errors, the only other actual compiler errors are related to builtins. I think this should be a proper syntax error, so that editors and other tools can report on it and users can find it in development sooner.



-- 
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/lists/ruby-core.ml.ruby-lang.org/

[ruby-core:123259] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[Earlopain (Earlopain _) via ruby-core]

Issue #21572 has been updated by Earlopain (Earlopain _).


Thanks for opening this.

It seems just like a normal though, no? I understand that this doesn't deviate from what parse.y does but it is a syntax error and right now consumers of prism simply accept such code. I guess there are tests in ruby/ruby that very specifically assert against this somehow? Other than that, is seems like an implementation detail.

----------------------------------------
Feature #21572: Make illegal variable in alternation pattern a syntax error
https://bugs.ruby-lang.org/issues/21572#change-114625

* Author: kddnewton (Kevin Newton)
* Status: Open
----------------------------------------
Currently when you have an illegal variable in an alternation pattern, you get a compile error, but no syntax error.

```ruby
case foo
in {a: } | Array
  "matched: #{a}"
end
```

yields

```
$ ruby -cv test.rb
ruby 3.5.0dev (2025-04-10T10:21:51Z master 756479324f) +PRISM [x86_64-linux]
Syntax OK
```

but

```
$ ruby test.rb
test.rb:2: illegal variable in alternative pattern (a)
test.rb: compile error (SyntaxError)
```

Looking at the compiler, since illegal jumps (like break, next, etc.) are now syntax errors, the only other actual compiler errors are related to builtins. I think this should be a proper syntax error, so that editors and other tools can report on it and users can find it in development sooner.



-- 
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/lists/ruby-core.ml.ruby-lang.org/

[ruby-core:123283] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[kddnewton (Kevin Newton) via ruby-core]

Issue #21572 has been updated by kddnewton (Kevin Newton).


I agree, but there's precedence here of some things only being detectable at run-time, like illegal `break` usage. I just want to make sure this change goes through the proper channels to make sure everyone is onboard.

----------------------------------------
Feature #21572: Make illegal variable in alternation pattern a syntax error
https://bugs.ruby-lang.org/issues/21572#change-114654

* Author: kddnewton (Kevin Newton)
* Status: Open
----------------------------------------
Currently when you have an illegal variable in an alternation pattern, you get a compile error, but no syntax error.

```ruby
case foo
in {a: } | Array
  "matched: #{a}"
end
```

yields

```
$ ruby -cv test.rb
ruby 3.5.0dev (2025-04-10T10:21:51Z master 756479324f) +PRISM [x86_64-linux]
Syntax OK
```

but

```
$ ruby test.rb
test.rb:2: illegal variable in alternative pattern (a)
test.rb: compile error (SyntaxError)
```

Looking at the compiler, since illegal jumps (like break, next, etc.) are now syntax errors, the only other actual compiler errors are related to builtins. I think this should be a proper syntax error, so that editors and other tools can report on it and users can find it in development sooner.



-- 
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/lists/ruby-core.ml.ruby-lang.org/

[ruby-core:123511] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[ktsj (Kazuki Tsujimoto) via ruby-core]

Issue #21572 has been updated by ktsj (Kazuki Tsujimoto).


I agree with you, @kddnewton.
Your proposal makes sense.

----------------------------------------
Feature #21572: Make illegal variable in alternation pattern a syntax error
https://bugs.ruby-lang.org/issues/21572#change-114884

* Author: kddnewton (Kevin Newton)
* Status: Open
----------------------------------------
Currently when you have an illegal variable in an alternation pattern, you get a compile error, but no syntax error.

```ruby
case foo
in {a: } | Array
  "matched: #{a}"
end
```

yields

```
$ ruby -cv test.rb
ruby 3.5.0dev (2025-04-10T10:21:51Z master 756479324f) +PRISM [x86_64-linux]
Syntax OK
```

but

```
$ ruby test.rb
test.rb:2: illegal variable in alternative pattern (a)
test.rb: compile error (SyntaxError)
```

Looking at the compiler, since illegal jumps (like break, next, etc.) are now syntax errors, the only other actual compiler errors are related to builtins. I think this should be a proper syntax error, so that editors and other tools can report on it and users can find it in development sooner.



-- 
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/lists/ruby-core.ml.ruby-lang.org/

[ruby-core:123524] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[kddnewton (Kevin Newton) via ruby-core]

Issue #21572 has been updated by kddnewton (Kevin Newton).


Thank you @ktsj — I will start working on a patch for Prism.

----------------------------------------
Feature #21572: Make illegal variable in alternation pattern a syntax error
https://bugs.ruby-lang.org/issues/21572#change-114900

* Author: kddnewton (Kevin Newton)
* Status: Open
----------------------------------------
Currently when you have an illegal variable in an alternation pattern, you get a compile error, but no syntax error.

```ruby
case foo
in {a: } | Array
  "matched: #{a}"
end
```

yields

```
$ ruby -cv test.rb
ruby 3.5.0dev (2025-04-10T10:21:51Z master 756479324f) +PRISM [x86_64-linux]
Syntax OK
```

but

```
$ ruby test.rb
test.rb:2: illegal variable in alternative pattern (a)
test.rb: compile error (SyntaxError)
```

Looking at the compiler, since illegal jumps (like break, next, etc.) are now syntax errors, the only other actual compiler errors are related to builtins. I think this should be a proper syntax error, so that editors and other tools can report on it and users can find it in development sooner.



-- 
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/lists/ruby-core.ml.ruby-lang.org/

[ruby-core:123537] [Ruby Feature#21572] Make illegal variable in alternation pattern a syntax error

[nobu (Nobuyoshi Nakada) via ruby-core]

Issue #21572 has been updated by nobu (Nobuyoshi Nakada).


https://github.com/ruby/ruby/pull/14923

----------------------------------------
Feature #21572: Make illegal variable in alternation pattern a syntax error
https://bugs.ruby-lang.org/issues/21572#change-114913

* Author: kddnewton (Kevin Newton)
* Status: Open
----------------------------------------
Currently when you have an illegal variable in an alternation pattern, you get a compile error, but no syntax error.

```ruby
case foo
in {a: } | Array
  "matched: #{a}"
end
```

yields

```
$ ruby -cv test.rb
ruby 3.5.0dev (2025-04-10T10:21:51Z master 756479324f) +PRISM [x86_64-linux]
Syntax OK
```

but

```
$ ruby test.rb
test.rb:2: illegal variable in alternative pattern (a)
test.rb: compile error (SyntaxError)
```

Looking at the compiler, since illegal jumps (like break, next, etc.) are now syntax errors, the only other actual compiler errors are related to builtins. I think this should be a proper syntax error, so that editors and other tools can report on it and users can find it in development sooner.



-- 
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/lists/ruby-core.ml.ruby-lang.org/