Issue #17724 has been updated by jeremyevans0 (Jeremy Evans).


I've added a pull request to directly support instance/class/global variables with the pin operator: https://github.com/ruby/ruby/pull/4502

You could already use all of those variables with the pin expression support by surrounding them in parantheses.  However, since local variables and constants are supported, I think it makes sense to also support instance/class/global variables directly.  I don't think it makes sense to support methods, as doing so is much more complex (arguments/blocks).  Users can use the pin expression support for methods.

My approach to fixing this bug is really introducing a new feature so the bug reported (confusing error message) isn't a problem anymore.  Since this changes the pattern matching syntax, it probably should be approved by both @ktsj and @matz).

----------------------------------------
Bug #17724: Pattern matching error message is confusing
https://bugs.ruby-lang.org/issues/17724#change-91958

* Author: jnchito (Junichi Ito)
* Status: Assigned
* Priority: Normal
* Assignee: ktsj (Kazuki Tsujimoto)
* ruby -v: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin20]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
When I use pattern match with instance variables, I get an error message like "expecting local variable or method"

``` ruby
@n = 1
case 1
in ^@n
  # ...
end
#=> syntax error, unexpected instance variable, expecting local variable or method (SyntaxError)
#   in ^@n
#       ^~
```

However using method is not allowed, either.

``` ruby
def n = 1
case 1
in ^n
  # ...
end
#=> n: no such local variable (SyntaxError)
```

I think the message "expecting local variable or method" is confusing and should be fixed like "expecting local variable."




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