[ruby-core:108111] [Ruby master Bug#18396] An unexpected "hash value omission" syntax error when without parentheses call expr follows

Issue #18396 has been updated by jeremyevans0 (Jeremy Evans).


mame (Yusuke Endoh) wrote in #note-6:
> ```diff
> diff --git a/parse.y b/parse.y
> index 0ff3ddbb4e..73deae8627 100644
> --- a/parse.y
> +++ b/parse.y
> @@ -9291,6 +9291,9 @@ parser_yylex(struct parser_params *p)
>         c = (IS_lex_state(EXPR_BEG|EXPR_CLASS|EXPR_FNAME|EXPR_DOT) &&
>              !IS_lex_state(EXPR_LABELED));
>         if (c || IS_lex_state_all(EXPR_ARG|EXPR_LABELED)) {
> +            if (IS_lex_state_all(EXPR_ARG|EXPR_LABELED) && !p->lex.paren_nest) {
> +               rb_warn0("keyword label followed by newline without parentheses will be changed in Ruby 3.3");
> +            }
>              if (!fallthru) {
>                  dispatch_scan_event(p, tIGNORED_NL);
>              }
> ```

I did some testing with this and found it that warns for method definitions with required keywords, such as:

```ruby
def obj.foo a:
  a
end
```

Since the behavior for that wouldn't change, I don't think this warning will work. We'll have to figure out a way to issue the warning only in the method call case and not in the method definition case.  I guess that means we'll have to move the warning from the lexer to the parser.

----------------------------------------
Bug #18396: An unexpected "hash value omission" syntax error when without parentheses call expr follows
https://bugs.ruby-lang.org/issues/18396#change-97076

* Author: koic (Koichi ITO)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.0dev (2021-12-07T23:18:11Z master 4a3e7984bf) [x86_64-darwin19]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
## Summary

I encountered an unexpected "hash value omission" syntax error when parentheses call expression follows:

```ruby
% cat example.rb
foo key:
foo arg
```

```console
% ruby -cv /tmp/b.rb
ruby 3.1.0dev (2021-12-07T23:18:11Z master 4a3e7984bf) [x86_64-darwin19]
example.rb:2: syntax error, unexpected local variable or method, expecting `do' or '{' or '('
foo arg
```

## Additional Information

The following is a traditional usage.

```ruby
# No errors.
foo key: key
foo arg
```

A syntax error is unexpectedly raised when hash value omission argument without parentheses is followed by a method call without parentheses.

```ruby
# No errors is expected, but syntax error is raised.
foo key:
foo arg
```

No error occurs if any of the calls have parentheses.

```ruby
# No errors.
foo(key:)
foo arg
```

```ruby
# Also no errors.
foo key:
foo(arg)
```

No error occurs when calling alone.

```ruby
# No errors.
foo key:
```

I encountered this error while trying to apply hash value omission to  RSpec code of a real-world application (proprietary) .
But this is a new Ruby 3.1 syntax and may not be supported yet. Thank you.



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