[ruby-core:106543] [Ruby master Bug#18396] An unexpected "hash value omission" syntax error when parentheses call expr follows

Issue #18396 has been reported by koic (Koichi ITO).

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Bug #18396: An unexpected "hash value omission" syntax error when parentheses call expr follows
https://bugs.ruby-lang.org/issues/18396

* 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
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## 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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