[ruby/prism] Reject pattern match with unexpected double splat inside array
a => [-2**b] should be SyntaxError
a => [-2**b]
Fixes: https://github.com/ruby/prism/issues/3381
https://github.com/ruby/prism/commit/ae8e83b389
[ruby/prism] Reject pattern match with unexpected double splat inside array
a => [-2**b]
should be SyntaxErrorFixes: https://github.com/ruby/prism/issues/3381
https://github.com/ruby/prism/commit/ae8e83b389