Bug #17727: Unexpected syntax error when passing hash to **arg with kwarg

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-darwin19]
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN

[colintherobot (Colin Hart)]

Background

Given a method that takes a kwarg and a **positional_arg it throws an unexpected syntax error if you pass it an intact hash. This happens when you call the method, but also when you declare the method if it is multi-line.

def foo(a:, **b)
   [a,b]
end 

Expectation

If you call this method without deconstructing the hash passed to the second argument first I would expect a message indicating that you need to deconstruct the hash first.

Steps to reproduce

Instead it throws a syntax error:

foo(a: '1', {b: 2})
SyntaxError: unexpected ')', expecting =>
foo(a: '1', {b: 2})
                  ^

Passing case when you deconstruct the hash first:

foo(a: '1', **{b: 2})
=> ["1", {:b=>2}]

But wondering if there's something else going on because you get a different error when defining this case on multiple lines. If you're trying to run this in a repl environment it won't even let you complete the method call.

from repl:

foo(
  a: '1',
  {b: 2}
SyntaxError: unexpected '\n', expecting =>

passing case:

foo(
  a: '1',  
  **{b:1}
)  
=> ["1", {:b=>1}]

Attached is a ruby script to reproduce the above cases.

[colintherobot (Colin Hart)]

• Description updated (diff)

Typos/readability

[colintherobot (Colin Hart)]

• Description updated (diff)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Rejected

Ruby syntax does not allow positional arguments after keyword arguments. a: '1' is a keyword argument and {b: 1} is a positional argument (**{b: 1} is a keyword argument, which is why that works). So the syntax errors are expected in this case, not a bug.