Strange ruby bug: can't put comment after linebreak in method args. Tested in 2.3.2.

1-works_fine.rb

def foo \
  a: 'a',
  # comment here is ok
  b: 'b'

  puts a, b
end

foo(a: 'a', b: 'b') # => a\nb

2-broken.rb

def foo \
  # comment here causes error
  a: 'a',
  b: 'b'

  puts a, b
end

foo(a: 'a', b: 'b')

since \ "escapes" the newline, what ruby sees in 2-broken.rb is:

def foo  # comment here causes error
  a: 'a',
  b: 'b'

  puts a, b
end

and that a: 'a', on the first line of what ruby considers to be the method body is a syntax error (syntax error, unexpected ':')

@apeiros Yep, I understand what you mean. Here's another way to illustrate.

puts "foo"\
"bar"
# stdout => foobar


puts "foo"\
# comment
"bar"
# stdout => foo

It's also consistent with leading period, which "reaches" for exactly previous line, and doesn't tolerate comments either:

r = 
  "foo"
    .strip
    # comment
    .upcase
# => syntax error, unexpected '.', expecting end-of-input

r =
  "foo"
    .strip \
    # comment
    .upcase

puts r
# stdout => FOO

r =
  "foo"
    .strip \
    # comment
    # comment2
    .upcase
# => syntax error, unexpected '.', expecting end-of-input

But I'm curious why \ or leading period wouldn't gain the extra meaning of expecting next/previous line anywhere, bypassing comments.

I see what you mean. Yeah, makes sense to allow \ to skip comments. Especially since you can't use \ in a comment to further continue.