class RuboCop::Cop::Style::SpaceAfterColon

instead handled by Style/SpaceAroundOperators.
N.B. this cop does not handle spaces after a ternary operator, which are
Checks for colon (:) not followed by some kind of space.

def autocorrect(range) 

def autocorrect(range)
  ->(corrector) { corrector.insert_after(range, ' ') }
end

def followed_by_space?(colon) 

def followed_by_space?(colon)
  colon.source_buffer.source[colon.end_pos] =~ /\s/
end

def on_kwoptarg(node) 

def on_kwoptarg(node)
  # We have no direct reference to the colon source range following an
  # optional keyword argument's name, so must construct one.
  colon = node.loc.name.end.resize(1)
  add_offense(colon, colon) unless followed_by_space?(colon)
end

def on_pair(node) 

def on_pair(node)
  colon = node.loc.operator
  return unless colon.is?(':')
  add_offense(colon, colon) unless followed_by_space?(colon)
end