class Opal::Rewriters::LogicalOperatorAssignment

def on_defined?(node)

to a static "assignment" string node
`defined?(a &&= 1)`
and
`defined?(a ||= 1)`
Rewrites any or_asgn and and_asgn node like 
def on_defined?(node)
  inner, _ = *node
  if %i[or_asgn and_asgn].include?(inner.type)
    ASSIGNMENT_STRING_NODE
  else
    super(node)
  end
end