class Opal::Nodes::YasgnNode

s(:yasgn, :a, s(:yield, arg1, arg2))
level will always be stmt as its the reason for this to exist
to a temp value to make yield expr into stmt.
special opal yield assign, for ‘a = yield(arg1, arg2)` to assign

def compile 

def compile
  compile_call(s(*yield_args[1..-1]), :stmt)
  wrap "(#{var_name} = ", ")"
end