class Opal::Rewriters::ExplicitWriterReturn

def on_masgn(node)

And this AST rewriter skips this node.

s(:int, 2)))
s(:int, 1),
s(:array,
s(:self), :b=)),
s(:send,
s(:self), :a=),
s(:send,
s(:mlhs,
s(:masgn,
For example, "self.a, self.b = 1, 2" parses to:

Multiple assignment is handled by Opal::Nodes::MassAssignNode 
def on_masgn(node)
  @in_masgn = true
  result = super
  @in_masgn = false
  result
end