Codegen fails if instance var has no type defined

[waj]

Example:

class Foo
  def foo
    @x
  end
end

Foo.new.foo

[asterite]

I tried to write the Lexer and has the same probelm.

I fixed it (didn't commit it) by doing this: when looking up an instance variable for read-access, if it doesn't have a type, assign it the Nil type. I think this can work, but to make it better we should bind it to a fictitious variable that has Nil type, so that when you assign it a value it becomes a union of Nil and that value's type.

What do you think?