Julia - Inserting subtype element to array of supertype

Question

I'm totally new to Julia,

I have the following class hierarchy, when I insert an instance of the subtype NonTerminal into an array that's declared of the supertype GrammarElement, an exception is thrown

 GrammarElement
 |--> Terminal
 |--> Nonterminal

As such

abstract GrammarElement

type Terminal <: GrammarElement
  name::String
end

type NonTerminal <: GrammarElement
  name::String
  rule::Array{GrammarElement,1}

  function NonTerminal(name::String)
     new(name,GrammarElement[])
   end
end

function and_with!(t,e)
  push!(t.rule,e)
end

But when I use the and_with! function the test throws an exception

@testset "Test" begin
  r = NonTerminal("A")
  t=Terminal("B")
  and_with!(r,t)
end

Failing on ( removed lots of garbage in the message )

TestFirst: Error During Test
  Got an exception of type MethodError outside of a @test
  MethodError: Cannot `convert` an object of type Terminal to an object of type GrammarElement
  This may have arisen from a call to the constructor GrammarElement(...)

• Why isn't that conversion possible?
• How can I solve this?
• Is it event useful to declare the parent type?

---

I'm aware that julia is mainly for scientific computing and not creating grammar parsers, but it should do the job and I'm learning it with that project

Answer 1

This seemed to be a problem due to having older compiled code still in the scope (see the comments). The easiest way to handle this is just to restart Julia.