Array of Union-type of Class.class and Struct.class

Question

I'm trying to get a list of classes of other classes and structs. I currently have the following code (reduced to minimum)

struct Foo
end

class Bar
end

alias Baz = Foo.class | Bar.class

types = [
  Foo, Bar, Foo, Foo, Bar, Baz
] of Baz

This gives me the following error:

Error in ./test.cr:9: instantiating 'Array(Bar:Class | Foo:Class):Class#build(Int32)'

types = [
        ^

in ./test.cr:9: instantiating 'Array(Bar:Class | Foo:Class):Class#build(Int32)'

types = [
        ^

in ./test.cr:9: no overload matches 'Pointer(Bar:Class | Foo:Class)#[]=' with types Int32, (Bar:Class | Foo:Class):Class
Overloads are:
 - Pointer(T)#[]=(offset, value : T)

types = [
        ^

I need this to perform type-checking on values generated at runtime and of an unknown type. The types inside the array are known at compile-time. The types against which I need to compare them are not. Small example (pseudocode)

types = [TString, TFunc] # struct, class
arg_0 = arguments[i]
arg_type = types[i]
if arg_0.is_a? arg_type
  # passed
else
  # failed
end

This code is being generated in a macro. Is this possible? Am I missing something?

Thanks in advance

Answer 1

You are putting Baz inside the array, which is neither Foo nor Bar, it's a union type class. If you remove Baz from the array then it works fine.