Reference (compile-time type is Object+) error on Crystal 1.2.0+

[jwoertink]

I have this code that works fine on Crystal 1.1.1, but on 1.2.0 I get a compile-time error

Showing last frame. Use --error-trace for full trace.

error in line 23
Error: undefined method 'name' for Reference (compile-time type is Object+)

I know there's some weirdness around using Object so generically, so in this case, changing it to Enumerable(Thing) fixes the error. However, my actual app is a bit more complicated of a fix.

class Thing
  property name : String
  
  def initialize(@name : String)
  end
end
 
class Decorator
  include Enumerable(Object)
  
  def initialize(@things : Array(Thing))
  end
  
  def each
  	@things.each do |t|
      yield t
    end
  end
end
 
dec = Decorator.new([Thing.new("foo")])
 
pp dec.find {|t| t.name == "foo" }

I'm ok with closing this out if this is intended, but I wanted to make sure it was at least reported just in case.

[straight-shoota]

I'd definitely say there are some weird things about this.

For example, I don't know how Enumerable(Object) was even working. I'd expected some error such as can't use Object as generic type argument or can't use Object as a Proc argument type. Both should be triggered by Enumerable(Object).

[HertzDevil]

i believe generic modules are allowed to use type arguments that aren't usable as the type of a variable; for example Comparable(Array) is okay, even though a variable cannot have the type Array, because Comparable(T) only uses T in non-block parameter restrictions.

Enumerable(Object) indeed should still be disallowed because of #each(& : T ->). It is by sheer coincidence the code worked before 1.2.0, and methods that return an Array(T) would still break.