Type deduction complains about missing Enumerable#each of unrelated class instance

[Papierkorb]

Hi,

In my code, I do a globbing lookup akin to Dir[*some_usergiven_patterns]. The method this Dir returns is restricted to Array(String) as result type, which works great with being Dir.[] : Array(String) too.

Now, I have a class further down which accepts and stores an Enumerable(String) in an instance variable. This enumerable happens to be generated by said method above. For some reason, the Crystal compiler complains that abstract 'def Enumerable(T)#each(&block)' must be implemented by Dir.

This worked fine in Crystal versions before 0.24.x. Also, the compiler is correct: Dir#each(&blk) is indeed missing, and this should be fixed. Maybe by Dir not being an Enumerable(String) itself. However, the compiler shouldn't complain in any case, as I never pass around an instance of Dir.

Example snippet

class Foo
  def initialize(@f : Enumerable(String))
    @f.each{ } # ERROR
    # f.each{ } # This is fine.
  end

  def bar; @f.each{ }; end # Same ERROR
end

Foo.new(Dir["*"])

Thanks

[bcardiff]

Note that although this occur in Dir, the underlying limitation of the compiler is that the compiler is not enforcing that abstract methods of generic modules are implemented.

The compiler does check for the implementation of abstract method of non generic modules though.

[Papierkorb]

A trip-wire in bindgen just notified me indirectly that this issue is now fixed: Papierkorb/qt5.cr#9 per Papierkorb/bindgen@a3c4376

Thanks