Can't cast symbol to enum in initialize() arg list

[hinrik]

I wanted to replace the fully-qualified enum references in my code with symbols following #6074 being released, but I can't do that everywhere it seems.

enum MyEnum
  One Two
end

# works
foo(:two)

def foo(number : MyEnum = MyEnum::One)
  p number
end

# works
Bar.new(:two)

class Bar
  @number : MyEnum
  def initialize(number : MyEnum = MyEnum::One)
    @number = number
    p @number
  end
end

# works
Baz.new(:two)

class Baz
  def initialize(@number : MyEnum = MyEnum::One)
    p @number
  end
end

# doesn't work: instance variable '@number' of Quux must be MyEnum, not Symbol
Quux.new(:two)

class Quux
  def initialize(@number = MyEnum::One)
    p number
  end
end

# doesn't work: instance variable '@number' of Bla must be MyEnum, not Symbol
Bla.new(:two)

class Bla
  @number : MyEnum
  def initialize(number = MyEnum::One)
    @number = number
    p @number
  end
end

Can this be made to work?

[asterite]

Right, the rule is: if there's an enum type restriction, you can pass a symbol. Going from there to "if there's an argument with a default value, and that argument gets assigned to an instance variable, and that instance variable has an enum type, then..." is a bit of a stretch, and it's way harder to implement and understand. Please let's not go this route.

It's simpler to add the type restrictions. It takes less time than writing a whole github issue ;-)

[hinrik]

I see. I thought a default value also imposed a type restriction on the argument.

[asterite]

Not necessarily. A default value's type could be a subset of the type. For example the default value could be MyEnum::One and the type could be MyEnum | String. Then we'd need to somehow record that the type restriction is a superset of MyEnum, because of the default value, but that will make things super complex to implement, really. I'd try to avoid this route.

[hinrik]

Makes sense.

[asterite]

By the way, you can also write:

def initialize(number : MyEnum = :one)
end

which is more or less the same as typing:

def initialize(number = MyEnum::One)
end

(if the problem you are having is having to type a lot)