Custom type for from_hash

[ksss]

This is an experimental PR for review.

You can make custom class for from_hash method.

Example.

class TypeStruct
  class PresentArrayOf < ArrayOf
    PresentError = Class.new(StandardError)
    def ===(ary)
      return false unless ary.empty?.!
      super
    end

    def try_convert(key, value, errors)
      raise PresentError, "array must not be empty" unless 0 < value.length
      super
    end
  end
end

Foo = TypeStruct.new(
  foo: TypeStruct::PresentArrayOf.new(String)
)

Foo.from_hash({foo: []})
#=> TypeStruct::PresentArrayOf::PresentError: must not be empty

Foo.from_hash({foo: [1]})
#=> TypeStruct::MultiTypeError
#=> TypeStruct#foo expect String got 1

Foo.from_hash({foo: ["bar"]})
#=> #<Foo foo=["bar"]>

[ksss]

current issues

• I don't like try_convert
• Not simple