gistfile1.txt

module Types
  include Dry::Types.module
  Percentage = Strict::Decimal.constrained(gt: 0, lt: 1)
  Quantity   = Strict::Int.constrained(gt: 0)
end

class Tier < Dry::Types::Struct
  attribute(:quantity,    Types::Quantity)
  attribute(:percentage,  Types::Percentage)
end

form_schema = Dry::Validation.Form do
  key(:quantity).required(Types::Quantity)
  key(:percentage).required(Types::Percentage)
end

gems/dry-types-0.7.1/lib/dry/types/compiler.rb:15:in `visit': undefined method `visit_[:type, "string"]' for #<Dry::Types::Compiler:0x007f7d16496f98 @registry=Dry::Types> (NoMethodError)