class Steep::Subtyping::Constraints::UnsatisfiableConstraint

def initialize(var:, sub_type:, super_type:, result:)
  @var = var
  @sub_type = sub_type
  @super_type = super_type
  @result = result
  super "Unsatisfiable constraint on #{var}: #{sub_type} <: #{super_type}"
end