class T::Types::TypeVariable

provides some syntax for the static type checker
Since we do type erasure at runtime, this just validates the variance and

def initialize(variance) 

def initialize(variance)
  case variance
  when Hash then raise ArgumentError.new("Pass bounds using a block. Got: #{variance}")
  when *VALID_VARIANCES then nil
  else
    raise TypeError.new("invalid variance #{variance}")
  end
  @variance = variance
end

def name 

def name
  Untyped.new.name
end

def subtype_of_single?(type) 

def subtype_of_single?(type)
  true
end

def valid?(obj) 

def valid?(obj)
  true
end