Represents a rank-1 polymorphic type scheme:

$$ \forall \alpha_1\dots\alpha_n.\, \tau $$

The quantified variables in vars are type variable references which appear inside the body type and are universally quantified at the outermost level (prenex form).

At each use site, schemes are instantiated into fresh monotypes via instantiate/1, which replaces every quantified variable with a fresh reference. This is the mechanism that allows polymorphic constants like $=^\alpha$ (with scheme $\forall\alpha.\,\alpha\to\alpha\to o$) to be used at different types within the same formula.

Monotypes can be lifted into trivial schemes (with empty vars) using mono/1.

Example

iex> alpha = make_ref()
iex> scheme = TypeScheme.new([alpha], Type.new(alpha, alpha))
iex> match?(%TypeScheme{vars: [^alpha]}, scheme)
true