constraints.fs

type ErrorMessage = Lazy<string>

type Constraint = Equal of TyExpr * TyExpr * ErrorMessage
                | And of Constraint * Constraint
                | Trivial

let (=~=) q1 q2 err = Equal (q1, q2, err)
let (&&&) c1 c2 = And (c1, c2)

let rec conjoinConstraints cc =
    match cc with
    | [] -> Trivial
    | [c] -> c
    | c::cs -> c &&& (conjoinConstraints cs)