Subst Tree Using Param into Lambda Body

macro constrain*[T](problem: Problem[T], input: untyped): untyped =
    var stmts = newStmtList()

    for i in 0..<input.len:
        let (vars, tree) = parseVars(input[i])

        stmts.add quote do: addConstraint(
            `problem`,
            proc(x: varargs[T]): bool = `tree`,
            `vars`)

    return stmts