From 79b81722d8cfe3c2c2fa16bbc8643e8243dfa015 Mon Sep 17 00:00:00 2001
From: Alasdair Armstrong
Date: Fri, 21 Jul 2017 17:31:08 +0100
Subject: Add a prove builtin that allows testing flow typing

For example:

default Order dec

val bit[64] -> unit effect pure test64

val cast forall 'n, 'n = 32 | 'n = 64. bit['n] -> unit effect pure test

function forall 'n. unit test addr =
{
  _prove(constraint('n != 16));
  assert(constraint('n = 64), "64-bit mode");
  _prove(constraint('n = 64));
  test64(addr);
}

This doesn't affect the AST at all as _prove is just a ordinary function
that the typechecker treats specially.
---
 src/type_check_new.ml | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'src')

diff --git a/src/type_check_new.ml b/src/type_check_new.ml
index f8845311..f3374fea 100644
--- a/src/type_check_new.ml
+++ b/src/type_check_new.ml
@@ -1626,6 +1626,10 @@ let rec check_exp env (E_aux (exp_aux, (l, ())) as exp : unit exp) (Typ_aux (typ
      end
   | E_app_infix (x, op, y), _ when List.length (Env.get_overloads (deinfix op) env) > 0 ->
      check_exp env (E_aux (E_app (deinfix op, [x; y]), (l, ()))) typ
+  | E_app (f, [E_aux (E_constraint nc, _)]), _ when Id.compare f (mk_id "_prove") = 0 ->
+     if prove env nc
+     then annot_exp (E_lit (L_aux (L_unit, Parse_ast.Unknown))) unit_typ
+     else typ_error l ("Cannot prove " ^ string_of_n_constraint nc)
   | E_app (f, xs), _ when List.length (Env.get_overloads f env) > 0 ->
      let rec try_overload = function
        | [] -> typ_error l ("No valid overloading for " ^ string_of_exp exp)
-- 
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