From 391e12124b4ee96849b8b5959c2cab824400a384 Mon Sep 17 00:00:00 2001 From: Brian Anderson Date: Sun, 16 Oct 2011 16:19:12 -0700 Subject: Tweak typecheck to enforce covariance on higher-order function arguments --- src/comp/middle/ty.rs | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'src/comp') diff --git a/src/comp/middle/ty.rs b/src/comp/middle/ty.rs index 71521abb538..84532e718e5 100644 --- a/src/comp/middle/ty.rs +++ b/src/comp/middle/ty.rs @@ -2004,8 +2004,11 @@ mod unify { (ures_err(terr_mode_mismatch(expected_input.mode, actual_input.mode))); } else { expected_input.mode }; + // The variance changes (flips basically) when descending + // into arguments of function types let result = unify_step( - cx, expected_input.ty, actual_input.ty, variance); + cx, expected_input.ty, actual_input.ty, + variance_transform(variance, contravariant)); alt result { ures_ok(rty) { result_ins += [{mode: result_mode, ty: rty}]; } _ { ret fn_common_res_err(result); } -- cgit 1.4.1-3-g733a5