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Tweak typecheck to enforce covariance on higher-order function arguments

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This commit is contained in:
Brian Anderson 2011-10-16 16:19:12 -07:00
parent 342a400e79
commit 391e12124b
2 changed files with 18 additions and 1 deletions
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5
src/comp/middle/ty.rs
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@ -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); }