diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/const_evaluatable.rs | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs index ad229e03b0b..b587ed6487e 100644 --- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs +++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs @@ -609,9 +609,29 @@ where /// Tries to unify two abstract constants using structural equality. pub(super) fn try_unify<'tcx>( tcx: TyCtxt<'tcx>, - a: AbstractConst<'tcx>, - b: AbstractConst<'tcx>, + mut a: AbstractConst<'tcx>, + mut b: AbstractConst<'tcx>, ) -> bool { + // We substitute generics repeatedly to allow AbstractConsts to unify where a + // ConstKind::Unevalated could be turned into an AbstractConst that would unify e.g. + // Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])] + while let Node::Leaf(a_ct) = a.root() { + let a_ct = a_ct.subst(tcx, a.substs); + match AbstractConst::from_const(tcx, a_ct) { + Ok(Some(a_act)) => a = a_act, + Ok(None) => break, + Err(_) => return true, + } + } + while let Node::Leaf(b_ct) = b.root() { + let b_ct = b_ct.subst(tcx, b.substs); + match AbstractConst::from_const(tcx, b_ct) { + Ok(Some(b_act)) => b = b_act, + Ok(None) => break, + Err(_) => return true, + } + } + match (a.root(), b.root()) { (Node::Leaf(a_ct), Node::Leaf(b_ct)) => { let a_ct = a_ct.subst(tcx, a.substs); @@ -632,8 +652,6 @@ pub(super) fn try_unify<'tcx>( // we do not want to use `assert_eq!(a(), b())` to infer that `N` and `M` have to be `1`. This // means that we only allow inference variables if they are equal. (ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val, - // We may want to instead recurse into unevaluated constants here. That may require some - // care to prevent infinite recursion, so let's just ignore this for now. ( ty::ConstKind::Unevaluated(a_def, a_substs, None), ty::ConstKind::Unevaluated(b_def, b_substs, None), |