diff options
| -rw-r--r-- | src/librustc/infer/higher_ranked/mod.rs | 4 | ||||
| -rw-r--r-- | src/librustc/infer/mod.rs | 11 | ||||
| -rw-r--r-- | src/librustc/ty/mod.rs | 40 | ||||
| -rw-r--r-- | src/librustc_mir/borrow_check/nll/region_infer/mod.rs | 10 | ||||
| -rw-r--r-- | src/librustc_mir/borrow_check/nll/region_infer/values.rs | 4 | ||||
| -rw-r--r-- | src/librustc_mir/borrow_check/nll/type_check/relate_tys.rs | 8 |
6 files changed, 39 insertions, 38 deletions
diff --git a/src/librustc/infer/higher_ranked/mod.rs b/src/librustc/infer/higher_ranked/mod.rs index 884aa956556..ae1892caa74 100644 --- a/src/librustc/infer/higher_ranked/mod.rs +++ b/src/librustc/infer/higher_ranked/mod.rs @@ -593,11 +593,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> { where T : TypeFoldable<'tcx>, { - let new_universe = self.create_superuniverse(); + let next_universe = self.create_next_universe(); let (result, map) = self.tcx.replace_late_bound_regions(binder, |br| { self.tcx.mk_region(ty::RePlaceholder(ty::Placeholder { - universe: new_universe, + universe: next_universe, name: br, })) }); diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs index 95ecec7d0d5..ef9886e06d4 100644 --- a/src/librustc/infer/mod.rs +++ b/src/librustc/infer/mod.rs @@ -1489,13 +1489,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> { self.universe.get() } - /// Create and return a new subunivese of the current universe; - /// update `self.universe` to that new universe. At present, - /// used only in the NLL subtyping code, which uses the new - /// universe-based scheme instead of the more limited leak-check - /// scheme. - pub fn create_superuniverse(&self) -> ty::UniverseIndex { - let u = self.universe.get().superuniverse(); + /// Create and return a fresh universe that extends all previous + /// universes. Updates `self.universe` to that new universe. + pub fn create_next_universe(&self) -> ty::UniverseIndex { + let u = self.universe.get().next_universe(); self.universe.set(u); u } diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs index 853b49098b9..4135d499c58 100644 --- a/src/librustc/ty/mod.rs +++ b/src/librustc/ty/mod.rs @@ -1457,10 +1457,10 @@ impl<'tcx> InstantiatedPredicates<'tcx> { /// "Universes" are used during type- and trait-checking in the /// presence of `for<..>` binders to control what sets of names are /// visible. Universes are arranged into a tree: the root universe -/// contains names that are always visible. But when you enter into -/// some superuniverse, then it may add names that are only visible -/// within that subtree (but it can still name the names of its -/// ancestor universes). +/// contains names that are always visible. Each child then adds a new +/// set of names that are visible, in addition to those of its parent. +/// We say that the child universe "extends" the parent universe with +/// new names. /// /// To make this more concrete, consider this program: /// @@ -1472,11 +1472,11 @@ impl<'tcx> InstantiatedPredicates<'tcx> { /// ``` /// /// The struct name `Foo` is in the root universe U0. But the type -/// parameter `T`, introduced on `bar`, is in a superuniverse U1 -- -/// i.e., within `bar`, we can name both `T` and `Foo`, but outside of -/// `bar`, we cannot name `T`. Then, within the type of `y`, the -/// region `'a` is in a superuniverse U2 of U1, because we can name it -/// inside the fn type but not outside. +/// parameter `T`, introduced on `bar`, is in an extended universe U1 +/// -- i.e., within `bar`, we can name both `T` and `Foo`, but outside +/// of `bar`, we cannot name `T`. Then, within the type of `y`, the +/// region `'a` is in a universe U2 that extends U1, because we can +/// name it inside the fn type but not outside. /// /// Universes are used to do type- and trait-checking around these /// "forall" binders (also called **universal quantification**). The @@ -1500,24 +1500,28 @@ impl_stable_hash_for!(struct UniverseIndex { private }); impl UniverseIndex { pub const ROOT: UniverseIndex = UniverseIndex::from_u32_const(0); - /// A "superuniverse" corresponds to being inside a `forall` quantifier. - /// So, for example, suppose we have this type in universe `U`: + /// Returns the "next" universe index in order -- this new index + /// is considered to extend all previous universes. This + /// corresponds to entering a `forall` quantifier. So, for + /// example, suppose we have this type in universe `U`: /// /// ``` /// for<'a> fn(&'a u32) /// ``` /// /// Once we "enter" into this `for<'a>` quantifier, we are in a - /// superuniverse of `U` -- in this new universe, we can name the - /// region `'a`, but that region was not nameable from `U` because - /// it was not in scope there. - pub fn superuniverse(self) -> UniverseIndex { + /// new universe that extends `U` -- in this new universe, we can + /// name the region `'a`, but that region was not nameable from + /// `U` because it was not in scope there. + pub fn next_universe(self) -> UniverseIndex { UniverseIndex::from_u32(self.private.checked_add(1).unwrap()) } - /// True if the names in this universe are a subset of the names in `other`. - pub fn is_subset_of(self, other: UniverseIndex) -> bool { - self.private <= other.private + /// True if `self` can name a name from `other` -- in other words, + /// if the set of names in `self` is a superset of those in + /// `other`. + pub fn can_name(self, other: UniverseIndex) -> bool { + self.private >= other.private } } diff --git a/src/librustc_mir/borrow_check/nll/region_infer/mod.rs b/src/librustc_mir/borrow_check/nll/region_infer/mod.rs index ca5759183c7..dd8a7f19a63 100644 --- a/src/librustc_mir/borrow_check/nll/region_infer/mod.rs +++ b/src/librustc_mir/borrow_check/nll/region_infer/mod.rs @@ -112,7 +112,7 @@ struct RegionDefinition<'tcx> { /// Which universe is this region variable defined in? This is /// most often `ty::UniverseIndex::ROOT`, but when we encounter /// forall-quantifiers like `for<'a> { 'a = 'b }`, we would create - /// the variable for `'a` in a superuniverse. + /// the variable for `'a` in a fresh universe that extends ROOT. universe: ty::UniverseIndex, /// If this is 'static or an early-bound region, then this is @@ -339,11 +339,11 @@ impl<'tcx> RegionInferenceContext<'tcx> { NLLRegionVariableOrigin::Placeholder(placeholder) => { // Each placeholder region is only visible from - // its universe `ui` and its superuniverses. So we + // its universe `ui` and its extensions. So we // can't just add it into `scc` unless the // universe of the scc can name this region. let scc_universe = self.scc_universes[scc]; - if placeholder.universe.is_subset_of(scc_universe) { + if scc_universe.can_name(placeholder.universe) { self.scc_values.add_element(scc, placeholder); } else { self.add_incompatible_universe(scc); @@ -541,7 +541,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { // Quick check: if scc_b's declared universe is a subset of // scc_a's declared univese (typically, both are ROOT), then // it cannot contain any problematic universe elements. - if self.scc_universes[scc_b].is_subset_of(universe_a) { + if universe_a.can_name(self.scc_universes[scc_b]) { return true; } @@ -550,7 +550,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { // from universe_a self.scc_values .placeholders_contained_in(scc_b) - .all(|p| p.universe.is_subset_of(universe_a)) + .all(|p| universe_a.can_name(p.universe)) } /// Extend `scc` so that it can outlive some placeholder region diff --git a/src/librustc_mir/borrow_check/nll/region_infer/values.rs b/src/librustc_mir/borrow_check/nll/region_infer/values.rs index f9c1c11c62a..3607ae4f508 100644 --- a/src/librustc_mir/borrow_check/nll/region_infer/values.rs +++ b/src/librustc_mir/borrow_check/nll/region_infer/values.rs @@ -148,8 +148,8 @@ crate enum RegionElement { /// a lifetime parameter). RootUniversalRegion(RegionVid), - /// A superuniverse from a superuniverse (e.g., instantiated from a - /// `for<'a> fn(&'a u32)` type). + /// A placeholder (e.g., instantiated from a `for<'a> fn(&'a u32)` + /// type). PlaceholderRegion(ty::Placeholder), } diff --git a/src/librustc_mir/borrow_check/nll/type_check/relate_tys.rs b/src/librustc_mir/borrow_check/nll/type_check/relate_tys.rs index a7657a57451..96cc1c0afec 100644 --- a/src/librustc_mir/borrow_check/nll/type_check/relate_tys.rs +++ b/src/librustc_mir/borrow_check/nll/type_check/relate_tys.rs @@ -159,7 +159,7 @@ trait TypeRelatingDelegate<'tcx> { fn push_outlives(&mut self, sup: ty::Region<'tcx>, sub: ty::Region<'tcx>); /// Creates a new universe index. Used when instantiating placeholders. - fn next_superuniverse(&mut self) -> ty::UniverseIndex; + fn create_next_universe(&mut self) -> ty::UniverseIndex; /// Creates a new region variable representing a higher-ranked /// region that is instantiated existentially. This creates an @@ -218,8 +218,8 @@ impl NllTypeRelatingDelegate<'me, 'bccx, 'gcx, 'tcx> { } impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, '_, 'tcx> { - fn next_superuniverse(&mut self) -> ty::UniverseIndex { - self.infcx.create_superuniverse() + fn create_next_universe(&mut self) -> ty::UniverseIndex { + self.infcx.create_next_universe() } fn next_existential_region_var(&mut self) -> ty::Region<'tcx> { @@ -324,7 +324,7 @@ where // new universe for the placeholders we will make // from here out. let universe = lazy_universe.unwrap_or_else(|| { - let universe = delegate.next_superuniverse(); + let universe = delegate.create_next_universe(); lazy_universe = Some(universe); universe }); |