diff options
| -rw-r--r-- | compiler/rustc_feature/src/builtin_attrs.rs | 15 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/collect.rs | 12 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/mod.rs | 10 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/trait_def.rs | 31 | ||||
| -rw-r--r-- | compiler/rustc_passes/src/check_attr.rs | 15 | ||||
| -rw-r--r-- | compiler/rustc_span/src/symbol.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/mod.rs | 10 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/search_graph/mod.rs | 18 | ||||
| -rw-r--r-- | library/core/src/marker.rs | 1 | ||||
| -rw-r--r-- | tests/ui/coinduction/canonicalization-rerun.rs | 54 |
10 files changed, 130 insertions, 37 deletions
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs index af56a0b2459..493a9cd89e3 100644 --- a/compiler/rustc_feature/src/builtin_attrs.rs +++ b/compiler/rustc_feature/src/builtin_attrs.rs @@ -414,7 +414,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[ ), // Linking: - gated!(naked, Normal, template!(Word), WarnFollowing, @only_local: true, naked_functions, experimental!(naked)), + gated!( + naked, Normal, template!(Word), WarnFollowing, @only_local: true, + naked_functions, experimental!(naked) + ), // Plugins: BuiltinAttribute { @@ -441,7 +444,8 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[ ), // RFC #1268 gated!( - marker, Normal, template!(Word), WarnFollowing, marker_trait_attr, experimental!(marker) + marker, Normal, template!(Word), WarnFollowing, @only_local: true, + marker_trait_attr, experimental!(marker) ), gated!( thread_local, Normal, template!(Word), WarnFollowing, @@ -682,8 +686,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[ "language items are subject to change", ), rustc_attr!( - rustc_pass_by_value, Normal, - template!(Word), ErrorFollowing, + rustc_pass_by_value, Normal, template!(Word), ErrorFollowing, "#[rustc_pass_by_value] is used to mark types that must be passed by value instead of reference." ), rustc_attr!( @@ -691,6 +694,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[ "#![rustc_coherence_is_core] allows inherent methods on builtin types, only intended to be used in `core`." ), rustc_attr!( + rustc_coinductive, AttributeType::Normal, template!(Word), WarnFollowing, @only_local: true, + "#![rustc_coinductive] changes a trait to be coinductive, allowing cycles in the trait solver." + ), + rustc_attr!( rustc_allow_incoherent_impl, AttributeType::Normal, template!(Word), ErrorFollowing, @only_local: true, "#[rustc_allow_incoherent_impl] has to be added to all impl items of an incoherent inherent impl." ), diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs index 80426c239ac..9f33d84ab52 100644 --- a/compiler/rustc_hir_analysis/src/collect.rs +++ b/compiler/rustc_hir_analysis/src/collect.rs @@ -934,9 +934,10 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef { } let is_marker = tcx.has_attr(def_id, sym::marker); + let rustc_coinductive = tcx.has_attr(def_id, sym::rustc_coinductive); let skip_array_during_method_dispatch = tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch); - let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) { + let specialization_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) { ty::trait_def::TraitSpecializationKind::Marker } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) { ty::trait_def::TraitSpecializationKind::AlwaysApplicable @@ -1036,16 +1037,17 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef { no_dups.then_some(list) }); - ty::TraitDef::new( + ty::TraitDef { def_id, unsafety, paren_sugar, - is_auto, + has_auto_impl: is_auto, is_marker, + is_coinductive: rustc_coinductive || is_auto, skip_array_during_method_dispatch, - spec_kind, + specialization_kind, must_implement_one_of, - ) + } } fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool { diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs index 6d8c9d73763..5b7ca750f78 100644 --- a/compiler/rustc_middle/src/ty/mod.rs +++ b/compiler/rustc_middle/src/ty/mod.rs @@ -2388,15 +2388,17 @@ impl<'tcx> TyCtxt<'tcx> { self.trait_def(trait_def_id).has_auto_impl } + /// Returns `true` if this is coinductive, either because it is + /// an auto trait or because it has the `#[rustc_coinductive]` attribute. + pub fn trait_is_coinductive(self, trait_def_id: DefId) -> bool { + self.trait_def(trait_def_id).is_coinductive + } + /// Returns `true` if this is a trait alias. pub fn trait_is_alias(self, trait_def_id: DefId) -> bool { self.def_kind(trait_def_id) == DefKind::TraitAlias } - pub fn trait_is_coinductive(self, trait_def_id: DefId) -> bool { - self.trait_is_auto(trait_def_id) || self.lang_items().sized_trait() == Some(trait_def_id) - } - /// Returns layout of a generator. Layout might be unavailable if the /// generator is tainted by errors. pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> { diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs index b38a5fbf20f..71353acaaa7 100644 --- a/compiler/rustc_middle/src/ty/trait_def.rs +++ b/compiler/rustc_middle/src/ty/trait_def.rs @@ -31,6 +31,15 @@ pub struct TraitDef { /// and thus `impl`s of it are allowed to overlap. pub is_marker: bool, + /// If `true`, then this trait has to `#[rustc_coinductive]` attribute or + /// is an auto trait. This indicates that trait solver cycles involving an + /// `X: ThisTrait` goal are accepted. + /// + /// In the future all traits should be coinductive, but we need a better + /// formal understanding of what exactly that means and should probably + /// also have already switched to the new trait solver. + pub is_coinductive: bool, + /// If `true`, then this trait has the `#[rustc_skip_array_during_method_dispatch]` /// attribute, indicating that editions before 2021 should not consider this trait /// during method dispatch if the receiver is an array. @@ -81,28 +90,6 @@ impl TraitImpls { } impl<'tcx> TraitDef { - pub fn new( - def_id: DefId, - unsafety: hir::Unsafety, - paren_sugar: bool, - has_auto_impl: bool, - is_marker: bool, - skip_array_during_method_dispatch: bool, - specialization_kind: TraitSpecializationKind, - must_implement_one_of: Option<Box<[Ident]>>, - ) -> TraitDef { - TraitDef { - def_id, - unsafety, - paren_sugar, - has_auto_impl, - is_marker, - skip_array_during_method_dispatch, - specialization_kind, - must_implement_one_of, - } - } - pub fn ancestors( &self, tcx: TyCtxt<'tcx>, diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs index 238ec9ca30f..225095948af 100644 --- a/compiler/rustc_passes/src/check_attr.rs +++ b/compiler/rustc_passes/src/check_attr.rs @@ -156,6 +156,7 @@ impl CheckAttrVisitor<'_> { | sym::rustc_dirty | sym::rustc_if_this_changed | sym::rustc_then_this_would_need => self.check_rustc_dirty_clean(&attr), + sym::rustc_coinductive => self.check_rustc_coinductive(&attr, span, target), sym::cmse_nonsecure_entry => { self.check_cmse_nonsecure_entry(hir_id, attr, span, target) } @@ -1608,6 +1609,20 @@ impl CheckAttrVisitor<'_> { } } + /// Checks if the `#[rustc_coinductive]` attribute is applied to a trait. + fn check_rustc_coinductive(&self, attr: &Attribute, span: Span, target: Target) -> bool { + match target { + Target::Trait => true, + _ => { + self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait { + attr_span: attr.span, + defn_span: span, + }); + false + } + } + } + /// Checks if `#[link_section]` is applied to a function or static. fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { match target { diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index ef417d3e0a7..56835a2466a 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -1224,6 +1224,7 @@ symbols! { rustc_capture_analysis, rustc_clean, rustc_coherence_is_core, + rustc_coinductive, rustc_const_stable, rustc_const_unstable, rustc_conversion_suggestion, diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs index e56588c58bd..38a86d55a2c 100644 --- a/compiler/rustc_trait_selection/src/solve/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/mod.rs @@ -265,12 +265,18 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> { // call `exists<U> <T as Trait>::Assoc == U` to enable better caching. This goal // could constrain `U` to `u32` which would cause this check to result in a // solver cycle. - if cfg!(debug_assertions) && has_changed && !self.in_projection_eq_hack { + if cfg!(debug_assertions) + && has_changed + && !self.in_projection_eq_hack + && !self.search_graph.in_cycle() + { let mut orig_values = OriginalQueryValues::default(); let canonical_goal = self.infcx.canonicalize_query(goal, &mut orig_values); let canonical_response = EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?; - assert!(canonical_response.value.var_values.is_identity()); + if !canonical_response.value.var_values.is_identity() { + bug!("unstable result: {goal:?} {canonical_goal:?} {canonical_response:?}"); + } assert_eq!(certainty, canonical_response.value.certainty); } diff --git a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs index a2ca4bc189c..e989c9145d1 100644 --- a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs @@ -42,6 +42,24 @@ impl<'tcx> SearchGraph<'tcx> { && !self.overflow_data.did_overflow() } + /// Whether we're currently in a cycle. This should only be used + /// for debug assertions. + pub(super) fn in_cycle(&self) -> bool { + if let Some(stack_depth) = self.stack.last() { + // Either the current goal on the stack is the root of a cycle... + if self.stack[stack_depth].has_been_used { + return true; + } + + // ...or it depends on a goal with a lower depth. + let current_goal = self.stack[stack_depth].goal; + let entry_index = self.provisional_cache.lookup_table[¤t_goal]; + self.provisional_cache.entries[entry_index].depth != stack_depth + } else { + false + } + } + /// Tries putting the new goal on the stack, returning an error if it is already cached. /// /// This correctly updates the provisional cache if there is a cycle. diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs index 07a7d45c7eb..520ae0edb09 100644 --- a/library/core/src/marker.rs +++ b/library/core/src/marker.rs @@ -97,6 +97,7 @@ unsafe impl<T: Sync + ?Sized> Send for &T {} #[fundamental] // for Default, for example, which requires that `[T]: !Default` be evaluatable #[rustc_specialization_trait] #[rustc_deny_explicit_impl] +#[cfg_attr(not(bootstrap), rustc_coinductive)] pub trait Sized { // Empty. } diff --git a/tests/ui/coinduction/canonicalization-rerun.rs b/tests/ui/coinduction/canonicalization-rerun.rs new file mode 100644 index 00000000000..b10ba3a810f --- /dev/null +++ b/tests/ui/coinduction/canonicalization-rerun.rs @@ -0,0 +1,54 @@ +// check-pass +// revisions: old new +//[new] compile-flags: -Ztrait-solver=next + +// If we use canonical goals during trait solving we have to reevaluate +// the root goal of a cycle until we hit a fixpoint. +// +// Here `main` has a goal `(?0, ?1): Trait` which is canonicalized to +// `exists<^0, ^1> (^0, ^1): Trait`. +// +// - `exists<^0, ^1> (^0, ^1): Trait` -instantiate-> `(?0, ?1): Trait` +// -`(?1, ?0): Trait` -canonicalize-> `exists<^0, ^1> (^0, ^1): Trait` +// - COINDUCTIVE CYCLE OK (no constraints) +// - `(): ConstrainToU32<?0>` -canonicalize-> `exists<^0> (): ConstrainToU32<^0>` +// - OK (^0 = u32 -apply-> ?0 = u32) +// - OK (?0 = u32 -canonicalize-> ^0 = u32) +// - coinductive cycle with provisional result != final result, rerun +// +// - `exists<^0, ^1> (^0, ^1): Trait` -instantiate-> `(?0, ?1): Trait` +// -`(?1, ?0): Trait` -canonicalize-> `exists<^0, ^1> (^0, ^1): Trait` +// - COINDUCTIVE CYCLE OK (^0 = u32 -apply-> ?1 = u32) +// - `(): ConstrainToU32<?0>` -canonicalize-> `exists<^0> (): ConstrainToU32<^0>` +// - OK (^0 = u32 -apply-> ?1 = u32) +// - OK (?0 = u32, ?1 = u32 -canonicalize-> ^0 = u32, ^1 = u32) +// - coinductive cycle with provisional result != final result, rerun +// +// - `exists<^0, ^1> (^0, ^1): Trait` -instantiate-> `(?0, ?1): Trait` +// -`(?1, ?0): Trait` -canonicalize-> `exists<^0, ^1> (^0, ^1): Trait` +// - COINDUCTIVE CYCLE OK (^0 = u32, ^1 = u32 -apply-> ?1 = u32, ?0 = u32) +// - `(): ConstrainToU32<?0>` -canonicalize-> `exists<^0> (): ConstrainToU32<^0>` +// - OK (^0 = u32 -apply-> ?1 = u32) +// - OK (?0 = u32, ?1 = u32 -canonicalize-> ^0 = u32, ^1 = u32) +// - coinductive cycle with provisional result == final result, DONE +#![feature(rustc_attrs)] +#[rustc_coinductive] +trait Trait {} + +impl<T, U> Trait for (T, U) +where + (U, T): Trait, + (): ConstrainToU32<T>, +{} + +trait ConstrainToU32<T> {} +impl ConstrainToU32<u32> for () {} + +fn impls_trait<T, U>() +where + (T, U): Trait, +{} + +fn main() { + impls_trait::<_, _>(); +} |