diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_feature/src/accepted.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_feature/src/unstable.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_hir_typeck/src/coercion.rs | 23 | ||||
| -rw-r--r-- | compiler/rustc_lint/src/deref_into_dyn_supertrait.rs | 13 | ||||
| -rw-r--r-- | compiler/rustc_lint/src/lib.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_lint/src/lints.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/lib.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs | 51 |
8 files changed, 90 insertions, 6 deletions
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs index 6e3996b4509..1155366db85 100644 --- a/compiler/rustc_feature/src/accepted.rs +++ b/compiler/rustc_feature/src/accepted.rs @@ -339,9 +339,6 @@ declare_features! ( /// Allows `#[track_caller]` to be used which provides /// accurate caller location reporting during panic (RFC 2091). (accepted, track_caller, "1.46.0", Some(47809)), - /// Allows dyn upcasting trait objects via supertraits. - /// Dyn upcasting is casting, e.g., `dyn Foo -> dyn Bar` where `Foo: Bar`. - (accepted, trait_upcasting, "1.76.0", Some(65991)), /// Allows #[repr(transparent)] on univariant enums (RFC 2645). (accepted, transparent_enums, "1.42.0", Some(60405)), /// Allows indexing tuples. diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs index 371b651f5e8..6eed2178ead 100644 --- a/compiler/rustc_feature/src/unstable.rs +++ b/compiler/rustc_feature/src/unstable.rs @@ -584,6 +584,9 @@ declare_features! ( (unstable, thread_local, "1.0.0", Some(29594)), /// Allows defining `trait X = A + B;` alias items. (unstable, trait_alias, "1.24.0", Some(41517)), + /// Allows dyn upcasting trait objects via supertraits. + /// Dyn upcasting is casting, e.g., `dyn Foo -> dyn Bar` where `Foo: Bar`. + (unstable, trait_upcasting, "1.56.0", Some(65991)), /// Allows for transmuting between arrays with sizes that contain generic consts. (unstable, transmute_generic_consts, "1.70.0", Some(109929)), /// Allows #[repr(transparent)] on unions (RFC 2645). diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs index e9d373119fa..858faf161f6 100644 --- a/compiler/rustc_hir_typeck/src/coercion.rs +++ b/compiler/rustc_hir_typeck/src/coercion.rs @@ -625,6 +625,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { )]; let mut has_unsized_tuple_coercion = false; + let mut has_trait_upcasting_coercion = None; // Keep resolving `CoerceUnsized` and `Unsize` predicates to avoid // emitting a coercion in cases like `Foo<$1>` -> `Foo<$2>`, where @@ -692,6 +693,13 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // these here and emit a feature error if coercion doesn't fail // due to another reason. match impl_source { + traits::ImplSource::Builtin( + BuiltinImplSource::TraitUpcasting { .. }, + _, + ) => { + has_trait_upcasting_coercion = + Some((trait_pred.self_ty(), trait_pred.trait_ref.args.type_at(1))); + } traits::ImplSource::Builtin(BuiltinImplSource::TupleUnsizing, _) => { has_unsized_tuple_coercion = true; } @@ -702,6 +710,21 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { } } + if let Some((sub, sup)) = has_trait_upcasting_coercion + && !self.tcx().features().trait_upcasting + { + // Renders better when we erase regions, since they're not really the point here. + let (sub, sup) = self.tcx.erase_regions((sub, sup)); + let mut err = feature_err( + &self.tcx.sess, + sym::trait_upcasting, + self.cause.span, + format!("cannot cast `{sub}` to `{sup}`, trait upcasting coercion is experimental"), + ); + err.note(format!("required when coercing `{source}` into `{target}`")); + err.emit(); + } + if has_unsized_tuple_coercion && !self.tcx.features().unsized_tuple_coercion { feature_err( &self.tcx.sess, diff --git a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs index 98bafc0f263..4673b801dc1 100644 --- a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs +++ b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs @@ -5,6 +5,7 @@ use crate::{ use rustc_hir as hir; use rustc_middle::ty; +use rustc_session::lint::FutureIncompatibilityReason; use rustc_span::sym; use rustc_trait_selection::traits::supertraits; @@ -12,6 +13,9 @@ declare_lint! { /// The `deref_into_dyn_supertrait` lint is output whenever there is a use of the /// `Deref` implementation with a `dyn SuperTrait` type as `Output`. /// + /// These implementations will become shadowed when the `trait_upcasting` feature is stabilized. + /// The `deref` functions will no longer be called implicitly, so there might be behavior change. + /// /// ### Example /// /// ```rust,compile_fail @@ -40,10 +44,15 @@ declare_lint! { /// /// ### Explanation /// - /// The implicit dyn upcasting coercion take priority over those `Deref` impls. + /// The dyn upcasting coercion feature adds new coercion rules, taking priority + /// over certain other coercion rules, which will cause some behavior change. pub DEREF_INTO_DYN_SUPERTRAIT, Warn, - "`Deref` implementation usage with a supertrait trait object for output are shadow by implicit coercion", + "`Deref` implementation usage with a supertrait trait object for output might be shadowed in the future", + @future_incompatible = FutureIncompatibleInfo { + reason: FutureIncompatibilityReason::FutureReleaseSemanticsChange, + reference: "issue #89460 <https://github.com/rust-lang/rust/issues/89460>", + }; } declare_lint_pass!(DerefIntoDynSupertrait => [DEREF_INTO_DYN_SUPERTRAIT]); diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs index a9996e4a155..b5798af7553 100644 --- a/compiler/rustc_lint/src/lib.rs +++ b/compiler/rustc_lint/src/lib.rs @@ -35,6 +35,7 @@ #![feature(iter_intersperse)] #![feature(iter_order_by)] #![feature(let_chains)] +#![cfg_attr(not(bootstrap), feature(trait_upcasting))] #![feature(min_specialization)] #![feature(never_type)] #![feature(rustc_attrs)] diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs index 65d47b9acc2..94ecc7d9587 100644 --- a/compiler/rustc_lint/src/lints.rs +++ b/compiler/rustc_lint/src/lints.rs @@ -532,7 +532,6 @@ pub enum BuiltinSpecialModuleNameUsed { // deref_into_dyn_supertrait.rs #[derive(LintDiagnostic)] #[diag(lint_supertrait_as_deref_target)] -#[help] pub struct SupertraitAsDerefTarget<'a> { pub self_ty: Ty<'a>, pub supertrait_principal: PolyExistentialTraitRef<'a>, diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs index 3475e582a8f..dec3419819f 100644 --- a/compiler/rustc_middle/src/lib.rs +++ b/compiler/rustc_middle/src/lib.rs @@ -49,6 +49,7 @@ #![feature(associated_type_bounds)] #![feature(rustc_attrs)] #![feature(control_flow_enum)] +#![cfg_attr(not(bootstrap), feature(trait_upcasting))] #![feature(trusted_step)] #![feature(try_blocks)] #![feature(try_reserve_kind)] diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs index 342b12ba498..12aea88e9b6 100644 --- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs +++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs @@ -9,10 +9,13 @@ use hir::def_id::DefId; use hir::LangItem; use rustc_hir as hir; +use rustc_infer::traits::ObligationCause; use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError}; use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams}; use rustc_middle::ty::{self, Ty, TypeVisitableExt}; +use crate::traits; +use crate::traits::query::evaluate_obligation::InferCtxtExt; use crate::traits::util; use super::BuiltinImplConditions; @@ -723,6 +726,45 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { }) } + /// Temporary migration for #89190 + fn need_migrate_deref_output_trait_object( + &mut self, + ty: Ty<'tcx>, + param_env: ty::ParamEnv<'tcx>, + cause: &ObligationCause<'tcx>, + ) -> Option<ty::PolyExistentialTraitRef<'tcx>> { + let tcx = self.tcx(); + if tcx.features().trait_upcasting { + return None; + } + + // <ty as Deref> + let trait_ref = ty::TraitRef::new(tcx, tcx.lang_items().deref_trait()?, [ty]); + + let obligation = + traits::Obligation::new(tcx, cause.clone(), param_env, ty::Binder::dummy(trait_ref)); + if !self.infcx.predicate_may_hold(&obligation) { + return None; + } + + self.infcx.probe(|_| { + let ty = traits::normalize_projection_type( + self, + param_env, + ty::AliasTy::new(tcx, tcx.lang_items().deref_target()?, trait_ref.args), + cause.clone(), + 0, + // We're *intentionally* throwing these away, + // since we don't actually use them. + &mut vec![], + ) + .ty() + .unwrap(); + + if let ty::Dynamic(data, ..) = ty.kind() { data.principal() } else { None } + }) + } + /// Searches for unsizing that might apply to `obligation`. fn assemble_candidates_for_unsizing( &mut self, @@ -780,6 +822,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { let principal_a = a_data.principal().unwrap(); let target_trait_did = principal_def_id_b.unwrap(); let source_trait_ref = principal_a.with_self_ty(self.tcx(), source); + if let Some(deref_trait_ref) = self.need_migrate_deref_output_trait_object( + source, + obligation.param_env, + &obligation.cause, + ) { + if deref_trait_ref.def_id() == target_trait_did { + return; + } + } for (idx, upcast_trait_ref) in util::supertraits(self.tcx(), source_trait_ref).enumerate() |