diff options
Diffstat (limited to 'compiler/rustc_borrowck/src/type_check/relate_tys.rs')
| -rw-r--r-- | compiler/rustc_borrowck/src/type_check/relate_tys.rs | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs new file mode 100644 index 000000000..c97a6a1a6 --- /dev/null +++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs @@ -0,0 +1,187 @@ +use rustc_infer::infer::nll_relate::{NormalizationStrategy, TypeRelating, TypeRelatingDelegate}; +use rustc_infer::infer::NllRegionVariableOrigin; +use rustc_infer::traits::ObligationCause; +use rustc_middle::mir::ConstraintCategory; +use rustc_middle::ty::error::TypeError; +use rustc_middle::ty::relate::TypeRelation; +use rustc_middle::ty::{self, Const, Ty}; +use rustc_span::Span; +use rustc_trait_selection::traits::query::Fallible; + +use crate::constraints::OutlivesConstraint; +use crate::diagnostics::UniverseInfo; +use crate::type_check::{InstantiateOpaqueType, Locations, TypeChecker}; + +impl<'a, 'tcx> TypeChecker<'a, 'tcx> { + /// Adds sufficient constraints to ensure that `a R b` where `R` depends on `v`: + /// + /// - "Covariant" `a <: b` + /// - "Invariant" `a == b` + /// - "Contravariant" `a :> b` + /// + /// N.B., the type `a` is permitted to have unresolved inference + /// variables, but not the type `b`. + #[instrument(skip(self), level = "debug")] + pub(super) fn relate_types( + &mut self, + a: Ty<'tcx>, + v: ty::Variance, + b: Ty<'tcx>, + locations: Locations, + category: ConstraintCategory<'tcx>, + ) -> Fallible<()> { + TypeRelating::new( + self.infcx, + NllTypeRelatingDelegate::new(self, locations, category, UniverseInfo::relate(a, b)), + v, + ) + .relate(a, b)?; + Ok(()) + } + + /// Add sufficient constraints to ensure `a == b`. See also [Self::relate_types]. + pub(super) fn eq_substs( + &mut self, + a: ty::SubstsRef<'tcx>, + b: ty::SubstsRef<'tcx>, + locations: Locations, + category: ConstraintCategory<'tcx>, + ) -> Fallible<()> { + TypeRelating::new( + self.infcx, + NllTypeRelatingDelegate::new(self, locations, category, UniverseInfo::other()), + ty::Variance::Invariant, + ) + .relate(a, b)?; + Ok(()) + } +} + +struct NllTypeRelatingDelegate<'me, 'bccx, 'tcx> { + type_checker: &'me mut TypeChecker<'bccx, 'tcx>, + + /// Where (and why) is this relation taking place? + locations: Locations, + + /// What category do we assign the resulting `'a: 'b` relationships? + category: ConstraintCategory<'tcx>, + + /// Information so that error reporting knows what types we are relating + /// when reporting a bound region error. + universe_info: UniverseInfo<'tcx>, +} + +impl<'me, 'bccx, 'tcx> NllTypeRelatingDelegate<'me, 'bccx, 'tcx> { + fn new( + type_checker: &'me mut TypeChecker<'bccx, 'tcx>, + locations: Locations, + category: ConstraintCategory<'tcx>, + universe_info: UniverseInfo<'tcx>, + ) -> Self { + Self { type_checker, locations, category, universe_info } + } +} + +impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> { + fn span(&self) -> Span { + self.locations.span(self.type_checker.body) + } + + fn param_env(&self) -> ty::ParamEnv<'tcx> { + self.type_checker.param_env + } + + fn create_next_universe(&mut self) -> ty::UniverseIndex { + let universe = self.type_checker.infcx.create_next_universe(); + self.type_checker + .borrowck_context + .constraints + .universe_causes + .insert(universe, self.universe_info.clone()); + universe + } + + fn next_existential_region_var(&mut self, from_forall: bool) -> ty::Region<'tcx> { + let origin = NllRegionVariableOrigin::Existential { from_forall }; + self.type_checker.infcx.next_nll_region_var(origin) + } + + fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> { + self.type_checker + .borrowck_context + .constraints + .placeholder_region(self.type_checker.infcx, placeholder) + } + + fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> { + self.type_checker.infcx.next_nll_region_var_in_universe( + NllRegionVariableOrigin::Existential { from_forall: false }, + universe, + ) + } + + fn push_outlives( + &mut self, + sup: ty::Region<'tcx>, + sub: ty::Region<'tcx>, + info: ty::VarianceDiagInfo<'tcx>, + ) { + let sub = self.type_checker.borrowck_context.universal_regions.to_region_vid(sub); + let sup = self.type_checker.borrowck_context.universal_regions.to_region_vid(sup); + self.type_checker.borrowck_context.constraints.outlives_constraints.push( + OutlivesConstraint { + sup, + sub, + locations: self.locations, + span: self.locations.span(self.type_checker.body), + category: self.category, + variance_info: info, + }, + ); + } + + // We don't have to worry about the equality of consts during borrow checking + // as consts always have a static lifetime. + // FIXME(oli-obk): is this really true? We can at least have HKL and with + // inline consts we may have further lifetimes that may be unsound to treat as + // 'static. + fn const_equate(&mut self, _a: Const<'tcx>, _b: Const<'tcx>) {} + + fn normalization() -> NormalizationStrategy { + NormalizationStrategy::Eager + } + + fn forbid_inference_vars() -> bool { + true + } + + fn register_opaque_type( + &mut self, + a: Ty<'tcx>, + b: Ty<'tcx>, + a_is_expected: bool, + ) -> Result<(), TypeError<'tcx>> { + let param_env = self.param_env(); + let span = self.span(); + let def_id = self.type_checker.body.source.def_id().expect_local(); + let body_id = self.type_checker.tcx().hir().local_def_id_to_hir_id(def_id); + let cause = ObligationCause::misc(span, body_id); + self.type_checker + .fully_perform_op( + self.locations, + self.category, + InstantiateOpaqueType { + obligations: self + .type_checker + .infcx + .handle_opaque_type(a, b, a_is_expected, &cause, param_env)? + .obligations, + // These fields are filled in during execution of the operation + base_universe: None, + region_constraints: None, + }, + ) + .unwrap(); + Ok(()) + } +} |