diff options
Diffstat (limited to 'compiler/rustc_infer/src')
| -rw-r--r-- | compiler/rustc_infer/src/infer/combine.rs | 593 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/equate.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/error_reporting/mod.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs | 17 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/generalize.rs | 479 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/mod.rs | 5 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/nll_relate/mod.rs | 276 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/opaque_types.rs | 12 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/test_type_match.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/sub.rs | 6 |
10 files changed, 577 insertions, 827 deletions
diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs index 2a51439b0a9..79fc02c6c79 100644 --- a/compiler/rustc_infer/src/infer/combine.rs +++ b/compiler/rustc_infer/src/infer/combine.rs @@ -26,24 +26,17 @@ use super::equate::Equate; use super::glb::Glb; use super::lub::Lub; use super::sub::Sub; -use super::type_variable::TypeVariableValue; -use super::{DefineOpaqueTypes, InferCtxt, MiscVariable, TypeTrace}; +use super::{DefineOpaqueTypes, InferCtxt, TypeTrace}; +use crate::infer::generalize::{self, CombineDelegate, Generalization}; use crate::traits::{Obligation, PredicateObligations}; -use rustc_data_structures::sso::SsoHashMap; -use rustc_hir::def_id::DefId; use rustc_middle::infer::canonical::OriginalQueryValues; use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue}; use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind}; -use rustc_middle::traits::ObligationCause; use rustc_middle::ty::error::{ExpectedFound, TypeError}; -use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation}; -use rustc_middle::ty::subst::SubstsRef; -use rustc_middle::ty::{ - self, AliasKind, FallibleTypeFolder, InferConst, ToPredicate, Ty, TyCtxt, TypeFoldable, - TypeSuperFoldable, TypeVisitableExt, -}; +use rustc_middle::ty::relate::{RelateResult, TypeRelation}; +use rustc_middle::ty::{self, AliasKind, InferConst, ToPredicate, Ty, TyCtxt, TypeVisitableExt}; use rustc_middle::ty::{IntType, UintType}; -use rustc_span::{Span, DUMMY_SP}; +use rustc_span::DUMMY_SP; #[derive(Clone)] pub struct CombineFields<'infcx, 'tcx> { @@ -55,13 +48,6 @@ pub struct CombineFields<'infcx, 'tcx> { pub define_opaque_types: DefineOpaqueTypes, } -#[derive(Copy, Clone, Debug)] -pub enum RelationDir { - SubtypeOf, - SupertypeOf, - EqTo, -} - impl<'tcx> InferCtxt<'tcx> { pub fn super_combine_tys<R>( &self, @@ -127,7 +113,8 @@ impl<'tcx> InferCtxt<'tcx> { bug!() } - (_, ty::Alias(AliasKind::Projection, _)) | (ty::Alias(AliasKind::Projection, _), _) + (_, ty::Alias(AliasKind::Projection | AliasKind::Inherent, _)) + | (ty::Alias(AliasKind::Projection | AliasKind::Inherent, _), _) if self.tcx.trait_solver_next() => { relation.register_type_relate_obligation(a, b); @@ -151,7 +138,7 @@ impl<'tcx> InferCtxt<'tcx> { Ok(a) } - _ => ty::relate::super_relate_tys(relation, a, b), + _ => ty::relate::structurally_relate_tys(relation, a, b), } } @@ -208,13 +195,13 @@ impl<'tcx> InferCtxt<'tcx> { // HACK: equating both sides with `[const error]` eagerly prevents us // from leaving unconstrained inference vars during things like impl // matching in the solver. - let a_error = self.tcx.const_error_with_guaranteed(a.ty(), guar); + let a_error = self.tcx.const_error(a.ty(), guar); if let ty::ConstKind::Infer(InferConst::Var(vid)) = a.kind() { - return self.unify_const_variable(vid, a_error); + return self.unify_const_variable(vid, a_error, relation.param_env()); } - let b_error = self.tcx.const_error_with_guaranteed(b.ty(), guar); + let b_error = self.tcx.const_error(b.ty(), guar); if let ty::ConstKind::Infer(InferConst::Var(vid)) = b.kind() { - return self.unify_const_variable(vid, b_error); + return self.unify_const_variable(vid, b_error, relation.param_env()); } return Ok(if relation.a_is_expected() { a_error } else { b_error }); @@ -236,11 +223,11 @@ impl<'tcx> InferCtxt<'tcx> { } (ty::ConstKind::Infer(InferConst::Var(vid)), _) => { - return self.unify_const_variable(vid, b); + return self.unify_const_variable(vid, b, relation.param_env()); } (_, ty::ConstKind::Infer(InferConst::Var(vid))) => { - return self.unify_const_variable(vid, a); + return self.unify_const_variable(vid, a, relation.param_env()); } (ty::ConstKind::Unevaluated(..), _) | (_, ty::ConstKind::Unevaluated(..)) if self.tcx.lazy_normalization() => @@ -251,7 +238,7 @@ impl<'tcx> InferCtxt<'tcx> { _ => {} } - ty::relate::super_relate_consts(relation, a, b) + ty::relate::structurally_relate_consts(relation, a, b) } /// Unifies the const variable `target_vid` with the given constant. @@ -293,24 +280,17 @@ impl<'tcx> InferCtxt<'tcx> { &self, target_vid: ty::ConstVid<'tcx>, ct: ty::Const<'tcx>, + param_env: ty::ParamEnv<'tcx>, ) -> RelateResult<'tcx, ty::Const<'tcx>> { - let (for_universe, span) = { - let mut inner = self.inner.borrow_mut(); - let variable_table = &mut inner.const_unification_table(); - let var_value = variable_table.probe_value(target_vid); - match var_value.val { - ConstVariableValue::Known { value } => { - bug!("instantiating {:?} which has a known value {:?}", target_vid, value) - } - ConstVariableValue::Unknown { universe } => (universe, var_value.origin.span), - } - }; - let value = ct.try_fold_with(&mut ConstInferUnifier { - infcx: self, - span, - for_universe, + let span = + self.inner.borrow_mut().const_unification_table().probe_value(target_vid).origin.span; + let Generalization { value, needs_wf: _ } = generalize::generalize( + self, + &mut CombineDelegate { infcx: self, span, param_env }, + ct, target_vid, - })?; + ty::Variance::Invariant, + )?; self.inner.borrow_mut().const_unification_table().union_value( target_vid, @@ -391,12 +371,10 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> { pub fn instantiate( &mut self, a_ty: Ty<'tcx>, - dir: RelationDir, + ambient_variance: ty::Variance, b_vid: ty::TyVid, a_is_expected: bool, ) -> RelateResult<'tcx, ()> { - use self::RelationDir::*; - // Get the actual variable that b_vid has been inferred to debug_assert!(self.infcx.inner.borrow_mut().type_variables().probe(b_vid).is_unknown()); @@ -411,7 +389,18 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> { // `'?2` and `?3` are fresh region/type inference // variables. (Down below, we will relate `a_ty <: b_ty`, // adding constraints like `'x: '?2` and `?1 <: ?3`.) - let Generalization { ty: b_ty, needs_wf } = self.generalize(a_ty, b_vid, dir)?; + let Generalization { value: b_ty, needs_wf } = generalize::generalize( + self.infcx, + &mut CombineDelegate { + infcx: self.infcx, + param_env: self.param_env, + span: self.trace.span(), + }, + a_ty, + b_vid, + ambient_variance, + )?; + debug!(?b_ty); self.infcx.inner.borrow_mut().type_variables().instantiate(b_vid, b_ty); @@ -430,78 +419,23 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> { // relations wind up attributed to the same spans. We need // to associate causes/spans with each of the relations in // the stack to get this right. - match dir { - EqTo => self.equate(a_is_expected).relate(a_ty, b_ty), - SubtypeOf => self.sub(a_is_expected).relate(a_ty, b_ty), - SupertypeOf => self.sub(a_is_expected).relate_with_variance( + match ambient_variance { + ty::Variance::Invariant => self.equate(a_is_expected).relate(a_ty, b_ty), + ty::Variance::Covariant => self.sub(a_is_expected).relate(a_ty, b_ty), + ty::Variance::Contravariant => self.sub(a_is_expected).relate_with_variance( ty::Contravariant, ty::VarianceDiagInfo::default(), a_ty, b_ty, ), + ty::Variance::Bivariant => { + unreachable!("no code should be generalizing bivariantly (currently)") + } }?; Ok(()) } - /// Attempts to generalize `ty` for the type variable `for_vid`. - /// This checks for cycle -- that is, whether the type `ty` - /// references `for_vid`. The `dir` is the "direction" for which we - /// a performing the generalization (i.e., are we producing a type - /// that can be used as a supertype etc). - /// - /// Preconditions: - /// - /// - `for_vid` is a "root vid" - #[instrument(skip(self), level = "trace", ret)] - fn generalize( - &self, - ty: Ty<'tcx>, - for_vid: ty::TyVid, - dir: RelationDir, - ) -> RelateResult<'tcx, Generalization<'tcx>> { - // Determine the ambient variance within which `ty` appears. - // The surrounding equation is: - // - // ty [op] ty2 - // - // where `op` is either `==`, `<:`, or `:>`. This maps quite - // naturally. - let ambient_variance = match dir { - RelationDir::EqTo => ty::Invariant, - RelationDir::SubtypeOf => ty::Covariant, - RelationDir::SupertypeOf => ty::Contravariant, - }; - - trace!(?ambient_variance); - - let for_universe = match self.infcx.inner.borrow_mut().type_variables().probe(for_vid) { - v @ TypeVariableValue::Known { .. } => { - bug!("instantiating {:?} which has a known value {:?}", for_vid, v,) - } - TypeVariableValue::Unknown { universe } => universe, - }; - - trace!(?for_universe); - trace!(?self.trace); - - let mut generalize = Generalizer { - infcx: self.infcx, - cause: &self.trace.cause, - for_vid_sub_root: self.infcx.inner.borrow_mut().type_variables().sub_root_var(for_vid), - for_universe, - ambient_variance, - needs_wf: false, - root_ty: ty, - param_env: self.param_env, - cache: SsoHashMap::new(), - }; - - let ty = generalize.relate(ty, ty)?; - let needs_wf = generalize.needs_wf; - Ok(Generalization { ty, needs_wf }) - } - pub fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) { self.obligations.extend(obligations.into_iter()); } @@ -513,313 +447,6 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> { } } -struct Generalizer<'cx, 'tcx> { - infcx: &'cx InferCtxt<'tcx>, - - /// The span, used when creating new type variables and things. - cause: &'cx ObligationCause<'tcx>, - - /// The vid of the type variable that is in the process of being - /// instantiated; if we find this within the type we are folding, - /// that means we would have created a cyclic type. - for_vid_sub_root: ty::TyVid, - - /// The universe of the type variable that is in the process of - /// being instantiated. Any fresh variables that we create in this - /// process should be in that same universe. - for_universe: ty::UniverseIndex, - - /// Track the variance as we descend into the type. - ambient_variance: ty::Variance, - - /// See the field `needs_wf` in `Generalization`. - needs_wf: bool, - - /// The root type that we are generalizing. Used when reporting cycles. - root_ty: Ty<'tcx>, - - param_env: ty::ParamEnv<'tcx>, - - cache: SsoHashMap<Ty<'tcx>, Ty<'tcx>>, -} - -/// Result from a generalization operation. This includes -/// not only the generalized type, but also a bool flag -/// indicating whether further WF checks are needed. -#[derive(Debug)] -struct Generalization<'tcx> { - ty: Ty<'tcx>, - - /// If true, then the generalized type may not be well-formed, - /// even if the source type is well-formed, so we should add an - /// additional check to enforce that it is. This arises in - /// particular around 'bivariant' type parameters that are only - /// constrained by a where-clause. As an example, imagine a type: - /// - /// struct Foo<A, B> where A: Iterator<Item = B> { - /// data: A - /// } - /// - /// here, `A` will be covariant, but `B` is - /// unconstrained. However, whatever it is, for `Foo` to be WF, it - /// must be equal to `A::Item`. If we have an input `Foo<?A, ?B>`, - /// then after generalization we will wind up with a type like - /// `Foo<?C, ?D>`. When we enforce that `Foo<?A, ?B> <: Foo<?C, - /// ?D>` (or `>:`), we will wind up with the requirement that `?A - /// <: ?C`, but no particular relationship between `?B` and `?D` - /// (after all, we do not know the variance of the normalized form - /// of `A::Item` with respect to `A`). If we do nothing else, this - /// may mean that `?D` goes unconstrained (as in #41677). So, in - /// this scenario where we create a new type variable in a - /// bivariant context, we set the `needs_wf` flag to true. This - /// will force the calling code to check that `WF(Foo<?C, ?D>)` - /// holds, which in turn implies that `?C::Item == ?D`. So once - /// `?C` is constrained, that should suffice to restrict `?D`. - needs_wf: bool, -} - -impl<'tcx> TypeRelation<'tcx> for Generalizer<'_, 'tcx> { - fn tcx(&self) -> TyCtxt<'tcx> { - self.infcx.tcx - } - - fn param_env(&self) -> ty::ParamEnv<'tcx> { - self.param_env - } - - fn tag(&self) -> &'static str { - "Generalizer" - } - - fn a_is_expected(&self) -> bool { - true - } - - fn binders<T>( - &mut self, - a: ty::Binder<'tcx, T>, - b: ty::Binder<'tcx, T>, - ) -> RelateResult<'tcx, ty::Binder<'tcx, T>> - where - T: Relate<'tcx>, - { - Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?)) - } - - fn relate_item_substs( - &mut self, - item_def_id: DefId, - a_subst: SubstsRef<'tcx>, - b_subst: SubstsRef<'tcx>, - ) -> RelateResult<'tcx, SubstsRef<'tcx>> { - if self.ambient_variance == ty::Variance::Invariant { - // Avoid fetching the variance if we are in an invariant - // context; no need, and it can induce dependency cycles - // (e.g., #41849). - relate::relate_substs(self, a_subst, b_subst) - } else { - let tcx = self.tcx(); - let opt_variances = tcx.variances_of(item_def_id); - relate::relate_substs_with_variances( - self, - item_def_id, - &opt_variances, - a_subst, - b_subst, - true, - ) - } - } - - fn relate_with_variance<T: Relate<'tcx>>( - &mut self, - variance: ty::Variance, - _info: ty::VarianceDiagInfo<'tcx>, - a: T, - b: T, - ) -> RelateResult<'tcx, T> { - let old_ambient_variance = self.ambient_variance; - self.ambient_variance = self.ambient_variance.xform(variance); - - let result = self.relate(a, b); - self.ambient_variance = old_ambient_variance; - result - } - - fn tys(&mut self, t: Ty<'tcx>, t2: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { - assert_eq!(t, t2); // we are abusing TypeRelation here; both LHS and RHS ought to be == - - if let Some(&result) = self.cache.get(&t) { - return Ok(result); - } - debug!("generalize: t={:?}", t); - - // Check to see whether the type we are generalizing references - // any other type variable related to `vid` via - // subtyping. This is basically our "occurs check", preventing - // us from creating infinitely sized types. - let result = match *t.kind() { - ty::Infer(ty::TyVar(vid)) => { - let vid = self.infcx.inner.borrow_mut().type_variables().root_var(vid); - let sub_vid = self.infcx.inner.borrow_mut().type_variables().sub_root_var(vid); - if sub_vid == self.for_vid_sub_root { - // If sub-roots are equal, then `for_vid` and - // `vid` are related via subtyping. - Err(TypeError::CyclicTy(self.root_ty)) - } else { - let probe = self.infcx.inner.borrow_mut().type_variables().probe(vid); - match probe { - TypeVariableValue::Known { value: u } => { - debug!("generalize: known value {:?}", u); - self.relate(u, u) - } - TypeVariableValue::Unknown { universe } => { - match self.ambient_variance { - // Invariant: no need to make a fresh type variable. - ty::Invariant => { - if self.for_universe.can_name(universe) { - return Ok(t); - } - } - - // Bivariant: make a fresh var, but we - // may need a WF predicate. See - // comment on `needs_wf` field for - // more info. - ty::Bivariant => self.needs_wf = true, - - // Co/contravariant: this will be - // sufficiently constrained later on. - ty::Covariant | ty::Contravariant => (), - } - - let origin = - *self.infcx.inner.borrow_mut().type_variables().var_origin(vid); - let new_var_id = self - .infcx - .inner - .borrow_mut() - .type_variables() - .new_var(self.for_universe, origin); - let u = self.tcx().mk_ty_var(new_var_id); - - // Record that we replaced `vid` with `new_var_id` as part of a generalization - // operation. This is needed to detect cyclic types. To see why, see the - // docs in the `type_variables` module. - self.infcx.inner.borrow_mut().type_variables().sub(vid, new_var_id); - debug!("generalize: replacing original vid={:?} with new={:?}", vid, u); - Ok(u) - } - } - } - } - ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => { - // No matter what mode we are in, - // integer/floating-point types must be equal to be - // relatable. - Ok(t) - } - ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => { - let s = self.relate(substs, substs)?; - Ok(if s == substs { t } else { self.infcx.tcx.mk_opaque(def_id, s) }) - } - _ => relate::super_relate_tys(self, t, t), - }?; - - self.cache.insert(t, result); - Ok(result) - } - - fn regions( - &mut self, - r: ty::Region<'tcx>, - r2: ty::Region<'tcx>, - ) -> RelateResult<'tcx, ty::Region<'tcx>> { - assert_eq!(r, r2); // we are abusing TypeRelation here; both LHS and RHS ought to be == - - debug!("generalize: regions r={:?}", r); - - match *r { - // Never make variables for regions bound within the type itself, - // nor for erased regions. - ty::ReLateBound(..) | ty::ReErased => { - return Ok(r); - } - - ty::ReError(_) => { - return Ok(r); - } - - ty::RePlaceholder(..) - | ty::ReVar(..) - | ty::ReStatic - | ty::ReEarlyBound(..) - | ty::ReFree(..) => { - // see common code below - } - } - - // If we are in an invariant context, we can re-use the region - // as is, unless it happens to be in some universe that we - // can't name. (In the case of a region *variable*, we could - // use it if we promoted it into our universe, but we don't - // bother.) - if let ty::Invariant = self.ambient_variance { - let r_universe = self.infcx.universe_of_region(r); - if self.for_universe.can_name(r_universe) { - return Ok(r); - } - } - - // FIXME: This is non-ideal because we don't give a - // very descriptive origin for this region variable. - Ok(self.infcx.next_region_var_in_universe(MiscVariable(self.cause.span), self.for_universe)) - } - - fn consts( - &mut self, - c: ty::Const<'tcx>, - c2: ty::Const<'tcx>, - ) -> RelateResult<'tcx, ty::Const<'tcx>> { - assert_eq!(c, c2); // we are abusing TypeRelation here; both LHS and RHS ought to be == - - match c.kind() { - ty::ConstKind::Infer(InferConst::Var(vid)) => { - let mut inner = self.infcx.inner.borrow_mut(); - let variable_table = &mut inner.const_unification_table(); - let var_value = variable_table.probe_value(vid); - match var_value.val { - ConstVariableValue::Known { value: u } => { - drop(inner); - self.relate(u, u) - } - ConstVariableValue::Unknown { universe } => { - if self.for_universe.can_name(universe) { - Ok(c) - } else { - let new_var_id = variable_table.new_key(ConstVarValue { - origin: var_value.origin, - val: ConstVariableValue::Unknown { universe: self.for_universe }, - }); - Ok(self.tcx().mk_const(new_var_id, c.ty())) - } - } - } - } - ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => { - let substs = self.relate_with_variance( - ty::Variance::Invariant, - ty::VarianceDiagInfo::default(), - substs, - substs, - )?; - Ok(self.tcx().mk_const(ty::UnevaluatedConst { def, substs }, c.ty())) - } - _ => relate::super_relate_consts(self, c, c), - } - } -} - pub trait ObligationEmittingRelation<'tcx>: TypeRelation<'tcx> { /// Register obligations that must hold in order for this relation to hold fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>); @@ -872,135 +499,3 @@ fn float_unification_error<'tcx>( let (ty::FloatVarValue(a), ty::FloatVarValue(b)) = v; TypeError::FloatMismatch(ExpectedFound::new(a_is_expected, a, b)) } - -struct ConstInferUnifier<'cx, 'tcx> { - infcx: &'cx InferCtxt<'tcx>, - - span: Span, - - for_universe: ty::UniverseIndex, - - /// The vid of the const variable that is in the process of being - /// instantiated; if we find this within the const we are folding, - /// that means we would have created a cyclic const. - target_vid: ty::ConstVid<'tcx>, -} - -impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ConstInferUnifier<'_, 'tcx> { - type Error = TypeError<'tcx>; - - fn interner(&self) -> TyCtxt<'tcx> { - self.infcx.tcx - } - - #[instrument(level = "debug", skip(self), ret)] - fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, TypeError<'tcx>> { - match t.kind() { - &ty::Infer(ty::TyVar(vid)) => { - let vid = self.infcx.inner.borrow_mut().type_variables().root_var(vid); - let probe = self.infcx.inner.borrow_mut().type_variables().probe(vid); - match probe { - TypeVariableValue::Known { value: u } => { - debug!("ConstOccursChecker: known value {:?}", u); - u.try_fold_with(self) - } - TypeVariableValue::Unknown { universe } => { - if self.for_universe.can_name(universe) { - return Ok(t); - } - - let origin = - *self.infcx.inner.borrow_mut().type_variables().var_origin(vid); - let new_var_id = self - .infcx - .inner - .borrow_mut() - .type_variables() - .new_var(self.for_universe, origin); - Ok(self.interner().mk_ty_var(new_var_id)) - } - } - } - ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => Ok(t), - _ => t.try_super_fold_with(self), - } - } - - #[instrument(level = "debug", skip(self), ret)] - fn try_fold_region( - &mut self, - r: ty::Region<'tcx>, - ) -> Result<ty::Region<'tcx>, TypeError<'tcx>> { - debug!("ConstInferUnifier: r={:?}", r); - - match *r { - // Never make variables for regions bound within the type itself, - // nor for erased regions. - ty::ReLateBound(..) | ty::ReErased | ty::ReError(_) => { - return Ok(r); - } - - ty::RePlaceholder(..) - | ty::ReVar(..) - | ty::ReStatic - | ty::ReEarlyBound(..) - | ty::ReFree(..) => { - // see common code below - } - } - - let r_universe = self.infcx.universe_of_region(r); - if self.for_universe.can_name(r_universe) { - return Ok(r); - } else { - // FIXME: This is non-ideal because we don't give a - // very descriptive origin for this region variable. - Ok(self.infcx.next_region_var_in_universe(MiscVariable(self.span), self.for_universe)) - } - } - - #[instrument(level = "debug", skip(self), ret)] - fn try_fold_const(&mut self, c: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, TypeError<'tcx>> { - match c.kind() { - ty::ConstKind::Infer(InferConst::Var(vid)) => { - // Check if the current unification would end up - // unifying `target_vid` with a const which contains - // an inference variable which is unioned with `target_vid`. - // - // Not doing so can easily result in stack overflows. - if self - .infcx - .inner - .borrow_mut() - .const_unification_table() - .unioned(self.target_vid, vid) - { - return Err(TypeError::CyclicConst(c)); - } - - let var_value = - self.infcx.inner.borrow_mut().const_unification_table().probe_value(vid); - match var_value.val { - ConstVariableValue::Known { value: u } => u.try_fold_with(self), - ConstVariableValue::Unknown { universe } => { - if self.for_universe.can_name(universe) { - Ok(c) - } else { - let new_var_id = - self.infcx.inner.borrow_mut().const_unification_table().new_key( - ConstVarValue { - origin: var_value.origin, - val: ConstVariableValue::Unknown { - universe: self.for_universe, - }, - }, - ); - Ok(self.interner().mk_const(new_var_id, c.ty())) - } - } - } - } - _ => c.try_super_fold_with(self), - } - } -} diff --git a/compiler/rustc_infer/src/infer/equate.rs b/compiler/rustc_infer/src/infer/equate.rs index f90f7674b55..793505e4ab2 100644 --- a/compiler/rustc_infer/src/infer/equate.rs +++ b/compiler/rustc_infer/src/infer/equate.rs @@ -1,7 +1,7 @@ use crate::infer::DefineOpaqueTypes; use crate::traits::PredicateObligations; -use super::combine::{CombineFields, ObligationEmittingRelation, RelationDir}; +use super::combine::{CombineFields, ObligationEmittingRelation}; use super::Subtype; use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation}; @@ -88,11 +88,11 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> { } (&ty::Infer(TyVar(a_id)), _) => { - self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?; + self.fields.instantiate(b, ty::Invariant, a_id, self.a_is_expected)?; } (_, &ty::Infer(TyVar(b_id))) => { - self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?; + self.fields.instantiate(a, ty::Invariant, b_id, self.a_is_expected)?; } ( diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs index 98da5ba65b7..ad4f5058b5e 100644 --- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs +++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs @@ -2354,7 +2354,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> { let labeled_user_string = match bound_kind { GenericKind::Param(ref p) => format!("the parameter type `{}`", p), GenericKind::Alias(ref p) => match p.kind(self.tcx) { - ty::AliasKind::Projection => format!("the associated type `{}`", p), + ty::AliasKind::Projection | ty::AliasKind::Inherent => { + format!("the associated type `{}`", p) + } ty::AliasKind::Opaque => format!("the opaque type `{}`", p), }, }; @@ -2721,7 +2723,7 @@ impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> { | (ty::Infer(ty::InferTy::TyVar(_)), _) | (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a), (ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch), - _ => relate::super_relate_tys(self, a, b), + _ => relate::structurally_relate_tys(self, a, b), } } diff --git a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs index a3116351940..421eb807a14 100644 --- a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs +++ b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs @@ -2,6 +2,7 @@ use super::TypeErrCtxt; use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect}; use rustc_errors::{pluralize, Diagnostic, MultiSpan}; use rustc_hir as hir; +use rustc_hir::def::DefKind; use rustc_middle::traits::ObligationCauseCode; use rustc_middle::ty::error::ExpectedFound; use rustc_middle::ty::print::Printer; @@ -71,9 +72,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> { #traits-as-parameters", ); } - (ty::Alias(ty::Projection, _), ty::Alias(ty::Projection, _)) => { + (ty::Alias(ty::Projection | ty::Inherent, _), ty::Alias(ty::Projection | ty::Inherent, _)) => { diag.note("an associated type was expected, but a different one was found"); } + // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too. (ty::Param(p), ty::Alias(ty::Projection, proj)) | (ty::Alias(ty::Projection, proj), ty::Param(p)) if !tcx.is_impl_trait_in_trait(proj.def_id) => { @@ -222,7 +224,7 @@ impl<T> Trait<T> for X { diag.span_label(p_span, "this type parameter"); } } - (ty::Alias(ty::Projection, proj_ty), _) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => { + (ty::Alias(ty::Projection | ty::Inherent, proj_ty), _) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => { self.expected_projection( diag, proj_ty, @@ -231,7 +233,7 @@ impl<T> Trait<T> for X { cause.code(), ); } - (_, ty::Alias(ty::Projection, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => { + (_, ty::Alias(ty::Projection | ty::Inherent, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => { let msg = format!( "consider constraining the associated type `{}` to `{}`", values.found, values.expected, @@ -255,6 +257,15 @@ impl<T> Trait<T> for X { ); } } + (ty::Alias(ty::Opaque, alias), _) | (_, ty::Alias(ty::Opaque, alias)) if alias.def_id.is_local() && matches!(tcx.def_kind(body_owner_def_id), DefKind::AssocFn | DefKind::AssocConst) => { + if tcx.is_type_alias_impl_trait(alias.def_id) { + if !tcx.opaque_types_defined_by(body_owner_def_id.expect_local()).contains(&alias.def_id.expect_local()) { + diag.span_note(tcx.def_span(body_owner_def_id), "\ + this item must have the opaque type in its signature \ + in order to be able to register hidden types"); + } + } + } (ty::FnPtr(_), ty::FnDef(def, _)) if let hir::def::DefKind::Fn = tcx.def_kind(def) => { diag.note( diff --git a/compiler/rustc_infer/src/infer/generalize.rs b/compiler/rustc_infer/src/infer/generalize.rs new file mode 100644 index 00000000000..d4a1dacde10 --- /dev/null +++ b/compiler/rustc_infer/src/infer/generalize.rs @@ -0,0 +1,479 @@ +use rustc_data_structures::sso::SsoHashMap; +use rustc_hir::def_id::DefId; +use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue}; +use rustc_middle::ty::error::TypeError; +use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation}; +use rustc_middle::ty::{self, InferConst, Term, Ty, TyCtxt, TypeVisitableExt}; +use rustc_span::Span; + +use crate::infer::nll_relate::TypeRelatingDelegate; +use crate::infer::type_variable::TypeVariableValue; +use crate::infer::{InferCtxt, RegionVariableOrigin}; + +/// Attempts to generalize `term` for the type variable `for_vid`. +/// This checks for cycles -- that is, whether the type `term` +/// references `for_vid`. +pub(super) fn generalize<'tcx, D: GeneralizerDelegate<'tcx>, T: Into<Term<'tcx>> + Relate<'tcx>>( + infcx: &InferCtxt<'tcx>, + delegate: &mut D, + term: T, + for_vid: impl Into<ty::TermVid<'tcx>>, + ambient_variance: ty::Variance, +) -> RelateResult<'tcx, Generalization<T>> { + let (for_universe, root_vid) = match for_vid.into() { + ty::TermVid::Ty(ty_vid) => ( + infcx.probe_ty_var(ty_vid).unwrap_err(), + ty::TermVid::Ty(infcx.inner.borrow_mut().type_variables().sub_root_var(ty_vid)), + ), + ty::TermVid::Const(ct_vid) => ( + infcx.probe_const_var(ct_vid).unwrap_err(), + ty::TermVid::Const(infcx.inner.borrow_mut().const_unification_table().find(ct_vid)), + ), + }; + + let mut generalizer = Generalizer { + infcx, + delegate, + ambient_variance, + root_vid, + for_universe, + root_term: term.into(), + needs_wf: false, + cache: Default::default(), + }; + + assert!(!term.has_escaping_bound_vars()); + let value = generalizer.relate(term, term)?; + let needs_wf = generalizer.needs_wf; + Ok(Generalization { value, needs_wf }) +} + +/// Abstracts the handling of region vars between HIR and MIR/NLL typechecking +/// in the generalizer code. +pub trait GeneralizerDelegate<'tcx> { + fn param_env(&self) -> ty::ParamEnv<'tcx>; + + fn forbid_inference_vars() -> bool; + + fn generalize_region(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx>; +} + +pub struct CombineDelegate<'cx, 'tcx> { + pub infcx: &'cx InferCtxt<'tcx>, + pub param_env: ty::ParamEnv<'tcx>, + pub span: Span, +} + +impl<'tcx> GeneralizerDelegate<'tcx> for CombineDelegate<'_, 'tcx> { + fn param_env(&self) -> ty::ParamEnv<'tcx> { + self.param_env + } + + fn forbid_inference_vars() -> bool { + false + } + + fn generalize_region(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> { + // FIXME: This is non-ideal because we don't give a + // very descriptive origin for this region variable. + self.infcx + .next_region_var_in_universe(RegionVariableOrigin::MiscVariable(self.span), universe) + } +} + +impl<'tcx, T> GeneralizerDelegate<'tcx> for T +where + T: TypeRelatingDelegate<'tcx>, +{ + fn param_env(&self) -> ty::ParamEnv<'tcx> { + <Self as TypeRelatingDelegate<'tcx>>::param_env(self) + } + + fn forbid_inference_vars() -> bool { + <Self as TypeRelatingDelegate<'tcx>>::forbid_inference_vars() + } + + fn generalize_region(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> { + <Self as TypeRelatingDelegate<'tcx>>::generalize_existential(self, universe) + } +} + +/// The "generalizer" is used when handling inference variables. +/// +/// The basic strategy for handling a constraint like `?A <: B` is to +/// apply a "generalization strategy" to the term `B` -- this replaces +/// all the lifetimes in the term `B` with fresh inference variables. +/// (You can read more about the strategy in this [blog post].) +/// +/// As an example, if we had `?A <: &'x u32`, we would generalize `&'x +/// u32` to `&'0 u32` where `'0` is a fresh variable. This becomes the +/// value of `A`. Finally, we relate `&'0 u32 <: &'x u32`, which +/// establishes `'0: 'x` as a constraint. +/// +/// [blog post]: https://is.gd/0hKvIr +struct Generalizer<'me, 'tcx, D> { + infcx: &'me InferCtxt<'tcx>, + + /// This is used to abstract the behaviors of the three previous + /// generalizer-like implementations (`Generalizer`, `TypeGeneralizer`, + /// and `ConstInferUnifier`). See [`GeneralizerDelegate`] for more + /// information. + delegate: &'me mut D, + + /// After we generalize this type, we are going to relate it to + /// some other type. What will be the variance at this point? + ambient_variance: ty::Variance, + + /// The vid of the type variable that is in the process of being + /// instantiated. If we find this within the value we are folding, + /// that means we would have created a cyclic value. + root_vid: ty::TermVid<'tcx>, + + /// The universe of the type variable that is in the process of being + /// instantiated. If we find anything that this universe cannot name, + /// we reject the relation. + for_universe: ty::UniverseIndex, + + /// The root term (const or type) we're generalizing. Used for cycle errors. + root_term: Term<'tcx>, + + cache: SsoHashMap<Ty<'tcx>, Ty<'tcx>>, + + /// See the field `needs_wf` in `Generalization`. + needs_wf: bool, +} + +impl<'tcx, D> Generalizer<'_, 'tcx, D> { + /// Create an error that corresponds to the term kind in `root_term` + fn cyclic_term_error(&self) -> TypeError<'tcx> { + match self.root_term.unpack() { + ty::TermKind::Ty(ty) => TypeError::CyclicTy(ty), + ty::TermKind::Const(ct) => TypeError::CyclicConst(ct), + } + } +} + +impl<'tcx, D> TypeRelation<'tcx> for Generalizer<'_, 'tcx, D> +where + D: GeneralizerDelegate<'tcx>, +{ + fn tcx(&self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + fn param_env(&self) -> ty::ParamEnv<'tcx> { + self.delegate.param_env() + } + + fn tag(&self) -> &'static str { + "Generalizer" + } + + fn a_is_expected(&self) -> bool { + true + } + + fn relate_item_substs( + &mut self, + item_def_id: DefId, + a_subst: ty::SubstsRef<'tcx>, + b_subst: ty::SubstsRef<'tcx>, + ) -> RelateResult<'tcx, ty::SubstsRef<'tcx>> { + if self.ambient_variance == ty::Variance::Invariant { + // Avoid fetching the variance if we are in an invariant + // context; no need, and it can induce dependency cycles + // (e.g., #41849). + relate::relate_substs(self, a_subst, b_subst) + } else { + let tcx = self.tcx(); + let opt_variances = tcx.variances_of(item_def_id); + relate::relate_substs_with_variances( + self, + item_def_id, + opt_variances, + a_subst, + b_subst, + true, + ) + } + } + + #[instrument(level = "debug", skip(self, variance, b), ret)] + fn relate_with_variance<T: Relate<'tcx>>( + &mut self, + variance: ty::Variance, + _info: ty::VarianceDiagInfo<'tcx>, + a: T, + b: T, + ) -> RelateResult<'tcx, T> { + let old_ambient_variance = self.ambient_variance; + self.ambient_variance = self.ambient_variance.xform(variance); + debug!(?self.ambient_variance, "new ambient variance"); + let r = self.relate(a, b)?; + self.ambient_variance = old_ambient_variance; + Ok(r) + } + + #[instrument(level = "debug", skip(self, t2), ret)] + fn tys(&mut self, t: Ty<'tcx>, t2: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { + assert_eq!(t, t2); // we are misusing TypeRelation here; both LHS and RHS ought to be == + + if let Some(&result) = self.cache.get(&t) { + return Ok(result); + } + + // Check to see whether the type we are generalizing references + // any other type variable related to `vid` via + // subtyping. This is basically our "occurs check", preventing + // us from creating infinitely sized types. + let g = match *t.kind() { + ty::Infer(ty::TyVar(_)) | ty::Infer(ty::IntVar(_)) | ty::Infer(ty::FloatVar(_)) + if D::forbid_inference_vars() => + { + bug!("unexpected inference variable encountered in NLL generalization: {t}"); + } + + ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { + bug!("unexpected infer type: {t}") + } + + ty::Infer(ty::TyVar(vid)) => { + let mut inner = self.infcx.inner.borrow_mut(); + let vid = inner.type_variables().root_var(vid); + let sub_vid = inner.type_variables().sub_root_var(vid); + + if ty::TermVid::Ty(sub_vid) == self.root_vid { + // If sub-roots are equal, then `root_vid` and + // `vid` are related via subtyping. + Err(self.cyclic_term_error()) + } else { + let probe = inner.type_variables().probe(vid); + match probe { + TypeVariableValue::Known { value: u } => { + drop(inner); + self.relate(u, u) + } + TypeVariableValue::Unknown { universe } => { + match self.ambient_variance { + // Invariant: no need to make a fresh type variable + // if we can name the universe. + ty::Invariant => { + if self.for_universe.can_name(universe) { + return Ok(t); + } + } + + // Bivariant: make a fresh var, but we + // may need a WF predicate. See + // comment on `needs_wf` field for + // more info. + ty::Bivariant => self.needs_wf = true, + + // Co/contravariant: this will be + // sufficiently constrained later on. + ty::Covariant | ty::Contravariant => (), + } + + let origin = *inner.type_variables().var_origin(vid); + let new_var_id = + inner.type_variables().new_var(self.for_universe, origin); + let u = self.tcx().mk_ty_var(new_var_id); + + // Record that we replaced `vid` with `new_var_id` as part of a generalization + // operation. This is needed to detect cyclic types. To see why, see the + // docs in the `type_variables` module. + inner.type_variables().sub(vid, new_var_id); + debug!("replacing original vid={:?} with new={:?}", vid, u); + Ok(u) + } + } + } + } + + ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => { + // No matter what mode we are in, + // integer/floating-point types must be equal to be + // relatable. + Ok(t) + } + + ty::Placeholder(placeholder) => { + if self.for_universe.can_name(placeholder.universe) { + Ok(t) + } else { + debug!( + "root universe {:?} cannot name placeholder in universe {:?}", + self.for_universe, placeholder.universe + ); + Err(TypeError::Mismatch) + } + } + + _ => relate::structurally_relate_tys(self, t, t), + }?; + + self.cache.insert(t, g); + Ok(g) + } + + #[instrument(level = "debug", skip(self, r2), ret)] + fn regions( + &mut self, + r: ty::Region<'tcx>, + r2: ty::Region<'tcx>, + ) -> RelateResult<'tcx, ty::Region<'tcx>> { + assert_eq!(r, r2); // we are misusing TypeRelation here; both LHS and RHS ought to be == + + match *r { + // Never make variables for regions bound within the type itself, + // nor for erased regions. + ty::ReLateBound(..) | ty::ReErased => { + return Ok(r); + } + + // It doesn't really matter for correctness if we generalize ReError, + // since we're already on a doomed compilation path. + ty::ReError(_) => { + return Ok(r); + } + + ty::RePlaceholder(..) + | ty::ReVar(..) + | ty::ReStatic + | ty::ReEarlyBound(..) + | ty::ReFree(..) => { + // see common code below + } + } + + // If we are in an invariant context, we can re-use the region + // as is, unless it happens to be in some universe that we + // can't name. + if let ty::Invariant = self.ambient_variance { + let r_universe = self.infcx.universe_of_region(r); + if self.for_universe.can_name(r_universe) { + return Ok(r); + } + } + + Ok(self.delegate.generalize_region(self.for_universe)) + } + + #[instrument(level = "debug", skip(self, c2), ret)] + fn consts( + &mut self, + c: ty::Const<'tcx>, + c2: ty::Const<'tcx>, + ) -> RelateResult<'tcx, ty::Const<'tcx>> { + assert_eq!(c, c2); // we are misusing TypeRelation here; both LHS and RHS ought to be == + + match c.kind() { + ty::ConstKind::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => { + bug!("unexpected inference variable encountered in NLL generalization: {:?}", c); + } + ty::ConstKind::Infer(InferConst::Var(vid)) => { + // If root const vids are equal, then `root_vid` and + // `vid` are related and we'd be inferring an infinitely + // deep const. + if ty::TermVid::Const( + self.infcx.inner.borrow_mut().const_unification_table().find(vid), + ) == self.root_vid + { + return Err(self.cyclic_term_error()); + } + + let mut inner = self.infcx.inner.borrow_mut(); + let variable_table = &mut inner.const_unification_table(); + let var_value = variable_table.probe_value(vid); + match var_value.val { + ConstVariableValue::Known { value: u } => { + drop(inner); + self.relate(u, u) + } + ConstVariableValue::Unknown { universe } => { + if self.for_universe.can_name(universe) { + Ok(c) + } else { + let new_var_id = variable_table.new_key(ConstVarValue { + origin: var_value.origin, + val: ConstVariableValue::Unknown { universe: self.for_universe }, + }); + Ok(self.tcx().mk_const(new_var_id, c.ty())) + } + } + } + } + // FIXME: remove this branch once `structurally_relate_consts` is fully + // structural. + ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => { + let substs = self.relate_with_variance( + ty::Variance::Invariant, + ty::VarianceDiagInfo::default(), + substs, + substs, + )?; + Ok(self.tcx().mk_const(ty::UnevaluatedConst { def, substs }, c.ty())) + } + ty::ConstKind::Placeholder(placeholder) => { + if self.for_universe.can_name(placeholder.universe) { + Ok(c) + } else { + debug!( + "root universe {:?} cannot name placeholder in universe {:?}", + self.for_universe, placeholder.universe + ); + Err(TypeError::Mismatch) + } + } + _ => relate::structurally_relate_consts(self, c, c), + } + } + + #[instrument(level = "debug", skip(self), ret)] + fn binders<T>( + &mut self, + a: ty::Binder<'tcx, T>, + _: ty::Binder<'tcx, T>, + ) -> RelateResult<'tcx, ty::Binder<'tcx, T>> + where + T: Relate<'tcx>, + { + let result = self.relate(a.skip_binder(), a.skip_binder())?; + Ok(a.rebind(result)) + } +} + +/// Result from a generalization operation. This includes +/// not only the generalized type, but also a bool flag +/// indicating whether further WF checks are needed. +#[derive(Debug)] +pub struct Generalization<T> { + pub value: T, + + /// If true, then the generalized type may not be well-formed, + /// even if the source type is well-formed, so we should add an + /// additional check to enforce that it is. This arises in + /// particular around 'bivariant' type parameters that are only + /// constrained by a where-clause. As an example, imagine a type: + /// + /// struct Foo<A, B> where A: Iterator<Item = B> { + /// data: A + /// } + /// + /// here, `A` will be covariant, but `B` is + /// unconstrained. However, whatever it is, for `Foo` to be WF, it + /// must be equal to `A::Item`. If we have an input `Foo<?A, ?B>`, + /// then after generalization we will wind up with a type like + /// `Foo<?C, ?D>`. When we enforce that `Foo<?A, ?B> <: Foo<?C, + /// ?D>` (or `>:`), we will wind up with the requirement that `?A + /// <: ?C`, but no particular relationship between `?B` and `?D` + /// (after all, we do not know the variance of the normalized form + /// of `A::Item` with respect to `A`). If we do nothing else, this + /// may mean that `?D` goes unconstrained (as in #41677). So, in + /// this scenario where we create a new type variable in a + /// bivariant context, we set the `needs_wf` flag to true. This + /// will force the calling code to check that `WF(Foo<?C, ?D>)` + /// holds, which in turn implies that `?C::Item == ?D`. So once + /// `?C` is constrained, that should suffice to restrict `?D`. + pub needs_wf: bool, +} diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs index a89b9931599..f8329965c43 100644 --- a/compiler/rustc_infer/src/infer/mod.rs +++ b/compiler/rustc_infer/src/infer/mod.rs @@ -58,6 +58,7 @@ pub mod error_reporting; pub mod free_regions; mod freshen; mod fudge; +mod generalize; mod glb; mod higher_ranked; pub mod lattice; @@ -1530,10 +1531,10 @@ impl<'tcx> InferCtxt<'tcx> { // variables let tcx = self.tcx; if substs.has_non_region_infer() { - if let Some(ct) = tcx.bound_abstract_const(unevaluated.def)? { + if let Some(ct) = tcx.thir_abstract_const(unevaluated.def)? { let ct = tcx.expand_abstract_consts(ct.subst(tcx, substs)); if let Err(e) = ct.error_reported() { - return Err(ErrorHandled::Reported(e)); + return Err(ErrorHandled::Reported(e.into())); } else if ct.has_non_region_infer() || ct.has_non_region_param() { return Err(ErrorHandled::TooGeneric); } else { diff --git a/compiler/rustc_infer/src/infer/nll_relate/mod.rs b/compiler/rustc_infer/src/infer/nll_relate/mod.rs index 88a0a81e276..4ae6af5f5be 100644 --- a/compiler/rustc_infer/src/infer/nll_relate/mod.rs +++ b/compiler/rustc_infer/src/infer/nll_relate/mod.rs @@ -21,21 +21,20 @@ //! thing we relate in chalk are basically domain goals and their //! constituents) -use crate::infer::InferCtxt; -use crate::infer::{ConstVarValue, ConstVariableValue}; -use crate::infer::{TypeVariableOrigin, TypeVariableOriginKind}; -use crate::traits::{Obligation, PredicateObligations}; use rustc_data_structures::fx::FxHashMap; use rustc_middle::traits::ObligationCause; -use rustc_middle::ty::error::TypeError; use rustc_middle::ty::fold::FnMutDelegate; -use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation}; +use rustc_middle::ty::relate::{Relate, RelateResult, TypeRelation}; use rustc_middle::ty::visit::TypeVisitableExt; use rustc_middle::ty::{self, InferConst, Ty, TyCtxt}; use rustc_span::{Span, Symbol}; use std::fmt::Debug; -use super::combine::ObligationEmittingRelation; +use crate::infer::combine::ObligationEmittingRelation; +use crate::infer::generalize::{self, Generalization}; +use crate::infer::InferCtxt; +use crate::infer::{TypeVariableOrigin, TypeVariableOriginKind}; +use crate::traits::{Obligation, PredicateObligations}; pub struct TypeRelating<'me, 'tcx, D> where @@ -198,7 +197,7 @@ where _ => (), } - let generalized_ty = self.generalize_value(value_ty, vid)?; + let generalized_ty = self.generalize(value_ty, vid)?; debug!("relate_ty_var: generalized_ty = {:?}", generalized_ty); if D::forbid_inference_vars() { @@ -217,26 +216,15 @@ where result } - fn generalize_value<T: Relate<'tcx>>( - &mut self, - value: T, - for_vid: ty::TyVid, - ) -> RelateResult<'tcx, T> { - let universe = self.infcx.probe_ty_var(for_vid).unwrap_err(); - - if value.has_escaping_bound_vars() { - bug!("trying to instantiate {for_vid:?} with escaping bound vars: {value:?}"); - } - - let mut generalizer = TypeGeneralizer { - infcx: self.infcx, - delegate: &mut self.delegate, - ambient_variance: self.ambient_variance, - for_vid_sub_root: self.infcx.inner.borrow_mut().type_variables().sub_root_var(for_vid), - universe, - }; - - generalizer.relate(value, value) + fn generalize(&mut self, ty: Ty<'tcx>, for_vid: ty::TyVid) -> RelateResult<'tcx, Ty<'tcx>> { + let Generalization { value: ty, needs_wf: _ } = generalize::generalize( + self.infcx, + &mut self.delegate, + ty, + for_vid, + self.ambient_variance, + )?; + Ok(ty) } fn relate_opaques(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { @@ -716,235 +704,3 @@ where })]); } } - -/// The "type generalizer" is used when handling inference variables. -/// -/// The basic strategy for handling a constraint like `?A <: B` is to -/// apply a "generalization strategy" to the type `B` -- this replaces -/// all the lifetimes in the type `B` with fresh inference -/// variables. (You can read more about the strategy in this [blog -/// post].) -/// -/// As an example, if we had `?A <: &'x u32`, we would generalize `&'x -/// u32` to `&'0 u32` where `'0` is a fresh variable. This becomes the -/// value of `A`. Finally, we relate `&'0 u32 <: &'x u32`, which -/// establishes `'0: 'x` as a constraint. -/// -/// [blog post]: https://is.gd/0hKvIr -struct TypeGeneralizer<'me, 'tcx, D> -where - D: TypeRelatingDelegate<'tcx>, -{ - infcx: &'me InferCtxt<'tcx>, - - delegate: &'me mut D, - - /// After we generalize this type, we are going to relate it to - /// some other type. What will be the variance at this point? - ambient_variance: ty::Variance, - - /// The vid of the type variable that is in the process of being - /// instantiated. If we find this within the value we are folding, - /// that means we would have created a cyclic value. - for_vid_sub_root: ty::TyVid, - - /// The universe of the type variable that is in the process of being - /// instantiated. If we find anything that this universe cannot name, - /// we reject the relation. - universe: ty::UniverseIndex, -} - -impl<'tcx, D> TypeRelation<'tcx> for TypeGeneralizer<'_, 'tcx, D> -where - D: TypeRelatingDelegate<'tcx>, -{ - fn tcx(&self) -> TyCtxt<'tcx> { - self.infcx.tcx - } - - fn param_env(&self) -> ty::ParamEnv<'tcx> { - self.delegate.param_env() - } - - fn tag(&self) -> &'static str { - "nll::generalizer" - } - - fn a_is_expected(&self) -> bool { - true - } - - fn relate_with_variance<T: Relate<'tcx>>( - &mut self, - variance: ty::Variance, - _info: ty::VarianceDiagInfo<'tcx>, - a: T, - b: T, - ) -> RelateResult<'tcx, T> { - debug!( - "TypeGeneralizer::relate_with_variance(variance={:?}, a={:?}, b={:?})", - variance, a, b - ); - - let old_ambient_variance = self.ambient_variance; - self.ambient_variance = self.ambient_variance.xform(variance); - - debug!( - "TypeGeneralizer::relate_with_variance: ambient_variance = {:?}", - self.ambient_variance - ); - - let r = self.relate(a, b)?; - - self.ambient_variance = old_ambient_variance; - - debug!("TypeGeneralizer::relate_with_variance: r={:?}", r); - - Ok(r) - } - - fn tys(&mut self, a: Ty<'tcx>, _: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { - use crate::infer::type_variable::TypeVariableValue; - - debug!("TypeGeneralizer::tys(a={:?})", a); - - match *a.kind() { - ty::Infer(ty::TyVar(_)) | ty::Infer(ty::IntVar(_)) | ty::Infer(ty::FloatVar(_)) - if D::forbid_inference_vars() => - { - bug!("unexpected inference variable encountered in NLL generalization: {:?}", a); - } - - ty::Infer(ty::TyVar(vid)) => { - let mut inner = self.infcx.inner.borrow_mut(); - let variables = &mut inner.type_variables(); - let vid = variables.root_var(vid); - let sub_vid = variables.sub_root_var(vid); - if sub_vid == self.for_vid_sub_root { - // If sub-roots are equal, then `for_vid` and - // `vid` are related via subtyping. - debug!("TypeGeneralizer::tys: occurs check failed"); - Err(TypeError::Mismatch) - } else { - match variables.probe(vid) { - TypeVariableValue::Known { value: u } => { - drop(variables); - self.relate(u, u) - } - TypeVariableValue::Unknown { universe: _universe } => { - if self.ambient_variance == ty::Bivariant { - // FIXME: we may need a WF predicate (related to #54105). - } - - let origin = *variables.var_origin(vid); - - // Replacing with a new variable in the universe `self.universe`, - // it will be unified later with the original type variable in - // the universe `_universe`. - let new_var_id = variables.new_var(self.universe, origin); - - let u = self.tcx().mk_ty_var(new_var_id); - debug!("generalize: replacing original vid={:?} with new={:?}", vid, u); - Ok(u) - } - } - } - } - - ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => { - // No matter what mode we are in, - // integer/floating-point types must be equal to be - // relatable. - Ok(a) - } - - ty::Placeholder(placeholder) => { - if self.universe.cannot_name(placeholder.universe) { - debug!( - "TypeGeneralizer::tys: root universe {:?} cannot name\ - placeholder in universe {:?}", - self.universe, placeholder.universe - ); - Err(TypeError::Mismatch) - } else { - Ok(a) - } - } - - _ => relate::super_relate_tys(self, a, a), - } - } - - fn regions( - &mut self, - a: ty::Region<'tcx>, - _: ty::Region<'tcx>, - ) -> RelateResult<'tcx, ty::Region<'tcx>> { - debug!("TypeGeneralizer::regions(a={:?})", a); - - if let ty::ReLateBound(..) = *a { - return Ok(a); - } - - // For now, we just always create a fresh region variable to - // replace all the regions in the source type. In the main - // type checker, we special case the case where the ambient - // variance is `Invariant` and try to avoid creating a fresh - // region variable, but since this comes up so much less in - // NLL (only when users use `_` etc) it is much less - // important. - // - // As an aside, since these new variables are created in - // `self.universe` universe, this also serves to enforce the - // universe scoping rules. - // - // FIXME(#54105) -- if the ambient variance is bivariant, - // though, we may however need to check well-formedness or - // risk a problem like #41677 again. - let replacement_region_vid = self.delegate.generalize_existential(self.universe); - - Ok(replacement_region_vid) - } - - fn consts( - &mut self, - a: ty::Const<'tcx>, - _: ty::Const<'tcx>, - ) -> RelateResult<'tcx, ty::Const<'tcx>> { - match a.kind() { - ty::ConstKind::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => { - bug!("unexpected inference variable encountered in NLL generalization: {:?}", a); - } - ty::ConstKind::Infer(InferConst::Var(vid)) => { - let mut inner = self.infcx.inner.borrow_mut(); - let variable_table = &mut inner.const_unification_table(); - let var_value = variable_table.probe_value(vid); - match var_value.val.known() { - Some(u) => self.relate(u, u), - None => { - let new_var_id = variable_table.new_key(ConstVarValue { - origin: var_value.origin, - val: ConstVariableValue::Unknown { universe: self.universe }, - }); - Ok(self.tcx().mk_const(new_var_id, a.ty())) - } - } - } - ty::ConstKind::Unevaluated(..) if self.tcx().lazy_normalization() => Ok(a), - _ => relate::super_relate_consts(self, a, a), - } - } - - fn binders<T>( - &mut self, - a: ty::Binder<'tcx, T>, - _: ty::Binder<'tcx, T>, - ) -> RelateResult<'tcx, ty::Binder<'tcx, T>> - where - T: Relate<'tcx>, - { - debug!("TypeGeneralizer::binders(a={:?})", a); - let result = self.relate(a.skip_binder(), a.skip_binder())?; - Ok(a.rebind(result)) - } -} diff --git a/compiler/rustc_infer/src/infer/opaque_types.rs b/compiler/rustc_infer/src/infer/opaque_types.rs index 334395945ea..545310ad351 100644 --- a/compiler/rustc_infer/src/infer/opaque_types.rs +++ b/compiler/rustc_infer/src/infer/opaque_types.rs @@ -149,7 +149,7 @@ impl<'tcx> InferCtxt<'tcx> { // no one encounters it in practice. // It does occur however in `fn fut() -> impl Future<Output = i32> { async { 42 } }`, // where it is of no concern, so we only check for TAITs. - if let Some(OpaqueTyOrigin::TyAlias) = + if let Some(OpaqueTyOrigin::TyAlias { .. }) = b_def_id.as_local().and_then(|b_def_id| self.opaque_type_origin(b_def_id)) { self.tcx.sess.emit_err(OpaqueHiddenTypeDiag { @@ -381,8 +381,12 @@ impl<'tcx> InferCtxt<'tcx> { // Anonymous `impl Trait` hir::OpaqueTyOrigin::FnReturn(parent) => parent == parent_def_id, // Named `type Foo = impl Bar;` - hir::OpaqueTyOrigin::TyAlias => { - may_define_opaque_type(self.tcx, parent_def_id, opaque_hir_id) + hir::OpaqueTyOrigin::TyAlias { in_assoc_ty } => { + if in_assoc_ty { + self.tcx.opaque_types_defined_by(parent_def_id).contains(&def_id) + } else { + may_define_opaque_type(self.tcx, parent_def_id, opaque_hir_id) + } } }; in_definition_scope.then_some(origin) @@ -549,6 +553,7 @@ impl<'tcx> InferCtxt<'tcx> { // We can't normalize associated types from `rustc_infer`, // but we can eagerly register inference variables for them. // FIXME(RPITIT): Don't replace RPITITs with inference vars. + // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too. ty::Alias(ty::Projection, projection_ty) if !projection_ty.has_escaping_bound_vars() && !tcx.is_impl_trait_in_trait(projection_ty.def_id) => @@ -569,6 +574,7 @@ impl<'tcx> InferCtxt<'tcx> { hidden_ty } // FIXME(RPITIT): This can go away when we move to associated types + // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too. ty::Alias( ty::Projection, ty::AliasTy { def_id: def_id2, substs: substs2, .. }, diff --git a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs index 75ce0f83fd6..cd2462d3c31 100644 --- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs +++ b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs @@ -187,7 +187,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> { } else if pattern == value { Ok(pattern) } else { - relate::super_relate_tys(self, pattern, value) + relate::structurally_relate_tys(self, pattern, value) } } @@ -201,7 +201,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> { if pattern == value { Ok(pattern) } else { - relate::super_relate_consts(self, pattern, value) + relate::structurally_relate_consts(self, pattern, value) } } diff --git a/compiler/rustc_infer/src/infer/sub.rs b/compiler/rustc_infer/src/infer/sub.rs index 3766c250a9c..e0f29a8de8f 100644 --- a/compiler/rustc_infer/src/infer/sub.rs +++ b/compiler/rustc_infer/src/infer/sub.rs @@ -1,4 +1,4 @@ -use super::combine::{CombineFields, RelationDir}; +use super::combine::CombineFields; use super::{DefineOpaqueTypes, ObligationEmittingRelation, SubregionOrigin}; use crate::traits::{Obligation, PredicateObligations}; @@ -108,11 +108,11 @@ impl<'tcx> TypeRelation<'tcx> for Sub<'_, '_, 'tcx> { Ok(a) } (&ty::Infer(TyVar(a_id)), _) => { - self.fields.instantiate(b, RelationDir::SupertypeOf, a_id, !self.a_is_expected)?; + self.fields.instantiate(b, ty::Contravariant, a_id, !self.a_is_expected)?; Ok(a) } (_, &ty::Infer(TyVar(b_id))) => { - self.fields.instantiate(a, RelationDir::SubtypeOf, b_id, self.a_is_expected)?; + self.fields.instantiate(a, ty::Covariant, b_id, self.a_is_expected)?; Ok(a) } |