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-rw-r--r--compiler/rustc_infer/src/infer/combine.rs586
-rw-r--r--compiler/rustc_infer/src/infer/equate.rs6
-rw-r--r--compiler/rustc_infer/src/infer/error_reporting/mod.rs2
-rw-r--r--compiler/rustc_infer/src/infer/generalize.rs479
-rw-r--r--compiler/rustc_infer/src/infer/mod.rs1
-rw-r--r--compiler/rustc_infer/src/infer/nll_relate/mod.rs276
-rw-r--r--compiler/rustc_infer/src/infer/outlives/test_type_match.rs4
-rw-r--r--compiler/rustc_infer/src/infer/sub.rs6
-rw-r--r--compiler/rustc_middle/src/ty/_match.rs4
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs18
-rw-r--r--compiler/rustc_middle/src/ty/relate.rs31
-rw-r--r--tests/ui/traits/non_lifetime_binders/universe-error1.rs18
-rw-r--r--tests/ui/traits/non_lifetime_binders/universe-error1.stderr27
13 files changed, 627 insertions, 831 deletions
diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
index 3f385c47f19..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,
@@ -152,7 +138,7 @@ impl<'tcx> InferCtxt<'tcx> {
Ok(a)
}
- _ => ty::relate::super_relate_tys(relation, a, b),
+ _ => ty::relate::structurally_relate_tys(relation, a, b),
}
}
@@ -211,11 +197,11 @@ impl<'tcx> InferCtxt<'tcx> {
// matching in the solver.
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(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 });
@@ -237,11 +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() =>
@@ -252,7 +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.
@@ -294,24 +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,
@@ -392,12 +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());
@@ -412,7 +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);
@@ -431,78 +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());
}
@@ -514,313 +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>);
@@ -873,135 +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 ce70f39cc40..ad4f5058b5e 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2723,7 +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/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 9a95a9c8375..e53319e3b86 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;
diff --git a/compiler/rustc_infer/src/infer/nll_relate/mod.rs b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
index 9c139d17c18..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(inner);
- 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/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)
}
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index 468c2c818b2..cbc68fde9d9 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -83,7 +83,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
(&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(self.tcx().ty_error(guar)),
- _ => relate::super_relate_tys(self, a, b),
+ _ => relate::structurally_relate_tys(self, a, b),
}
}
@@ -109,7 +109,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
_ => {}
}
- relate::super_relate_consts(self, a, b)
+ relate::structurally_relate_consts(self, a, b)
}
fn binders<T>(
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index a497b6a335d..df324bcc52c 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1072,6 +1072,24 @@ impl ParamTerm {
}
}
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub enum TermVid<'tcx> {
+ Ty(ty::TyVid),
+ Const(ty::ConstVid<'tcx>),
+}
+
+impl From<ty::TyVid> for TermVid<'_> {
+ fn from(value: ty::TyVid) -> Self {
+ TermVid::Ty(value)
+ }
+}
+
+impl<'tcx> From<ty::ConstVid<'tcx>> for TermVid<'tcx> {
+ fn from(value: ty::ConstVid<'tcx>) -> Self {
+ TermVid::Const(value)
+ }
+}
+
/// This kind of predicate has no *direct* correspondent in the
/// syntax, but it roughly corresponds to the syntactic forms:
///
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index da43475941e..3bbe6a23b66 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -388,24 +388,24 @@ impl<'tcx> Relate<'tcx> for Ty<'tcx> {
}
}
-/// The main "type relation" routine. Note that this does not handle
-/// inference artifacts, so you should filter those out before calling
-/// it.
-pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
+/// Relates `a` and `b` structurally, calling the relation for all nested values.
+/// Any semantic equality, e.g. of projections, and inference variables have to be
+/// handled by the caller.
+pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
relation: &mut R,
a: Ty<'tcx>,
b: Ty<'tcx>,
) -> RelateResult<'tcx, Ty<'tcx>> {
let tcx = relation.tcx();
- debug!("super_relate_tys: a={:?} b={:?}", a, b);
+ debug!("structurally_relate_tys: a={:?} b={:?}", a, b);
match (a.kind(), b.kind()) {
(&ty::Infer(_), _) | (_, &ty::Infer(_)) => {
// The caller should handle these cases!
- bug!("var types encountered in super_relate_tys")
+ bug!("var types encountered in structurally_relate_tys")
}
(ty::Bound(..), _) | (_, ty::Bound(..)) => {
- bug!("bound types encountered in super_relate_tys")
+ bug!("bound types encountered in structurally_relate_tys")
}
(&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(tcx.ty_error(guar)),
@@ -575,15 +575,18 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
}
}
-/// The main "const relation" routine. Note that this does not handle
-/// inference artifacts, so you should filter those out before calling
-/// it.
-pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
+/// Relates `a` and `b` structurally, calling the relation for all nested values.
+/// Any semantic equality, e.g. of unevaluated consts, and inference variables have
+/// to be handled by the caller.
+///
+/// FIXME: This is not totally structual, which probably should be fixed.
+/// See the HACKs below.
+pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
relation: &mut R,
mut a: ty::Const<'tcx>,
mut b: ty::Const<'tcx>,
) -> RelateResult<'tcx, ty::Const<'tcx>> {
- debug!("{}.super_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b);
+ debug!("{}.structurally_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b);
let tcx = relation.tcx();
// HACK(const_generics): We still need to eagerly evaluate consts when
@@ -602,7 +605,7 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
b = tcx.expand_abstract_consts(b);
}
- debug!("{}.super_relate_consts(normed_a = {:?}, normed_b = {:?})", relation.tag(), a, b);
+ debug!("{}.structurally_relate_consts(normed_a = {:?}, normed_b = {:?})", relation.tag(), a, b);
// Currently, the values that can be unified are primitive types,
// and those that derive both `PartialEq` and `Eq`, corresponding
@@ -610,7 +613,7 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
let is_match = match (a.kind(), b.kind()) {
(ty::ConstKind::Infer(_), _) | (_, ty::ConstKind::Infer(_)) => {
// The caller should handle these cases!
- bug!("var types encountered in super_relate_consts: {:?} {:?}", a, b)
+ bug!("var types encountered in structurally_relate_consts: {:?} {:?}", a, b)
}
(ty::ConstKind::Error(_), _) => return Ok(a),
diff --git a/tests/ui/traits/non_lifetime_binders/universe-error1.rs b/tests/ui/traits/non_lifetime_binders/universe-error1.rs
new file mode 100644
index 00000000000..eadee6b711e
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/universe-error1.rs
@@ -0,0 +1,18 @@
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+trait Other<U: ?Sized> {}
+
+impl<U: ?Sized> Other<U> for U {}
+
+#[rustfmt::skip]
+fn foo<U: ?Sized>()
+where
+ for<T> T: Other<U> {}
+
+fn bar() {
+ foo::<_>();
+ //~^ ERROR the trait bound `T: Other<_>` is not satisfied
+}
+
+fn main() {}
diff --git a/tests/ui/traits/non_lifetime_binders/universe-error1.stderr b/tests/ui/traits/non_lifetime_binders/universe-error1.stderr
new file mode 100644
index 00000000000..bfcad72e352
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/universe-error1.stderr
@@ -0,0 +1,27 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+ --> $DIR/universe-error1.rs:1:12
+ |
+LL | #![feature(non_lifetime_binders)]
+ | ^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
+ = note: `#[warn(incomplete_features)]` on by default
+
+error[E0277]: the trait bound `T: Other<_>` is not satisfied
+ --> $DIR/universe-error1.rs:14:11
+ |
+LL | foo::<_>();
+ | ^ the trait `Other<_>` is not implemented for `T`
+ |
+note: required by a bound in `foo`
+ --> $DIR/universe-error1.rs:11:15
+ |
+LL | fn foo<U: ?Sized>()
+ | --- required by a bound in this function
+LL | where
+LL | for<T> T: Other<U> {}
+ | ^^^^^^^^ required by this bound in `foo`
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0277`.
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