diff options
| -rw-r--r-- | compiler/rustc_infer/src/infer/combine.rs | 77 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/equate.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/generalize.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/sub.rs | 6 |
4 files changed, 29 insertions, 63 deletions
diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs index 9559bfab6da..79fc02c6c79 100644 --- a/compiler/rustc_infer/src/infer/combine.rs +++ b/compiler/rustc_infer/src/infer/combine.rs @@ -48,13 +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, @@ -378,12 +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()); @@ -398,7 +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 { value: 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); @@ -417,62 +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( - &mut self, - ty: Ty<'tcx>, - for_vid: ty::TyVid, - dir: RelationDir, - ) -> RelateResult<'tcx, Generalization<Ty<'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, - }; - - generalize::generalize( - self.infcx, - &mut CombineDelegate { - infcx: self.infcx, - param_env: self.param_env, - span: self.trace.span(), - }, - ty, - for_vid, - ambient_variance, - ) - } - pub fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) { self.obligations.extend(obligations.into_iter()); } 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/generalize.rs b/compiler/rustc_infer/src/infer/generalize.rs index 3eeb55ae744..d4a1dacde10 100644 --- a/compiler/rustc_infer/src/infer/generalize.rs +++ b/compiler/rustc_infer/src/infer/generalize.rs @@ -10,6 +10,9 @@ 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, 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) } |