diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/nll_relate/mod.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/nll_relate/mod.rs | 276 |
1 files changed, 16 insertions, 260 deletions
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)) - } -} |