diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/solve/eval_ctxt.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/eval_ctxt.rs | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs new file mode 100644 index 000000000..95612674e --- /dev/null +++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs @@ -0,0 +1,184 @@ +use rustc_hir::def_id::DefId; +use rustc_infer::infer::at::ToTrace; +use rustc_infer::infer::canonical::CanonicalVarValues; +use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use rustc_infer::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime}; +use rustc_infer::traits::query::NoSolution; +use rustc_infer::traits::ObligationCause; +use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind}; +use rustc_middle::ty::{ + self, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, + TypeVisitor, +}; +use rustc_span::DUMMY_SP; +use std::ops::ControlFlow; + +use super::search_graph::SearchGraph; +use super::Goal; + +pub struct EvalCtxt<'a, 'tcx> { + // FIXME: should be private. + pub(super) infcx: &'a InferCtxt<'tcx>, + pub(super) var_values: CanonicalVarValues<'tcx>, + /// The highest universe index nameable by the caller. + /// + /// When we enter a new binder inside of the query we create new universes + /// which the caller cannot name. We have to be careful with variables from + /// these new universes when creating the query response. + /// + /// Both because these new universes can prevent us from reaching a fixpoint + /// if we have a coinductive cycle and because that's the only way we can return + /// new placeholders to the caller. + pub(super) max_input_universe: ty::UniverseIndex, + + pub(super) search_graph: &'a mut SearchGraph<'tcx>, + + /// This field is used by a debug assertion in [`EvalCtxt::evaluate_goal`], + /// see the comment in that method for more details. + pub in_projection_eq_hack: bool, +} + +impl<'tcx> EvalCtxt<'_, 'tcx> { + pub(super) fn probe<T>(&mut self, f: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> T) -> T { + self.infcx.probe(|_| f(self)) + } + + pub(super) fn tcx(&self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + pub(super) fn next_ty_infer(&self) -> Ty<'tcx> { + self.infcx.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::MiscVariable, + span: DUMMY_SP, + }) + } + + pub(super) fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx> { + self.infcx.next_const_var( + ty, + ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span: DUMMY_SP }, + ) + } + + /// Is the projection predicate is of the form `exists<T> <Ty as Trait>::Assoc = T`. + /// + /// This is the case if the `term` is an inference variable in the innermost universe + /// and does not occur in any other part of the predicate. + pub(super) fn term_is_fully_unconstrained( + &self, + goal: Goal<'tcx, ty::ProjectionPredicate<'tcx>>, + ) -> bool { + let term_is_infer = match goal.predicate.term.unpack() { + ty::TermKind::Ty(ty) => { + if let &ty::Infer(ty::TyVar(vid)) = ty.kind() { + match self.infcx.probe_ty_var(vid) { + Ok(value) => bug!("resolved var in query: {goal:?} {value:?}"), + Err(universe) => universe == self.universe(), + } + } else { + false + } + } + ty::TermKind::Const(ct) => { + if let ty::ConstKind::Infer(ty::InferConst::Var(vid)) = ct.kind() { + match self.infcx.probe_const_var(vid) { + Ok(value) => bug!("resolved var in query: {goal:?} {value:?}"), + Err(universe) => universe == self.universe(), + } + } else { + false + } + } + }; + + // Guard against `<T as Trait<?0>>::Assoc = ?0>`. + struct ContainsTerm<'tcx> { + term: ty::Term<'tcx>, + } + impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsTerm<'tcx> { + type BreakTy = (); + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + if t.needs_infer() { + if ty::Term::from(t) == self.term { + ControlFlow::Break(()) + } else { + t.super_visit_with(self) + } + } else { + ControlFlow::Continue(()) + } + } + + fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { + if c.needs_infer() { + if ty::Term::from(c) == self.term { + ControlFlow::Break(()) + } else { + c.super_visit_with(self) + } + } else { + ControlFlow::Continue(()) + } + } + } + + let mut visitor = ContainsTerm { term: goal.predicate.term }; + + term_is_infer + && goal.predicate.projection_ty.visit_with(&mut visitor).is_continue() + && goal.param_env.visit_with(&mut visitor).is_continue() + } + + #[instrument(level = "debug", skip(self, param_env), ret)] + pub(super) fn eq<T: ToTrace<'tcx>>( + &self, + param_env: ty::ParamEnv<'tcx>, + lhs: T, + rhs: T, + ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> { + self.infcx + .at(&ObligationCause::dummy(), param_env) + .eq(lhs, rhs) + .map(|InferOk { value: (), obligations }| { + obligations.into_iter().map(|o| o.into()).collect() + }) + .map_err(|e| { + debug!(?e, "failed to equate"); + NoSolution + }) + } + + pub(super) fn instantiate_binder_with_infer<T: TypeFoldable<TyCtxt<'tcx>> + Copy>( + &self, + value: ty::Binder<'tcx, T>, + ) -> T { + self.infcx.instantiate_binder_with_fresh_vars( + DUMMY_SP, + LateBoundRegionConversionTime::HigherRankedType, + value, + ) + } + + pub(super) fn instantiate_binder_with_placeholders<T: TypeFoldable<TyCtxt<'tcx>> + Copy>( + &self, + value: ty::Binder<'tcx, T>, + ) -> T { + self.infcx.instantiate_binder_with_placeholders(value) + } + + pub(super) fn resolve_vars_if_possible<T>(&self, value: T) -> T + where + T: TypeFoldable<TyCtxt<'tcx>>, + { + self.infcx.resolve_vars_if_possible(value) + } + + pub(super) fn fresh_substs_for_item(&self, def_id: DefId) -> ty::SubstsRef<'tcx> { + self.infcx.fresh_substs_for_item(DUMMY_SP, def_id) + } + + pub(super) fn universe(&self) -> ty::UniverseIndex { + self.infcx.universe() + } +} |