add deep normalization via the new solver

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -26,6 +26,7 @@ mod canonicalize;
 mod eval_ctxt;
 mod fulfill;
 pub mod inspect;
+mod normalize;
 mod opaques;
 mod project_goals;
 mod search_graph;
@@ -34,6 +35,7 @@ mod weak_types;
 
 pub use eval_ctxt::{EvalCtxt, InferCtxtEvalExt};
 pub use fulfill::FulfillmentCtxt;
+pub(crate) use normalize::deeply_normalize;
 
 #[derive(Debug, Clone, Copy)]
 enum SolverMode {

compiler/rustc_trait_selection/src/solve/normalize.rs

@@ -0,0 +1,222 @@
+use crate::traits::error_reporting::TypeErrCtxtExt;
+use crate::traits::query::evaluate_obligation::InferCtxtExt;
+use crate::traits::{needs_normalization, TraitEngineExt as _};
+use crate::traits::{BoundVarReplacer, PlaceholderReplacer};
+use rustc_data_structures::stack::ensure_sufficient_stack;
+use rustc_infer::infer::at::At;
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_infer::traits::TraitEngineExt;
+use rustc_infer::traits::{FulfillmentError, Obligation, TraitEngine};
+use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
+use rustc_middle::traits::Reveal;
+use rustc_middle::ty::{self, AliasTy, Ty, TyCtxt, UniverseIndex};
+use rustc_middle::ty::{FallibleTypeFolder, TypeSuperFoldable};
+use rustc_middle::ty::{TypeFoldable, TypeVisitableExt};
+
+/// Deeply normalize all aliases in `value`. This does not handle inference and expects
+/// its input to be already fully resolved.
+pub(crate) fn deeply_normalize<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
+    at: At<'_, 'tcx>,
+    value: T,
+) -> Result<T, Vec<FulfillmentError<'tcx>>> {
+    let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(&at.infcx);
+    let mut folder =
+        NormalizationFolder { at, fulfill_cx: &mut *fulfill_cx, depth: 0, universes: Vec::new() };
+
+    value.try_fold_with(&mut folder)
+}
+
+struct NormalizationFolder<'me, 'tcx> {
+    at: At<'me, 'tcx>,
+    fulfill_cx: &'me mut dyn TraitEngine<'tcx>,
+    depth: usize,
+    universes: Vec<Option<UniverseIndex>>,
+}
+
+impl<'tcx> NormalizationFolder<'_, 'tcx> {
+    fn normalize_alias_ty(
+        &mut self,
+        alias: AliasTy<'tcx>,
+    ) -> Result<Ty<'tcx>, Vec<FulfillmentError<'tcx>>> {
+        let infcx = self.at.infcx;
+        let tcx = infcx.tcx;
+        let recursion_limit = tcx.recursion_limit();
+        if !recursion_limit.value_within_limit(self.depth) {
+            self.at.infcx.err_ctxt().report_overflow_error(
+                &alias.to_ty(tcx),
+                self.at.cause.span,
+                true,
+                |_| {},
+            );
+        }
+
+        self.depth += 1;
+
+        let new_infer_ty = infcx.next_ty_var(TypeVariableOrigin {
+            kind: TypeVariableOriginKind::NormalizeProjectionType,
+            span: self.at.cause.span,
+        });
+        let obligation = Obligation::new(
+            tcx,
+            self.at.cause.clone(),
+            self.at.param_env,
+            ty::Binder::dummy(ty::ProjectionPredicate {
+                projection_ty: alias,
+                term: new_infer_ty.into(),
+            }),
+        );
+
+        // Do not emit an error if normalization is known to fail but instead
+        // keep the projection unnormalized. This is the case for projections
+        // with a `T: Trait` where-clause and opaque types outside of the defining
+        // scope.
+        let result = if infcx.predicate_may_hold(&obligation) {
+            self.fulfill_cx.register_predicate_obligation(infcx, obligation);
+            let errors = self.fulfill_cx.select_all_or_error(infcx);
+            if !errors.is_empty() {
+                return Err(errors);
+            }
+            let ty = infcx.resolve_vars_if_possible(new_infer_ty);
+            ty.try_fold_with(self)?
+        } else {
+            alias.to_ty(tcx).try_super_fold_with(self)?
+        };
+
+        self.depth -= 1;
+        Ok(result)
+    }
+
+    fn normalize_unevaluated_const(
+        &mut self,
+        ty: Ty<'tcx>,
+        uv: ty::UnevaluatedConst<'tcx>,
+    ) -> Result<ty::Const<'tcx>, Vec<FulfillmentError<'tcx>>> {
+        let infcx = self.at.infcx;
+        let tcx = infcx.tcx;
+        let recursion_limit = tcx.recursion_limit();
+        if !recursion_limit.value_within_limit(self.depth) {
+            self.at.infcx.err_ctxt().report_overflow_error(
+                &tcx.mk_const(uv, ty),
+                self.at.cause.span,
+                true,
+                |_| {},
+            );
+        }
+
+        self.depth += 1;
+
+        let new_infer_ct = infcx.next_const_var(
+            ty,
+            ConstVariableOrigin {
+                kind: ConstVariableOriginKind::MiscVariable,
+                span: self.at.cause.span,
+            },
+        );
+        let obligation = Obligation::new(
+            tcx,
+            self.at.cause.clone(),
+            self.at.param_env,
+            ty::Binder::dummy(ty::ProjectionPredicate {
+                projection_ty: tcx.mk_alias_ty(uv.def, uv.substs),
+                term: new_infer_ct.into(),
+            }),
+        );
+
+        let result = if infcx.predicate_may_hold(&obligation) {
+            self.fulfill_cx.register_predicate_obligation(infcx, obligation);
+            let errors = self.fulfill_cx.select_all_or_error(infcx);
+            if !errors.is_empty() {
+                return Err(errors);
+            }
+            let ct = infcx.resolve_vars_if_possible(new_infer_ct);
+            ct.try_fold_with(self)?
+        } else {
+            tcx.mk_const(uv, ty).try_super_fold_with(self)?
+        };
+
+        self.depth -= 1;
+        Ok(result)
+    }
+}
+
+impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for NormalizationFolder<'_, 'tcx> {
+    type Error = Vec<FulfillmentError<'tcx>>;
+
+    fn interner(&self) -> TyCtxt<'tcx> {
+        self.at.infcx.tcx
+    }
+
+    fn try_fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
+        &mut self,
+        t: ty::Binder<'tcx, T>,
+    ) -> Result<ty::Binder<'tcx, T>, Self::Error> {
+        self.universes.push(None);
+        let t = t.try_super_fold_with(self)?;
+        self.universes.pop();
+        Ok(t)
+    }
+
+    fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
+        let reveal = self.at.param_env.reveal();
+        let infcx = self.at.infcx;
+        if !needs_normalization(&ty, reveal) {
+            return Ok(ty);
+        }
+
+        let (kind, data) = match *ty.kind() {
+            ty::Alias(kind, alias_ty) => (kind, alias_ty),
+            _ => return ty.try_super_fold_with(self),
+        };
+
+        // We don't normalize opaque types unless we have
+        // `Reveal::All`, even if we're in the defining scope.
+        if matches!(kind, ty::Opaque) && reveal == Reveal::UserFacing {
+            return ty.try_super_fold_with(self);
+        }
+
+        if data.has_escaping_bound_vars() {
+            let (data, mapped_regions, mapped_types, mapped_consts) =
+                BoundVarReplacer::replace_bound_vars(infcx, &mut self.universes, data);
+            let result = ensure_sufficient_stack(|| self.normalize_alias_ty(data))?;
+            Ok(PlaceholderReplacer::replace_placeholders(
+                infcx,
+                mapped_regions,
+                mapped_types,
+                mapped_consts,
+                &mut self.universes,
+                result,
+            ))
+        } else {
+            ensure_sufficient_stack(|| self.normalize_alias_ty(data))
+        }
+    }
+
+    fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
+        let reveal = self.at.param_env.reveal();
+        let infcx = self.at.infcx;
+        if !needs_normalization(&ct, reveal) {
+            return Ok(ct);
+        }
+
+        let uv = match ct.kind() {
+            ty::ConstKind::Unevaluated(ct) => ct,
+            _ => return ct.try_super_fold_with(self),
+        };
+
+        if uv.has_escaping_bound_vars() {
+            let (uv, mapped_regions, mapped_types, mapped_consts) =
+                BoundVarReplacer::replace_bound_vars(infcx, &mut self.universes, uv);
+            let result = ensure_sufficient_stack(|| self.normalize_unevaluated_const(ct.ty(), uv))?;
+            Ok(PlaceholderReplacer::replace_placeholders(
+                infcx,
+                mapped_regions,
+                mapped_types,
+                mapped_consts,
+                &mut self.universes,
+                result,
+            ))
+        } else {
+            ensure_sufficient_stack(|| self.normalize_unevaluated_const(ct.ty(), uv))
+        }
+    }
+}

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -40,6 +40,8 @@ use rustc_span::Span;
 use std::fmt::Debug;
 use std::ops::ControlFlow;
 
+pub(crate) use self::project::{needs_normalization, BoundVarReplacer, PlaceholderReplacer};
+
 pub use self::FulfillmentErrorCode::*;
 pub use self::ImplSource::*;
 pub use self::ObligationCauseCode::*;

compiler/rustc_trait_selection/src/traits/project.rs

@@ -20,6 +20,7 @@ use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
 use crate::traits::error_reporting::TypeErrCtxtExt as _;
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 use crate::traits::select::ProjectionMatchesProjection;
+use crate::traits::TraitEngineExt as _;
 use rustc_data_structures::sso::SsoHashSet;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::ErrorGuaranteed;
@@ -28,7 +29,10 @@ use rustc_hir::lang_items::LangItem;
 use rustc_infer::infer::at::At;
 use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_infer::infer::DefineOpaqueTypes;
+use rustc_infer::traits::FulfillmentError;
 use rustc_infer::traits::ObligationCauseCode;
+use rustc_infer::traits::TraitEngine;
+use rustc_infer::traits::TraitEngineExt as _;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::visit::{MaxUniverse, TypeVisitable, TypeVisitableExt};
@@ -53,14 +57,48 @@ pub trait NormalizeExt<'tcx> {
     /// This normalization should be used when the type contains inference variables or the
     /// projection may be fallible.
     fn normalize<T: TypeFoldable<TyCtxt<'tcx>>>(&self, t: T) -> InferOk<'tcx, T>;
+
+    /// Deeply normalizes `value`, replacing all aliases which can by normalized in
+    /// the current environment. Unlike other normalization routines, this errors
+    /// in case normalization fails or is ambiguous.
+    ///
+    /// In the old solver this simply uses `normalize` and errors in
+    /// case of ambiguity. The new solver only normalizes in this function and
+    /// `normalize` is a noop.
+    ///
+    /// This only normalize opaque types with `Reveal::All`.
+    fn deeply_normalize<T: TypeFoldable<TyCtxt<'tcx>>>(
+        self,
+        value: T,
+    ) -> Result<T, Vec<FulfillmentError<'tcx>>>;
 }
 
 impl<'tcx> NormalizeExt<'tcx> for At<'_, 'tcx> {
     fn normalize<T: TypeFoldable<TyCtxt<'tcx>>>(&self, value: T) -> InferOk<'tcx, T> {
-        let mut selcx = SelectionContext::new(self.infcx);
-        let Normalized { value, obligations } =
-            normalize_with_depth(&mut selcx, self.param_env, self.cause.clone(), 0, value);
-        InferOk { value, obligations }
+        if self.infcx.next_trait_solver() {
+            InferOk { value, obligations: Vec::new() }
+        } else {
+            let mut selcx = SelectionContext::new(self.infcx);
+            let Normalized { value, obligations } =
+                normalize_with_depth(&mut selcx, self.param_env, self.cause.clone(), 0, value);
+            InferOk { value, obligations }
+        }
+    }
+
+    fn deeply_normalize<T: TypeFoldable<TyCtxt<'tcx>>>(
+        self,
+        value: T,
+    ) -> Result<T, Vec<FulfillmentError<'tcx>>> {
+        if self.infcx.next_trait_solver() {
+            crate::solve::deeply_normalize(self, value)
+        } else {
+            let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(&self.infcx);
+            let value = self
+                .normalize(value)
+                .into_value_registering_obligations(self.infcx, &mut *fulfill_cx);
+            let errors = fulfill_cx.select_all_or_error(self.infcx);
+            if errors.is_empty() { Ok(value) } else { Err(errors) }
+        }
     }
 }
 

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -30,7 +30,7 @@ pub trait QueryNormalizeExt<'tcx> {
     ///
     /// After codegen, when lifetimes do not matter, it is preferable to instead
     /// use [`TyCtxt::normalize_erasing_regions`], which wraps this procedure.
-    fn query_normalize<T>(&self, value: T) -> Result<Normalized<'tcx, T>, NoSolution>
+    fn query_normalize<T>(self, value: T) -> Result<Normalized<'tcx, T>, NoSolution>
     where
         T: TypeFoldable<TyCtxt<'tcx>>;
 }
@@ -49,7 +49,7 @@ impl<'cx, 'tcx> QueryNormalizeExt<'tcx> for At<'cx, 'tcx> {
     /// normalizing, but for now should be used only when we actually
     /// know that normalization will succeed, since error reporting
     /// and other details are still "under development".
-    fn query_normalize<T>(&self, value: T) -> Result<Normalized<'tcx, T>, NoSolution>
+    fn query_normalize<T>(self, value: T) -> Result<Normalized<'tcx, T>, NoSolution>
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
@@ -60,6 +60,16 @@ impl<'cx, 'tcx> QueryNormalizeExt<'tcx> for At<'cx, 'tcx> {
             self.param_env,
             self.cause,
         );
+
+        if self.infcx.next_trait_solver() {
+            match crate::solve::deeply_normalize(self, value) {
+                Ok(value) => return Ok(Normalized { value, obligations: vec![] }),
+                Err(_errors) => {
+                    return Err(NoSolution);
+                }
+            }
+        }
+
         if !needs_normalization(&value, self.param_env.reveal()) {
             return Ok(Normalized { value, obligations: vec![] });
         }