Auto merge of #106742 - compiler-errors:new-solver-make-it-not-ice, r=lcnr

Implement some FIXME methods in the new trait solver

Implement just enough of the solver's response logic to make it not ICE.

Also, fix a bug with `no_bound_vars` call failing due to canonical bound vars.

r? `@lcnr`

compiler/rustc_middle/src/ty/sty.rs

@@ -7,8 +7,8 @@ use crate::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
 use crate::ty::visit::ValidateBoundVars;
 use crate::ty::InferTy::*;
 use crate::ty::{
-    self, AdtDef, DefIdTree, Discr, Term, Ty, TyCtxt, TypeFlags, TypeSuperVisitable, TypeVisitable,
-    TypeVisitor,
+    self, AdtDef, DefIdTree, Discr, FallibleTypeFolder, Term, Ty, TyCtxt, TypeFlags, TypeFoldable,
+    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
 use crate::ty::{List, ParamEnv};
 use hir::def::DefKind;
@@ -1106,6 +1106,17 @@ impl<'tcx, T> Binder<'tcx, T> {
         if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
     }
 
+    pub fn no_bound_vars_ignoring_escaping(self, tcx: TyCtxt<'tcx>) -> Option<T>
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        if !self.0.has_escaping_bound_vars() {
+            Some(self.skip_binder())
+        } else {
+            self.0.try_fold_with(&mut SkipBindersAt { index: ty::INNERMOST, tcx }).ok()
+        }
+    }
+
     /// Splits the contents into two things that share the same binder
     /// level as the original, returning two distinct binders.
     ///
@@ -1135,6 +1146,81 @@ impl<'tcx, T: IntoIterator> Binder<'tcx, T> {
     }
 }
 
+struct SkipBindersAt<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    index: ty::DebruijnIndex,
+}
+
+impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
+    type Error = ();
+
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error>
+    where
+        T: ty::TypeFoldable<'tcx>,
+    {
+        self.index.shift_in(1);
+        let value = t.try_map_bound(|t| t.try_fold_with(self));
+        self.index.shift_out(1);
+        value
+    }
+
+    fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
+        if !ty.has_escaping_bound_vars() {
+            Ok(ty)
+        } else if let ty::Bound(index, bv) = *ty.kind() {
+            if index == self.index {
+                Err(())
+            } else {
+                Ok(self.tcx().mk_ty(ty::Bound(index.shifted_out(1), bv)))
+            }
+        } else {
+            ty.try_super_fold_with(self)
+        }
+    }
+
+    fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> {
+        if !r.has_escaping_bound_vars() {
+            Ok(r)
+        } else if let ty::ReLateBound(index, bv) = r.kind() {
+            if index == self.index {
+                Err(())
+            } else {
+                Ok(self.tcx().mk_region(ty::ReLateBound(index.shifted_out(1), bv)))
+            }
+        } else {
+            r.try_super_fold_with(self)
+        }
+    }
+
+    fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
+        if !ct.has_escaping_bound_vars() {
+            Ok(ct)
+        } else if let ty::ConstKind::Bound(index, bv) = ct.kind() {
+            if index == self.index {
+                Err(())
+            } else {
+                Ok(self.tcx().mk_const(
+                    ty::ConstKind::Bound(index.shifted_out(1), bv),
+                    ct.ty().try_fold_with(self)?,
+                ))
+            }
+        } else {
+            ct.try_super_fold_with(self)
+        }
+    }
+
+    fn try_fold_predicate(
+        &mut self,
+        p: ty::Predicate<'tcx>,
+    ) -> Result<ty::Predicate<'tcx>, Self::Error> {
+        if !p.has_escaping_bound_vars() { Ok(p) } else { p.try_super_fold_with(self) }
+    }
+}
+
 /// Represents the projection of an associated type.
 ///
 /// For a projection, this would be `<Ty as Trait<...>>::N`.

compiler/rustc_trait_selection/src/solve/assembly.rs

@@ -2,8 +2,8 @@
 
 use super::infcx_ext::InferCtxtExt;
 use super::{
-    fixme_instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty,
-    EvalCtxt, Goal,
+    instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty, EvalCtxt,
+    Goal,
 };
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
@@ -121,11 +121,8 @@ impl<'a, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'tcx, G> {
             // canonical wrt the caller.
             for Candidate { source, result } in normalized_candidates {
                 self.infcx.probe(|_| {
-                    let candidate_certainty = fixme_instantiate_canonical_query_response(
-                        &self.infcx,
-                        &orig_values,
-                        result,
-                    );
+                    let candidate_certainty =
+                        instantiate_canonical_query_response(&self.infcx, &orig_values, result);
 
                     // FIXME: This is a bit scary if the `normalizes_to_goal` overflows.
                     //

compiler/rustc_trait_selection/src/solve/cache.rs

@@ -9,11 +9,12 @@
 //! FIXME(@lcnr): Write that section, feel free to ping me if you need help here
 //! before then or if I still haven't done that before January 2023.
 use super::overflow::OverflowData;
-use super::CanonicalGoal;
+use super::{CanonicalGoal, Certainty, MaybeCause, Response};
 use super::{EvalCtxt, QueryResult};
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_middle::ty::TyCtxt;
+use rustc_infer::infer::canonical::{Canonical, CanonicalVarKind, CanonicalVarValues};
+use rustc_middle::ty::{self, TyCtxt};
 use std::{cmp::Ordering, collections::hash_map::Entry};
 
 #[derive(Debug, Clone)]
@@ -111,11 +112,11 @@ impl<'tcx> EvalCtxt<'tcx> {
             // No entry, simply push this goal on the stack after dealing with overflow.
             Entry::Vacant(v) => {
                 if self.overflow_data.has_overflow(cache.stack.len()) {
-                    return Err(self.deal_with_overflow());
+                    return Err(self.deal_with_overflow(goal));
                 }
 
                 v.insert(ProvisionalEntry {
-                    response: fixme_response_yes_no_constraints(),
+                    response: response_no_constraints(self.tcx, goal, Certainty::Yes),
                     depth: cache.stack.len(),
                 });
                 cache.stack.push(StackElem { goal, has_been_used: false });
@@ -150,7 +151,11 @@ impl<'tcx> EvalCtxt<'tcx> {
                 {
                     Err(entry.response)
                 } else {
-                    Err(fixme_response_maybe_no_constraints())
+                    Err(response_no_constraints(
+                        self.tcx,
+                        goal,
+                        Certainty::Maybe(MaybeCause::Ambiguity),
+                    ))
                 }
             }
         }
@@ -248,10 +253,39 @@ impl<'tcx> EvalCtxt<'tcx> {
     }
 }
 
-fn fixme_response_yes_no_constraints<'tcx>() -> QueryResult<'tcx> {
-    unimplemented!()
-}
+pub(super) fn response_no_constraints<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    goal: Canonical<'tcx, impl Sized>,
+    certainty: Certainty,
+) -> QueryResult<'tcx> {
+    let var_values = goal
+        .variables
+        .iter()
+        .enumerate()
+        .map(|(i, info)| match info.kind {
+            CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
+                tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into())).into()
+            }
+            CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
+                let br = ty::BoundRegion {
+                    var: ty::BoundVar::from_usize(i),
+                    kind: ty::BrAnon(i as u32, None),
+                };
+                tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
+            }
+            CanonicalVarKind::Const(_, ty) | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
+                .mk_const(ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)), ty)
+                .into(),
+        })
+        .collect();
 
-fn fixme_response_maybe_no_constraints<'tcx>() -> QueryResult<'tcx> {
-    unimplemented!()
+    Ok(Canonical {
+        max_universe: goal.max_universe,
+        variables: goal.variables,
+        value: Response {
+            var_values: CanonicalVarValues { var_values },
+            external_constraints: Default::default(),
+            certainty,
+        },
+    })
 }

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -62,7 +62,7 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
         let mut errors = Vec::new();
         for i in 0.. {
             if !infcx.tcx.recursion_limit().value_within_limit(i) {
-                unimplemented!("overflow")
+                unimplemented!("overflowed on pending obligations: {:?}", self.obligations);
             }
 
             let mut has_changed = false;

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -19,15 +19,19 @@
 
 use std::mem;
 
-use rustc_infer::infer::canonical::OriginalQueryValues;
-use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
+use rustc_infer::infer::canonical::{OriginalQueryValues, QueryRegionConstraints, QueryResponse};
+use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::traits::Obligation;
+use rustc_middle::infer::canonical::Certainty as OldCertainty;
 use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{RegionOutlivesPredicate, ToPredicate, TypeOutlivesPredicate};
 use rustc_span::DUMMY_SP;
 
+use crate::traits::ObligationCause;
+
+use self::cache::response_no_constraints;
 use self::infcx_ext::InferCtxtExt;
 
 mod assembly;
@@ -119,7 +123,7 @@ pub enum MaybeCause {
 }
 
 /// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Hash, TypeFoldable, TypeVisitable, Default)]
 pub struct ExternalConstraints<'tcx> {
     // FIXME: implement this.
     regions: (),
@@ -175,7 +179,7 @@ impl<'tcx> EvalCtxt<'tcx> {
         let canonical_response = self.evaluate_canonical_goal(canonical_goal)?;
         Ok((
             true, // FIXME: check whether `var_values` are an identity substitution.
-            fixme_instantiate_canonical_query_response(infcx, &orig_values, canonical_response),
+            instantiate_canonical_query_response(infcx, &orig_values, canonical_response),
         ))
     }
 
@@ -208,7 +212,8 @@ impl<'tcx> EvalCtxt<'tcx> {
         // of `PredicateKind` this is the case and it is and faster than instantiating and
         // recanonicalizing.
         let Goal { param_env, predicate } = canonical_goal.value;
-        if let Some(kind) = predicate.kind().no_bound_vars() {
+
+        if let Some(kind) = predicate.kind().no_bound_vars_ignoring_escaping(self.tcx) {
             match kind {
                 ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => self.compute_trait_goal(
                     canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
@@ -234,7 +239,10 @@ impl<'tcx> EvalCtxt<'tcx> {
                 | ty::PredicateKind::ConstEvaluatable(_)
                 | ty::PredicateKind::ConstEquate(_, _)
                 | ty::PredicateKind::TypeWellFormedFromEnv(_)
-                | ty::PredicateKind::Ambiguous => unimplemented!(),
+                | ty::PredicateKind::Ambiguous => {
+                    // FIXME
+                    response_no_constraints(self.tcx, canonical_goal, Certainty::Yes)
+                }
             }
         } else {
             let (infcx, goal, var_values) =
@@ -248,16 +256,18 @@ impl<'tcx> EvalCtxt<'tcx> {
 
     fn compute_type_outlives_goal(
         &mut self,
-        _goal: CanonicalGoal<'tcx, TypeOutlivesPredicate<'tcx>>,
+        goal: CanonicalGoal<'tcx, TypeOutlivesPredicate<'tcx>>,
     ) -> QueryResult<'tcx> {
-        todo!()
+        // FIXME
+        response_no_constraints(self.tcx, goal, Certainty::Yes)
     }
 
     fn compute_region_outlives_goal(
         &mut self,
-        _goal: CanonicalGoal<'tcx, RegionOutlivesPredicate<'tcx>>,
+        goal: CanonicalGoal<'tcx, RegionOutlivesPredicate<'tcx>>,
     ) -> QueryResult<'tcx> {
-        todo!()
+        // FIXME
+        response_no_constraints(self.tcx, goal, Certainty::Yes)
     }
 }
 
@@ -300,10 +310,27 @@ impl<'tcx> EvalCtxt<'tcx> {
     }
 }
 
-fn fixme_instantiate_canonical_query_response<'tcx>(
-    _: &InferCtxt<'tcx>,
-    _: &OriginalQueryValues<'tcx>,
-    _: CanonicalResponse<'tcx>,
+fn instantiate_canonical_query_response<'tcx>(
+    infcx: &InferCtxt<'tcx>,
+    original_values: &OriginalQueryValues<'tcx>,
+    response: CanonicalResponse<'tcx>,
 ) -> Certainty {
-    unimplemented!()
+    let Ok(InferOk { value, obligations }) = infcx
+        .instantiate_query_response_and_region_obligations(
+            &ObligationCause::dummy(),
+            ty::ParamEnv::empty(),
+            original_values,
+            &response.unchecked_map(|resp| QueryResponse {
+                var_values: resp.var_values,
+                region_constraints: QueryRegionConstraints::default(),
+                certainty: match resp.certainty {
+                    Certainty::Yes => OldCertainty::Proven,
+                    Certainty::Maybe(_) => OldCertainty::Ambiguous,
+                },
+                opaque_types: resp.external_constraints.opaque_types,
+                value: resp.certainty,
+            }),
+        ) else { bug!(); };
+    assert!(obligations.is_empty());
+    value
 }

compiler/rustc_trait_selection/src/solve/overflow.rs

@@ -1,7 +1,9 @@
+use rustc_infer::infer::canonical::Canonical;
 use rustc_infer::traits::query::NoSolution;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Limit;
 
+use super::cache::response_no_constraints;
 use super::{Certainty, EvalCtxt, MaybeCause, QueryResult};
 
 /// When detecting a solver overflow, we return ambiguity. Overflow can be
@@ -49,9 +51,12 @@ impl OverflowData {
 }
 
 impl<'tcx> EvalCtxt<'tcx> {
-    pub(super) fn deal_with_overflow(&mut self) -> QueryResult<'tcx> {
+    pub(super) fn deal_with_overflow(
+        &mut self,
+        goal: Canonical<'tcx, impl Sized>,
+    ) -> QueryResult<'tcx> {
         self.overflow_data.deal_with_overflow();
-        fixme_response_overflow_no_constraints()
+        response_no_constraints(self.tcx, goal, Certainty::Maybe(MaybeCause::Overflow))
     }
 
     /// A `while`-loop which tracks overflow.
@@ -74,7 +79,3 @@ impl<'tcx> EvalCtxt<'tcx> {
         Ok(Certainty::Maybe(MaybeCause::Overflow))
     }
 }
-
-fn fixme_response_overflow_no_constraints<'tcx>() -> QueryResult<'tcx> {
-    unimplemented!()
-}