fix make_ambiguous_response_no_constraints

we previously had incorrect universes in the query response.

Author: lcnr

compiler/rustc_trait_selection/src/solve/eval_ctxt.rs

@@ -3,11 +3,11 @@ use rustc_infer::infer::at::ToTrace;
 use rustc_infer::infer::canonical::CanonicalVarValues;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{
-    DefineOpaqueTypes, InferCtxt, InferOk, LateBoundRegionConversionTime, RegionVariableOrigin,
-    TyCtxtInferExt,
+    DefineOpaqueTypes, InferCtxt, InferOk, LateBoundRegionConversionTime, TyCtxtInferExt,
 };
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::traits::ObligationCause;
+use rustc_middle::infer::canonical::CanonicalVarInfos;
 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
 use rustc_middle::traits::solve::inspect;
 use rustc_middle::traits::solve::{
@@ -55,6 +55,9 @@ pub struct EvalCtxt<'a, 'tcx> {
     /// the job already.
     infcx: &'a InferCtxt<'tcx>,
 
+    /// The variable info for the `var_values`, only used to make an ambiguous response
+    /// with no constraints.
+    variables: CanonicalVarInfos<'tcx>,
     pub(super) var_values: CanonicalVarValues<'tcx>,
 
     predefined_opaques_in_body: PredefinedOpaques<'tcx>,
@@ -184,18 +187,19 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
 
         let mut ecx = EvalCtxt {
             search_graph: &mut search_graph,
-            infcx: infcx,
+            infcx,
+            nested_goals: NestedGoals::new(),
+            inspect: ProofTreeBuilder::new_maybe_root(infcx.tcx, generate_proof_tree),
+
             // Only relevant when canonicalizing the response,
             // which we don't do within this evaluation context.
             predefined_opaques_in_body: infcx
                 .tcx
                 .mk_predefined_opaques_in_body(PredefinedOpaquesData::default()),
-            // Only relevant when canonicalizing the response.
             max_input_universe: ty::UniverseIndex::ROOT,
+            variables: ty::List::empty(),
             var_values: CanonicalVarValues::dummy(),
-            nested_goals: NestedGoals::new(),
             tainted: Ok(()),
-            inspect: ProofTreeBuilder::new_maybe_root(infcx.tcx, generate_proof_tree),
         };
         let result = f(&mut ecx);
 
@@ -245,6 +249,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
 
         let mut ecx = EvalCtxt {
             infcx,
+            variables: canonical_input.variables,
             var_values,
             predefined_opaques_in_body: input.predefined_opaques_in_body,
             max_input_universe: canonical_input.max_universe,
@@ -593,10 +598,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         })
     }
 
-    pub(super) fn next_region_infer(&self) -> ty::Region<'tcx> {
-        self.infcx.next_region_var(RegionVariableOrigin::MiscVariable(DUMMY_SP))
-    }
-
     pub(super) fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx> {
         self.infcx.next_const_var(
             ty,

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -10,7 +10,7 @@
 //! [c]: https://rustc-dev-guide.rust-lang.org/solve/canonicalization.html
 use super::{CanonicalInput, Certainty, EvalCtxt, Goal};
 use crate::solve::canonicalize::{CanonicalizeMode, Canonicalizer};
-use crate::solve::{CanonicalResponse, QueryResult, Response};
+use crate::solve::{response_no_constraints_raw, CanonicalResponse, QueryResult, Response};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_index::IndexVec;
 use rustc_infer::infer::canonical::query_response::make_query_region_constraints;
@@ -109,29 +109,11 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         &self,
         maybe_cause: MaybeCause,
     ) -> CanonicalResponse<'tcx> {
-        let unconstrained_response = Response {
-            var_values: CanonicalVarValues {
-                var_values: self.tcx().mk_args_from_iter(self.var_values.var_values.iter().map(
-                    |arg| -> ty::GenericArg<'tcx> {
-                        match arg.unpack() {
-                            GenericArgKind::Lifetime(_) => self.next_region_infer().into(),
-                            GenericArgKind::Type(_) => self.next_ty_infer().into(),
-                            GenericArgKind::Const(ct) => self.next_const_infer(ct.ty()).into(),
-                        }
-                    },
-                )),
-            },
-            external_constraints: self
-                .tcx()
-                .mk_external_constraints(ExternalConstraintsData::default()),
-            certainty: Certainty::Maybe(maybe_cause),
-        };
-
-        Canonicalizer::canonicalize(
-            self.infcx,
-            CanonicalizeMode::Response { max_input_universe: self.max_input_universe },
-            &mut Default::default(),
-            unconstrained_response,
+        response_no_constraints_raw(
+            self.tcx(),
+            self.max_input_universe,
+            self.variables,
+            Certainty::Maybe(maybe_cause),
         )
     }
 

compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs

@@ -17,6 +17,7 @@ where
 
         let mut nested_ecx = EvalCtxt {
             infcx: outer_ecx.infcx,
+            variables: outer_ecx.variables,
             var_values: outer_ecx.var_values,
             predefined_opaques_in_body: outer_ecx.predefined_opaques_in_body,
             max_input_universe: outer_ecx.max_input_universe,

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -17,10 +17,11 @@
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::canonical::{Canonical, CanonicalVarValues};
 use rustc_infer::traits::query::NoSolution;
+use rustc_middle::infer::canonical::CanonicalVarInfos;
 use rustc_middle::traits::solve::{
     CanonicalResponse, Certainty, ExternalConstraintsData, Goal, QueryResult, Response,
 };
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, UniverseIndex};
 use rustc_middle::ty::{
     CoercePredicate, RegionOutlivesPredicate, SubtypePredicate, TypeOutlivesPredicate,
 };
@@ -284,20 +285,21 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     }
 }
 
-pub(super) fn response_no_constraints<'tcx>(
+fn response_no_constraints_raw<'tcx>(
     tcx: TyCtxt<'tcx>,
-    goal: Canonical<'tcx, impl Sized>,
+    max_universe: UniverseIndex,
+    variables: CanonicalVarInfos<'tcx>,
     certainty: Certainty,
-) -> QueryResult<'tcx> {
-    Ok(Canonical {
-        max_universe: goal.max_universe,
-        variables: goal.variables,
+) -> CanonicalResponse<'tcx> {
+    Canonical {
+        max_universe,
+        variables,
         value: Response {
-            var_values: CanonicalVarValues::make_identity(tcx, goal.variables),
+            var_values: CanonicalVarValues::make_identity(tcx, variables),
             // FIXME: maybe we should store the "no response" version in tcx, like
             // we do for tcx.types and stuff.
             external_constraints: tcx.mk_external_constraints(ExternalConstraintsData::default()),
             certainty,
         },
-    })
+    }
 }

compiler/rustc_trait_selection/src/solve/search_graph/mod.rs

@@ -107,7 +107,7 @@ impl<'tcx> SearchGraph<'tcx> {
                 }
 
                 let depth = self.stack.push(StackElem { input, has_been_used: false });
-                let response = super::response_no_constraints(tcx, input, Certainty::Yes);
+                let response = Self::response_no_constraints(tcx, input, Certainty::Yes);
                 let entry_index = cache.entries.push(ProvisionalEntry { response, depth, input });
                 v.insert(entry_index);
                 Ok(())
@@ -144,7 +144,7 @@ impl<'tcx> SearchGraph<'tcx> {
                 {
                     Err(cache.provisional_result(entry_index))
                 } else {
-                    Err(super::response_no_constraints(tcx, input, Certainty::OVERFLOW))
+                    Err(Self::response_no_constraints(tcx, input, Certainty::OVERFLOW))
                 }
             }
         }
@@ -283,4 +283,12 @@ impl<'tcx> SearchGraph<'tcx> {
 
         result
     }
+
+    fn response_no_constraints(
+        tcx: TyCtxt<'tcx>,
+        goal: CanonicalInput<'tcx>,
+        certainty: Certainty,
+    ) -> QueryResult<'tcx> {
+        Ok(super::response_no_constraints_raw(tcx, goal.max_universe, goal.variables, certainty))
+    }
 }

compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs

@@ -5,7 +5,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_session::Limit;
 
 use super::SearchGraph;
-use crate::solve::{response_no_constraints, EvalCtxt};
+use crate::solve::{response_no_constraints_raw, EvalCtxt};
 
 /// When detecting a solver overflow, we return ambiguity. Overflow can be
 /// *hidden* by either a fatal error in an **AND** or a trivial success in an **OR**.
@@ -115,6 +115,6 @@ impl<'tcx> SearchGraph<'tcx> {
         goal: Canonical<'tcx, impl Sized>,
     ) -> QueryResult<'tcx> {
         self.overflow_data.deal_with_overflow();
-        response_no_constraints(tcx, goal, Certainty::OVERFLOW)
+        Ok(response_no_constraints_raw(tcx, goal.max_universe, goal.variables, Certainty::OVERFLOW))
     }
 }