Rollup merge of rust-lang#124809 - lcnr:prepopulate-opaques, r=compiler-errors

borrowck: prepopulate opaque storage more eagerly

otherwise we ICE due to ambiguity when normalizing while computing implied bounds.

r? ``@compiler-errors``

Author: matthiaskrgr

compiler/rustc_borrowck/src/consumers.rs

@@ -2,7 +2,6 @@
 
 use rustc_hir::def_id::LocalDefId;
 use rustc_index::{IndexSlice, IndexVec};
-use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::mir::{Body, Promoted};
 use rustc_middle::ty::TyCtxt;
 use std::rc::Rc;
@@ -105,8 +104,7 @@ pub fn get_body_with_borrowck_facts(
     options: ConsumerOptions,
 ) -> BodyWithBorrowckFacts<'_> {
     let (input_body, promoted) = tcx.mir_promoted(def);
-    let infcx = tcx.infer_ctxt().with_opaque_type_inference(def).build();
     let input_body: &Body<'_> = &input_body.borrow();
     let promoted: &IndexSlice<_, _> = &promoted.borrow();
-    *super::do_mir_borrowck(&infcx, input_body, promoted, Some(options)).1.unwrap()
+    *super::do_mir_borrowck(tcx, input_body, promoted, Some(options)).1.unwrap()
 }

compiler/rustc_borrowck/src/lib.rs

@@ -23,9 +23,8 @@ use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_index::bit_set::{BitSet, ChunkedBitSet};
 use rustc_index::{IndexSlice, IndexVec};
-use rustc_infer::infer::{
-    InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin, TyCtxtInferExt,
-};
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin};
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
@@ -123,9 +122,8 @@ fn mir_borrowck(tcx: TyCtxt<'_>, def: LocalDefId) -> &BorrowCheckResult<'_> {
         return tcx.arena.alloc(result);
     }
 
-    let infcx = tcx.infer_ctxt().with_opaque_type_inference(def).build();
     let promoted: &IndexSlice<_, _> = &promoted.borrow();
-    let opt_closure_req = do_mir_borrowck(&infcx, input_body, promoted, None).0;
+    let opt_closure_req = do_mir_borrowck(tcx, input_body, promoted, None).0;
     debug!("mir_borrowck done");
 
     tcx.arena.alloc(opt_closure_req)
@@ -136,18 +134,15 @@ fn mir_borrowck(tcx: TyCtxt<'_>, def: LocalDefId) -> &BorrowCheckResult<'_> {
 /// Use `consumer_options: None` for the default behavior of returning
 /// [`BorrowCheckResult`] only. Otherwise, return [`BodyWithBorrowckFacts`] according
 /// to the given [`ConsumerOptions`].
-#[instrument(skip(infcx, input_body, input_promoted), fields(id=?input_body.source.def_id()), level = "debug")]
+#[instrument(skip(tcx, input_body, input_promoted), fields(id=?input_body.source.def_id()), level = "debug")]
 fn do_mir_borrowck<'tcx>(
-    infcx: &InferCtxt<'tcx>,
+    tcx: TyCtxt<'tcx>,
     input_body: &Body<'tcx>,
     input_promoted: &IndexSlice<Promoted, Body<'tcx>>,
     consumer_options: Option<ConsumerOptions>,
 ) -> (BorrowCheckResult<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) {
     let def = input_body.source.def_id().expect_local();
-    debug!(?def);
-
-    let tcx = infcx.tcx;
-    let infcx = BorrowckInferCtxt::new(infcx);
+    let infcx = BorrowckInferCtxt::new(tcx, def);
     let param_env = tcx.param_env(def);
 
     let mut local_names = IndexVec::from_elem(None, &input_body.local_decls);
@@ -187,6 +182,12 @@ fn do_mir_borrowck<'tcx>(
         nll::replace_regions_in_mir(&infcx, param_env, &mut body_owned, &mut promoted);
     let body = &body_owned; // no further changes
 
+    // FIXME(-Znext-solver): A bit dubious that we're only registering
+    // predefined opaques in the typeck root.
+    if infcx.next_trait_solver() && !infcx.tcx.is_typeck_child(body.source.def_id()) {
+        infcx.register_predefined_opaques_for_next_solver(def);
+    }
+
     let location_table = LocationTable::new(body);
 
     let move_data = MoveData::gather_moves(body, tcx, param_env, |_| true);
@@ -440,13 +441,14 @@ fn do_mir_borrowck<'tcx>(
     (result, body_with_facts)
 }
 
-pub struct BorrowckInferCtxt<'cx, 'tcx> {
-    pub(crate) infcx: &'cx InferCtxt<'tcx>,
+pub struct BorrowckInferCtxt<'tcx> {
+    pub(crate) infcx: InferCtxt<'tcx>,
     pub(crate) reg_var_to_origin: RefCell<FxIndexMap<ty::RegionVid, RegionCtxt>>,
 }
 
-impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
-    pub(crate) fn new(infcx: &'cx InferCtxt<'tcx>) -> Self {
+impl<'tcx> BorrowckInferCtxt<'tcx> {
+    pub(crate) fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
+        let infcx = tcx.infer_ctxt().with_opaque_type_inference(def_id).build();
         BorrowckInferCtxt { infcx, reg_var_to_origin: RefCell::new(Default::default()) }
     }
 
@@ -492,18 +494,40 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
 
         next_region
     }
+
+    /// With the new solver we prepopulate the opaque type storage during
+    /// MIR borrowck with the hidden types from HIR typeck. This is necessary
+    /// to avoid ambiguities as earlier goals can rely on the hidden type
+    /// of an opaque which is only constrained by a later goal.
+    fn register_predefined_opaques_for_next_solver(&self, def_id: LocalDefId) {
+        let tcx = self.tcx;
+        // OK to use the identity arguments for each opaque type key, since
+        // we remap opaques from HIR typeck back to their definition params.
+        for data in tcx.typeck(def_id).concrete_opaque_types.iter().map(|(k, v)| (*k, *v)) {
+            // HIR typeck did not infer the regions of the opaque, so we instantiate
+            // them with fresh inference variables.
+            let (key, hidden_ty) = tcx.fold_regions(data, |_, _| {
+                self.next_nll_region_var_in_universe(
+                    NllRegionVariableOrigin::Existential { from_forall: false },
+                    ty::UniverseIndex::ROOT,
+                )
+            });
+
+            self.inject_new_hidden_type_unchecked(key, hidden_ty);
+        }
+    }
 }
 
-impl<'cx, 'tcx> Deref for BorrowckInferCtxt<'cx, 'tcx> {
+impl<'tcx> Deref for BorrowckInferCtxt<'tcx> {
     type Target = InferCtxt<'tcx>;
 
-    fn deref(&self) -> &'cx Self::Target {
-        self.infcx
+    fn deref(&self) -> &Self::Target {
+        &self.infcx
     }
 }
 
 struct MirBorrowckCtxt<'cx, 'tcx> {
-    infcx: &'cx BorrowckInferCtxt<'cx, 'tcx>,
+    infcx: &'cx BorrowckInferCtxt<'tcx>,
     param_env: ParamEnv<'tcx>,
     body: &'cx Body<'tcx>,
     move_data: &'cx MoveData<'tcx>,

compiler/rustc_borrowck/src/nll.rs

@@ -51,7 +51,7 @@ pub(crate) struct NllOutput<'tcx> {
 /// `compute_regions`.
 #[instrument(skip(infcx, param_env, body, promoted), level = "debug")]
 pub(crate) fn replace_regions_in_mir<'tcx>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body: &mut Body<'tcx>,
     promoted: &mut IndexSlice<Promoted, Body<'tcx>>,
@@ -75,7 +75,7 @@ pub(crate) fn replace_regions_in_mir<'tcx>(
 ///
 /// This may result in errors being reported.
 pub(crate) fn compute_regions<'cx, 'tcx>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     universal_regions: UniversalRegions<'tcx>,
     body: &Body<'tcx>,
     promoted: &IndexSlice<Promoted, Body<'tcx>>,
@@ -202,7 +202,7 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
 }
 
 pub(super) fn dump_mir_results<'tcx>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
@@ -254,7 +254,7 @@ pub(super) fn dump_mir_results<'tcx>(
 #[allow(rustc::diagnostic_outside_of_impl)]
 #[allow(rustc::untranslatable_diagnostic)]
 pub(super) fn dump_annotation<'tcx>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -250,10 +250,7 @@ pub enum ExtraConstraintInfo {
 }
 
 #[instrument(skip(infcx, sccs), level = "debug")]
-fn sccs_info<'cx, 'tcx>(
-    infcx: &'cx BorrowckInferCtxt<'cx, 'tcx>,
-    sccs: Rc<Sccs<RegionVid, ConstraintSccIndex>>,
-) {
+fn sccs_info<'tcx>(infcx: &BorrowckInferCtxt<'tcx>, sccs: Rc<Sccs<RegionVid, ConstraintSccIndex>>) {
     use crate::renumber::RegionCtxt;
 
     let var_to_origin = infcx.reg_var_to_origin.borrow();
@@ -322,8 +319,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ///
     /// The `outlives_constraints` and `type_tests` are an initial set
     /// of constraints produced by the MIR type check.
-    pub(crate) fn new<'cx>(
-        _infcx: &BorrowckInferCtxt<'cx, 'tcx>,
+    pub(crate) fn new(
+        _infcx: &BorrowckInferCtxt<'tcx>,
         var_infos: VarInfos,
         universal_regions: Rc<UniversalRegions<'tcx>>,
         placeholder_indices: Rc<PlaceholderIndices>,

compiler/rustc_borrowck/src/renumber.rs

@@ -11,7 +11,7 @@ use rustc_span::Symbol;
 /// inference variables, returning the number of variables created.
 #[instrument(skip(infcx, body, promoted), level = "debug")]
 pub fn renumber_mir<'tcx>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     body: &mut Body<'tcx>,
     promoted: &mut IndexSlice<Promoted, Body<'tcx>>,
 ) {
@@ -57,7 +57,7 @@ impl RegionCtxt {
 }
 
 struct RegionRenumberer<'a, 'tcx> {
-    infcx: &'a BorrowckInferCtxt<'a, 'tcx>,
+    infcx: &'a BorrowckInferCtxt<'tcx>,
 }
 
 impl<'a, 'tcx> RegionRenumberer<'a, 'tcx> {

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -24,7 +24,6 @@ use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::traits::query::NoSolution;
-use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::visit::TypeVisitableExt;
@@ -122,7 +121,7 @@ mod relate_tys;
 /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis
 /// - `elements` -- MIR region map
 pub(crate) fn type_check<'mir, 'tcx>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body: &Body<'tcx>,
     promoted: &IndexSlice<Promoted, Body<'tcx>>,
@@ -865,7 +864,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
 /// way, it accrues region constraints -- these can later be used by
 /// NLL region checking.
 struct TypeChecker<'a, 'tcx> {
-    infcx: &'a BorrowckInferCtxt<'a, 'tcx>,
+    infcx: &'a BorrowckInferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     last_span: Span,
     body: &'a Body<'tcx>,
@@ -1020,15 +1019,15 @@ impl Locations {
 
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     fn new(
-        infcx: &'a BorrowckInferCtxt<'a, 'tcx>,
+        infcx: &'a BorrowckInferCtxt<'tcx>,
         body: &'a Body<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         region_bound_pairs: &'a RegionBoundPairs<'tcx>,
         known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
         implicit_region_bound: ty::Region<'tcx>,
         borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
     ) -> Self {
-        let mut checker = Self {
+        Self {
             infcx,
             last_span: body.span,
             body,
@@ -1039,74 +1038,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             implicit_region_bound,
             borrowck_context,
             reported_errors: Default::default(),
-        };
-
-        // FIXME(-Znext-solver): A bit dubious that we're only registering
-        // predefined opaques in the typeck root.
-        if infcx.next_trait_solver() && !infcx.tcx.is_typeck_child(body.source.def_id()) {
-            checker.register_predefined_opaques_for_next_solver();
-        }
-
-        checker
-    }
-
-    pub(super) fn register_predefined_opaques_for_next_solver(&mut self) {
-        // OK to use the identity arguments for each opaque type key, since
-        // we remap opaques from HIR typeck back to their definition params.
-        let opaques: Vec<_> = self
-            .infcx
-            .tcx
-            .typeck(self.body.source.def_id().expect_local())
-            .concrete_opaque_types
-            .iter()
-            .map(|(k, v)| (*k, *v))
-            .collect();
-
-        let renumbered_opaques = self.infcx.tcx.fold_regions(opaques, |_, _| {
-            self.infcx.next_nll_region_var_in_universe(
-                NllRegionVariableOrigin::Existential { from_forall: false },
-                ty::UniverseIndex::ROOT,
-            )
-        });
-
-        let param_env = self.param_env;
-        let result = self.fully_perform_op(
-            Locations::All(self.body.span),
-            ConstraintCategory::OpaqueType,
-            CustomTypeOp::new(
-                |ocx| {
-                    let mut obligations = Vec::new();
-                    for (opaque_type_key, hidden_ty) in renumbered_opaques {
-                        let cause = ObligationCause::dummy();
-                        ocx.infcx.insert_hidden_type(
-                            opaque_type_key,
-                            &cause,
-                            param_env,
-                            hidden_ty.ty,
-                            &mut obligations,
-                        )?;
-
-                        ocx.infcx.add_item_bounds_for_hidden_type(
-                            opaque_type_key.def_id.to_def_id(),
-                            opaque_type_key.args,
-                            cause,
-                            param_env,
-                            hidden_ty.ty,
-                            &mut obligations,
-                        );
-                    }
-
-                    ocx.register_obligations(obligations);
-                    Ok(())
-                },
-                "register pre-defined opaques",
-            ),
-        );
-
-        if result.is_err() {
-            self.infcx
-                .dcx()
-                .span_bug(self.body.span, "failed re-defining predefined opaques in mir typeck");
         }
     }
 

compiler/rustc_borrowck/src/universal_regions.rs

@@ -240,7 +240,7 @@ impl<'tcx> UniversalRegions<'tcx> {
     /// signature. This will also compute the relationships that are
     /// known between those regions.
     pub fn new(
-        infcx: &BorrowckInferCtxt<'_, 'tcx>,
+        infcx: &BorrowckInferCtxt<'tcx>,
         mir_def: LocalDefId,
         param_env: ty::ParamEnv<'tcx>,
     ) -> Self {
@@ -411,7 +411,7 @@ impl<'tcx> UniversalRegions<'tcx> {
 }
 
 struct UniversalRegionsBuilder<'cx, 'tcx> {
-    infcx: &'cx BorrowckInferCtxt<'cx, 'tcx>,
+    infcx: &'cx BorrowckInferCtxt<'tcx>,
     mir_def: LocalDefId,
     param_env: ty::ParamEnv<'tcx>,
 }
@@ -796,7 +796,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
 }
 
 #[extension(trait InferCtxtExt<'tcx>)]
-impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
+impl<'tcx> BorrowckInferCtxt<'tcx> {
     #[instrument(skip(self), level = "debug")]
     fn replace_free_regions_with_nll_infer_vars<T>(
         &self,

compiler/rustc_infer/src/infer/opaque_types/mod.rs

@@ -485,6 +485,19 @@ impl<'tcx> InferCtxt<'tcx> {
         Ok(InferOk { value: (), obligations })
     }
 
+    /// Insert a hidden type into the opaque type storage, making sure
+    /// it hasn't previously been defined. This does not emit any
+    /// constraints and it's the responsibility of the caller to make
+    /// sure that the item bounds of the opaque are checked.
+    pub fn inject_new_hidden_type_unchecked(
+        &self,
+        opaque_type_key: OpaqueTypeKey<'tcx>,
+        hidden_ty: OpaqueHiddenType<'tcx>,
+    ) {
+        let prev = self.inner.borrow_mut().opaque_types().register(opaque_type_key, hidden_ty);
+        assert_eq!(prev, None);
+    }
+
     /// Insert a hidden type into the opaque type storage, equating it
     /// with any previous entries if necessary.
     ///