Prepare to use borrowck to resolve opaque types

Author: matthewjasper

src/librustc/mir/query.rs

@@ -1,8 +1,10 @@
 //! Values computed by queries that use MIR.
 
 use crate::ty::{self, Ty};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
 use rustc_index::bit_set::BitMatrix;
 use rustc_index::vec::IndexVec;
 use rustc_span::{Span, Symbol};
@@ -59,8 +61,12 @@ pub struct GeneratorLayout<'tcx> {
     pub storage_conflicts: BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal>,
 }
 
-#[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
+#[derive(Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct BorrowCheckResult<'tcx> {
+    /// All the opaque types that are restricted to concrete types
+    /// by this function. Unlike the value in `TypeckTables`, this has
+    /// unerased regions.
+    pub concrete_opaque_types: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
     pub used_mut_upvars: SmallVec<[Field; 8]>,
 }

src/librustc_mir/borrow_check/mod.rs

@@ -204,19 +204,24 @@ fn do_mir_borrowck<'a, 'tcx>(
         Rc::new(BorrowSet::build(tcx, body, locals_are_invalidated_at_exit, &mdpe.move_data));
 
     // Compute non-lexical lifetimes.
-    let nll::NllOutput { regioncx, polonius_output, opt_closure_req, nll_errors } =
-        nll::compute_regions(
-            infcx,
-            def_id,
-            free_regions,
-            body,
-            &promoted,
-            location_table,
-            param_env,
-            &mut flow_inits,
-            &mdpe.move_data,
-            &borrow_set,
-        );
+    let nll::NllOutput {
+        regioncx,
+        opaque_type_values,
+        polonius_output,
+        opt_closure_req,
+        nll_errors,
+    } = nll::compute_regions(
+        infcx,
+        def_id,
+        free_regions,
+        body,
+        &promoted,
+        location_table,
+        param_env,
+        &mut flow_inits,
+        &mdpe.move_data,
+        &borrow_set,
+    );
 
     // Dump MIR results into a file, if that is enabled. This let us
     // write unit-tests, as well as helping with debugging.
@@ -404,6 +409,7 @@ fn do_mir_borrowck<'a, 'tcx>(
     }
 
     let result = BorrowCheckResult {
+        concrete_opaque_types: opaque_type_values,
         closure_requirements: opt_closure_req,
         used_mut_upvars: mbcx.used_mut_upvars,
     };

src/librustc_mir/borrow_check/nll.rs

@@ -6,6 +6,7 @@ use rustc::mir::{
     Location, Promoted, ReadOnlyBodyAndCache,
 };
 use rustc::ty::{self, RegionKind, RegionVid};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::DefId;
 use rustc_index::vec::IndexVec;
@@ -46,6 +47,7 @@ crate type PoloniusOutput = Output<RustcFacts>;
 /// closure requirements to propagate, and any generated errors.
 crate struct NllOutput<'tcx> {
     pub regioncx: RegionInferenceContext<'tcx>,
+    pub opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
     pub polonius_output: Option<Rc<PoloniusOutput>>,
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
     pub nll_errors: RegionErrors<'tcx>,
@@ -160,20 +162,21 @@ pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>(
     let elements = &Rc::new(RegionValueElements::new(&body));
 
     // Run the MIR type-checker.
-    let MirTypeckResults { constraints, universal_region_relations } = type_check::type_check(
-        infcx,
-        param_env,
-        body,
-        promoted,
-        def_id,
-        &universal_regions,
-        location_table,
-        borrow_set,
-        &mut all_facts,
-        flow_inits,
-        move_data,
-        elements,
-    );
+    let MirTypeckResults { constraints, universal_region_relations, opaque_type_values } =
+        type_check::type_check(
+            infcx,
+            param_env,
+            body,
+            promoted,
+            def_id,
+            &universal_regions,
+            location_table,
+            borrow_set,
+            &mut all_facts,
+            flow_inits,
+            move_data,
+            elements,
+        );
 
     if let Some(all_facts) = &mut all_facts {
         let _prof_timer = infcx.tcx.prof.generic_activity("polonius_fact_generation");
@@ -281,6 +284,7 @@ pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>(
 
     NllOutput {
         regioncx,
+        opaque_type_values,
         polonius_output,
         opt_closure_req: closure_region_requirements,
         nll_errors,

src/librustc_mir/borrow_check/type_check/mod.rs

@@ -159,7 +159,7 @@ pub(crate) fn type_check<'tcx>(
         constraints: &mut constraints,
     };
 
-    type_check_internal(
+    let opaque_type_values = type_check_internal(
         infcx,
         mir_def_id,
         param_env,
@@ -174,10 +174,11 @@ pub(crate) fn type_check<'tcx>(
             liveness::generate(&mut cx, body, elements, flow_inits, move_data, location_table);
 
             translate_outlives_facts(&mut cx);
+            cx.opaque_type_values
         },
     );
 
-    MirTypeckResults { constraints, universal_region_relations }
+    MirTypeckResults { constraints, universal_region_relations, opaque_type_values }
 }
 
 fn type_check_internal<'a, 'tcx, R>(
@@ -190,7 +191,7 @@ fn type_check_internal<'a, 'tcx, R>(
     implicit_region_bound: ty::Region<'tcx>,
     borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
     universal_region_relations: &'a UniversalRegionRelations<'tcx>,
-    mut extra: impl FnMut(&mut TypeChecker<'a, 'tcx>) -> R,
+    extra: impl FnOnce(TypeChecker<'a, 'tcx>) -> R,
 ) -> R {
     let mut checker = TypeChecker::new(
         infcx,
@@ -213,7 +214,7 @@ fn type_check_internal<'a, 'tcx, R>(
         checker.typeck_mir(body);
     }
 
-    extra(&mut checker)
+    extra(checker)
 }
 
 fn translate_outlives_facts(typeck: &mut TypeChecker<'_, '_>) {
@@ -800,6 +801,7 @@ struct TypeChecker<'a, 'tcx> {
     reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
     borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
     universal_region_relations: &'a UniversalRegionRelations<'tcx>,
+    opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
 }
 
 struct BorrowCheckContext<'a, 'tcx> {
@@ -813,6 +815,7 @@ struct BorrowCheckContext<'a, 'tcx> {
 crate struct MirTypeckResults<'tcx> {
     crate constraints: MirTypeckRegionConstraints<'tcx>,
     crate universal_region_relations: Rc<UniversalRegionRelations<'tcx>>,
+    crate opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
 }
 
 /// A collection of region constraints that must be satisfied for the
@@ -959,6 +962,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             borrowck_context,
             reported_errors: Default::default(),
             universal_region_relations,
+            opaque_type_values: FxHashMap::default(),
         };
         checker.check_user_type_annotations();
         checker
@@ -1196,6 +1200,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         let tcx = infcx.tcx;
         let param_env = self.param_env;
         let body = self.body;
+        let concrete_opaque_types = &tcx.typeck_tables_of(anon_owner_def_id).concrete_opaque_types;
+        let mut opaque_type_values = Vec::new();
+
         debug!("eq_opaque_type_and_type: mir_def_id={:?}", self.mir_def_id);
         let opaque_type_map = self.fully_perform_op(
             locations,
@@ -1227,47 +1234,65 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     );
 
                     for (&opaque_def_id, opaque_decl) in &opaque_type_map {
-                        let opaque_defn_ty = tcx.type_of(opaque_def_id);
-                        let opaque_defn_ty = opaque_defn_ty.subst(tcx, opaque_decl.substs);
-                        let opaque_defn_ty = renumber::renumber_regions(infcx, &opaque_defn_ty);
-                        let concrete_is_opaque = infcx
-                            .resolve_vars_if_possible(&opaque_decl.concrete_ty)
-                            .is_impl_trait();
+                        let resolved_ty = infcx.resolve_vars_if_possible(&opaque_decl.concrete_ty);
+                        let concrete_is_opaque = if let ty::Opaque(def_id, _) = resolved_ty.kind {
+                            def_id == opaque_def_id
+                        } else {
+                            false
+                        };
+                        let opaque_defn_ty = match concrete_opaque_types.get(&opaque_def_id) {
+                            None => {
+                                assert!(
+                                    concrete_is_opaque,
+                                    "Non-defining use of {:?} with revealed type",
+                                    opaque_def_id,
+                                );
+                                continue;
+                            }
+                            Some(opaque_defn_ty) => opaque_defn_ty,
+                        };
+                        debug!("opaque_defn_ty = {:?}", opaque_defn_ty);
+                        let subst_opaque_defn_ty =
+                            opaque_defn_ty.concrete_type.subst(tcx, opaque_decl.substs);
+                        let renumbered_opaque_defn_ty =
+                            renumber::renumber_regions(infcx, &subst_opaque_defn_ty);
 
                         debug!(
-                            "eq_opaque_type_and_type: concrete_ty={:?}={:?} opaque_defn_ty={:?} \
-                            concrete_is_opaque={}",
-                            opaque_decl.concrete_ty,
-                            infcx.resolve_vars_if_possible(&opaque_decl.concrete_ty),
-                            opaque_defn_ty,
-                            concrete_is_opaque
+                            "eq_opaque_type_and_type: concrete_ty={:?}={:?} opaque_defn_ty={:?}",
+                            opaque_decl.concrete_ty, resolved_ty, renumbered_opaque_defn_ty,
                         );
 
-                        // concrete_is_opaque is `true` when we're using an opaque `impl Trait`
-                        // type without 'revealing' it. For example, code like this:
-                        //
-                        // type Foo = impl Debug;
-                        // fn foo1() -> Foo { ... }
-                        // fn foo2() -> Foo { foo1() }
-                        //
-                        // In `foo2`, we're not revealing the type of `Foo` - we're
-                        // just treating it as the opaque type.
-                        //
-                        // When this occurs, we do *not* want to try to equate
-                        // the concrete type with the underlying defining type
-                        // of the opaque type - this will always fail, since
-                        // the defining type of an opaque type is always
-                        // some other type (e.g. not itself)
-                        // Essentially, none of the normal obligations apply here -
-                        // we're just passing around some unknown opaque type,
-                        // without actually looking at the underlying type it
-                        // gets 'revealed' into
-
                         if !concrete_is_opaque {
                             obligations.add(
                                 infcx
                                     .at(&ObligationCause::dummy(), param_env)
-                                    .eq(opaque_decl.concrete_ty, opaque_defn_ty)?,
+                                    .eq(opaque_decl.concrete_ty, renumbered_opaque_defn_ty)?,
+                            );
+                            opaque_type_values
+                                .push((opaque_def_id, ty::ResolvedOpaqueTy { ..*opaque_defn_ty }));
+                        } else {
+                            // We're using an opaque `impl Trait` type without
+                            // 'revealing' it. For example, code like this:
+                            //
+                            // type Foo = impl Debug;
+                            // fn foo1() -> Foo { ... }
+                            // fn foo2() -> Foo { foo1() }
+                            //
+                            // In `foo2`, we're not revealing the type of `Foo` - we're
+                            // just treating it as the opaque type.
+                            //
+                            // When this occurs, we do *not* want to try to equate
+                            // the concrete type with the underlying defining type
+                            // of the opaque type - this will always fail, since
+                            // the defining type of an opaque type is always
+                            // some other type (e.g. not itself)
+                            // Essentially, none of the normal obligations apply here -
+                            // we're just passing around some unknown opaque type,
+                            // without actually looking at the underlying type it
+                            // gets 'revealed' into
+                            debug!(
+                                "eq_opaque_type_and_type: non-defining use of {:?}",
+                                opaque_def_id,
                             );
                         }
                     }
@@ -1283,6 +1308,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             ),
         )?;
 
+        self.opaque_type_values.extend(opaque_type_values);
+
         let universal_region_relations = self.universal_region_relations;
 
         // Finally, if we instantiated the anon types successfully, we

src/librustc_typeck/collect.rs

@@ -1353,7 +1353,7 @@ fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                 }
                 // Opaque types desugared from `impl Trait`.
                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(owner), .. }) => {
-                    tcx.typeck_tables_of(owner)
+                    tcx.mir_borrowck(owner)
                         .concrete_opaque_types
                         .get(&def_id)
                         .map(|opaque| opaque.concrete_type)
@@ -1576,7 +1576,7 @@ fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
 }
 
 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
-    use rustc_hir::{ImplItem, Item, TraitItem};
+    use rustc_hir::{Expr, ImplItem, Item, TraitItem};
 
     debug!("find_opaque_ty_constraints({:?})", def_id);
 
@@ -1602,7 +1602,17 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                 );
                 return;
             }
-            let ty = self.tcx.typeck_tables_of(def_id).concrete_opaque_types.get(&self.def_id);
+            // Calling `mir_borrowck` can lead to cycle errors through
+            // const-checking, avoid calling it if we don't have to.
+            if !self.tcx.typeck_tables_of(def_id).concrete_opaque_types.contains_key(&self.def_id) {
+                debug!(
+                    "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
+                    self.def_id, def_id,
+                );
+                return;
+            }
+            // Use borrowck to get the type with unerased regions.
+            let ty = self.tcx.mir_borrowck(def_id).concrete_opaque_types.get(&self.def_id);
             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
                 debug!(
                     "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
@@ -1738,6 +1748,13 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
             intravisit::NestedVisitorMap::All(&self.tcx.hir())
         }
+        fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
+            if let hir::ExprKind::Closure(..) = ex.kind {
+                let def_id = self.tcx.hir().local_def_id(ex.hir_id);
+                self.check(def_id);
+            }
+            intravisit::walk_expr(self, ex);
+        }
         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
             debug!("find_existential_constraints: visiting {:?}", it);
             let def_id = self.tcx.hir().local_def_id(it.hir_id);