Auto merge of #55229 - nikomatsakis:issue-54692-closure-signatures, r=MatthewJasper

enforce user annotations in closure signatures

Not *quite* ready yet but I'm opening anyway. Still have to finish running tests locally.

Fixes #54692
Fixes #54124

r? @matthewjasper

Author: bors

src/librustc/ty/context.rs

@@ -50,7 +50,8 @@ use ty::query;
 use ty::steal::Steal;
 use ty::BindingMode;
 use ty::CanonicalTy;
-use util::nodemap::{DefIdSet, ItemLocalMap};
+use ty::CanonicalPolyFnSig;
+use util::nodemap::{DefIdMap, DefIdSet, ItemLocalMap};
 use util::nodemap::{FxHashMap, FxHashSet};
 use smallvec::SmallVec;
 use rustc_data_structures::stable_hasher::{HashStable, hash_stable_hashmap,
@@ -344,10 +345,6 @@ pub struct TypeckTables<'tcx> {
     /// belongs, but it may not exist if it's a tuple field (`tuple.0`).
     field_indices: ItemLocalMap<usize>,
 
-    /// Stores the canonicalized types provided by the user. See also
-    /// `AscribeUserType` statement in MIR.
-    user_provided_tys: ItemLocalMap<CanonicalTy<'tcx>>,
-
     /// Stores the types for various nodes in the AST.  Note that this table
     /// is not guaranteed to be populated until after typeck.  See
     /// typeck::check::fn_ctxt for details.
@@ -359,6 +356,14 @@ pub struct TypeckTables<'tcx> {
     /// other items.
     node_substs: ItemLocalMap<&'tcx Substs<'tcx>>,
 
+    /// Stores the canonicalized types provided by the user. See also
+    /// `AscribeUserType` statement in MIR.
+    user_provided_tys: ItemLocalMap<CanonicalTy<'tcx>>,
+
+    /// Stores the canonicalized types provided by the user. See also
+    /// `AscribeUserType` statement in MIR.
+    pub user_provided_sigs: DefIdMap<CanonicalPolyFnSig<'tcx>>,
+
     /// Stores the substitutions that the user explicitly gave (if any)
     /// attached to `id`. These will not include any inferred
     /// values. The canonical form is used to capture things like `_`
@@ -442,6 +447,7 @@ impl<'tcx> TypeckTables<'tcx> {
             type_dependent_defs: ItemLocalMap(),
             field_indices: ItemLocalMap(),
             user_provided_tys: ItemLocalMap(),
+            user_provided_sigs: Default::default(),
             node_types: ItemLocalMap(),
             node_substs: ItemLocalMap(),
             user_substs: ItemLocalMap(),
@@ -748,6 +754,7 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for TypeckTables<'gcx> {
             ref type_dependent_defs,
             ref field_indices,
             ref user_provided_tys,
+            ref user_provided_sigs,
             ref node_types,
             ref node_substs,
             ref user_substs,
@@ -771,6 +778,7 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for TypeckTables<'gcx> {
             type_dependent_defs.hash_stable(hcx, hasher);
             field_indices.hash_stable(hcx, hasher);
             user_provided_tys.hash_stable(hcx, hasher);
+            user_provided_sigs.hash_stable(hcx, hasher);
             node_types.hash_stable(hcx, hasher);
             node_substs.hash_stable(hcx, hasher);
             user_substs.hash_stable(hcx, hasher);

src/librustc/ty/mod.rs

@@ -64,7 +64,7 @@ use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
 use hir;
 
 pub use self::sty::{Binder, BoundTy, BoundTyIndex, DebruijnIndex, INNERMOST};
-pub use self::sty::{FnSig, GenSig, PolyFnSig, PolyGenSig};
+pub use self::sty::{FnSig, GenSig, CanonicalPolyFnSig, PolyFnSig, PolyGenSig};
 pub use self::sty::{InferTy, ParamTy, ProjectionTy, ExistentialPredicate};
 pub use self::sty::{ClosureSubsts, GeneratorSubsts, UpvarSubsts, TypeAndMut};
 pub use self::sty::{TraitRef, TyKind, PolyTraitRef};

src/librustc/ty/sty.rs

@@ -11,7 +11,7 @@
 //! This module contains TyKind and its major components
 
 use hir::def_id::DefId;
-
+use infer::canonical::Canonical;
 use mir::interpret::ConstValue;
 use middle::region;
 use polonius_engine::Atom;
@@ -980,6 +980,9 @@ impl<'tcx> PolyFnSig<'tcx> {
     }
 }
 
+pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
+
+
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct ParamTy {
     pub idx: u32,

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -1208,6 +1208,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // to report the error. This gives better error messages
             // in some cases.
             self.report_error(mir, infcx, mir_def_id, longer_fr, shorter_fr, errors_buffer);
+            return; // continuing to iterate just reports more errors than necessary
         }
     }
 

src/librustc_mir/borrow_check/nll/type_check/input_output.rs

@@ -18,6 +18,7 @@
 //! contain revealed `impl Trait` values).
 
 use borrow_check::nll::universal_regions::UniversalRegions;
+use rustc::infer::LateBoundRegionConversionTime;
 use rustc::mir::*;
 use rustc::ty::Ty;
 
@@ -36,9 +37,47 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
         let (&normalized_output_ty, normalized_input_tys) =
             normalized_inputs_and_output.split_last().unwrap();
 
+        // If the user explicitly annotated the input types, extract
+        // those.
+        //
+        // e.g. `|x: FxHashMap<_, &'static u32>| ...`
+        let user_provided_sig;
+        if !self.tcx().is_closure(self.mir_def_id) {
+            user_provided_sig = None;
+        } else {
+            let typeck_tables = self.tcx().typeck_tables_of(self.mir_def_id);
+            user_provided_sig = match typeck_tables.user_provided_sigs.get(&self.mir_def_id) {
+                None => None,
+                Some(user_provided_poly_sig) => {
+                    // Instantiate the canonicalized variables from
+                    // user-provided signature (e.g. the `_` in the code
+                    // above) with fresh variables.
+                    let (poly_sig, _) = self.infcx.instantiate_canonical_with_fresh_inference_vars(
+                        mir.span,
+                        &user_provided_poly_sig,
+                    );
+
+                    // Replace the bound items in the fn sig with fresh
+                    // variables, so that they represent the view from
+                    // "inside" the closure.
+                    Some(
+                        self.infcx
+                            .replace_late_bound_regions_with_fresh_var(
+                                mir.span,
+                                LateBoundRegionConversionTime::FnCall,
+                                &poly_sig,
+                            )
+                            .0,
+                    )
+                }
+            }
+        };
+
         // Equate expected input tys with those in the MIR.
-        let argument_locals = (1..).map(Local::new);
-        for (&normalized_input_ty, local) in normalized_input_tys.iter().zip(argument_locals) {
+        for (&normalized_input_ty, argument_index) in normalized_input_tys.iter().zip(0..) {
+            // In MIR, argument N is stored in local N+1.
+            let local = Local::new(argument_index + 1);
+
             debug!(
                 "equate_inputs_and_outputs: normalized_input_ty = {:?}",
                 normalized_input_ty
@@ -53,6 +92,27 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             );
         }
 
+        if let Some(user_provided_sig) = user_provided_sig {
+            for (&user_provided_input_ty, argument_index) in
+                user_provided_sig.inputs().iter().zip(0..)
+            {
+                // In MIR, closures begin an implicit `self`, so
+                // argument N is stored in local N+2.
+                let local = Local::new(argument_index + 2);
+                let mir_input_ty = mir.local_decls[local].ty;
+                let mir_input_span = mir.local_decls[local].source_info.span;
+
+                // If the user explicitly annotated the input types, enforce those.
+                let user_provided_input_ty =
+                    self.normalize(user_provided_input_ty, Locations::All(mir_input_span));
+                self.equate_normalized_input_or_output(
+                    user_provided_input_ty,
+                    mir_input_ty,
+                    mir_input_span,
+                );
+            }
+        }
+
         assert!(
             mir.yield_ty.is_some() && universal_regions.yield_ty.is_some()
                 || mir.yield_ty.is_none() && universal_regions.yield_ty.is_none()
@@ -83,6 +143,18 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 terr
             );
         };
+
+        // If the user explicitly annotated the output types, enforce those.
+        if let Some(user_provided_sig) = user_provided_sig {
+            let user_provided_output_ty = user_provided_sig.output();
+            let user_provided_output_ty =
+                self.normalize(user_provided_output_ty, Locations::All(output_span));
+            self.equate_normalized_input_or_output(
+                user_provided_output_ty,
+                mir_output_ty,
+                output_span,
+            );
+        }
     }
 
     fn equate_normalized_input_or_output(&mut self, a: Ty<'tcx>, b: Ty<'tcx>, span: Span) {

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -1033,6 +1033,12 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                     assert!(!impl_self_ty.has_infer_types());
 
                     self.eq_types(self_ty, impl_self_ty, locations, category)?;
+
+                    self.prove_predicate(
+                        ty::Predicate::WellFormed(impl_self_ty),
+                        locations,
+                        category,
+                    );
                 }
 
                 // Prove the predicates coming along with `def_id`.
@@ -1070,11 +1076,9 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
     /// particularly necessary -- we'll do it lazilly as we process
     /// the value anyway -- but in some specific cases it is useful to
     /// normalize so we can suppress duplicate error messages.
-    fn fold_to_region_vid<T>(
-        &self,
-        value: T
-    ) -> T
-    where T: TypeFoldable<'tcx>
+    fn fold_to_region_vid<T>(&self, value: T) -> T
+    where
+        T: TypeFoldable<'tcx>,
     {
         if let Some(borrowck_context) = &self.borrowck_context {
             self.tcx().fold_regions(&value, &mut false, |r, _debruijn| {
@@ -1210,20 +1214,22 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 // though.
                 let category = match *place {
                     Place::Local(RETURN_PLACE) => if let Some(BorrowCheckContext {
-                        universal_regions: UniversalRegions {
-                            defining_ty: DefiningTy::Const(def_id, _),
-                            ..
-                        },
+                        universal_regions:
+                            UniversalRegions {
+                                defining_ty: DefiningTy::Const(def_id, _),
+                                ..
+                            },
                         ..
-                    }) = self.borrowck_context {
+                    }) = self.borrowck_context
+                    {
                         if tcx.is_static(*def_id).is_some() {
                             ConstraintCategory::UseAsStatic
                         } else {
                             ConstraintCategory::UseAsConst
                         }
                     } else {
                         ConstraintCategory::Return
-                    }
+                    },
                     Place::Local(l) if !mir.local_decls[l].is_user_variable.is_some() => {
                         ConstraintCategory::Boring
                     }
@@ -1510,12 +1516,14 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 let category = match *dest {
                     Place::Local(RETURN_PLACE) => {
                         if let Some(BorrowCheckContext {
-                            universal_regions: UniversalRegions {
-                                defining_ty: DefiningTy::Const(def_id, _),
-                                ..
-                            },
+                            universal_regions:
+                                UniversalRegions {
+                                    defining_ty: DefiningTy::Const(def_id, _),
+                                    ..
+                                },
                             ..
-                        }) = self.borrowck_context {
+                        }) = self.borrowck_context
+                        {
                             if tcx.is_static(*def_id).is_some() {
                                 ConstraintCategory::UseAsStatic
                             } else {
@@ -1524,7 +1532,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                         } else {
                             ConstraintCategory::Return
                         }
-                    },
+                    }
                     Place::Local(l) if !mir.local_decls[l].is_user_variable.is_some() => {
                         ConstraintCategory::Boring
                     }
@@ -1582,12 +1590,9 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             } else {
                 ConstraintCategory::Boring
             };
-            if let Err(terr) = self.sub_types(
-                op_arg_ty,
-                fn_arg,
-                term_location.to_locations(),
-                category,
-            ) {
+            if let Err(terr) =
+                self.sub_types(op_arg_ty, fn_arg, term_location.to_locations(), category)
+            {
                 span_mirbug!(
                     self,
                     term,

src/librustc_typeck/check/closure.rs

@@ -377,7 +377,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     ) -> ClosureSignatures<'tcx> {
         debug!("sig_of_closure_no_expectation()");
 
-        let bound_sig = self.supplied_sig_of_closure(decl);
+        let bound_sig = self.supplied_sig_of_closure(expr_def_id, decl);
 
         self.closure_sigs(expr_def_id, body, bound_sig)
     }
@@ -479,7 +479,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // Along the way, it also writes out entries for types that the user
         // wrote into our tables, which are then later used by the privacy
         // check.
-        match self.check_supplied_sig_against_expectation(decl, &closure_sigs) {
+        match self.check_supplied_sig_against_expectation(expr_def_id, decl, &closure_sigs) {
             Ok(infer_ok) => self.register_infer_ok_obligations(infer_ok),
             Err(_) => return self.sig_of_closure_no_expectation(expr_def_id, decl, body),
         }
@@ -521,14 +521,15 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     /// strategy.
     fn check_supplied_sig_against_expectation(
         &self,
+        expr_def_id: DefId,
         decl: &hir::FnDecl,
         expected_sigs: &ClosureSignatures<'tcx>,
     ) -> InferResult<'tcx, ()> {
         // Get the signature S that the user gave.
         //
         // (See comment on `sig_of_closure_with_expectation` for the
         // meaning of these letters.)
-        let supplied_sig = self.supplied_sig_of_closure(decl);
+        let supplied_sig = self.supplied_sig_of_closure(expr_def_id, decl);
 
         debug!(
             "check_supplied_sig_against_expectation: supplied_sig={:?}",
@@ -598,7 +599,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
     /// If there is no expected signature, then we will convert the
     /// types that the user gave into a signature.
-    fn supplied_sig_of_closure(&self, decl: &hir::FnDecl) -> ty::PolyFnSig<'tcx> {
+    ///
+    /// Also, record this closure signature for later.
+    fn supplied_sig_of_closure(
+        &self,
+        expr_def_id: DefId,
+        decl: &hir::FnDecl,
+    ) -> ty::PolyFnSig<'tcx> {
         let astconv: &dyn AstConv = self;
 
         // First, convert the types that the user supplied (if any).
@@ -618,6 +625,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         debug!("supplied_sig_of_closure: result={:?}", result);
 
+        let c_result = self.inh.infcx.canonicalize_response(&result);
+        self.tables.borrow_mut().user_provided_sigs.insert(
+            expr_def_id,
+            c_result,
+        );
+
         result
     }