Rollup of 11 pull requests

compiler/rustc_ast_lowering/src/expr.rs

@@ -505,14 +505,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_arm(&mut self, arm: &Arm) -> hir::Arm<'hir> {
+        let pat = self.lower_pat(&arm.pat);
+        let guard = arm.guard.as_ref().map(|cond| {
+            if let ExprKind::Let(ref pat, ref scrutinee) = cond.kind {
+                hir::Guard::IfLet(self.lower_pat(pat), self.lower_expr(scrutinee))
+            } else {
+                hir::Guard::If(self.lower_expr(cond))
+            }
+        });
         hir::Arm {
             hir_id: self.next_id(),
             attrs: self.lower_attrs(&arm.attrs),
-            pat: self.lower_pat(&arm.pat),
-            guard: match arm.guard {
-                Some(ref x) => Some(hir::Guard::If(self.lower_expr(x))),
-                _ => None,
-            },
+            pat,
+            guard,
             body: self.lower_expr(&arm.body),
             span: arm.span,
         }

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -480,17 +480,19 @@ impl<'tcx> CPlace<'tcx> {
                     // fn(&T) -> for<'l> fn(&'l T) is allowed
                 }
                 (&ty::Dynamic(from_traits, _), &ty::Dynamic(to_traits, _)) => {
-                    let from_traits = fx
-                        .tcx
-                        .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from_traits);
-                    let to_traits = fx
-                        .tcx
-                        .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to_traits);
-                    assert_eq!(
-                        from_traits, to_traits,
-                        "Can't write trait object of incompatible traits {:?} to place with traits {:?}\n\n{:#?}",
-                        from_traits, to_traits, fx,
-                    );
+                    for (from, to) in from_traits.iter().zip(to_traits) {
+                        let from = fx
+                            .tcx
+                            .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from);
+                        let to = fx
+                            .tcx
+                            .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to);
+                        assert_eq!(
+                            from, to,
+                            "Can't write trait object of incompatible traits {:?} to place with traits {:?}\n\n{:#?}",
+                            from_traits, to_traits, fx,
+                        );
+                    }
                     // dyn for<'r> Trait<'r> -> dyn Trait<'_> is allowed
                 }
                 _ => {

compiler/rustc_hir/src/hir.rs

@@ -1160,6 +1160,7 @@ pub struct Arm<'hir> {
 #[derive(Debug, HashStable_Generic)]
 pub enum Guard<'hir> {
     If(&'hir Expr<'hir>),
+    IfLet(&'hir Pat<'hir>, &'hir Expr<'hir>),
 }
 
 #[derive(Debug, HashStable_Generic)]
@@ -1721,6 +1722,8 @@ pub enum MatchSource {
     IfDesugar { contains_else_clause: bool },
     /// An `if let _ = _ { .. }` (optionally with `else { .. }`).
     IfLetDesugar { contains_else_clause: bool },
+    /// An `if let _ = _ => { .. }` match guard.
+    IfLetGuardDesugar,
     /// A `while _ { .. }` (which was desugared to a `loop { match _ { .. } }`).
     WhileDesugar,
     /// A `while let _ = _ { .. }` (which was desugared to a
@@ -1739,7 +1742,7 @@ impl MatchSource {
         use MatchSource::*;
         match self {
             Normal => "match",
-            IfDesugar { .. } | IfLetDesugar { .. } => "if",
+            IfDesugar { .. } | IfLetDesugar { .. } | IfLetGuardDesugar => "if",
             WhileDesugar | WhileLetDesugar => "while",
             ForLoopDesugar => "for",
             TryDesugar => "?",

compiler/rustc_hir/src/intravisit.rs

@@ -1228,6 +1228,10 @@ pub fn walk_arm<'v, V: Visitor<'v>>(visitor: &mut V, arm: &'v Arm<'v>) {
     if let Some(ref g) = arm.guard {
         match g {
             Guard::If(ref e) => visitor.visit_expr(e),
+            Guard::IfLet(ref pat, ref e) => {
+                visitor.visit_pat(pat);
+                visitor.visit_expr(e);
+            }
         }
     }
     visitor.visit_expr(&arm.body);

compiler/rustc_hir_pretty/src/lib.rs

@@ -2002,6 +2002,15 @@ impl<'a> State<'a> {
                     self.print_expr(&e);
                     self.s.space();
                 }
+                hir::Guard::IfLet(pat, e) => {
+                    self.word_nbsp("if");
+                    self.word_nbsp("let");
+                    self.print_pat(&pat);
+                    self.s.space();
+                    self.word_space("=");
+                    self.print_expr(&e);
+                    self.s.space();
+                }
             }
         }
         self.word_space("=>");

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

@@ -496,7 +496,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
             fn print_dyn_existential(
                 self,
-                _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
+                _predicates: &'tcx ty::List<ty::Binder<ty::ExistentialPredicate<'tcx>>>,
             ) -> Result<Self::DynExistential, Self::Error> {
                 Err(NonTrivialPath)
             }

compiler/rustc_lint/src/context.rs

@@ -786,7 +786,7 @@ impl<'tcx> LateContext<'tcx> {
 
             fn print_dyn_existential(
                 self,
-                _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
+                _predicates: &'tcx ty::List<ty::Binder<ty::ExistentialPredicate<'tcx>>>,
             ) -> Result<Self::DynExistential, Self::Error> {
                 Ok(())
             }

compiler/rustc_lint/src/unused.rs

@@ -218,8 +218,10 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                 }
                 ty::Dynamic(binder, _) => {
                     let mut has_emitted = false;
-                    for predicate in binder.skip_binder().iter() {
-                        if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate {
+                    for predicate in binder.iter() {
+                        if let ty::ExistentialPredicate::Trait(ref trait_ref) =
+                            predicate.skip_binder()
+                        {
                             let def_id = trait_ref.def_id;
                             let descr_post =
                                 &format!(" trait object{}{}", plural_suffix, descr_post,);

compiler/rustc_middle/src/middle/stability.rs

@@ -132,37 +132,37 @@ pub fn report_unstable(
 /// Checks whether an item marked with `deprecated(since="X")` is currently
 /// deprecated (i.e., whether X is not greater than the current rustc version).
 pub fn deprecation_in_effect(is_since_rustc_version: bool, since: Option<&str>) -> bool {
-    let since = if let Some(since) = since {
-        if is_since_rustc_version {
-            since
-        } else {
-            // We assume that the deprecation is in effect if it's not a
-            // rustc version.
-            return true;
-        }
-    } else {
-        // If since attribute is not set, then we're definitely in effect.
-        return true;
-    };
     fn parse_version(ver: &str) -> Vec<u32> {
         // We ignore non-integer components of the version (e.g., "nightly").
         ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
     }
 
-    if let Some(rustc) = option_env!("CFG_RELEASE") {
-        let since: Vec<u32> = parse_version(&since);
-        let rustc: Vec<u32> = parse_version(rustc);
-        // We simply treat invalid `since` attributes as relating to a previous
-        // Rust version, thus always displaying the warning.
-        if since.len() != 3 {
-            return true;
-        }
-        since <= rustc
-    } else {
-        // By default, a deprecation warning applies to
-        // the current version of the compiler.
-        true
+    if !is_since_rustc_version {
+        // The `since` field doesn't have semantic purpose in the stable `deprecated`
+        // attribute, only in `rustc_deprecated`.
+        return true;
     }
+
+    if let Some(since) = since {
+        if since == "TBD" {
+            return false;
+        }
+
+        if let Some(rustc) = option_env!("CFG_RELEASE") {
+            let since: Vec<u32> = parse_version(&since);
+            let rustc: Vec<u32> = parse_version(rustc);
+            // We simply treat invalid `since` attributes as relating to a previous
+            // Rust version, thus always displaying the warning.
+            if since.len() != 3 {
+                return true;
+            }
+            return since <= rustc;
+        }
+    };
+
+    // Assume deprecation is in effect if "since" field is missing
+    // or if we can't determine the current Rust version.
+    true
 }
 
 pub fn deprecation_suggestion(
@@ -182,19 +182,24 @@ pub fn deprecation_suggestion(
 }
 
 pub fn deprecation_message(depr: &Deprecation, kind: &str, path: &str) -> (String, &'static Lint) {
-    let (message, lint) = if deprecation_in_effect(
-        depr.is_since_rustc_version,
-        depr.since.map(Symbol::as_str).as_deref(),
-    ) {
+    let since = depr.since.map(Symbol::as_str);
+    let (message, lint) = if deprecation_in_effect(depr.is_since_rustc_version, since.as_deref()) {
         (format!("use of deprecated {} `{}`", kind, path), DEPRECATED)
     } else {
         (
-            format!(
-                "use of {} `{}` that will be deprecated in future version {}",
-                kind,
-                path,
-                depr.since.unwrap()
-            ),
+            if since.as_deref() == Some("TBD") {
+                format!(
+                    "use of {} `{}` that will be deprecated in a future Rust version",
+                    kind, path
+                )
+            } else {
+                format!(
+                    "use of {} `{}` that will be deprecated in future version {}",
+                    kind,
+                    path,
+                    since.unwrap()
+                )
+            },
             DEPRECATED_IN_FUTURE,
         )
     };

compiler/rustc_middle/src/mir/interpret/mod.rs

@@ -132,7 +132,6 @@ pub use self::pointer::{Pointer, PointerArithmetic};
 /// Uniquely identifies one of the following:
 /// - A constant
 /// - A static
-/// - A const fn where all arguments (if any) are zero-sized types
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, Lift)]
 pub struct GlobalId<'tcx> {

compiler/rustc_middle/src/ty/codec.rs

@@ -321,10 +321,14 @@ impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
     }
 }
 
-impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<ty::ExistentialPredicate<'tcx>> {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D>
+    for ty::List<ty::Binder<ty::ExistentialPredicate<'tcx>>>
+{
     fn decode(decoder: &mut D) -> Result<&'tcx Self, D::Error> {
         let len = decoder.read_usize()?;
-        Ok(decoder.tcx().mk_existential_predicates((0..len).map(|_| Decodable::decode(decoder)))?)
+        Ok(decoder
+            .tcx()
+            .mk_poly_existential_predicates((0..len).map(|_| Decodable::decode(decoder)))?)
     }
 }
 
@@ -373,7 +377,7 @@ impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [mir::abstract_const::N
 impl_decodable_via_ref! {
     &'tcx ty::TypeckResults<'tcx>,
     &'tcx ty::List<Ty<'tcx>>,
-    &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
+    &'tcx ty::List<ty::Binder<ty::ExistentialPredicate<'tcx>>>,
     &'tcx Allocation,
     &'tcx mir::Body<'tcx>,
     &'tcx mir::UnsafetyCheckResult,

compiler/rustc_middle/src/ty/context.rs

@@ -87,7 +87,7 @@ pub struct CtxtInterners<'tcx> {
     substs: InternedSet<'tcx, InternalSubsts<'tcx>>,
     canonical_var_infos: InternedSet<'tcx, List<CanonicalVarInfo<'tcx>>>,
     region: InternedSet<'tcx, RegionKind>,
-    existential_predicates: InternedSet<'tcx, List<ExistentialPredicate<'tcx>>>,
+    poly_existential_predicates: InternedSet<'tcx, List<ty::Binder<ExistentialPredicate<'tcx>>>>,
     predicate: InternedSet<'tcx, PredicateInner<'tcx>>,
     predicates: InternedSet<'tcx, List<Predicate<'tcx>>>,
     projs: InternedSet<'tcx, List<ProjectionKind>>,
@@ -103,7 +103,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             type_list: Default::default(),
             substs: Default::default(),
             region: Default::default(),
-            existential_predicates: Default::default(),
+            poly_existential_predicates: Default::default(),
             canonical_var_infos: Default::default(),
             predicate: Default::default(),
             predicates: Default::default(),
@@ -1623,7 +1623,7 @@ nop_lift! {const_; &'a Const<'a> => &'tcx Const<'tcx>}
 nop_lift! {predicate; &'a PredicateInner<'a> => &'tcx PredicateInner<'tcx>}
 
 nop_list_lift! {type_list; Ty<'a> => Ty<'tcx>}
-nop_list_lift! {existential_predicates; ExistentialPredicate<'a> => ExistentialPredicate<'tcx>}
+nop_list_lift! {poly_existential_predicates; ty::Binder<ExistentialPredicate<'a>> => ty::Binder<ExistentialPredicate<'tcx>>}
 nop_list_lift! {predicates; Predicate<'a> => Predicate<'tcx>}
 nop_list_lift! {canonical_var_infos; CanonicalVarInfo<'a> => CanonicalVarInfo<'tcx>}
 nop_list_lift! {projs; ProjectionKind => ProjectionKind}
@@ -2064,7 +2064,8 @@ slice_interners!(
     type_list: _intern_type_list(Ty<'tcx>),
     substs: _intern_substs(GenericArg<'tcx>),
     canonical_var_infos: _intern_canonical_var_infos(CanonicalVarInfo<'tcx>),
-    existential_predicates: _intern_existential_predicates(ExistentialPredicate<'tcx>),
+    poly_existential_predicates:
+        _intern_poly_existential_predicates(ty::Binder<ExistentialPredicate<'tcx>>),
     predicates: _intern_predicates(Predicate<'tcx>),
     projs: _intern_projs(ProjectionKind),
     place_elems: _intern_place_elems(PlaceElem<'tcx>),
@@ -2295,7 +2296,7 @@ impl<'tcx> TyCtxt<'tcx> {
     #[inline]
     pub fn mk_dynamic(
         self,
-        obj: ty::Binder<&'tcx List<ExistentialPredicate<'tcx>>>,
+        obj: &'tcx List<ty::Binder<ExistentialPredicate<'tcx>>>,
         reg: ty::Region<'tcx>,
     ) -> Ty<'tcx> {
         self.mk_ty(Dynamic(obj, reg))
@@ -2425,13 +2426,17 @@ impl<'tcx> TyCtxt<'tcx> {
         Place { local: place.local, projection: self.intern_place_elems(&projection) }
     }
 
-    pub fn intern_existential_predicates(
+    pub fn intern_poly_existential_predicates(
         self,
-        eps: &[ExistentialPredicate<'tcx>],
-    ) -> &'tcx List<ExistentialPredicate<'tcx>> {
+        eps: &[ty::Binder<ExistentialPredicate<'tcx>>],
+    ) -> &'tcx List<ty::Binder<ExistentialPredicate<'tcx>>> {
         assert!(!eps.is_empty());
-        assert!(eps.array_windows().all(|[a, b]| a.stable_cmp(self, b) != Ordering::Greater));
-        self._intern_existential_predicates(eps)
+        assert!(
+            eps.array_windows()
+                .all(|[a, b]| a.skip_binder().stable_cmp(self, &b.skip_binder())
+                    != Ordering::Greater)
+        );
+        self._intern_poly_existential_predicates(eps)
     }
 
     pub fn intern_predicates(self, preds: &[Predicate<'tcx>]) -> &'tcx List<Predicate<'tcx>> {
@@ -2488,13 +2493,16 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn mk_existential_predicates<
-        I: InternAs<[ExistentialPredicate<'tcx>], &'tcx List<ExistentialPredicate<'tcx>>>,
+    pub fn mk_poly_existential_predicates<
+        I: InternAs<
+            [ty::Binder<ExistentialPredicate<'tcx>>],
+            &'tcx List<ty::Binder<ExistentialPredicate<'tcx>>>,
+        >,
     >(
         self,
         iter: I,
     ) -> I::Output {
-        iter.intern_with(|xs| self.intern_existential_predicates(xs))
+        iter.intern_with(|xs| self.intern_poly_existential_predicates(xs))
     }
 
     pub fn mk_predicates<I: InternAs<[Predicate<'tcx>], &'tcx List<Predicate<'tcx>>>>(

compiler/rustc_middle/src/ty/error.rs

@@ -58,7 +58,7 @@ pub enum TypeError<'tcx> {
     CyclicTy(Ty<'tcx>),
     CyclicConst(&'tcx ty::Const<'tcx>),
     ProjectionMismatched(ExpectedFound<DefId>),
-    ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>),
+    ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::Binder<ty::ExistentialPredicate<'tcx>>>>),
     ObjectUnsafeCoercion(DefId),
     ConstMismatch(ExpectedFound<&'tcx ty::Const<'tcx>>),
 

compiler/rustc_middle/src/ty/flags.rs

@@ -160,19 +160,15 @@ impl FlagComputation {
             }
 
             &ty::Dynamic(obj, r) => {
-                self.bound_computation(obj, |computation, obj| {
-                    for predicate in obj.iter() {
-                        match predicate {
-                            ty::ExistentialPredicate::Trait(tr) => {
-                                computation.add_substs(tr.substs)
-                            }
-                            ty::ExistentialPredicate::Projection(p) => {
-                                computation.add_existential_projection(&p);
-                            }
-                            ty::ExistentialPredicate::AutoTrait(_) => {}
+                for predicate in obj.iter() {
+                    self.bound_computation(predicate, |computation, predicate| match predicate {
+                        ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
+                        ty::ExistentialPredicate::Projection(p) => {
+                            computation.add_existential_projection(&p);
                         }
-                    }
-                });
+                        ty::ExistentialPredicate::AutoTrait(_) => {}
+                    });
+                }
 
                 self.add_region(r);
             }