Rollup of 6 pull requests

src/libcore/fmt/builders.rs

@@ -133,7 +133,7 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn field(&mut self, name: &str, value: &dyn fmt::Debug) -> &mut DebugStruct<'a, 'b> {
+    pub fn field(&mut self, name: &str, value: &dyn fmt::Debug) -> &mut Self {
         self.result = self.result.and_then(|_| {
             if self.is_pretty() {
                 if !self.has_fields {
@@ -330,7 +330,7 @@ impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn field(&mut self, value: &dyn fmt::Debug) -> &mut DebugTuple<'a, 'b> {
+    pub fn field(&mut self, value: &dyn fmt::Debug) -> &mut Self {
         self.result = self.result.and_then(|_| {
             if self.is_pretty() {
                 if self.fields == 0 {
@@ -492,7 +492,7 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut DebugSet<'a, 'b> {
+    pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut Self {
         self.inner.entry(entry);
         self
     }
@@ -521,7 +521,7 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entries<D, I>(&mut self, entries: I) -> &mut DebugSet<'a, 'b>
+    pub fn entries<D, I>(&mut self, entries: I) -> &mut Self
     where
         D: fmt::Debug,
         I: IntoIterator<Item = D>,
@@ -624,7 +624,7 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut DebugList<'a, 'b> {
+    pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut Self {
         self.inner.entry(entry);
         self
     }
@@ -653,7 +653,7 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entries<D, I>(&mut self, entries: I) -> &mut DebugList<'a, 'b>
+    pub fn entries<D, I>(&mut self, entries: I) -> &mut Self
     where
         D: fmt::Debug,
         I: IntoIterator<Item = D>,
@@ -760,7 +760,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entry(&mut self, key: &dyn fmt::Debug, value: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {
+    pub fn entry(&mut self, key: &dyn fmt::Debug, value: &dyn fmt::Debug) -> &mut Self {
         self.key(key).value(value)
     }
 
@@ -797,7 +797,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// );
     /// ```
     #[unstable(feature = "debug_map_key_value", reason = "recently added", issue = "62482")]
-    pub fn key(&mut self, key: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {
+    pub fn key(&mut self, key: &dyn fmt::Debug) -> &mut Self {
         self.result = self.result.and_then(|_| {
             assert!(
                 !self.has_key,
@@ -862,7 +862,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// );
     /// ```
     #[unstable(feature = "debug_map_key_value", reason = "recently added", issue = "62482")]
-    pub fn value(&mut self, value: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {
+    pub fn value(&mut self, value: &dyn fmt::Debug) -> &mut Self {
         self.result = self.result.and_then(|_| {
             assert!(self.has_key, "attempted to format a map value before its key");
 
@@ -908,7 +908,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entries<K, V, I>(&mut self, entries: I) -> &mut DebugMap<'a, 'b>
+    pub fn entries<K, V, I>(&mut self, entries: I) -> &mut Self
     where
         K: fmt::Debug,
         V: fmt::Debug,

src/librustc/mir/mod.rs

@@ -1773,7 +1773,7 @@ rustc_index::newtype_index! {
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct PlaceRef<'a, 'tcx> {
-    pub local: &'a Local,
+    pub local: Local,
     pub projection: &'a [PlaceElem<'tcx>],
 }
 
@@ -1797,8 +1797,8 @@ impl<'tcx> Place<'tcx> {
     // FIXME: can we safely swap the semantics of `fn base_local` below in here instead?
     pub fn local_or_deref_local(&self) -> Option<Local> {
         match self.as_ref() {
-            PlaceRef { local, projection: &[] }
-            | PlaceRef { local, projection: &[ProjectionElem::Deref] } => Some(*local),
+            PlaceRef { local, projection: [] }
+            | PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(local),
             _ => None,
         }
     }
@@ -1810,7 +1810,7 @@ impl<'tcx> Place<'tcx> {
     }
 
     pub fn as_ref(&self) -> PlaceRef<'_, 'tcx> {
-        PlaceRef { local: &self.local, projection: &self.projection }
+        PlaceRef { local: self.local, projection: &self.projection }
     }
 }
 
@@ -1826,18 +1826,18 @@ impl<'a, 'tcx> PlaceRef<'a, 'tcx> {
     //
     // FIXME: can we safely swap the semantics of `fn base_local` below in here instead?
     pub fn local_or_deref_local(&self) -> Option<Local> {
-        match self {
+        match *self {
             PlaceRef { local, projection: [] }
-            | PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(**local),
+            | PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(local),
             _ => None,
         }
     }
 
     /// If this place represents a local variable like `_X` with no
     /// projections, return `Some(_X)`.
     pub fn as_local(&self) -> Option<Local> {
-        match self {
-            PlaceRef { local, projection: [] } => Some(**local),
+        match *self {
+            PlaceRef { local, projection: [] } => Some(local),
             _ => None,
         }
     }

src/librustc/mir/tcx.rs

@@ -114,7 +114,7 @@ impl<'tcx> PlaceTy<'tcx> {
 
 impl<'tcx> Place<'tcx> {
     pub fn ty_from<D>(
-        local: &Local,
+        local: Local,
         projection: &[PlaceElem<'tcx>],
         local_decls: &D,
         tcx: TyCtxt<'tcx>,
@@ -124,7 +124,7 @@ impl<'tcx> Place<'tcx> {
     {
         projection
             .iter()
-            .fold(PlaceTy::from_ty(local_decls.local_decls()[*local].ty), |place_ty, elem| {
+            .fold(PlaceTy::from_ty(local_decls.local_decls()[local].ty), |place_ty, elem| {
                 place_ty.projection_ty(tcx, elem)
             })
     }
@@ -133,7 +133,7 @@ impl<'tcx> Place<'tcx> {
     where
         D: HasLocalDecls<'tcx>,
     {
-        Place::ty_from(&self.local, &self.projection, local_decls, tcx)
+        Place::ty_from(self.local, &self.projection, local_decls, tcx)
     }
 }
 

src/librustc/traits/error_reporting/suggestions.rs

@@ -601,17 +601,24 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
         // Visit to make sure there's a single `return` type to suggest `impl Trait`,
         // otherwise suggest using `Box<dyn Trait>` or an enum.
-        let mut visitor = ReturnsVisitor(vec![]);
+        let mut visitor = ReturnsVisitor::default();
         visitor.visit_body(&body);
 
         let tables = self.in_progress_tables.map(|t| t.borrow()).unwrap();
 
-        let mut ret_types = visitor.0.iter().filter_map(|expr| tables.node_type_opt(expr.hir_id));
-        let (last_ty, all_returns_have_same_type) =
-            ret_types.clone().fold((None, true), |(last_ty, mut same), returned_ty| {
-                same &= last_ty.map_or(true, |ty| ty == returned_ty);
-                (Some(returned_ty), same)
-            });
+        let mut ret_types = visitor
+            .returns
+            .iter()
+            .filter_map(|expr| tables.node_type_opt(expr.hir_id))
+            .map(|ty| self.resolve_vars_if_possible(&ty));
+        let (last_ty, all_returns_have_same_type) = ret_types.clone().fold(
+            (None, true),
+            |(last_ty, mut same): (std::option::Option<Ty<'_>>, bool), ty| {
+                let ty = self.resolve_vars_if_possible(&ty);
+                same &= last_ty.map_or(true, |last_ty| last_ty == ty) && ty.kind != ty::Error;
+                (Some(ty), same)
+            },
+        );
         let all_returns_conform_to_trait =
             if let Some(ty_ret_ty) = tables.node_type_opt(ret_ty.hir_id) {
                 match ty_ret_ty.kind {
@@ -626,7 +633,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             })
                         })
                     }
-                    _ => true,
+                    _ => false,
                 }
             } else {
                 true
@@ -676,7 +683,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 // Suggest `-> Box<dyn Trait>` and `Box::new(returned_value)`.
                 // Get all the return values and collect their span and suggestion.
                 let mut suggestions = visitor
-                    .0
+                    .returns
                     .iter()
                     .map(|expr| {
                         (
@@ -736,10 +743,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         {
             let body = hir.body(*body_id);
             // Point at all the `return`s in the function as they have failed trait bounds.
-            let mut visitor = ReturnsVisitor(vec![]);
+            let mut visitor = ReturnsVisitor::default();
             visitor.visit_body(&body);
             let tables = self.in_progress_tables.map(|t| t.borrow()).unwrap();
-            for expr in &visitor.0 {
+            for expr in &visitor.returns {
                 if let Some(returned_ty) = tables.node_type_opt(expr.hir_id) {
                     let ty = self.resolve_vars_if_possible(&returned_ty);
                     err.span_label(expr.span, &format!("this returned value is of type `{}`", ty));
@@ -1716,7 +1723,11 @@ pub fn suggest_constraining_type_param(
 
 /// Collect all the returned expressions within the input expression.
 /// Used to point at the return spans when we want to suggest some change to them.
-struct ReturnsVisitor<'v>(Vec<&'v hir::Expr<'v>>);
+#[derive(Default)]
+struct ReturnsVisitor<'v> {
+    returns: Vec<&'v hir::Expr<'v>>,
+    in_block_tail: bool,
+}
 
 impl<'v> Visitor<'v> for ReturnsVisitor<'v> {
     type Map = rustc::hir::map::Map<'v>;
@@ -1726,17 +1737,41 @@ impl<'v> Visitor<'v> for ReturnsVisitor<'v> {
     }
 
     fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
-        if let hir::ExprKind::Ret(Some(ex)) = ex.kind {
-            self.0.push(ex);
+        // Visit every expression to detect `return` paths, either through the function's tail
+        // expression or `return` statements. We walk all nodes to find `return` statements, but
+        // we only care about tail expressions when `in_block_tail` is `true`, which means that
+        // they're in the return path of the function body.
+        match ex.kind {
+            hir::ExprKind::Ret(Some(ex)) => {
+                self.returns.push(ex);
+            }
+            hir::ExprKind::Block(block, _) if self.in_block_tail => {
+                self.in_block_tail = false;
+                for stmt in block.stmts {
+                    hir::intravisit::walk_stmt(self, stmt);
+                }
+                self.in_block_tail = true;
+                if let Some(expr) = block.expr {
+                    self.visit_expr(expr);
+                }
+            }
+            hir::ExprKind::Match(_, arms, _) if self.in_block_tail => {
+                for arm in arms {
+                    self.visit_expr(arm.body);
+                }
+            }
+            // We need to walk to find `return`s in the entire body.
+            _ if !self.in_block_tail => hir::intravisit::walk_expr(self, ex),
+            _ => self.returns.push(ex),
         }
-        hir::intravisit::walk_expr(self, ex);
     }
 
     fn visit_body(&mut self, body: &'v hir::Body<'v>) {
+        assert!(!self.in_block_tail);
         if body.generator_kind().is_none() {
             if let hir::ExprKind::Block(block, None) = body.value.kind {
-                if let Some(expr) = block.expr {
-                    self.0.push(expr);
+                if block.expr.is_some() {
+                    self.in_block_tail = true;
                 }
             }
         }

src/librustc_codegen_ssa/mir/analyze.rs

@@ -134,7 +134,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
                 // ZSTs don't require any actual memory access.
                 let elem_ty = base_ty.projection_ty(cx.tcx(), elem).ty;
                 let elem_ty = self.fx.monomorphize(&elem_ty);
-                let span = self.fx.mir.local_decls[*place_ref.local].source_info.span;
+                let span = self.fx.mir.local_decls[place_ref.local].source_info.span;
                 if cx.spanned_layout_of(elem_ty, span).is_zst() {
                     return;
                 }
@@ -174,7 +174,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
                     // We use `NonUseContext::VarDebugInfo` for the base,
                     // which might not force the base local to memory,
                     // so we have to do it manually.
-                    self.visit_local(place_ref.local, context, location);
+                    self.visit_local(&place_ref.local, context, location);
                 }
             }
 
@@ -212,8 +212,8 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
                 };
             }
 
-            self.visit_place_base(place_ref.local, context, location);
-            self.visit_projection(place_ref.local, place_ref.projection, context, location);
+            self.visit_place_base(&place_ref.local, context, location);
+            self.visit_projection(&place_ref.local, place_ref.projection, context, location);
         }
     }
 }

src/librustc_codegen_ssa/mir/block.rs

@@ -264,7 +264,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             PassMode::Direct(_) | PassMode::Pair(..) => {
-                let op = self.codegen_consume(&mut bx, &mir::Place::return_place().as_ref());
+                let op = self.codegen_consume(&mut bx, mir::Place::return_place().as_ref());
                 if let Ref(llval, _, align) = op.val {
                     bx.load(llval, align)
                 } else {
@@ -319,7 +319,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             return;
         }
 
-        let place = self.codegen_place(&mut bx, &location.as_ref());
+        let place = self.codegen_place(&mut bx, location.as_ref());
         let (args1, args2);
         let mut args = if let Some(llextra) = place.llextra {
             args2 = [place.llval, llextra];
@@ -1111,7 +1111,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         } else {
             self.codegen_place(
                 bx,
-                &mir::PlaceRef { local: &dest.local, projection: &dest.projection },
+                mir::PlaceRef { local: dest.local, projection: &dest.projection },
             )
         };
         if fn_ret.is_indirect() {
@@ -1137,7 +1137,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
                 LocalRef::Operand(None) => {
-                    let dst_layout = bx.layout_of(self.monomorphized_place_ty(&dst.as_ref()));
+                    let dst_layout = bx.layout_of(self.monomorphized_place_ty(dst.as_ref()));
                     assert!(!dst_layout.ty.has_erasable_regions());
                     let place = PlaceRef::alloca(bx, dst_layout);
                     place.storage_live(bx);
@@ -1151,7 +1151,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
             }
         } else {
-            let dst = self.codegen_place(bx, &dst.as_ref());
+            let dst = self.codegen_place(bx, dst.as_ref());
             self.codegen_transmute_into(bx, src, dst);
         }
     }

src/librustc_codegen_ssa/mir/operand.rs

@@ -369,11 +369,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     fn maybe_codegen_consume_direct(
         &mut self,
         bx: &mut Bx,
-        place_ref: &mir::PlaceRef<'_, 'tcx>,
+        place_ref: mir::PlaceRef<'_, 'tcx>,
     ) -> Option<OperandRef<'tcx, Bx::Value>> {
         debug!("maybe_codegen_consume_direct(place_ref={:?})", place_ref);
 
-        match self.locals[*place_ref.local] {
+        match self.locals[place_ref.local] {
             LocalRef::Operand(Some(mut o)) => {
                 // Moves out of scalar and scalar pair fields are trivial.
                 for elem in place_ref.projection.iter() {
@@ -413,7 +413,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     pub fn codegen_consume(
         &mut self,
         bx: &mut Bx,
-        place_ref: &mir::PlaceRef<'_, 'tcx>,
+        place_ref: mir::PlaceRef<'_, 'tcx>,
     ) -> OperandRef<'tcx, Bx::Value> {
         debug!("codegen_consume(place_ref={:?})", place_ref);
 
@@ -444,7 +444,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         match *operand {
             mir::Operand::Copy(ref place) | mir::Operand::Move(ref place) => {
-                self.codegen_consume(bx, &place.as_ref())
+                self.codegen_consume(bx, place.as_ref())
             }
 
             mir::Operand::Constant(ref constant) => {