diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index 602ce12c37d818c2bf0e536d189378c731a964c3..0ebc70750a6bba18aaffb2f1372e03ca7c723da0 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -1547,7 +1547,7 @@ pub struct Statement<'tcx> {
 
 // `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert_size!(Statement<'_>, 64);
+static_assert_size!(Statement<'_>, 32);
 
 impl Statement<'_> {
     /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
@@ -1568,7 +1568,7 @@ pub fn replace_nop(&mut self) -> Self {
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub enum StatementKind<'tcx> {
     /// Write the RHS Rvalue to the LHS Place.
-    Assign(Place<'tcx>, Box<Rvalue<'tcx>>),
+    Assign(Box<(Place<'tcx>, Rvalue<'tcx>)>),
 
     /// This represents all the reading that a pattern match may do
     /// (e.g., inspecting constants and discriminant values), and the
@@ -1577,10 +1577,10 @@ pub enum StatementKind<'tcx> {
     ///
     /// Note that this also is emitted for regular `let` bindings to ensure that locals that are
     /// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
-    FakeRead(FakeReadCause, Place<'tcx>),
+    FakeRead(FakeReadCause, Box<Place<'tcx>>),
 
     /// Write the discriminant for a variant to the enum Place.
-    SetDiscriminant { place: Place<'tcx>, variant_index: VariantIdx },
+    SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
 
     /// Start a live range for the storage of the local.
     StorageLive(Local),
@@ -1597,7 +1597,7 @@ pub enum StatementKind<'tcx> {
     /// by miri and only generated when "-Z mir-emit-retag" is passed.
     /// See <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/>
     /// for more details.
-    Retag(RetagKind, Place<'tcx>),
+    Retag(RetagKind, Box<Place<'tcx>>),
 
     /// Encodes a user's type ascription. These need to be preserved
     /// intact so that NLL can respect them. For example:
@@ -1611,7 +1611,7 @@ pub enum StatementKind<'tcx> {
     /// - `Contravariant` -- requires that `T_y :> T`
     /// - `Invariant` -- requires that `T_y == T`
     /// - `Bivariant` -- no effect
-    AscribeUserType(Place<'tcx>, ty::Variance, Box<UserTypeProjection>),
+    AscribeUserType(Box<(Place<'tcx>, UserTypeProjection)>, ty::Variance),
 
     /// No-op. Useful for deleting instructions without affecting statement indices.
     Nop,
@@ -1675,7 +1675,7 @@ impl Debug for Statement<'_> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         use self::StatementKind::*;
         match self.kind {
-            Assign(ref place, ref rv) => write!(fmt, "{:?} = {:?}", place, rv),
+            Assign(box(ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
             FakeRead(ref cause, ref place) => write!(fmt, "FakeRead({:?}, {:?})", cause, place),
             Retag(ref kind, ref place) => write!(
                 fmt,
@@ -1696,7 +1696,7 @@ fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
             InlineAsm(ref asm) => {
                 write!(fmt, "asm!({:?} : {:?} : {:?})", asm.asm, asm.outputs, asm.inputs)
             }
-            AscribeUserType(ref place, ref variance, ref c_ty) => {
+            AscribeUserType(box(ref place, ref c_ty), ref variance) => {
                 write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
             }
             Nop => write!(fmt, "nop"),
@@ -2998,14 +2998,14 @@ impl<'tcx> TypeFoldable<'tcx> for Statement<'tcx> {
 
 EnumTypeFoldableImpl! {
     impl<'tcx> TypeFoldable<'tcx> for StatementKind<'tcx> {
-        (StatementKind::Assign)(a, b),
+        (StatementKind::Assign)(a),
         (StatementKind::FakeRead)(cause, place),
         (StatementKind::SetDiscriminant) { place, variant_index },
         (StatementKind::StorageLive)(a),
         (StatementKind::StorageDead)(a),
         (StatementKind::InlineAsm)(a),
         (StatementKind::Retag)(kind, place),
-        (StatementKind::AscribeUserType)(a, v, b),
+        (StatementKind::AscribeUserType)(a, v),
         (StatementKind::Nop),
     }
 }
diff --git a/src/librustc/mir/visit.rs b/src/librustc/mir/visit.rs
index 9f3df7cc58f60799b695cd9798bc028987d84b9e..1e3b9eb29c79d0f07198409ccc43ee32f66eb1c3 100644
--- a/src/librustc/mir/visit.rs
+++ b/src/librustc/mir/visit.rs
@@ -344,7 +344,9 @@ fn super_statement(&mut self,
 
                 self.visit_source_info(source_info);
                 match kind {
-                    StatementKind::Assign(place, rvalue) => {
+                    StatementKind::Assign(
+                        box(ref $($mutability)? place, ref $($mutability)? rvalue)
+                    ) => {
                         self.visit_assign(place, rvalue, location);
                     }
                     StatementKind::FakeRead(_, place) => {
@@ -391,7 +393,10 @@ fn super_statement(&mut self,
                     StatementKind::Retag(kind, place) => {
                         self.visit_retag(kind, place, location);
                     }
-                    StatementKind::AscribeUserType(place, variance, user_ty) => {
+                    StatementKind::AscribeUserType(
+                        box(ref $($mutability)? place, ref $($mutability)? user_ty),
+                        variance
+                    ) => {
                         self.visit_ascribe_user_ty(place, variance, user_ty, location);
                     }
                     StatementKind::Nop => {}
diff --git a/src/librustc_codegen_ssa/mir/statement.rs b/src/librustc_codegen_ssa/mir/statement.rs
index b1bc57c2e90ec88fa85564585d16f0ac0073b05b..dab7dfc04175110b57b369126d2817c1d9bb34fe 100644
--- a/src/librustc_codegen_ssa/mir/statement.rs
+++ b/src/librustc_codegen_ssa/mir/statement.rs
@@ -16,12 +16,12 @@ pub fn codegen_statement(
 
         self.set_debug_loc(&mut bx, statement.source_info);
         match statement.kind {
-            mir::StatementKind::Assign(ref place, ref rvalue) => {
+            mir::StatementKind::Assign(box(ref place, ref rvalue)) => {
                 if let mir::Place {
                     base: mir::PlaceBase::Local(index),
                     projection: box [],
-                } = *place {
-                    match self.locals[index] {
+                } = place {
+                    match self.locals[*index] {
                         LocalRef::Place(cg_dest) => {
                             self.codegen_rvalue(bx, cg_dest, rvalue)
                         }
@@ -30,7 +30,7 @@ pub fn codegen_statement(
                         }
                         LocalRef::Operand(None) => {
                             let (mut bx, operand) = self.codegen_rvalue_operand(bx, rvalue);
-                            if let Some(name) = self.mir.local_decls[index].name {
+                            if let Some(name) = self.mir.local_decls[*index].name {
                                 match operand.val {
                                     OperandValue::Ref(x, ..) |
                                     OperandValue::Immediate(x) => {
@@ -44,7 +44,7 @@ pub fn codegen_statement(
                                     }
                                 }
                             }
-                            self.locals[index] = LocalRef::Operand(Some(operand));
+                            self.locals[*index] = LocalRef::Operand(Some(operand));
                             bx
                         }
                         LocalRef::Operand(Some(op)) => {
@@ -64,7 +64,7 @@ pub fn codegen_statement(
                     self.codegen_rvalue(bx, cg_dest, rvalue)
                 }
             }
-            mir::StatementKind::SetDiscriminant{ref place, variant_index} => {
+            mir::StatementKind::SetDiscriminant{box ref place, variant_index} => {
                 self.codegen_place(&mut bx, &place.as_ref())
                     .codegen_set_discr(&mut bx, variant_index);
                 bx
diff --git a/src/librustc_mir/borrow_check/conflict_errors.rs b/src/librustc_mir/borrow_check/conflict_errors.rs
index a6f7c8f227c99b03c42f1edfbe20718973e211b9..413f7e2e406356c43573fe59dfa8cd2de0c115e1 100644
--- a/src/librustc_mir/borrow_check/conflict_errors.rs
+++ b/src/librustc_mir/borrow_check/conflict_errors.rs
@@ -1600,7 +1600,7 @@ fn annotate_argument_and_return_for_borrow(
             "annotate_argument_and_return_for_borrow: location={:?}",
             location
         );
-        if let Some(&Statement { kind: StatementKind::Assign(ref reservation, _), ..})
+        if let Some(&Statement { kind: StatementKind::Assign(box(ref reservation, _)), ..})
              = &self.body[location.block].statements.get(location.statement_index)
         {
             debug!(
@@ -1625,11 +1625,13 @@ fn annotate_argument_and_return_for_borrow(
                     target, stmt
                 );
                 if let StatementKind::Assign(
-                    Place {
-                        base: PlaceBase::Local(assigned_to),
-                        projection: box [],
-                    },
-                    box rvalue
+                    box(
+                        Place {
+                            base: PlaceBase::Local(assigned_to),
+                            projection: box [],
+                        },
+                        rvalue
+                    )
                 ) = &stmt.kind {
                     debug!(
                         "annotate_argument_and_return_for_borrow: assigned_to={:?} \
diff --git a/src/librustc_mir/borrow_check/error_reporting.rs b/src/librustc_mir/borrow_check/error_reporting.rs
index aeee961d2d35457b0cf30671a61ec7fd9b34529a..5bccd2835c980d32f6d75caee10ead5fa486e834 100644
--- a/src/librustc_mir/borrow_check/error_reporting.rs
+++ b/src/librustc_mir/borrow_check/error_reporting.rs
@@ -41,7 +41,7 @@ pub(super) fn add_moved_or_invoked_closure_note(
         let mut target = place.local_or_deref_local();
         for stmt in &self.body[location.block].statements[location.statement_index..] {
             debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
-            if let StatementKind::Assign(into, box Rvalue::Use(from)) = &stmt.kind {
+            if let StatementKind::Assign(box(into, Rvalue::Use(from))) = &stmt.kind {
                 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
                 match from {
                     Operand::Copy(ref place) |
@@ -792,8 +792,7 @@ pub(super) fn move_spans(
 
         debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
         if let  StatementKind::Assign(
-            _,
-            box Rvalue::Aggregate(ref kind, ref places)
+            box(_, Rvalue::Aggregate(ref kind, ref places))
         ) = stmt.kind {
             let (def_id, is_generator) = match kind {
                 box AggregateKind::Closure(def_id, _) => (def_id, false),
@@ -830,10 +829,10 @@ pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpan
             .get(location.statement_index)
         {
             Some(&Statement {
-                kind: StatementKind::Assign(Place {
+                kind: StatementKind::Assign(box(Place {
                     base: PlaceBase::Local(local),
                     projection: box [],
-                }, _),
+                }, _)),
                 ..
             }) => local,
             _ => return OtherUse(use_span),
@@ -846,7 +845,7 @@ pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpan
 
         for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
             if let StatementKind::Assign(
-                _, box Rvalue::Aggregate(ref kind, ref places)
+                box(_, Rvalue::Aggregate(ref kind, ref places))
             ) = stmt.kind {
                 let (def_id, is_generator) = match kind {
                     box AggregateKind::Closure(def_id, _) => (def_id, false),
diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs
index 2305984a017d0d3515525f6d978d597c2ccb995e..3b10d8f19668c26950bf82a30c05170816e96d0d 100644
--- a/src/librustc_mir/borrow_check/mod.rs
+++ b/src/librustc_mir/borrow_check/mod.rs
@@ -546,7 +546,7 @@ fn visit_statement_entry(
         self.check_activations(location, span, flow_state);
 
         match stmt.kind {
-            StatementKind::Assign(ref lhs, ref rhs) => {
+            StatementKind::Assign(box(ref lhs, ref rhs)) => {
                 self.consume_rvalue(
                     location,
                     (rhs, span),
@@ -561,7 +561,7 @@ fn visit_statement_entry(
                     flow_state,
                 );
             }
-            StatementKind::FakeRead(_, ref place) => {
+            StatementKind::FakeRead(_, box ref place) => {
                 // Read for match doesn't access any memory and is used to
                 // assert that a place is safe and live. So we don't have to
                 // do any checks here.
@@ -1387,7 +1387,7 @@ fn propagate_closure_used_mut_upvar(&mut self, operand: &Operand<'tcx>) {
                 let stmt = &bbd.statements[loc.statement_index];
                 debug!("temporary assigned in: stmt={:?}", stmt);
 
-                if let StatementKind::Assign(_, box Rvalue::Ref(_, _, ref source)) = stmt.kind {
+                if let StatementKind::Assign(box(_, Rvalue::Ref(_, _, ref source))) = stmt.kind {
                     propagate_closure_used_mut_place(self, source);
                 } else {
                     bug!("closures should only capture user variables \
diff --git a/src/librustc_mir/borrow_check/move_errors.rs b/src/librustc_mir/borrow_check/move_errors.rs
index cdba1aafdacb0500ccc32654ea765a48fe8c3fc3..aa732b0092a223f300a5528c6420ceab3498115b 100644
--- a/src/librustc_mir/borrow_check/move_errors.rs
+++ b/src/librustc_mir/borrow_check/move_errors.rs
@@ -89,11 +89,13 @@ fn append_to_grouped_errors(
                 // If that ever stops being the case, then the ever initialized
                 // flow could be used.
                 if let Some(StatementKind::Assign(
-                    Place {
-                        base: PlaceBase::Local(local),
-                        projection: box [],
-                    },
-                    box Rvalue::Use(Operand::Move(move_from)),
+                    box(
+                        Place {
+                            base: PlaceBase::Local(local),
+                            projection: box [],
+                        },
+                        Rvalue::Use(Operand::Move(move_from))
+                    )
                 )) = self.body.basic_blocks()[location.block]
                     .statements
                     .get(location.statement_index)
diff --git a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
index ad68b4bc054bb7006c18308e797868a489d8482a..eae2f832ba7918c80ed68a97061100a312ff8073 100644
--- a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
@@ -541,10 +541,10 @@ fn was_captured_by_trait_object(&self, borrow: &BorrowData<'tcx>) -> bool {
         // it which simplifies the termination logic.
         let mut queue = vec![location];
         let mut target = if let Some(&Statement {
-            kind: StatementKind::Assign(Place {
+            kind: StatementKind::Assign(box(Place {
                 base: PlaceBase::Local(local),
                 projection: box [],
-            }, _),
+            }, _)),
             ..
         }) = stmt
         {
@@ -567,7 +567,7 @@ fn was_captured_by_trait_object(&self, borrow: &BorrowData<'tcx>) -> bool {
                 debug!("was_captured_by_trait_object: stmt={:?}", stmt);
 
                 // The only kind of statement that we care about is assignments...
-                if let StatementKind::Assign(place, box rvalue) = &stmt.kind {
+                if let StatementKind::Assign(box(place, rvalue)) = &stmt.kind {
                     let into = match place.local_or_deref_local() {
                         Some(into) => into,
                         None => {
diff --git a/src/librustc_mir/borrow_check/nll/invalidation.rs b/src/librustc_mir/borrow_check/nll/invalidation.rs
index 71106af767064683378eb16223a81fd01466ca34..1d429e3a6dee6c721daa18e3e2b26d6700ccbda8 100644
--- a/src/librustc_mir/borrow_check/nll/invalidation.rs
+++ b/src/librustc_mir/borrow_check/nll/invalidation.rs
@@ -66,7 +66,7 @@ fn visit_statement(
         self.check_activations(location);
 
         match statement.kind {
-            StatementKind::Assign(ref lhs, ref rhs) => {
+            StatementKind::Assign(box(ref lhs, ref rhs)) => {
                 self.consume_rvalue(
                     location,
                     rhs,
diff --git a/src/librustc_mir/borrow_check/nll/type_check/mod.rs b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
index 599472958f4fcf12f110f70f22c0eaed84613707..10c038bc3336fc51a2e809ed566545a24b02ceb5 100644
--- a/src/librustc_mir/borrow_check/nll/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
@@ -1343,7 +1343,7 @@ fn check_stmt(&mut self, body: &Body<'tcx>, stmt: &Statement<'tcx>, location: Lo
         debug!("check_stmt: {:?}", stmt);
         let tcx = self.tcx();
         match stmt.kind {
-            StatementKind::Assign(ref place, ref rv) => {
+            StatementKind::Assign(box(ref place, ref rv)) => {
                 // Assignments to temporaries are not "interesting";
                 // they are not caused by the user, but rather artifacts
                 // of lowering. Assignments to other sorts of places *are* interesting
@@ -1450,7 +1450,7 @@ fn check_stmt(&mut self, body: &Body<'tcx>, stmt: &Statement<'tcx>, location: Lo
                     );
                 };
             }
-            StatementKind::AscribeUserType(ref place, variance, box ref projection) => {
+            StatementKind::AscribeUserType(box(ref place, ref projection), variance) => {
                 let place_ty = place.ty(body, tcx).ty;
                 if let Err(terr) = self.relate_type_and_user_type(
                     place_ty,
diff --git a/src/librustc_mir/borrow_check/used_muts.rs b/src/librustc_mir/borrow_check/used_muts.rs
index 8bfd24a1e59156926b4463d36ac90b547c0acbd2..695080dfe23d90e2e41b0d7ef870b576d3e17930 100644
--- a/src/librustc_mir/borrow_check/used_muts.rs
+++ b/src/librustc_mir/borrow_check/used_muts.rs
@@ -89,7 +89,7 @@ fn visit_statement(
         _location: Location,
     ) {
         match &statement.kind {
-            StatementKind::Assign(into, _) => {
+            StatementKind::Assign(box(into, _)) => {
                 if let PlaceBase::Local(local) = into.base {
                     debug!(
                         "visit_statement: statement={:?} local={:?} \
diff --git a/src/librustc_mir/build/cfg.rs b/src/librustc_mir/build/cfg.rs
index 778d1e71cedfc3d8bd2414270ec06ec29bc63866..3ed6b4ff346784c66e27a4fc17a664ece3acae91 100644
--- a/src/librustc_mir/build/cfg.rs
+++ b/src/librustc_mir/build/cfg.rs
@@ -37,7 +37,7 @@ pub fn push_assign(&mut self,
                        rvalue: Rvalue<'tcx>) {
         self.push(block, Statement {
             source_info,
-            kind: StatementKind::Assign(place.clone(), box rvalue)
+            kind: StatementKind::Assign(box(place.clone(), rvalue))
         });
     }
 
diff --git a/src/librustc_mir/build/expr/as_place.rs b/src/librustc_mir/build/expr/as_place.rs
index 5af66faf6ee1e8d81883183264389a831266dc22..09b33c6654a9db084a0bc431d1ed99bc81e54ec8 100644
--- a/src/librustc_mir/build/expr/as_place.rs
+++ b/src/librustc_mir/build/expr/as_place.rs
@@ -147,9 +147,11 @@ fn expr_as_place(
                         Statement {
                             source_info,
                             kind: StatementKind::AscribeUserType(
-                                place.clone(),
+                                box(
+                                    place.clone(),
+                                    UserTypeProjection { base: annotation_index, projs: vec![], }
+                                ),
                                 Variance::Invariant,
-                                box UserTypeProjection { base: annotation_index, projs: vec![], },
                             ),
                         },
                     );
@@ -174,9 +176,11 @@ fn expr_as_place(
                         Statement {
                             source_info,
                             kind: StatementKind::AscribeUserType(
-                                Place::from(temp.clone()),
+                                box(
+                                    Place::from(temp.clone()),
+                                    UserTypeProjection { base: annotation_index, projs: vec![], },
+                                ),
                                 Variance::Invariant,
-                                box UserTypeProjection { base: annotation_index, projs: vec![], },
                             ),
                         },
                     );
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index 64368ab604645d6a8986e4a4210fd8846ef42f44..613044dba29022ba32aa7b87716810fd7aa65f0c 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -135,7 +135,7 @@ pub fn match_expr(
             source_info,
             kind: StatementKind::FakeRead(
                 FakeReadCause::ForMatchedPlace,
-                scrutinee_place.clone(),
+                box(scrutinee_place.clone()),
             ),
         });
 
@@ -320,7 +320,7 @@ pub(super) fn expr_into_pattern(
                     block,
                     Statement {
                         source_info,
-                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, place),
+                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, box(place)),
                     },
                 );
 
@@ -362,12 +362,12 @@ pub(super) fn expr_into_pattern(
                     block,
                     Statement {
                         source_info: pattern_source_info,
-                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, place.clone()),
+                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, box(place.clone())),
                     },
                 );
 
                 let ty_source_info = self.source_info(user_ty_span);
-                let user_ty = box pat_ascription_ty.user_ty(
+                let user_ty = pat_ascription_ty.user_ty(
                     &mut self.canonical_user_type_annotations,
                     place.ty(&self.local_decls, self.hir.tcx()).ty,
                     ty_source_info.span,
@@ -377,7 +377,10 @@ pub(super) fn expr_into_pattern(
                     Statement {
                         source_info: ty_source_info,
                         kind: StatementKind::AscribeUserType(
-                            place,
+                            box(
+                                place,
+                                user_ty,
+                            ),
                             // We always use invariant as the variance here. This is because the
                             // variance field from the ascription refers to the variance to use
                             // when applying the type to the value being matched, but this
@@ -393,7 +396,6 @@ pub(super) fn expr_into_pattern(
                             // contrast, is intended to be used to relate `T` to the type of
                             // `<expr>`.
                             ty::Variance::Invariant,
-                            user_ty,
                         ),
                     },
                 );
@@ -1523,7 +1525,7 @@ fn bind_and_guard_matched_candidate<'pat>(
                     source_info: guard_end,
                     kind: StatementKind::FakeRead(
                         FakeReadCause::ForMatchGuard,
-                        Place::from(temp),
+                        box(Place::from(temp)),
                     ),
                 });
             }
@@ -1573,7 +1575,7 @@ fn bind_and_guard_matched_candidate<'pat>(
                     post_guard_block,
                     Statement {
                         source_info: guard_end,
-                        kind: StatementKind::FakeRead(FakeReadCause::ForGuardBinding, place),
+                        kind: StatementKind::FakeRead(FakeReadCause::ForGuardBinding, box(place)),
                     },
                 );
             }
@@ -1606,7 +1608,7 @@ fn ascribe_types(&mut self, block: BasicBlock, ascriptions: &[Ascription<'tcx>])
                 ascription.user_ty,
             );
 
-            let user_ty = box ascription.user_ty.clone().user_ty(
+            let user_ty = ascription.user_ty.clone().user_ty(
                 &mut self.canonical_user_type_annotations,
                 ascription.source.ty(&self.local_decls, self.hir.tcx()).ty,
                 source_info.span
@@ -1616,9 +1618,11 @@ fn ascribe_types(&mut self, block: BasicBlock, ascriptions: &[Ascription<'tcx>])
                 Statement {
                     source_info,
                     kind: StatementKind::AscribeUserType(
-                        ascription.source.clone(),
+                        box(
+                            ascription.source.clone(),
+                            user_ty,
+                        ),
                         ascription.variance,
-                        user_ty,
                     ),
                 },
             );
diff --git a/src/librustc_mir/dataflow/impls/borrows.rs b/src/librustc_mir/dataflow/impls/borrows.rs
index 04674fb58cb9f6ffa6c76cb3bab4917f8ae05f0d..a86fcb30f4d36ca97bbf7c94fec381eaf69e9834 100644
--- a/src/librustc_mir/dataflow/impls/borrows.rs
+++ b/src/librustc_mir/dataflow/impls/borrows.rs
@@ -268,8 +268,8 @@ fn statement_effect(&self,
 
         debug!("Borrows::statement_effect: stmt={:?}", stmt);
         match stmt.kind {
-            mir::StatementKind::Assign(ref lhs, ref rhs) => {
-                if let mir::Rvalue::Ref(_, _, ref place) = **rhs {
+            mir::StatementKind::Assign(box(ref lhs, ref rhs)) => {
+                if let mir::Rvalue::Ref(_, _, ref place) = *rhs {
                     if place.ignore_borrow(
                         self.tcx,
                         self.body,
diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs
index 0e01701ea9e4467ccd068289ebaf4578538a8e33..0f66b13fdc51af33d7404e3113583334aec274d9 100644
--- a/src/librustc_mir/dataflow/impls/storage_liveness.rs
+++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs
@@ -119,8 +119,8 @@ fn statement_effect(&self,
         match stmt.kind {
             StatementKind::StorageLive(l) => sets.gen(l),
             StatementKind::StorageDead(l) => sets.kill(l),
-            StatementKind::Assign(ref place, _)
-            | StatementKind::SetDiscriminant { ref place, .. } => {
+            StatementKind::Assign(box(ref place, _))
+            | StatementKind::SetDiscriminant { box ref place, .. } => {
                 if let PlaceBase::Local(local) = place.base {
                     sets.gen(local);
                 }
diff --git a/src/librustc_mir/dataflow/move_paths/builder.rs b/src/librustc_mir/dataflow/move_paths/builder.rs
index a4427287c4f80003207c4734206cf5a0e23af9f8..698c50166270a2bea6b3b5d684df8ded2d746a1b 100644
--- a/src/librustc_mir/dataflow/move_paths/builder.rs
+++ b/src/librustc_mir/dataflow/move_paths/builder.rs
@@ -268,7 +268,7 @@ struct Gatherer<'b, 'a, 'tcx> {
 impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
     fn gather_statement(&mut self, stmt: &Statement<'tcx>) {
         match stmt.kind {
-            StatementKind::Assign(ref place, ref rval) => {
+            StatementKind::Assign(box(ref place, ref rval)) => {
                 self.create_move_path(place);
                 if let RvalueInitializationState::Shallow = rval.initialization_state() {
                     // Box starts out uninitialized - need to create a separate
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index ca4da451a1f2d58f9f57879c683073b107fcb980..affca10bf5265e01db586b9e71eb60e50185841f 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -82,7 +82,7 @@ fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> InterpResult<'tcx> {
         self.memory.tcx.span = stmt.source_info.span;
 
         match stmt.kind {
-            Assign(ref place, ref rvalue) => self.eval_rvalue_into_place(rvalue, place)?,
+            Assign(box(ref place, ref rvalue)) => self.eval_rvalue_into_place(rvalue, place)?,
 
             SetDiscriminant {
                 ref place,
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index 9086ae844dd520086a2c470ee5bc7748d8140a42..6daca5e261431f7d4149c79b1945badd4e355f53 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -217,7 +217,7 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
             // Function arguments should be retagged, and we make this one raw.
             body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
                 source_info,
-                kind: StatementKind::Retag(RetagKind::Raw, dropee_ptr.clone()),
+                kind: StatementKind::Retag(RetagKind::Raw, box(dropee_ptr.clone())),
             });
         }
         let patch = {
@@ -415,8 +415,10 @@ fn copy_shim(&mut self) {
         let rcvr = Place::from(Local::new(1+0)).deref();
         let ret_statement = self.make_statement(
             StatementKind::Assign(
-                Place::return_place(),
-                box Rvalue::Use(Operand::Copy(rcvr))
+                box(
+                    Place::return_place(),
+                    Rvalue::Use(Operand::Copy(rcvr))
+                )
             )
         );
         self.block(vec![ret_statement], TerminatorKind::Return, false);
@@ -458,8 +460,10 @@ fn make_clone_call(
         // `let ref_loc: &ty = &src;`
         let statement = self.make_statement(
             StatementKind::Assign(
-                ref_loc.clone(),
-                box Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
+                box(
+                    ref_loc.clone(),
+                    Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
+                )
             )
         );
 
@@ -486,8 +490,10 @@ fn loop_header(
         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
         let compute_cond = self.make_statement(
             StatementKind::Assign(
-                cond.clone(),
-                box Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
+                box(
+                    cond.clone(),
+                    Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
+                )
             )
         );
 
@@ -521,14 +527,18 @@ fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len:
         let inits = vec![
             self.make_statement(
                 StatementKind::Assign(
-                    Place::from(beg),
-                    box Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                    box(
+                        Place::from(beg),
+                        Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                    )
                 )
             ),
             self.make_statement(
                 StatementKind::Assign(
-                    end.clone(),
-                    box Rvalue::Use(Operand::Constant(self.make_usize(len)))
+                    box(
+                        end.clone(),
+                        Rvalue::Use(Operand::Constant(self.make_usize(len)))
+                    )
                 )
             )
         ];
@@ -559,11 +569,13 @@ fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len:
         let statements = vec![
             self.make_statement(
                 StatementKind::Assign(
-                    Place::from(beg),
-                    box Rvalue::BinaryOp(
-                        BinOp::Add,
-                        Operand::Copy(Place::from(beg)),
-                        Operand::Constant(self.make_usize(1))
+                    box(
+                        Place::from(beg),
+                        Rvalue::BinaryOp(
+                            BinOp::Add,
+                            Operand::Copy(Place::from(beg)),
+                            Operand::Constant(self.make_usize(1))
+                        )
                     )
                 )
             )
@@ -582,8 +594,10 @@ fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len:
         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
         let init = self.make_statement(
             StatementKind::Assign(
-                Place::from(beg),
-                box Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                box(
+                    Place::from(beg),
+                    Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                )
             )
         );
         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
@@ -609,11 +623,13 @@ fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len:
         // `goto #6;`
         let statement = self.make_statement(
             StatementKind::Assign(
-                Place::from(beg),
-                box Rvalue::BinaryOp(
-                    BinOp::Add,
-                    Operand::Copy(Place::from(beg)),
-                    Operand::Constant(self.make_usize(1))
+                box(
+                    Place::from(beg),
+                    Rvalue::BinaryOp(
+                        BinOp::Add,
+                        Operand::Copy(Place::from(beg)),
+                        Operand::Constant(self.make_usize(1))
+                    )
                 )
             )
         );
@@ -727,8 +743,10 @@ fn build_call_shim<'tcx>(
             statements.push(Statement {
                 source_info,
                 kind: StatementKind::Assign(
-                    Place::from(ref_rcvr),
-                    box Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
+                    box(
+                        Place::from(ref_rcvr),
+                        Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
+                    )
                 )
             });
             Operand::Move(Place::from(ref_rcvr))
diff --git a/src/librustc_mir/transform/add_retag.rs b/src/librustc_mir/transform/add_retag.rs
index 466f6060827ec1d7b15f95538157982bfbb841e0..833c8b1646bb68d2ec31ad55f5db9a8809c927e2 100644
--- a/src/librustc_mir/transform/add_retag.rs
+++ b/src/librustc_mir/transform/add_retag.rs
@@ -89,7 +89,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _src: MirSource<'tcx>, body: &mut Body<'tc
             basic_blocks[START_BLOCK].statements.splice(0..0,
                 places.into_iter().map(|place| Statement {
                     source_info,
-                    kind: StatementKind::Retag(RetagKind::FnEntry, place),
+                    kind: StatementKind::Retag(RetagKind::FnEntry, box(place)),
                 })
             );
         }
@@ -125,7 +125,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _src: MirSource<'tcx>, body: &mut Body<'tc
         for (source_info, dest_place, dest_block) in returns {
             basic_blocks[dest_block].statements.insert(0, Statement {
                 source_info,
-                kind: StatementKind::Retag(RetagKind::Default, dest_place),
+                kind: StatementKind::Retag(RetagKind::Default, box(dest_place)),
             });
         }
 
@@ -137,11 +137,11 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _src: MirSource<'tcx>, body: &mut Body<'tc
             for i in (0..block_data.statements.len()).rev() {
                 let (retag_kind, place) = match block_data.statements[i].kind {
                     // If we are casting *from* a reference, we may have to retag-as-raw.
-                    StatementKind::Assign(ref place, box Rvalue::Cast(
+                    StatementKind::Assign(box(ref place, Rvalue::Cast(
                         CastKind::Misc,
                         ref src,
                         dest_ty,
-                    )) => {
+                    ))) => {
                         let src_ty = src.ty(&*local_decls, tcx);
                         if src_ty.is_region_ptr() {
                             // The only `Misc` casts on references are those creating raw pointers.
@@ -155,7 +155,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _src: MirSource<'tcx>, body: &mut Body<'tc
                     // Assignments of reference or ptr type are the ones where we may have
                     // to update tags.  This includes `x = &[mut] ...` and hence
                     // we also retag after taking a reference!
-                    StatementKind::Assign(ref place, box ref rvalue) if needs_retag(place) => {
+                    StatementKind::Assign(box(ref place, ref rvalue)) if needs_retag(place) => {
                         let kind = match rvalue {
                             Rvalue::Ref(_, borrow_kind, _)
                                 if borrow_kind.allows_two_phase_borrow()
@@ -173,7 +173,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _src: MirSource<'tcx>, body: &mut Body<'tc
                 let source_info = block_data.statements[i].source_info;
                 block_data.statements.insert(i+1, Statement {
                     source_info,
-                    kind: StatementKind::Retag(retag_kind, place),
+                    kind: StatementKind::Retag(retag_kind, box(place)),
                 });
             }
         }
diff --git a/src/librustc_mir/transform/cleanup_post_borrowck.rs b/src/librustc_mir/transform/cleanup_post_borrowck.rs
index ede1cb62f9451475583c390ec82bf5aea48014fd..ea173279aa07321604650d5ae7fb19ec33b93895 100644
--- a/src/librustc_mir/transform/cleanup_post_borrowck.rs
+++ b/src/librustc_mir/transform/cleanup_post_borrowck.rs
@@ -39,7 +39,7 @@ fn visit_statement(&mut self,
                        location: Location) {
         match statement.kind {
             StatementKind::AscribeUserType(..)
-            | StatementKind::Assign(_, box Rvalue::Ref(_, BorrowKind::Shallow, _))
+            | StatementKind::Assign(box(_, Rvalue::Ref(_, BorrowKind::Shallow, _)))
             | StatementKind::FakeRead(..) => statement.make_nop(),
             _ => (),
         }
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 2e91561f2eee1c1d1f3cf5fb7c52dbd59f799821..614d5d2a4a2fbd5174564b233523934b1274ef63 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -665,7 +665,7 @@ fn visit_statement(
         location: Location,
     ) {
         trace!("visit_statement: {:?}", statement);
-        if let StatementKind::Assign(ref place, ref mut rval) = statement.kind {
+        if let StatementKind::Assign(box(ref place, ref mut rval)) = statement.kind {
             let place_ty: Ty<'tcx> = place
                 .ty(&self.local_decls, self.tcx)
                 .ty;
diff --git a/src/librustc_mir/transform/copy_prop.rs b/src/librustc_mir/transform/copy_prop.rs
index 20bdb4b03f0813dfa94d85991f1b071ed6a741d6..28f97f41b50cf7027d4d0181f3e6e71fcedab517 100644
--- a/src/librustc_mir/transform/copy_prop.rs
+++ b/src/librustc_mir/transform/copy_prop.rs
@@ -94,11 +94,13 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _source: MirSource<'tcx>, body: &mut Body<
                     // That use of the source must be an assignment.
                     match statement.kind {
                         StatementKind::Assign(
-                            Place {
-                                base: PlaceBase::Local(local),
-                                projection: box [],
-                            },
-                            box Rvalue::Use(ref operand)
+                            box(
+                                Place {
+                                    base: PlaceBase::Local(local),
+                                    projection: box [],
+                                },
+                                Rvalue::Use(ref operand)
+                            )
                         ) if local == dest_local => {
                             let maybe_action = match *operand {
                                 Operand::Copy(ref src_place) |
@@ -148,24 +150,28 @@ fn eliminate_self_assignments(
             if let Some(stmt) = body[location.block].statements.get(location.statement_index) {
                 match stmt.kind {
                     StatementKind::Assign(
-                        Place {
-                            base: PlaceBase::Local(local),
-                            projection: box [],
-                        },
-                        box Rvalue::Use(Operand::Copy(Place {
-                            base: PlaceBase::Local(src_local),
-                            projection: box [],
-                        })),
+                        box(
+                            Place {
+                                base: PlaceBase::Local(local),
+                                projection: box [],
+                            },
+                            Rvalue::Use(Operand::Copy(Place {
+                                base: PlaceBase::Local(src_local),
+                                projection: box [],
+                            })),
+                        )
                     ) |
                     StatementKind::Assign(
-                        Place {
-                            base: PlaceBase::Local(local),
-                            projection: box [],
-                        },
-                        box Rvalue::Use(Operand::Move(Place {
-                            base: PlaceBase::Local(src_local),
-                            projection: box [],
-                        })),
+                        box(
+                            Place {
+                                base: PlaceBase::Local(local),
+                                projection: box [],
+                            },
+                            Rvalue::Use(Operand::Move(Place {
+                                base: PlaceBase::Local(src_local),
+                                projection: box [],
+                            })),
+                        )
                     ) if local == dest_local && dest_local == src_local => {}
                     _ => {
                         continue;
diff --git a/src/librustc_mir/transform/deaggregator.rs b/src/librustc_mir/transform/deaggregator.rs
index 1fc7ce09aa647db7a2d2229f3956578a79ba5794..c1224be6324e20bd58379e882864c0e89420d1e2 100644
--- a/src/librustc_mir/transform/deaggregator.rs
+++ b/src/librustc_mir/transform/deaggregator.rs
@@ -12,8 +12,8 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _source: MirSource<'tcx>, body: &mut Body<
         for bb in basic_blocks {
             bb.expand_statements(|stmt| {
                 // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
-                if let StatementKind::Assign(_, ref rhs) = stmt.kind {
-                    if let Rvalue::Aggregate(ref kind, _) = **rhs {
+                if let StatementKind::Assign(box(_, ref rhs)) = stmt.kind {
+                    if let Rvalue::Aggregate(ref kind, _) = *rhs {
                         // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
                         if let AggregateKind::Array(_) = **kind {
                             return None;
@@ -28,7 +28,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, _source: MirSource<'tcx>, body: &mut Body<
                 let stmt = stmt.replace_nop();
                 let source_info = stmt.source_info;
                 let (lhs, kind, operands) = match stmt.kind {
-                    StatementKind::Assign(lhs, box rvalue) => {
+                    StatementKind::Assign(box(lhs, rvalue)) => {
                         match rvalue {
                             Rvalue::Aggregate(kind, operands) => (lhs, kind, operands),
                             _ => bug!()
diff --git a/src/librustc_mir/transform/elaborate_drops.rs b/src/librustc_mir/transform/elaborate_drops.rs
index de5978c3a3525a5c345d87ce347519fdaa5463bf..a9c66b3c8c6d18dac2a90fa39358599414668692 100644
--- a/src/librustc_mir/transform/elaborate_drops.rs
+++ b/src/librustc_mir/transform/elaborate_drops.rs
@@ -452,7 +452,7 @@ fn elaborate_replace(
         assert!(!data.is_cleanup, "DropAndReplace in unwind path not supported");
 
         let assign = Statement {
-            kind: StatementKind::Assign(location.clone(), box Rvalue::Use(value.clone())),
+            kind: StatementKind::Assign(box(location.clone(), Rvalue::Use(value.clone()))),
             source_info: terminator.source_info
         };
 
diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs
index cf899c64406bca8759e5275c306527ce987f6de9..0ce2db93c421d0ce99d7e835aa19180e8ce7d783 100644
--- a/src/librustc_mir/transform/generator.rs
+++ b/src/librustc_mir/transform/generator.rs
@@ -217,7 +217,10 @@ fn set_discr(&self, state_disc: VariantIdx, source_info: SourceInfo) -> Statemen
         let self_place = Place::from(self_arg());
         Statement {
             source_info,
-            kind: StatementKind::SetDiscriminant { place: self_place, variant_index: state_disc },
+            kind: StatementKind::SetDiscriminant {
+                place: box self_place,
+                variant_index: state_disc,
+            },
         }
     }
 
@@ -230,7 +233,7 @@ fn get_discr(&self, body: &mut Body<'tcx>) -> (Statement<'tcx>, Place<'tcx>) {
         let self_place = Place::from(self_arg());
         let assign = Statement {
             source_info: source_info(body),
-            kind: StatementKind::Assign(temp.clone(), box Rvalue::Discriminant(self_place)),
+            kind: StatementKind::Assign(box(temp.clone(), Rvalue::Discriminant(self_place))),
         };
         (assign, temp)
     }
@@ -288,8 +291,12 @@ fn visit_basic_block_data(&mut self,
             // We must assign the value first in case it gets declared dead below
             data.statements.push(Statement {
                 source_info,
-                kind: StatementKind::Assign(Place::return_place(),
-                                            box self.make_state(state_idx, v)),
+                kind: StatementKind::Assign(
+                    box(
+                        Place::return_place(),
+                        self.make_state(state_idx, v)
+                    )
+                ),
             });
             let state = if let Some(resume) = resume { // Yield
                 let state = 3 + self.suspension_points.len();
@@ -929,7 +936,7 @@ fn create_generator_drop_shim<'tcx>(
         // Alias tracking must know we changed the type
         body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
             source_info,
-            kind: StatementKind::Retag(RetagKind::Raw, Place::from(self_arg())),
+            kind: StatementKind::Retag(RetagKind::Raw, box Place::from(self_arg())),
         })
     }
 
diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs
index 2b3c6d55f24ddd4ab69784bd2cf8dbf0192c2a34..5ad026dc143c9574c4dbce509b8371555877eacf 100644
--- a/src/librustc_mir/transform/inline.rs
+++ b/src/librustc_mir/transform/inline.rs
@@ -457,7 +457,7 @@ fn dest_needs_borrow(place: &Place<'_>) -> bool {
 
                     let stmt = Statement {
                         source_info: callsite.location,
-                        kind: StatementKind::Assign(tmp.clone(), box dest)
+                        kind: StatementKind::Assign(box(tmp.clone(), dest))
                     };
                     caller_body[callsite.bb]
                         .statements.push(stmt);
@@ -608,7 +608,7 @@ fn create_temp_if_necessary(
 
         let stmt = Statement {
             source_info: callsite.location,
-            kind: StatementKind::Assign(Place::from(arg_tmp), box arg),
+            kind: StatementKind::Assign(box(Place::from(arg_tmp), arg)),
         };
         caller_body[callsite.bb].statements.push(stmt);
         arg_tmp
diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs
index 0723a0c992e8e2a4b5cbdef82bbcc641654e0524..7d1b96b8be170dc89d11cde8d5194285a88cf723 100644
--- a/src/librustc_mir/transform/promote_consts.rs
+++ b/src/librustc_mir/transform/promote_consts.rs
@@ -187,7 +187,7 @@ fn assign(&mut self, dest: Local, rvalue: Rvalue<'tcx>, span: Span) {
                 span,
                 scope: OUTERMOST_SOURCE_SCOPE
             },
-            kind: StatementKind::Assign(Place::from(dest), box rvalue)
+            kind: StatementKind::Assign(box(Place::from(dest), rvalue))
         });
     }
 
@@ -222,10 +222,10 @@ fn promote_temp(&mut self, temp: Local) -> Local {
         // First, take the Rvalue or Call out of the source MIR,
         // or duplicate it, depending on keep_original.
         if loc.statement_index < no_stmts {
-            let (rvalue, source_info) = {
+            let (mut rvalue, source_info) = {
                 let statement = &mut self.source[loc.block].statements[loc.statement_index];
                 let rhs = match statement.kind {
-                    StatementKind::Assign(_, ref mut rhs) => rhs,
+                    StatementKind::Assign(box(_, ref mut rhs)) => rhs,
                     _ => {
                         span_bug!(statement.source_info.span, "{:?} is not an assignment",
                                   statement);
@@ -235,12 +235,11 @@ fn promote_temp(&mut self, temp: Local) -> Local {
                 (if self.keep_original {
                     rhs.clone()
                 } else {
-                    let unit = box Rvalue::Aggregate(box AggregateKind::Tuple, vec![]);
+                    let unit = Rvalue::Aggregate(box AggregateKind::Tuple, vec![]);
                     mem::replace(rhs, unit)
                 }, statement.source_info)
             };
 
-            let mut rvalue = *rvalue;
             self.visit_rvalue(&mut rvalue, loc);
             self.assign(new_temp, rvalue, source_info.span);
         } else {
@@ -326,7 +325,7 @@ fn promote_candidate(
                 Candidate::Ref(loc) => {
                     let ref mut statement = blocks[loc.block].statements[loc.statement_index];
                     match statement.kind {
-                        StatementKind::Assign(_, box Rvalue::Ref(_, _, ref mut place)) => {
+                        StatementKind::Assign(box(_, Rvalue::Ref(_, _, ref mut place))) => {
                             // Use the underlying local for this (necessarily interior) borrow.
                             let ty = place.base.ty(local_decls).ty;
                             let span = statement.source_info.span;
@@ -345,7 +344,7 @@ fn promote_candidate(
                 Candidate::Repeat(loc) => {
                     let ref mut statement = blocks[loc.block].statements[loc.statement_index];
                     match statement.kind {
-                        StatementKind::Assign(_, box Rvalue::Repeat(ref mut operand, _)) => {
+                        StatementKind::Assign(box(_, Rvalue::Repeat(ref mut operand, _))) => {
                             let ty = operand.ty(local_decls, self.tcx);
                             let span = statement.source_info.span;
                             mem::replace(
@@ -420,10 +419,10 @@ pub fn promote_candidates<'tcx>(
             Candidate::Repeat(Location { block, statement_index }) |
             Candidate::Ref(Location { block, statement_index }) => {
                 match body[block].statements[statement_index].kind {
-                    StatementKind::Assign(Place {
+                    StatementKind::Assign(box(Place {
                         base: PlaceBase::Local(local),
                         projection: box [],
-                    }, _) => {
+                    }, _)) => {
                         if temps[local] == TempState::PromotedOut {
                             // Already promoted.
                             continue;
@@ -473,10 +472,10 @@ pub fn promote_candidates<'tcx>(
     for block in body.basic_blocks_mut() {
         block.statements.retain(|statement| {
             match statement.kind {
-                StatementKind::Assign(Place {
+                StatementKind::Assign(box(Place {
                     base: PlaceBase::Local(index),
                     projection: box [],
-                }, _) |
+                }, _)) |
                 StatementKind::StorageLive(index) |
                 StatementKind::StorageDead(index) => {
                     !promoted(index)
diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs
index e05b0c96620565e58713494f7c1abf0ba84e5e9d..7cc1e634cf812da820c6aa6428d4e134eef85e83 100644
--- a/src/librustc_mir/transform/qualify_consts.rs
+++ b/src/librustc_mir/transform/qualify_consts.rs
@@ -982,23 +982,25 @@ fn check_const(&mut self) -> (u8, &'tcx BitSet<Local>) {
         for candidate in &self.promotion_candidates {
             match *candidate {
                 Candidate::Repeat(Location { block: bb, statement_index: stmt_idx }) => {
-                    if let StatementKind::Assign(_, box Rvalue::Repeat(
+                    if let StatementKind::Assign(box(_, Rvalue::Repeat(
                         Operand::Move(Place {
                             base: PlaceBase::Local(index),
                             projection: box [],
                         }),
                         _
-                    )) = self.body[bb].statements[stmt_idx].kind {
+                    ))) = self.body[bb].statements[stmt_idx].kind {
                         promoted_temps.insert(index);
                     }
                 }
                 Candidate::Ref(Location { block: bb, statement_index: stmt_idx }) => {
                     if let StatementKind::Assign(
-                        _,
-                        box Rvalue::Ref(_, _, Place {
-                            base: PlaceBase::Local(index),
-                            projection: box [],
-                        })
+                        box(
+                            _,
+                            Rvalue::Ref(_, _, Place {
+                                base: PlaceBase::Local(index),
+                                projection: box [],
+                            })
+                        )
                     ) = self.body[bb].statements[stmt_idx].kind {
                         promoted_temps.insert(index);
                     }
diff --git a/src/librustc_mir/transform/qualify_min_const_fn.rs b/src/librustc_mir/transform/qualify_min_const_fn.rs
index cb2da1d5ff916009b30172bfaa390fcd10845d00..80e020a9eb7e65b8442040178ddb657c975c554e 100644
--- a/src/librustc_mir/transform/qualify_min_const_fn.rs
+++ b/src/librustc_mir/transform/qualify_min_const_fn.rs
@@ -206,7 +206,7 @@ fn check_statement(
 ) -> McfResult {
     let span = statement.source_info.span;
     match &statement.kind {
-        StatementKind::Assign(place, rval) => {
+        StatementKind::Assign(box(place, rval)) => {
             check_place(place, span)?;
             check_rvalue(tcx, body, rval, span)
         }
diff --git a/src/librustc_mir/transform/remove_noop_landing_pads.rs b/src/librustc_mir/transform/remove_noop_landing_pads.rs
index 07669e2c0c986c606ca678c581134cc4f36d9ed9..70b11944e2fbcc463288cf09b745cd47a5121fc1 100644
--- a/src/librustc_mir/transform/remove_noop_landing_pads.rs
+++ b/src/librustc_mir/transform/remove_noop_landing_pads.rs
@@ -41,10 +41,10 @@ fn is_nop_landing_pad(
                     // These are all nops in a landing pad
                 }
 
-                StatementKind::Assign(Place {
+                StatementKind::Assign(box(Place {
                     base: PlaceBase::Local(_),
                     projection: box [],
-                }, box Rvalue::Use(_)) => {
+                }, Rvalue::Use(_))) => {
                     // Writing to a local (e.g., a drop flag) does not
                     // turn a landing pad to a non-nop
                 }
diff --git a/src/librustc_mir/transform/rustc_peek.rs b/src/librustc_mir/transform/rustc_peek.rs
index 208407bb9a5e088b84348b60f9769d57a921d79f..68fa082d2940786ab737eca0b02c30fcb1b73a17 100644
--- a/src/librustc_mir/transform/rustc_peek.rs
+++ b/src/librustc_mir/transform/rustc_peek.rs
@@ -150,7 +150,7 @@ fn each_block<'tcx, O>(
     for (j, stmt) in statements.iter().enumerate() {
         debug!("rustc_peek: ({:?},{}) {:?}", bb, j, stmt);
         let (place, rvalue) = match stmt.kind {
-            mir::StatementKind::Assign(ref place, ref rvalue) => {
+            mir::StatementKind::Assign(box(ref place, ref rvalue)) => {
                 (place, rvalue)
             }
             mir::StatementKind::FakeRead(..) |
@@ -166,7 +166,7 @@ fn each_block<'tcx, O>(
         };
 
         if place == peek_arg_place {
-            if let mir::Rvalue::Ref(_, mir::BorrowKind::Shared, ref peeking_at_place) = **rvalue {
+            if let mir::Rvalue::Ref(_, mir::BorrowKind::Shared, ref peeking_at_place) = *rvalue {
                 // Okay, our search is over.
                 match move_data.rev_lookup.find(peeking_at_place.as_ref()) {
                     LookupResult::Exact(peek_mpi) => {
diff --git a/src/librustc_mir/transform/uniform_array_move_out.rs b/src/librustc_mir/transform/uniform_array_move_out.rs
index 2f900f2638f48314e08d38961fe74f963b0bc9b8..34ad5cb5dc787d8762262a0b327a54e3a7fb476d 100644
--- a/src/librustc_mir/transform/uniform_array_move_out.rs
+++ b/src/librustc_mir/transform/uniform_array_move_out.rs
@@ -200,8 +200,8 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx
 
             for candidate in &visitor.candidates {
                 let statement = &body[candidate.block].statements[candidate.statement_index];
-                if let StatementKind::Assign(ref dst_place, ref rval) = statement.kind {
-                    if let Rvalue::Aggregate(box AggregateKind::Array(_), ref items) = **rval {
+                if let StatementKind::Assign(box(ref dst_place, ref rval)) = statement.kind {
+                    if let Rvalue::Aggregate(box AggregateKind::Array(_), ref items) = *rval {
                         let items : Vec<_> = items.iter().map(|item| {
                             if let Operand::Move(Place {
                                 base: PlaceBase::Local(local),
@@ -293,24 +293,28 @@ fn try_get_item_source<'a, 'tcx>(local_use: &LocalUse,
             if block.statements.len() > location.statement_index {
                 let statement = &block.statements[location.statement_index];
                 if let StatementKind::Assign(
-                    Place {
-                        base: PlaceBase::Local(_),
-                        projection: box [],
-                    },
-                    box Rvalue::Use(Operand::Move(Place {
-                        base: _,
-                        projection: box [.., ProjectionElem::ConstantIndex {
+                    box(
+                        Place {
+                            base: PlaceBase::Local(_),
+                            projection: box [],
+                        },
+                        Rvalue::Use(Operand::Move(Place {
+                            base: _,
+                            projection: box [.., ProjectionElem::ConstantIndex {
                                 offset, min_length: _, from_end: false
-                        }],
-                    })),
+                            }],
+                        })),
+                    )
                 ) = &statement.kind {
                     // FIXME remove once we can use slices patterns
                     if let StatementKind::Assign(
-                        _,
-                        box Rvalue::Use(Operand::Move(Place {
-                            base,
-                            projection: box [proj_base @ .., _],
-                        })),
+                        box(
+                            _,
+                            Rvalue::Use(Operand::Move(Place {
+                                base,
+                                projection: box [proj_base @ .., _],
+                            })),
+                        )
                     ) = &statement.kind {
                         return Some((*offset, PlaceRef {
                             base,
diff --git a/src/librustc_mir/util/aggregate.rs b/src/librustc_mir/util/aggregate.rs
index 98e70671ab71562bfc1a0007eba8fdf58eacc9b6..b3565d40b8e217e9bdab4f4f2a737adfb3654481 100644
--- a/src/librustc_mir/util/aggregate.rs
+++ b/src/librustc_mir/util/aggregate.rs
@@ -24,7 +24,7 @@ pub fn expand_aggregate<'tcx>(
             if adt_def.is_enum() {
                 set_discriminant = Some(Statement {
                     kind: StatementKind::SetDiscriminant {
-                        place: lhs.clone(),
+                        place: box(lhs.clone()),
                         variant_index,
                     },
                     source_info,
@@ -39,7 +39,7 @@ pub fn expand_aggregate<'tcx>(
             let variant_index = VariantIdx::new(0);
             set_discriminant = Some(Statement {
                 kind: StatementKind::SetDiscriminant {
-                    place: lhs.clone(),
+                    place: box(lhs.clone()),
                     variant_index,
                 },
                 source_info,
@@ -70,7 +70,7 @@ pub fn expand_aggregate<'tcx>(
         };
         Statement {
             source_info,
-            kind: StatementKind::Assign(lhs_field, box Rvalue::Use(op)),
+            kind: StatementKind::Assign(box(lhs_field, Rvalue::Use(op))),
         }
     }).chain(set_discriminant)
 }
diff --git a/src/librustc_mir/util/elaborate_drops.rs b/src/librustc_mir/util/elaborate_drops.rs
index c60af70712d1b60c2bdb1b835295b08d667f8f30..52ad97bbde1d7ce6a471d9ccc33d8dcaf22f06d1 100644
--- a/src/librustc_mir/util/elaborate_drops.rs
+++ b/src/librustc_mir/util/elaborate_drops.rs
@@ -978,7 +978,7 @@ fn constant_usize(&self, val: u16) -> Operand<'tcx> {
     fn assign(&self, lhs: &Place<'tcx>, rhs: Rvalue<'tcx>) -> Statement<'tcx> {
         Statement {
             source_info: self.source_info,
-            kind: StatementKind::Assign(lhs.clone(), box rhs)
+            kind: StatementKind::Assign(box(lhs.clone(), rhs))
         }
     }
 }
diff --git a/src/librustc_mir/util/patch.rs b/src/librustc_mir/util/patch.rs
index eb457dacf8467982a39222e1330580d982ac024f..2ea9924af7f28d427ccb150392262f8ce2032056 100644
--- a/src/librustc_mir/util/patch.rs
+++ b/src/librustc_mir/util/patch.rs
@@ -120,7 +120,7 @@ pub fn add_statement(&mut self, loc: Location, stmt: StatementKind<'tcx>) {
     }
 
     pub fn add_assign(&mut self, loc: Location, place: Place<'tcx>, rv: Rvalue<'tcx>) {
-        self.add_statement(loc, StatementKind::Assign(place, box rv));
+        self.add_statement(loc, StatementKind::Assign(box(place, rv)));
     }
 
     pub fn make_nop(&mut self, loc: Location) {