Check explicitly that tuple initializer is Sized.

src/librustc/traits/error_reporting.rs

@@ -1097,6 +1097,9 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             ObligationCauseCode::AssignmentLhsSized => {
                 err.note("the left-hand-side of an assignment must have a statically known size");
             }
+            ObligationCauseCode::TupleInitializerSized => {
+                err.note("tuples must have a statically known size to be initialized");
+            }
             ObligationCauseCode::StructInitializerSized => {
                 err.note("structs must have a statically known size to be initialized");
             }

src/librustc/traits/mod.rs

@@ -121,6 +121,8 @@ pub enum ObligationCauseCode<'tcx> {
     // Various cases where expressions must be sized/copy/etc:
     /// L = X implies that L is Sized
     AssignmentLhsSized,
+    /// (x1, .., xn) must be Sized
+    TupleInitializerSized,
     /// S { ... } must be Sized
     StructInitializerSized,
     /// Type of each variable must be Sized

src/librustc/traits/structural_impls.rs

@@ -189,6 +189,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
                 tcx.lift(&ty).map(super::ObjectCastObligation)
             }
             super::AssignmentLhsSized => Some(super::AssignmentLhsSized),
+            super::TupleInitializerSized => Some(super::TupleInitializerSized),
             super::StructInitializerSized => Some(super::StructInitializerSized),
             super::VariableType(id) => Some(super::VariableType(id)),
             super::ReturnType(id) => Some(super::ReturnType(id)),
@@ -476,6 +477,7 @@ impl<'tcx> TypeFoldable<'tcx> for traits::ObligationCauseCode<'tcx> {
             super::TupleElem |
             super::ItemObligation(_) |
             super::AssignmentLhsSized |
+            super::TupleInitializerSized |
             super::StructInitializerSized |
             super::VariableType(_) |
             super::ReturnType(_) |
@@ -523,6 +525,7 @@ impl<'tcx> TypeFoldable<'tcx> for traits::ObligationCauseCode<'tcx> {
             super::TupleElem |
             super::ItemObligation(_) |
             super::AssignmentLhsSized |
+            super::TupleInitializerSized |
             super::StructInitializerSized |
             super::VariableType(_) |
             super::ReturnType(_) |

src/librustc_typeck/check/mod.rs

@@ -3854,6 +3854,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             if tuple.references_error() {
                 tcx.types.err
             } else {
+                self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
                 tuple
             }
           }

src/test/compile-fail/unsized3.rs

@@ -54,6 +54,7 @@ fn f9<X: ?Sized>(x1: Box<S<X>>) {
 fn f10<X: ?Sized>(x1: Box<S<X>>) {
     f5(&(32, *x1));
     //~^ ERROR `X: std::marker::Sized` is not satisfied
+    //~| ERROR `X: std::marker::Sized` is not satisfied
 }
 
 pub fn main() {