diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 7e0e4abef9d35..1c5f09482458a 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -2590,30 +2590,7 @@ pub fn type_is_machine(ty: t) -> bool {
 // Is the type's representation size known at compile time?
 #[allow(dead_code)] // leaving in for DST
 pub fn type_is_sized(cx: &ctxt, ty: ty::t) -> bool {
-    match get(ty).sty {
-        ty_param(tp) => {
-            assert_eq!(tp.def_id.krate, ast::LOCAL_CRATE);
-
-            let ty_param_defs = cx.ty_param_defs.borrow();
-            let param_def = ty_param_defs.get(&tp.def_id.node);
-            param_def.bounds.builtin_bounds.contains_elem(BoundSized)
-        },
-        ty_self(def_id) => {
-            let trait_def = lookup_trait_def(cx, def_id);
-            trait_def.bounds.contains_elem(BoundSized)
-        },
-        ty_struct(def_id, ref substs) => {
-            let flds = lookup_struct_fields(cx, def_id);
-            let mut tps = flds.iter().map(|f| lookup_field_type(cx, def_id, f.id, substs));
-            !tps.any(|ty| !type_is_sized(cx, ty))
-        }
-        ty_tup(ref ts) => !ts.iter().any(|t| !type_is_sized(cx, *t)),
-        ty_enum(did, ref substs) => {
-            let variants = substd_enum_variants(cx, did, substs);
-            !variants.iter().any(|v| v.args.iter().any(|t| !type_is_sized(cx, *t)))
-        }
-        _ => true
-    }
+    type_contents(cx, ty).is_sized(cx)
 }
 
 // Whether a type is enum like, that is an enum type with only nullary
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index b4f22f3fa6ed6..5e05be1ac9152 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -576,15 +576,20 @@ fn check_for_field_shadowing(tcx: &ty::ctxt,
 }
 
 fn check_fields_sized(tcx: &ty::ctxt,
-                      struct_def: @ast::StructDef) {
+                      struct_def: &ast::StructDef) {
     let len = struct_def.fields.len();
-    for i in range(0, len) {
-        let f = struct_def.fields.get(i);
+    if len == 0 {
+        return;
+    }
+    for f in struct_def.fields.slice_to(len - 1).iter() {
         let t = ty::node_id_to_type(tcx, f.node.id);
-        if !ty::type_is_sized(tcx, t) && i < (len - 1) {
+        if !ty::type_is_sized(tcx, t) {
             match f.node.kind {
                 ast::NamedField(ident, _) => {
-                    tcx.sess.span_err(f.span, format!("type of field {} is dynamically sized",
+                    tcx.sess.span_err(f.span, format!("type `{}` is dynamically sized. \
+                                                       dynamically sized types may only \
+                                                       appear as the type of the final \
+                                                       field in a struct",
                                                       token::get_ident(ident)));
                 }
                 ast::UnnamedField(_) => {
@@ -3519,16 +3524,18 @@ pub fn check_representable(tcx: &ty::ctxt,
 /// is representable, but not instantiable.
 pub fn check_instantiable(tcx: &ty::ctxt,
                           sp: Span,
-                          item_id: ast::NodeId) -> bool {
+                          item_id: ast::NodeId)
+                          -> bool {
     let item_ty = ty::node_id_to_type(tcx, item_id);
     if !ty::is_instantiable(tcx, item_ty) {
         tcx.sess.span_err(sp, format!("this type cannot be instantiated \
                   without an instance of itself; \
                   consider using `Option<{}>`",
                                    ppaux::ty_to_str(tcx, item_ty)));
-        return false
+        false
+    } else {
+        true
     }
-    true
 }
 
 pub fn check_simd(tcx: &ty::ctxt, sp: Span, id: ast::NodeId) {
@@ -3567,12 +3574,20 @@ pub fn check_enum_variants_sized(ccx: &CrateCtxt,
             ast::TupleVariantKind(ref args) if args.len() > 0 => {
                 let ctor_ty = ty::node_id_to_type(ccx.tcx, v.node.id);
                 let arg_tys: Vec<ty::t> = ty::ty_fn_args(ctor_ty).iter().map(|a| *a).collect();
-                for i in range(0, args.len()) {
-                    let t = arg_tys.get(i);
+                let len = arg_tys.len();
+                if len == 0 {
+                    return;
+                }
+                for (i, t) in arg_tys.slice_to(len - 1).iter().enumerate() {
                     // Allow the last field in an enum to be unsized.
-                    if !ty::type_is_sized(ccx.tcx, *t) && i < args.len() -1 {
+                    // We want to do this so that we can support smart pointers.
+                    // A struct value with an unsized final field is itself
+                    // unsized and we must track this in the type system.
+                    if !ty::type_is_sized(ccx.tcx, *t) {
                         ccx.tcx.sess.span_err(args.get(i).ty.span,
-                                              format!("type {} is dynamically sized",
+                                              format!("type `{}` is dynamically sized. \
+                                                       dynamically sized types may only \
+                                                       appear as the final type in a variant",
                                                       ppaux::ty_to_str(ccx.tcx, *t)));
                     }
                 }
diff --git a/src/librustc/middle/typeck/collect.rs b/src/librustc/middle/typeck/collect.rs
index 0e1419dafa09c..9c49512d4dc0d 100644
--- a/src/librustc/middle/typeck/collect.rs
+++ b/src/librustc/middle/typeck/collect.rs
@@ -1141,14 +1141,12 @@ fn ty_generics(ccx: &CrateCtxt,
                                                  param_bounds.trait_bounds.as_slice(),
                                                  |trait_ref| {
                 let trait_def = ty::lookup_trait_def(tcx, trait_ref.def_id);
-                for bound in trait_def.bounds.iter() {
-                    if bound == ty::BoundSized {
-                        tcx.sess.span_err(span,
-                            format!("incompatible bounds on type parameter {}, \
-                                     bound {} does not allow unsized type",
-                            token::get_ident(ident),
-                            ppaux::trait_ref_to_str(tcx, trait_ref)));
-                    }
+                if trait_def.bounds.contains_elem(ty::BoundSized) {
+                    tcx.sess.span_err(span,
+                        format!("incompatible bounds on type parameter {}, \
+                                 bound {} does not allow unsized type",
+                        token::get_ident(ident),
+                        ppaux::trait_ref_to_str(tcx, &*trait_ref)));
                 }
                 true
             });
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 57438169d6da3..f768bf22ce0ce 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -678,7 +678,8 @@ impl<'a> State<'a> {
                 try!(self.print_ident(item.ident));
                 try!(self.print_generics(generics));
                 if *sized == ast::DynSize {
-                    try!(self.word_space("for type"));
+                    try!(space(&mut self.s));
+                    try!(word(&mut self.s, "for type"));
                 }
                 if traits.len() != 0u {
                     try!(word(&mut self.s, ":"));
diff --git a/src/test/compile-fail/unsized5.rs b/src/test/compile-fail/unsized5.rs
index c3b50dcdcafea..9608b7e6b2023 100644
--- a/src/test/compile-fail/unsized5.rs
+++ b/src/test/compile-fail/unsized5.rs
@@ -23,18 +23,18 @@ fn f6<type X: T>(x: &X) {
 }*/
 
 struct S1<type X> {
-    f1: X, //~ ERROR type of field f1 is dynamically sized
+    f1: X, //~ ERROR type `f1` is dynamically sized. dynamically sized types may only appear as the
     f2: int,
 }
 struct S2<type X> {
     f: int,
-    g: X, //~ ERROR type of field g is dynamically sized
+    g: X, //~ ERROR type `g` is dynamically sized. dynamically sized types may only appear as the ty
     h: int,
 }
 
 enum E<type X> {
-    V1(X, int), //~ERROR type X is dynamically sized
-    V2{f1: X, f: int}, //~ERROR type of field f1 is dynamically sized
+    V1(X, int), //~ERROR type `X` is dynamically sized. dynamically sized types may only appear as t
+    V2{f1: X, f: int}, //~ERROR type `f1` is dynamically sized. dynamically sized types may only app
 }
 
 pub fn main() {
diff --git a/src/test/run-pass/unsized2.rs b/src/test/run-pass/unsized2.rs
index 7cc2dfd816f35..7883adad46a37 100644
--- a/src/test/run-pass/unsized2.rs
+++ b/src/test/run-pass/unsized2.rs
@@ -66,7 +66,8 @@ trait T4<X> {
     fn m2(x: &T5<X>);
 }
 trait T5<type X> {
-    fn m1(x: &T4<X>); // not an error (for now)
+    // not an error (for now)
+    fn m1(x: &T4<X>);
     fn m2(x: &T5<X>);
 }
 
@@ -75,7 +76,8 @@ trait T6<X: T> {
     fn m2(x: &T5<X>);
 }
 trait T7<type X: T> {
-    fn m1(x: &T4<X>); // not an error (for now)
+    // not an error (for now)
+    fn m1(x: &T4<X>);
     fn m2(x: &T5<X>);
 }