diff --git a/src/test/compile-fail/dynsized/no-manual-impl.rs b/src/test/compile-fail/dynsized/no-manual-impl.rs
new file mode 100644
index 0000000000000..b591bc49246c1
--- /dev/null
+++ b/src/test/compile-fail/dynsized/no-manual-impl.rs
@@ -0,0 +1,25 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test that DynSized cannot be implemented manually.
+
+#![feature(extern_types)]
+#![feature(dynsized)]
+
+use std::marker::DynSized;
+
+extern {
+    type foo;
+}
+
+impl DynSized for foo { }
+//~^ ERROR explicit impls for the `DynSized` trait are not permitted
+
+fn main() { }
diff --git a/src/test/compile-fail/dynsized/size_of_val.rs b/src/test/compile-fail/dynsized/size_of_val.rs
new file mode 100644
index 0000000000000..756372978360e
--- /dev/null
+++ b/src/test/compile-fail/dynsized/size_of_val.rs
@@ -0,0 +1,29 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Ensure `size_of_val` / `align_of_val` can't be used on !DynSized types
+
+#![feature(extern_types)]
+
+use std::mem::{size_of_val, align_of_val};
+
+extern {
+    type A;
+}
+
+fn main() {
+    let x: &A = unsafe {
+        &*(1usize as *const A)
+    };
+
+    size_of_val(x); //~ERROR the trait bound `A: std::marker::DynSized` is not satisfied
+
+    align_of_val(x); //~ERROR the trait bound `A: std::marker::DynSized` is not satisfied
+}
diff --git a/src/test/compile-fail/dynsized/struct-last-field.rs b/src/test/compile-fail/dynsized/struct-last-field.rs
new file mode 100644
index 0000000000000..de27126748855
--- /dev/null
+++ b/src/test/compile-fail/dynsized/struct-last-field.rs
@@ -0,0 +1,36 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Ensure !DynSized fields can't be used in structs, even as the last field.
+
+#![feature(extern_types)]
+#![feature(dynsized)]
+
+use std::marker::DynSized;
+
+extern {
+    type foo;
+}
+
+struct A {
+    x: foo, //~ERROR the trait bound `foo: std::marker::DynSized` is not satisfied
+}
+
+struct B {
+    x: usize,
+    y: foo, //~ERROR the trait bound `foo: std::marker::DynSized` is not satisfied
+}
+
+struct C<T: ?DynSized> {
+    x: usize,
+    y: T, //~ERROR the trait bound `T: std::marker::DynSized` is not satisfied
+}
+
+fn main() { }
diff --git a/src/test/compile-fail/dynsized/supertait-unbound.rs b/src/test/compile-fail/dynsized/supertait-unbound.rs
new file mode 100644
index 0000000000000..e4d6ae3cbf213
--- /dev/null
+++ b/src/test/compile-fail/dynsized/supertait-unbound.rs
@@ -0,0 +1,28 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test that traits can opt-out of being DynSized by default.
+// See also run-pass/dynsized/supertrait-default.rs
+
+#![feature(dynsized)]
+
+use std::marker::DynSized;
+
+fn assert_dynsized<T: ?Sized>() { }
+
+trait Tr: ?DynSized {
+    fn foo() {
+        assert_dynsized::<Self>();
+        //~^ ERROR the trait bound `Self: std::marker::DynSized` is not satisfied
+    }
+}
+
+fn main() { }
+
diff --git a/src/test/compile-fail/dynsized/tuple-last-field.rs b/src/test/compile-fail/dynsized/tuple-last-field.rs
new file mode 100644
index 0000000000000..df86a100f90b4
--- /dev/null
+++ b/src/test/compile-fail/dynsized/tuple-last-field.rs
@@ -0,0 +1,28 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Ensure !DynSized fields can't be used in tuples, even as the last field.
+
+#![feature(extern_types)]
+#![feature(dynsized)]
+
+use std::marker::DynSized;
+
+extern {
+    type foo;
+}
+
+fn baz<T: ?DynSized>() {
+    let x: &(u8, foo); //~ERROR the trait bound `foo: std::marker::DynSized` is not satisfied
+
+    let y: &(u8, T); //~ERROR the trait bound `T: std::marker::DynSized` is not satisfied
+}
+
+fn main() { }
diff --git a/src/test/run-pass/dynsized/sized-implies-dynsized.rs b/src/test/run-pass/dynsized/sized-implies-dynsized.rs
new file mode 100644
index 0000000000000..9aa61b4e6b595
--- /dev/null
+++ b/src/test/run-pass/dynsized/sized-implies-dynsized.rs
@@ -0,0 +1,26 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(dynsized)]
+
+use std::marker::DynSized;
+
+fn foo<T: ?DynSized>() {
+}
+
+fn bar<T: ?Sized>() {
+    foo::<T>();
+}
+
+fn baz<T>() {
+    bar::<T>();
+}
+
+fn main() { }
diff --git a/src/test/run-pass/dynsized/supertrait-default.rs b/src/test/run-pass/dynsized/supertrait-default.rs
new file mode 100644
index 0000000000000..dabc76112fe07
--- /dev/null
+++ b/src/test/run-pass/dynsized/supertrait-default.rs
@@ -0,0 +1,27 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test that traits have DynSized as a super trait by default.
+// See also compile-fail/dynsized/supertrait-unbound.rs
+
+#![feature(dynsized)]
+
+use std::marker::DynSized;
+
+fn assert_dynsized<T: ?Sized>() { }
+
+trait Tr {
+    fn foo() {
+        assert_dynsized::<Self>();
+    }
+}
+
+fn main() { }
+