diff --git a/src/libcore/any.rs b/src/libcore/any.rs
index 94f23db1ccc..6b26093439e 100644
--- a/src/libcore/any.rs
+++ b/src/libcore/any.rs
@@ -120,7 +120,7 @@ impl<T: 'static + ?Sized > Any for T {
 ///////////////////////////////////////////////////////////////////////////////
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl fmt::Debug for Any {
+impl fmt::Debug for dyn Any {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("Any")
     }
@@ -130,20 +130,20 @@ impl fmt::Debug for Any {
 // hence used with `unwrap`. May eventually no longer be needed if
 // dispatch works with upcasting.
 #[stable(feature = "rust1", since = "1.0.0")]
-impl fmt::Debug for Any + Send {
+impl fmt::Debug for dyn Any + Send {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("Any")
     }
 }
 
 #[stable(feature = "any_send_sync_methods", since = "1.28.0")]
-impl fmt::Debug for Any + Send + Sync {
+impl fmt::Debug for dyn Any + Send + Sync {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("Any")
     }
 }
 
-impl Any {
+impl dyn Any {
     /// Returns `true` if the boxed type is the same as `T`.
     ///
     /// # Examples
@@ -203,7 +203,7 @@ impl Any {
     pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
         if self.is::<T>() {
             unsafe {
-                Some(&*(self as *const Any as *const T))
+                Some(&*(self as *const dyn Any as *const T))
             }
         } else {
             None
@@ -240,7 +240,7 @@ impl Any {
     pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
         if self.is::<T>() {
             unsafe {
-                Some(&mut *(self as *mut Any as *mut T))
+                Some(&mut *(self as *mut dyn Any as *mut T))
             }
         } else {
             None
@@ -248,7 +248,7 @@ impl Any {
     }
 }
 
-impl Any+Send {
+impl dyn Any+Send {
     /// Forwards to the method defined on the type `Any`.
     ///
     /// # Examples
@@ -332,7 +332,7 @@ impl Any+Send {
     }
 }
 
-impl Any+Send+Sync {
+impl dyn Any+Send+Sync {
     /// Forwards to the method defined on the type `Any`.
     ///
     /// # Examples
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index b6087628ea6..137e9fe2c15 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -1532,7 +1532,7 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> {}
 
 #[allow(unused)]
 fn assert_coerce_unsized(a: UnsafeCell<&i32>, b: Cell<&i32>, c: RefCell<&i32>) {
-    let _: UnsafeCell<&Send> = a;
-    let _: Cell<&Send> = b;
-    let _: RefCell<&Send> = c;
+    let _: UnsafeCell<&dyn Send> = a;
+    let _: Cell<&dyn Send> = b;
+    let _: RefCell<&dyn Send> = c;
 }
diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs
index e8ea2e743da..3c5f934d4d8 100644
--- a/src/libcore/fmt/builders.rs
+++ b/src/libcore/fmt/builders.rs
@@ -11,7 +11,7 @@
 use fmt;
 
 struct PadAdapter<'a> {
-    buf: &'a mut (fmt::Write + 'a),
+    buf: &'a mut (dyn fmt::Write + 'a),
     on_newline: bool,
 }
 
@@ -107,7 +107,7 @@ pub fn debug_struct_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>,
 impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
     /// Adds a new field to the generated struct output.
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn field(&mut self, name: &str, value: &fmt::Debug) -> &mut DebugStruct<'a, 'b> {
+    pub fn field(&mut self, name: &str, value: &dyn fmt::Debug) -> &mut DebugStruct<'a, 'b> {
         self.result = self.result.and_then(|_| {
             let prefix = if self.has_fields {
                 ","
@@ -204,7 +204,7 @@ pub fn debug_tuple_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>, name: &str) -> D
 impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
     /// Adds a new field to the generated tuple struct output.
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn field(&mut self, value: &fmt::Debug) -> &mut DebugTuple<'a, 'b> {
+    pub fn field(&mut self, value: &dyn fmt::Debug) -> &mut DebugTuple<'a, 'b> {
         self.result = self.result.and_then(|_| {
             let (prefix, space) = if self.fields > 0 {
                 (",", " ")
@@ -258,7 +258,7 @@ struct DebugInner<'a, 'b: 'a> {
 }
 
 impl<'a, 'b: 'a> DebugInner<'a, 'b> {
-    fn entry(&mut self, entry: &fmt::Debug) {
+    fn entry(&mut self, entry: &dyn fmt::Debug) {
         self.result = self.result.and_then(|_| {
             if self.is_pretty() {
                 let mut slot = None;
@@ -340,7 +340,7 @@ pub fn debug_set_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugSet<'a, 'b
 impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     /// Adds a new entry to the set output.
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entry(&mut self, entry: &fmt::Debug) -> &mut DebugSet<'a, 'b> {
+    pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut DebugSet<'a, 'b> {
         self.inner.entry(entry);
         self
     }
@@ -411,7 +411,7 @@ pub fn debug_list_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugList<'a,
 impl<'a, 'b: 'a> DebugList<'a, 'b> {
     /// Adds a new entry to the list output.
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entry(&mut self, entry: &fmt::Debug) -> &mut DebugList<'a, 'b> {
+    pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut DebugList<'a, 'b> {
         self.inner.entry(entry);
         self
     }
@@ -482,7 +482,7 @@ pub fn debug_map_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugMap<'a, 'b
 impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// Adds a new entry to the map output.
     #[stable(feature = "debug_builders", since = "1.2.0")]
-    pub fn entry(&mut self, key: &fmt::Debug, value: &fmt::Debug) -> &mut DebugMap<'a, 'b> {
+    pub fn entry(&mut self, key: &dyn fmt::Debug, value: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {
         self.result = self.result.and_then(|_| {
             if self.is_pretty() {
                 let mut slot = None;
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index d91bf463383..928f95e3ba2 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -255,7 +255,7 @@ pub struct Formatter<'a> {
     width: Option<usize>,
     precision: Option<usize>,
 
-    buf: &'a mut (Write+'a),
+    buf: &'a mut (dyn Write+'a),
     curarg: slice::Iter<'a, ArgumentV1<'a>>,
     args: &'a [ArgumentV1<'a>],
 }
@@ -272,7 +272,7 @@ struct Void {
     ///
     /// It was added after #45197 showed that one could share a `!Sync`
     /// object across threads by passing it into `format_args!`.
-    _oibit_remover: PhantomData<*mut Fn()>,
+    _oibit_remover: PhantomData<*mut dyn Fn()>,
 }
 
 /// This struct represents the generic "argument" which is taken by the Xprintf
@@ -1020,7 +1020,7 @@ pub trait UpperExp {
 ///
 /// [`write!`]: ../../std/macro.write.html
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn write(output: &mut Write, args: Arguments) -> Result {
+pub fn write(output: &mut dyn Write, args: Arguments) -> Result {
     let mut formatter = Formatter {
         flags: 0,
         width: None,
@@ -1062,7 +1062,7 @@ pub fn write(output: &mut Write, args: Arguments) -> Result {
 
 impl<'a> Formatter<'a> {
     fn wrap_buf<'b, 'c, F>(&'b mut self, wrap: F) -> Formatter<'c>
-        where 'b: 'c, F: FnOnce(&'b mut (Write+'b)) -> &'c mut (Write+'c)
+        where 'b: 'c, F: FnOnce(&'b mut (dyn Write+'b)) -> &'c mut (dyn Write+'c)
     {
         Formatter {
             // We want to change this
@@ -1342,7 +1342,7 @@ impl<'a> Formatter<'a> {
     }
 
     fn write_formatted_parts(&mut self, formatted: &flt2dec::Formatted) -> Result {
-        fn write_bytes(buf: &mut Write, s: &[u8]) -> Result {
+        fn write_bytes(buf: &mut dyn Write, s: &[u8]) -> Result {
             buf.write_str(unsafe { str::from_utf8_unchecked(s) })
         }
 
diff --git a/src/libcore/iter/iterator.rs b/src/libcore/iter/iterator.rs
index afc273d265b..48c6eb94144 100644
--- a/src/libcore/iter/iterator.rs
+++ b/src/libcore/iter/iterator.rs
@@ -18,7 +18,7 @@ use super::{Inspect, Map, Peekable, Scan, Skip, SkipWhile, StepBy, Take, TakeWhi
 use super::{Zip, Sum, Product};
 use super::{ChainState, FromIterator, ZipImpl};
 
-fn _assert_is_object_safe(_: &Iterator<Item=()>) {}
+fn _assert_is_object_safe(_: &dyn Iterator<Item=()>) {}
 
 /// An interface for dealing with iterators.
 ///
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 72074e1dbce..ae0469bfa04 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -70,6 +70,7 @@
        test(attr(allow(dead_code, deprecated, unused_variables, unused_mut))))]
 
 #![no_core]
+#![deny(bare_trait_objects)]
 #![deny(missing_docs)]
 #![deny(missing_debug_implementations)]
 
diff --git a/src/libcore/panic.rs b/src/libcore/panic.rs
index 10f02ca2fdc..17cac5aa0a0 100644
--- a/src/libcore/panic.rs
+++ b/src/libcore/panic.rs
@@ -43,7 +43,7 @@ use fmt;
 #[stable(feature = "panic_hooks", since = "1.10.0")]
 #[derive(Debug)]
 pub struct PanicInfo<'a> {
-    payload: &'a (Any + Send),
+    payload: &'a (dyn Any + Send),
     message: Option<&'a fmt::Arguments<'a>>,
     location: Location<'a>,
 }
@@ -64,7 +64,7 @@ impl<'a> PanicInfo<'a> {
 
     #[doc(hidden)]
     #[inline]
-    pub fn set_payload(&mut self, info: &'a (Any + Send)) {
+    pub fn set_payload(&mut self, info: &'a (dyn Any + Send)) {
         self.payload = info;
     }
 
@@ -86,7 +86,7 @@ impl<'a> PanicInfo<'a> {
     /// panic!("Normal panic");
     /// ```
     #[stable(feature = "panic_hooks", since = "1.10.0")]
-    pub fn payload(&self) -> &(Any + Send) {
+    pub fn payload(&self) -> &(dyn Any + Send) {
         self.payload
     }
 
@@ -270,6 +270,6 @@ impl<'a> fmt::Display for Location<'a> {
 #[unstable(feature = "std_internals", issue = "0")]
 #[doc(hidden)]
 pub unsafe trait BoxMeUp {
-    fn box_me_up(&mut self) -> *mut (Any + Send);
-    fn get(&mut self) -> &(Any + Send);
+    fn box_me_up(&mut self) -> *mut (dyn Any + Send);
+    fn get(&mut self) -> &(dyn Any + Send);
 }
diff --git a/src/libcore/task/context.rs b/src/libcore/task/context.rs
index c69d45248a5..1fc975cb178 100644
--- a/src/libcore/task/context.rs
+++ b/src/libcore/task/context.rs
@@ -21,7 +21,7 @@ use super::{Executor, Waker, LocalWaker};
 /// when performing a single `poll` step on a task.
 pub struct Context<'a> {
     local_waker: &'a LocalWaker,
-    executor: &'a mut Executor,
+    executor: &'a mut dyn Executor,
 }
 
 impl<'a> fmt::Debug for Context<'a> {
@@ -34,7 +34,7 @@ impl<'a> fmt::Debug for Context<'a> {
 impl<'a> Context<'a> {
     /// Create a new task `Context` with the provided `local_waker`, `waker`, and `executor`.
     #[inline]
-    pub fn new(local_waker: &'a LocalWaker, executor: &'a mut Executor) -> Context<'a> {
+    pub fn new(local_waker: &'a LocalWaker, executor: &'a mut dyn Executor) -> Context<'a> {
         Context {
             local_waker,
             executor,
@@ -58,7 +58,7 @@ impl<'a> Context<'a> {
     /// This method is useful primarily if you want to explicitly handle
     /// spawn failures.
     #[inline]
-    pub fn executor(&mut self) -> &mut Executor {
+    pub fn executor(&mut self) -> &mut dyn Executor {
         self.executor
     }
 
diff --git a/src/libcore/task/wake.rs b/src/libcore/task/wake.rs
index 3b901c9aef0..321b432d3f4 100644
--- a/src/libcore/task/wake.rs
+++ b/src/libcore/task/wake.rs
@@ -23,7 +23,7 @@ use ptr::NonNull;
 /// trait, allowing notifications to get routed through it.
 #[repr(transparent)]
 pub struct Waker {
-    inner: NonNull<UnsafeWake>,
+    inner: NonNull<dyn UnsafeWake>,
 }
 
 impl Unpin for Waker {}
@@ -41,7 +41,7 @@ impl Waker {
     /// use the `Waker::from` function instead which works with the safe
     /// `Arc` type and the safe `Wake` trait.
     #[inline]
-    pub unsafe fn new(inner: NonNull<UnsafeWake>) -> Self {
+    pub unsafe fn new(inner: NonNull<dyn UnsafeWake>) -> Self {
         Waker { inner: inner }
     }
 
@@ -98,7 +98,7 @@ impl Drop for Waker {
 /// behavior.
 #[repr(transparent)]
 pub struct LocalWaker {
-    inner: NonNull<UnsafeWake>,
+    inner: NonNull<dyn UnsafeWake>,
 }
 
 impl Unpin for LocalWaker {}
@@ -119,7 +119,7 @@ impl LocalWaker {
     /// For this function to be used safely, it must be sound to call `inner.wake_local()`
     /// on the current thread.
     #[inline]
-    pub unsafe fn new(inner: NonNull<UnsafeWake>) -> Self {
+    pub unsafe fn new(inner: NonNull<dyn UnsafeWake>) -> Self {
         LocalWaker { inner: inner }
     }