diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index da37278..ce92ce0 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -37,7 +37,7 @@
             let mut new = None;
             if let Some(current_as_str) = args[i].to_str() {
                 if (&*args[i - 1] == "-C" && current_as_str.starts_with("metadata")) ||
-                   current_as_str.starts_with("-Cmetadata") {
+                    current_as_str.starts_with("-Cmetadata") {
                     new = Some(format!("{}-{}", current_as_str, s));
                 }
             }
@@ -89,7 +89,7 @@
     if let Some(crate_name) = crate_name {
         if let Some(target) = env::var_os("RUSTC_TIME") {
             if target == "all" ||
-               target.into_string().unwrap().split(",").any(|c| c.trim() == crate_name)
+                target.into_string().unwrap().split(",").any(|c| c.trim() == crate_name)
             {
                 cmd.arg("-Ztime");
             }
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index c92db51..c61e318 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -91,8 +91,10 @@
     CoerceUnsized, DispatchFromDyn, Deref, DerefMut, Receiver, Generator, GeneratorState
 };
 use core::ptr::{self, NonNull, Unique};
+use core::slice;
 use core::task::{Context, Poll};
 
+use crate::alloc::{self, Global, Alloc};
 use crate::vec::Vec;
 use crate::raw_vec::RawVec;
 use crate::str::from_boxed_utf8_unchecked;
@@ -121,6 +123,34 @@
         box x
     }
 
+    /// Constructs a new box with uninitialized contents.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    ///
+    /// let mut five = Box::<u32>::new_uninit();
+    ///
+    /// let five = unsafe {
+    ///     // Deferred initialization:
+    ///     five.as_mut_ptr().write(5);
+    ///
+    ///     five.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*five, 5)
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
+        let layout = alloc::Layout::new::<mem::MaybeUninit<T>>();
+        let ptr = unsafe {
+            Global.alloc(layout)
+                .unwrap_or_else(|_| alloc::handle_alloc_error(layout))
+        };
+        Box(ptr.cast().into())
+    }
+
     /// Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then
     /// `x` will be pinned in memory and unable to be moved.
     #[stable(feature = "pin", since = "1.33.0")]
@@ -130,6 +160,111 @@
     }
 }
 
+impl<T> Box<[T]> {
+    /// Constructs a new boxed slice with uninitialized contents.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    ///
+    /// let mut values = Box::<[u32]>::new_uninit_slice(3);
+    ///
+    /// let values = unsafe {
+    ///     // Deferred initialization:
+    ///     values[0].as_mut_ptr().write(1);
+    ///     values[1].as_mut_ptr().write(2);
+    ///     values[2].as_mut_ptr().write(3);
+    ///
+    ///     values.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*values, [1, 2, 3])
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
+        let layout = alloc::Layout::array::<mem::MaybeUninit<T>>(len).unwrap();
+        let ptr = unsafe { alloc::alloc(layout) };
+        let unique = Unique::new(ptr).unwrap_or_else(|| alloc::handle_alloc_error(layout));
+        let slice = unsafe { slice::from_raw_parts_mut(unique.cast().as_ptr(), len) };
+        Box(Unique::from(slice))
+    }
+}
+
+impl<T> Box<mem::MaybeUninit<T>> {
+    /// Converts to `Box<T>`.
+    ///
+    /// # Safety
+    ///
+    /// As with [`MaybeUninit::assume_init`],
+    /// it is up to the caller to guarantee that the value
+    /// really is in an initialized state.
+    /// Calling this when the content is not yet fully initialized
+    /// causes immediate undefined behavior.
+    ///
+    /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    ///
+    /// let mut five = Box::<u32>::new_uninit();
+    ///
+    /// let five: Box<u32> = unsafe {
+    ///     // Deferred initialization:
+    ///     five.as_mut_ptr().write(5);
+    ///
+    ///     five.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*five, 5)
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    #[inline]
+    pub unsafe fn assume_init(self) -> Box<T> {
+        Box(Box::into_unique(self).cast())
+    }
+}
+
+impl<T> Box<[mem::MaybeUninit<T>]> {
+    /// Converts to `Box<[T]>`.
+    ///
+    /// # Safety
+    ///
+    /// As with [`MaybeUninit::assume_init`],
+    /// it is up to the caller to guarantee that the values
+    /// really are in an initialized state.
+    /// Calling this when the content is not yet fully initialized
+    /// causes immediate undefined behavior.
+    ///
+    /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    ///
+    /// let mut values = Box::<[u32]>::new_uninit_slice(3);
+    ///
+    /// let values = unsafe {
+    ///     // Deferred initialization:
+    ///     values[0].as_mut_ptr().write(1);
+    ///     values[1].as_mut_ptr().write(2);
+    ///     values[2].as_mut_ptr().write(3);
+    ///
+    ///     values.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*values, [1, 2, 3])
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    #[inline]
+    pub unsafe fn assume_init(self) -> Box<[T]> {
+        Box(Unique::new_unchecked(Box::into_raw(self) as _))
+    }
+}
+
 impl<T: ?Sized> Box<T> {
     /// Constructs a box from a raw pointer.
     ///
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 0c406a9..2b222ca 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -327,6 +327,37 @@
         }))
     }
 
+    /// Constructs a new `Rc` with uninitialized contents.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::rc::Rc;
+    ///
+    /// let mut five = Rc::<u32>::new_uninit();
+    ///
+    /// let five = unsafe {
+    ///     // Deferred initialization:
+    ///     Rc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+    ///
+    ///     five.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*five, 5)
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    pub fn new_uninit() -> Rc<mem::MaybeUninit<T>> {
+        unsafe {
+            Rc::from_ptr(Rc::allocate_for_layout(
+                Layout::new::<T>(),
+                |mem| mem as *mut RcBox<mem::MaybeUninit<T>>,
+            ))
+        }
+    }
+
     /// Constructs a new `Pin<Rc<T>>`. If `T` does not implement `Unpin`, then
     /// `value` will be pinned in memory and unable to be moved.
     #[stable(feature = "pin", since = "1.33.0")]
@@ -377,6 +408,118 @@
     }
 }
 
+impl<T> Rc<[T]> {
+    /// Constructs a new reference-counted slice with uninitialized contents.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::rc::Rc;
+    ///
+    /// let mut values = Rc::<[u32]>::new_uninit_slice(3);
+    ///
+    /// let values = unsafe {
+    ///     // Deferred initialization:
+    ///     Rc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+    ///     Rc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+    ///     Rc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+    ///
+    ///     values.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*values, [1, 2, 3])
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    pub fn new_uninit_slice(len: usize) -> Rc<[mem::MaybeUninit<T>]> {
+        unsafe {
+            Rc::from_ptr(Rc::allocate_for_slice(len))
+        }
+    }
+}
+
+impl<T> Rc<mem::MaybeUninit<T>> {
+    /// Converts to `Rc<T>`.
+    ///
+    /// # Safety
+    ///
+    /// As with [`MaybeUninit::assume_init`],
+    /// it is up to the caller to guarantee that the value
+    /// really is in an initialized state.
+    /// Calling this when the content is not yet fully initialized
+    /// causes immediate undefined behavior.
+    ///
+    /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::rc::Rc;
+    ///
+    /// let mut five = Rc::<u32>::new_uninit();
+    ///
+    /// let five = unsafe {
+    ///     // Deferred initialization:
+    ///     Rc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+    ///
+    ///     five.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*five, 5)
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    #[inline]
+    pub unsafe fn assume_init(self) -> Rc<T> {
+        Rc::from_inner(mem::ManuallyDrop::new(self).ptr.cast())
+    }
+}
+
+impl<T> Rc<[mem::MaybeUninit<T>]> {
+    /// Converts to `Rc<[T]>`.
+    ///
+    /// # Safety
+    ///
+    /// As with [`MaybeUninit::assume_init`],
+    /// it is up to the caller to guarantee that the value
+    /// really is in an initialized state.
+    /// Calling this when the content is not yet fully initialized
+    /// causes immediate undefined behavior.
+    ///
+    /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::rc::Rc;
+    ///
+    /// let mut values = Rc::<[u32]>::new_uninit_slice(3);
+    ///
+    /// let values = unsafe {
+    ///     // Deferred initialization:
+    ///     Rc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+    ///     Rc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+    ///     Rc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+    ///
+    ///     values.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*values, [1, 2, 3])
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    #[inline]
+    pub unsafe fn assume_init(self) -> Rc<[T]> {
+        Rc::from_ptr(mem::ManuallyDrop::new(self).ptr.as_ptr() as _)
+    }
+}
+
 impl<T: ?Sized> Rc<T> {
     /// Consumes the `Rc`, returning the wrapped pointer.
     ///
@@ -560,13 +703,46 @@
     pub fn get_mut(this: &mut Self) -> Option<&mut T> {
         if Rc::is_unique(this) {
             unsafe {
-                Some(&mut this.ptr.as_mut().value)
+                Some(Rc::get_mut_unchecked(this))
             }
         } else {
             None
         }
     }
 
+    /// Returns a mutable reference to the inner value,
+    /// without any check.
+    ///
+    /// See also [`get_mut`], which is safe and does appropriate checks.
+    ///
+    /// [`get_mut`]: struct.Rc.html#method.get_mut
+    ///
+    /// # Safety
+    ///
+    /// Any other `Rc` or [`Weak`] pointers to the same value must not be dereferenced
+    /// for the duration of the returned borrow.
+    /// This is trivially the case if no such pointers exist,
+    /// for example immediately after `Rc::new`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::rc::Rc;
+    ///
+    /// let mut x = Rc::new(String::new());
+    /// unsafe {
+    ///     Rc::get_mut_unchecked(&mut x).push_str("foo")
+    /// }
+    /// assert_eq!(*x, "foo");
+    /// ```
+    #[inline]
+    #[unstable(feature = "get_mut_unchecked", issue = "63292")]
+    pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {
+        &mut this.ptr.as_mut().value
+    }
+
     #[inline]
     #[stable(feature = "ptr_eq", since = "1.17.0")]
     /// Returns `true` if the two `Rc`s point to the same value (not
@@ -704,11 +880,11 @@
 
 impl<T: ?Sized> Rc<T> {
     /// Allocates an `RcBox<T>` with sufficient space for
-    /// an unsized value where the value has the layout provided.
+    /// a possibly-unsized value where the value has the layout provided.
     ///
     /// The function `mem_to_rcbox` is called with the data pointer
     /// and must return back a (potentially fat)-pointer for the `RcBox<T>`.
-    unsafe fn allocate_for_unsized(
+    unsafe fn allocate_for_layout(
         value_layout: Layout,
         mem_to_rcbox: impl FnOnce(*mut u8) -> *mut RcBox<T>
     ) -> *mut RcBox<T> {
@@ -737,7 +913,7 @@
     /// Allocates an `RcBox<T>` with sufficient space for an unsized value
     unsafe fn allocate_for_ptr(ptr: *const T) -> *mut RcBox<T> {
         // Allocate for the `RcBox<T>` using the given value.
-        Self::allocate_for_unsized(
+        Self::allocate_for_layout(
             Layout::for_value(&*ptr),
             |mem| set_data_ptr(ptr as *mut T, mem) as *mut RcBox<T>,
         )
@@ -768,7 +944,7 @@
 impl<T> Rc<[T]> {
     /// Allocates an `RcBox<[T]>` with the given length.
     unsafe fn allocate_for_slice(len: usize) -> *mut RcBox<[T]> {
-        Self::allocate_for_unsized(
+        Self::allocate_for_layout(
             Layout::array::<T>(len).unwrap(),
             |mem| ptr::slice_from_raw_parts_mut(mem as *mut T, len) as *mut RcBox<[T]>,
         )
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index 7d3b265..3411721 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -311,6 +311,37 @@
         Self::from_inner(Box::into_raw_non_null(x))
     }
 
+    /// Constructs a new `Arc` with uninitialized contents.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::sync::Arc;
+    ///
+    /// let mut five = Arc::<u32>::new_uninit();
+    ///
+    /// let five = unsafe {
+    ///     // Deferred initialization:
+    ///     Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+    ///
+    ///     five.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*five, 5)
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    pub fn new_uninit() -> Arc<mem::MaybeUninit<T>> {
+        unsafe {
+            Arc::from_ptr(Arc::allocate_for_layout(
+                Layout::new::<T>(),
+                |mem| mem as *mut ArcInner<mem::MaybeUninit<T>>,
+            ))
+        }
+    }
+
     /// Constructs a new `Pin<Arc<T>>`. If `T` does not implement `Unpin`, then
     /// `data` will be pinned in memory and unable to be moved.
     #[stable(feature = "pin", since = "1.33.0")]
@@ -361,6 +392,118 @@
     }
 }
 
+impl<T> Arc<[T]> {
+    /// Constructs a new reference-counted slice with uninitialized contents.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::sync::Arc;
+    ///
+    /// let mut values = Arc::<[u32]>::new_uninit_slice(3);
+    ///
+    /// let values = unsafe {
+    ///     // Deferred initialization:
+    ///     Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+    ///     Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+    ///     Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+    ///
+    ///     values.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*values, [1, 2, 3])
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    pub fn new_uninit_slice(len: usize) -> Arc<[mem::MaybeUninit<T>]> {
+        unsafe {
+            Arc::from_ptr(Arc::allocate_for_slice(len))
+        }
+    }
+}
+
+impl<T> Arc<mem::MaybeUninit<T>> {
+    /// Converts to `Arc<T>`.
+    ///
+    /// # Safety
+    ///
+    /// As with [`MaybeUninit::assume_init`],
+    /// it is up to the caller to guarantee that the value
+    /// really is in an initialized state.
+    /// Calling this when the content is not yet fully initialized
+    /// causes immediate undefined behavior.
+    ///
+    /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::sync::Arc;
+    ///
+    /// let mut five = Arc::<u32>::new_uninit();
+    ///
+    /// let five = unsafe {
+    ///     // Deferred initialization:
+    ///     Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+    ///
+    ///     five.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*five, 5)
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    #[inline]
+    pub unsafe fn assume_init(self) -> Arc<T> {
+        Arc::from_inner(mem::ManuallyDrop::new(self).ptr.cast())
+    }
+}
+
+impl<T> Arc<[mem::MaybeUninit<T>]> {
+    /// Converts to `Arc<[T]>`.
+    ///
+    /// # Safety
+    ///
+    /// As with [`MaybeUninit::assume_init`],
+    /// it is up to the caller to guarantee that the value
+    /// really is in an initialized state.
+    /// Calling this when the content is not yet fully initialized
+    /// causes immediate undefined behavior.
+    ///
+    /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(new_uninit)]
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::sync::Arc;
+    ///
+    /// let mut values = Arc::<[u32]>::new_uninit_slice(3);
+    ///
+    /// let values = unsafe {
+    ///     // Deferred initialization:
+    ///     Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+    ///     Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+    ///     Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+    ///
+    ///     values.assume_init()
+    /// };
+    ///
+    /// assert_eq!(*values, [1, 2, 3])
+    /// ```
+    #[unstable(feature = "new_uninit", issue = "63291")]
+    #[inline]
+    pub unsafe fn assume_init(self) -> Arc<[T]> {
+        Arc::from_ptr(mem::ManuallyDrop::new(self).ptr.as_ptr() as _)
+    }
+}
+
 impl<T: ?Sized> Arc<T> {
     /// Consumes the `Arc`, returning the wrapped pointer.
     ///
@@ -593,11 +736,11 @@
 
 impl<T: ?Sized> Arc<T> {
     /// Allocates an `ArcInner<T>` with sufficient space for
-    /// an unsized value where the value has the layout provided.
+    /// a possibly-unsized value where the value has the layout provided.
     ///
     /// The function `mem_to_arcinner` is called with the data pointer
     /// and must return back a (potentially fat)-pointer for the `ArcInner<T>`.
-    unsafe fn allocate_for_unsized(
+    unsafe fn allocate_for_layout(
         value_layout: Layout,
         mem_to_arcinner: impl FnOnce(*mut u8) -> *mut ArcInner<T>
     ) -> *mut ArcInner<T> {
@@ -625,7 +768,7 @@
     /// Allocates an `ArcInner<T>` with sufficient space for an unsized value.
     unsafe fn allocate_for_ptr(ptr: *const T) -> *mut ArcInner<T> {
         // Allocate for the `ArcInner<T>` using the given value.
-        Self::allocate_for_unsized(
+        Self::allocate_for_layout(
             Layout::for_value(&*ptr),
             |mem| set_data_ptr(ptr as *mut T, mem) as *mut ArcInner<T>,
         )
@@ -656,7 +799,7 @@
 impl<T> Arc<[T]> {
     /// Allocates an `ArcInner<[T]>` with the given length.
     unsafe fn allocate_for_slice(len: usize) -> *mut ArcInner<[T]> {
-        Self::allocate_for_unsized(
+        Self::allocate_for_layout(
             Layout::array::<T>(len).unwrap(),
             |mem| ptr::slice_from_raw_parts_mut(mem as *mut T, len) as *mut ArcInner<[T]>,
         )
@@ -945,13 +1088,46 @@
             // the Arc itself to be `mut`, so we're returning the only possible
             // reference to the inner data.
             unsafe {
-                Some(&mut this.ptr.as_mut().data)
+                Some(Arc::get_mut_unchecked(this))
             }
         } else {
             None
         }
     }
 
+    /// Returns a mutable reference to the inner value,
+    /// without any check.
+    ///
+    /// See also [`get_mut`], which is safe and does appropriate checks.
+    ///
+    /// [`get_mut`]: struct.Arc.html#method.get_mut
+    ///
+    /// # Safety
+    ///
+    /// Any other `Arc` or [`Weak`] pointers to the same value must not be dereferenced
+    /// for the duration of the returned borrow.
+    /// This is trivially the case if no such pointers exist,
+    /// for example immediately after `Arc::new`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(get_mut_unchecked)]
+    ///
+    /// use std::sync::Arc;
+    ///
+    /// let mut x = Arc::new(String::new());
+    /// unsafe {
+    ///     Arc::get_mut_unchecked(&mut x).push_str("foo")
+    /// }
+    /// assert_eq!(*x, "foo");
+    /// ```
+    #[inline]
+    #[unstable(feature = "get_mut_unchecked", issue = "63292")]
+    pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {
+        &mut this.ptr.as_mut().data
+    }
+
     /// Determine whether this is the unique reference (including weak refs) to
     /// the underlying data.
     ///
diff --git a/src/libcore/clone.rs b/src/libcore/clone.rs
index ec22a7c..ec70d39 100644
--- a/src/libcore/clone.rs
+++ b/src/libcore/clone.rs
@@ -135,7 +135,7 @@
 
 /// Derive macro generating an impl of the trait `Clone`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics, derive_clone_copy)]
 pub macro Clone($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/cmp.rs b/src/libcore/cmp.rs
index b802216..cb9feb0 100644
--- a/src/libcore/cmp.rs
+++ b/src/libcore/cmp.rs
@@ -202,7 +202,7 @@
 
 /// Derive macro generating an impl of the trait `PartialEq`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics)]
 pub macro PartialEq($item:item) { /* compiler built-in */ }
@@ -265,7 +265,7 @@
 
 /// Derive macro generating an impl of the trait `Eq`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics, derive_eq)]
 pub macro Eq($item:item) { /* compiler built-in */ }
@@ -616,7 +616,7 @@
 
 /// Derive macro generating an impl of the trait `Ord`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics)]
 pub macro Ord($item:item) { /* compiler built-in */ }
@@ -865,7 +865,7 @@
 
 /// Derive macro generating an impl of the trait `PartialOrd`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics)]
 pub macro PartialOrd($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/default.rs b/src/libcore/default.rs
index 9b1616c..66acc51 100644
--- a/src/libcore/default.rs
+++ b/src/libcore/default.rs
@@ -117,7 +117,7 @@
 
 /// Derive macro generating an impl of the trait `Default`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics)]
 pub macro Default($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs
index cb4e326..15ce227 100644
--- a/src/libcore/fmt/builders.rs
+++ b/src/libcore/fmt/builders.rs
@@ -98,7 +98,7 @@
     has_fields: bool,
 }
 
-pub fn debug_struct_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>,
+pub(super) fn debug_struct_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>,
                                 name: &str)
                                 -> DebugStruct<'a, 'b> {
     let result = fmt.write_str(name);
@@ -251,7 +251,10 @@
     empty_name: bool,
 }
 
-pub fn debug_tuple_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>, name: &str) -> DebugTuple<'a, 'b> {
+pub(super) fn debug_tuple_new<'a, 'b>(
+    fmt: &'a mut fmt::Formatter<'b>,
+    name: &str,
+) -> DebugTuple<'a, 'b> {
     let result = fmt.write_str(name);
     DebugTuple {
         fmt,
@@ -418,7 +421,7 @@
     inner: DebugInner<'a, 'b>,
 }
 
-pub fn debug_set_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugSet<'a, 'b> {
+pub(super) fn debug_set_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugSet<'a, 'b> {
     let result = fmt.write_str("{");
     DebugSet {
         inner: DebugInner {
@@ -555,7 +558,7 @@
     inner: DebugInner<'a, 'b>,
 }
 
-pub fn debug_list_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugList<'a, 'b> {
+pub(super) fn debug_list_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugList<'a, 'b> {
     let result = fmt.write_str("[");
     DebugList {
         inner: DebugInner {
@@ -697,7 +700,7 @@
     state: PadAdapterState,
 }
 
-pub fn debug_map_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugMap<'a, 'b> {
+pub(super) fn debug_map_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugMap<'a, 'b> {
     let result = fmt.write_str("{");
     DebugMap {
         fmt,
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index d5fae9e..bd31d25 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -549,7 +549,7 @@
 pub(crate) mod macros {
     /// Derive macro generating an impl of the trait `Debug`.
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
+    #[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
     #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
     #[allow_internal_unstable(core_intrinsics)]
     pub macro Debug($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/hash/mod.rs b/src/libcore/hash/mod.rs
index b397119..bf3daa3 100644
--- a/src/libcore/hash/mod.rs
+++ b/src/libcore/hash/mod.rs
@@ -202,7 +202,7 @@
 pub(crate) mod macros {
     /// Derive macro generating an impl of the trait `Hash`.
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
+    #[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
     #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
     #[allow_internal_unstable(core_intrinsics)]
     pub macro Hash($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index e114f3a..6c88a76 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -1263,14 +1263,14 @@
 
     /// Unstable implementation detail of the `rustc` compiler, do not use.
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
+    #[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[allow_internal_unstable(core_intrinsics, libstd_sys_internals)]
     pub macro RustcDecodable($item:item) { /* compiler built-in */ }
 
     /// Unstable implementation detail of the `rustc` compiler, do not use.
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
+    #[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[allow_internal_unstable(core_intrinsics)]
     pub macro RustcEncodable($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/marker.rs b/src/libcore/marker.rs
index 3befd42..89af252 100644
--- a/src/libcore/marker.rs
+++ b/src/libcore/marker.rs
@@ -290,7 +290,7 @@
 
 /// Derive macro generating an impl of the trait `Copy`.
 #[rustc_builtin_macro]
-#[rustc_macro_transparency = "semitransparent"]
+#[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow_internal_unstable(core_intrinsics, derive_clone_copy)]
 pub macro Copy($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/ptr/unique.rs b/src/libcore/ptr/unique.rs
index f0d011f..3521dd7 100644
--- a/src/libcore/ptr/unique.rs
+++ b/src/libcore/ptr/unique.rs
@@ -122,6 +122,14 @@
     pub unsafe fn as_mut(&mut self) -> &mut T {
         &mut *self.as_ptr()
     }
+
+    /// Casts to a pointer of another type.
+    #[inline]
+    pub const fn cast<U>(self) -> Unique<U> {
+        unsafe {
+            Unique::new_unchecked(self.as_ptr() as *mut U)
+        }
+    }
 }
 
 #[unstable(feature = "ptr_internals", issue = "0")]
diff --git a/src/librustc/hir/lowering/expr.rs b/src/librustc/hir/lowering/expr.rs
index 4ba61e9..ff0c44a 100644
--- a/src/librustc/hir/lowering/expr.rs
+++ b/src/librustc/hir/lowering/expr.rs
@@ -984,7 +984,6 @@
             volatile: asm.volatile,
             alignstack: asm.alignstack,
             dialect: asm.dialect,
-            ctxt: asm.ctxt,
         };
 
         let outputs = asm.outputs
diff --git a/src/librustc/hir/lowering/item.rs b/src/librustc/hir/lowering/item.rs
index 51a0c41..4f9a9ed 100644
--- a/src/librustc/hir/lowering/item.rs
+++ b/src/librustc/hir/lowering/item.rs
@@ -750,10 +750,7 @@
     }
 
     fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
-        P(hir::GlobalAsm {
-            asm: ga.asm,
-            ctxt: ga.ctxt,
-        })
+        P(hir::GlobalAsm { asm: ga.asm })
     }
 
     fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
diff --git a/src/librustc/hir/map/def_collector.rs b/src/librustc/hir/map/def_collector.rs
index df9bd3a..d725afa 100644
--- a/src/librustc/hir/map/def_collector.rs
+++ b/src/librustc/hir/map/def_collector.rs
@@ -74,7 +74,7 @@
         })
     }
 
-    fn visit_macro_invoc(&mut self, id: NodeId) {
+    pub fn visit_macro_invoc(&mut self, id: NodeId) {
         self.definitions.set_invocation_parent(id.placeholder_to_expn_id(), self.parent_def);
     }
 }
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index 5b15cf9..b469b70 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -23,7 +23,6 @@
 use syntax::ast::{self, CrateSugar, Ident, Name, NodeId, AsmDialect};
 use syntax::ast::{Attribute, Label, LitKind, StrStyle, FloatTy, IntTy, UintTy};
 use syntax::attr::{InlineAttr, OptimizeAttr};
-use syntax::ext::hygiene::SyntaxContext;
 use syntax::symbol::{Symbol, kw};
 use syntax::tokenstream::TokenStream;
 use syntax::util::parser::ExprPrecedence;
@@ -2009,8 +2008,6 @@
     pub volatile: bool,
     pub alignstack: bool,
     pub dialect: AsmDialect,
-    #[stable_hasher(ignore)] // This is used for error reporting
-    pub ctxt: SyntaxContext,
 }
 
 /// Represents an argument in a function header.
@@ -2189,8 +2186,6 @@
 #[derive(RustcEncodable, RustcDecodable, Debug, HashStable)]
 pub struct GlobalAsm {
     pub asm: Symbol,
-    #[stable_hasher(ignore)] // This is used for error reporting
-    pub ctxt: SyntaxContext,
 }
 
 #[derive(RustcEncodable, RustcDecodable, Debug, HashStable)]
diff --git a/src/librustc/mir/interpret/allocation.rs b/src/librustc/mir/interpret/allocation.rs
index ce04cca..84b4cd9 100644
--- a/src/librustc/mir/interpret/allocation.rs
+++ b/src/librustc/mir/interpret/allocation.rs
@@ -306,7 +306,7 @@
     ///
     /// zsts can't be read out of two reasons:
     /// * byteorder cannot work with zero element buffers
-    /// * in oder to obtain a `Pointer` we need to check for ZSTness anyway due to integer pointers
+    /// * in order to obtain a `Pointer` we need to check for ZSTness anyway due to integer pointers
     ///   being valid for ZSTs
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
diff --git a/src/librustc_codegen_llvm/asm.rs b/src/librustc_codegen_llvm/asm.rs
index 9763d52..b68ee2c 100644
--- a/src/librustc_codegen_llvm/asm.rs
+++ b/src/librustc_codegen_llvm/asm.rs
@@ -6,9 +6,9 @@
 
 use rustc::hir;
 use rustc_codegen_ssa::traits::*;
-
 use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::mir::operand::OperandValue;
+use syntax_pos::Span;
 
 use std::ffi::{CStr, CString};
 use libc::{c_uint, c_char};
@@ -19,7 +19,8 @@
         &mut self,
         ia: &hir::InlineAsm,
         outputs: Vec<PlaceRef<'tcx, &'ll Value>>,
-        mut inputs: Vec<&'ll Value>
+        mut inputs: Vec<&'ll Value>,
+        span: Span,
     ) -> bool {
         let mut ext_constraints = vec![];
         let mut output_types = vec![];
@@ -102,7 +103,7 @@
             let kind = llvm::LLVMGetMDKindIDInContext(self.llcx,
                 key.as_ptr() as *const c_char, key.len() as c_uint);
 
-            let val: &'ll Value = self.const_i32(ia.ctxt.outer_expn().as_u32() as i32);
+            let val: &'ll Value = self.const_i32(span.ctxt().outer_expn().as_u32() as i32);
 
             llvm::LLVMSetMetadata(r, kind,
                 llvm::LLVMMDNodeInContext(self.llcx, &val, 1));
diff --git a/src/librustc_codegen_ssa/mir/statement.rs b/src/librustc_codegen_ssa/mir/statement.rs
index 3717be4..3617f3a 100644
--- a/src/librustc_codegen_ssa/mir/statement.rs
+++ b/src/librustc_codegen_ssa/mir/statement.rs
@@ -89,7 +89,12 @@
                 });
 
                 if input_vals.len() == asm.inputs.len() {
-                    let res = bx.codegen_inline_asm(&asm.asm, outputs, input_vals);
+                    let res = bx.codegen_inline_asm(
+                        &asm.asm,
+                        outputs,
+                        input_vals,
+                        statement.source_info.span,
+                    );
                     if !res {
                         span_err!(bx.sess(), statement.source_info.span, E0668,
                                   "malformed inline assembly");
diff --git a/src/librustc_codegen_ssa/traits/asm.rs b/src/librustc_codegen_ssa/traits/asm.rs
index fd3c868..c9e1ed8 100644
--- a/src/librustc_codegen_ssa/traits/asm.rs
+++ b/src/librustc_codegen_ssa/traits/asm.rs
@@ -1,6 +1,7 @@
 use super::BackendTypes;
 use crate::mir::place::PlaceRef;
 use rustc::hir::{GlobalAsm, InlineAsm};
+use syntax_pos::Span;
 
 pub trait AsmBuilderMethods<'tcx>: BackendTypes {
     /// Take an inline assembly expression and splat it out via LLVM
@@ -9,6 +10,7 @@
         ia: &InlineAsm,
         outputs: Vec<PlaceRef<'tcx, Self::Value>>,
         inputs: Vec<Self::Value>,
+        span: Span,
     ) -> bool;
 }
 
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 8216008..ce7681c 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -1876,16 +1876,70 @@
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr) {
 
-        const ZEROED_PATH: &[Symbol] = &[sym::core, sym::mem, sym::zeroed];
-        const UININIT_PATH: &[Symbol] = &[sym::core, sym::mem, sym::uninitialized];
+        #[derive(Debug, Copy, Clone, PartialEq)]
+        enum InitKind { Zeroed, Uninit };
 
         /// Information about why a type cannot be initialized this way.
         /// Contains an error message and optionally a span to point at.
         type InitError = (String, Option<Span>);
 
+        /// Test if this constant is all-0.
+        fn is_zero(expr: &hir::Expr) -> bool {
+            use hir::ExprKind::*;
+            use syntax::ast::LitKind::*;
+            match &expr.node {
+                Lit(lit) =>
+                    if let Int(i, _) = lit.node {
+                        i == 0
+                    } else {
+                        false
+                    },
+                Tup(tup) =>
+                    tup.iter().all(is_zero),
+                _ =>
+                    false
+            }
+        }
+
+        /// Determine if this expression is a "dangerous initialization".
+        fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<InitKind> {
+            const ZEROED_PATH: &[Symbol] = &[sym::core, sym::mem, sym::zeroed];
+            const UININIT_PATH: &[Symbol] = &[sym::core, sym::mem, sym::uninitialized];
+            // `transmute` is inside an anonymous module (the `extern` block?);
+            // `Invalid` represents the empty string and matches that.
+            const TRANSMUTE_PATH: &[Symbol] =
+                &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
+
+            if let hir::ExprKind::Call(ref path_expr, ref args) = expr.node {
+                if let hir::ExprKind::Path(ref qpath) = path_expr.node {
+                    let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
+
+                    if cx.match_def_path(def_id, ZEROED_PATH) {
+                        return Some(InitKind::Zeroed);
+                    }
+                    if cx.match_def_path(def_id, UININIT_PATH) {
+                        return Some(InitKind::Uninit);
+                    }
+                    if cx.match_def_path(def_id, TRANSMUTE_PATH) {
+                        if is_zero(&args[0]) {
+                            return Some(InitKind::Zeroed);
+                        }
+                    }
+                    // FIXME: Also detect `MaybeUninit::zeroed().assume_init()` and
+                    // `MaybeUninit::uninit().assume_init()`.
+                }
+            }
+
+            None
+        }
+
         /// Return `Some` only if we are sure this type does *not*
         /// allow zero initialization.
-        fn ty_find_init_error<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<InitError> {
+        fn ty_find_init_error<'tcx>(
+            tcx: TyCtxt<'tcx>,
+            ty: Ty<'tcx>,
+            init: InitKind,
+        ) -> Option<InitError> {
             use rustc::ty::TyKind::*;
             match ty.sty {
                 // Primitive types that don't like 0 as a value.
@@ -1893,8 +1947,30 @@
                 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
                 FnPtr(..) => Some((format!("Function pointers must be non-null"), None)),
                 Never => Some((format!("The never type (`!`) has no valid value"), None)),
-                // Recurse for some compound types.
+                // Primitive types with other constraints.
+                Bool if init == InitKind::Uninit =>
+                    Some((format!("Booleans must be `true` or `false`"), None)),
+                Char if init == InitKind::Uninit =>
+                    Some((format!("Characters must be a valid unicode codepoint"), None)),
+                // Recurse and checks for some compound types.
                 Adt(adt_def, substs) if !adt_def.is_union() => {
+                    // First check f this ADT has a layout attribute (like `NonNull` and friends).
+                    use std::ops::Bound;
+                    match tcx.layout_scalar_valid_range(adt_def.did) {
+                        // We exploit here that `layout_scalar_valid_range` will never
+                        // return `Bound::Excluded`.  (And we have tests checking that we
+                        // handle the attribute correctly.)
+                        (Bound::Included(lo), _) if lo > 0 =>
+                            return Some((format!("{} must be non-null", ty), None)),
+                        (Bound::Included(_), _) | (_, Bound::Included(_))
+                        if init == InitKind::Uninit =>
+                            return Some((
+                                format!("{} must be initialized inside its custom valid range", ty),
+                                None,
+                            )),
+                        _ => {}
+                    }
+                    // Now, recurse.
                     match adt_def.variants.len() {
                         0 => Some((format!("0-variant enums have no valid value"), None)),
                         1 => {
@@ -1905,6 +1981,7 @@
                                 ty_find_init_error(
                                     tcx,
                                     field.ty(tcx, substs),
+                                    init,
                                 ).map(|(mut msg, span)| if span.is_none() {
                                     // Point to this field, should be helpful for figuring
                                     // out where the source of the error is.
@@ -1918,57 +1995,48 @@
                                 })
                             })
                         }
+                        // Multi-variant enums are tricky: if all but one variant are
+                        // uninhabited, we might actually do layout like for a single-variant
+                        // enum, and then even leaving them uninitialized could be okay.
                         _ => None, // Conservative fallback for multi-variant enum.
                     }
                 }
                 Tuple(..) => {
                     // Proceed recursively, check all fields.
-                    ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field))
+                    ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
                 }
-                // FIXME: Would be nice to also warn for `NonNull`/`NonZero*`.
-                // FIXME: *Only for `mem::uninitialized`*, we could also warn for `bool`,
-                //        `char`, and any multivariant enum.
                 // Conservative fallback.
                 _ => None,
             }
         }
 
-        if let hir::ExprKind::Call(ref path_expr, ref _args) = expr.node {
-            if let hir::ExprKind::Path(ref qpath) = path_expr.node {
-                if let Some(def_id) = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id() {
-                    if cx.match_def_path(def_id, &ZEROED_PATH) ||
-                        cx.match_def_path(def_id, &UININIT_PATH)
-                    {
-                        // This conjures an instance of a type out of nothing,
-                        // using zeroed or uninitialized memory.
-                        // We are extremely conservative with what we warn about.
-                        let conjured_ty = cx.tables.expr_ty(expr);
-                        if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty) {
-                            let mut err = cx.struct_span_lint(
-                                INVALID_VALUE,
-                                expr.span,
-                                &format!(
-                                    "the type `{}` does not permit {}",
-                                    conjured_ty,
-                                    if cx.match_def_path(def_id, &ZEROED_PATH) {
-                                        "zero-initialization"
-                                    } else {
-                                        "being left uninitialized"
-                                    }
-                                ),
-                            );
-                            err.span_label(expr.span,
-                                "this code causes undefined behavior when executed");
-                            err.span_label(expr.span, "help: use `MaybeUninit<T>` instead");
-                            if let Some(span) = span {
-                                err.span_note(span, &msg);
-                            } else {
-                                err.note(&msg);
-                            }
-                            err.emit();
-                        }
-                    }
+        if let Some(init) = is_dangerous_init(cx, expr) {
+            // This conjures an instance of a type out of nothing,
+            // using zeroed or uninitialized memory.
+            // We are extremely conservative with what we warn about.
+            let conjured_ty = cx.tables.expr_ty(expr);
+            if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
+                let mut err = cx.struct_span_lint(
+                    INVALID_VALUE,
+                    expr.span,
+                    &format!(
+                        "the type `{}` does not permit {}",
+                        conjured_ty,
+                        match init {
+                            InitKind::Zeroed => "zero-initialization",
+                            InitKind::Uninit => "being left uninitialized",
+                        },
+                    ),
+                );
+                err.span_label(expr.span,
+                    "this code causes undefined behavior when executed");
+                err.span_label(expr.span, "help: use `MaybeUninit<T>` instead");
+                if let Some(span) = span {
+                    err.span_note(span, &msg);
+                } else {
+                    err.note(&msg);
                 }
+                err.emit();
             }
         }
     }
diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 0bec31d..772b2d3 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -348,6 +348,14 @@
     }
 }
 
+impl SpecializedDecoder<Ident> for DecodeContext<'_, '_> {
+    fn specialized_decode(&mut self) -> Result<Ident, Self::Error> {
+        // FIXME(jseyfried): intercrate hygiene
+
+        Ok(Ident::with_dummy_span(Symbol::decode(self)?))
+    }
+}
+
 impl<'a, 'tcx> SpecializedDecoder<Fingerprint> for DecodeContext<'a, 'tcx> {
     fn specialized_decode(&mut self) -> Result<Fingerprint, Self::Error> {
         Fingerprint::decode_opaque(&mut self.opaque)
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index fb675d7..e2de055 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -31,7 +31,7 @@
 use syntax::ast;
 use syntax::attr;
 use syntax::source_map::Spanned;
-use syntax::symbol::{kw, sym};
+use syntax::symbol::{kw, sym, Ident};
 use syntax_pos::{self, FileName, SourceFile, Span};
 use log::{debug, trace};
 
@@ -173,6 +173,13 @@
     }
 }
 
+impl SpecializedEncoder<Ident> for EncodeContext<'tcx> {
+    fn specialized_encode(&mut self, ident: &Ident) -> Result<(), Self::Error> {
+        // FIXME(jseyfried): intercrate hygiene
+        ident.name.encode(self)
+    }
+}
+
 impl<'tcx> SpecializedEncoder<LocalDefId> for EncodeContext<'tcx> {
     #[inline]
     fn specialized_encode(&mut self, def_id: &LocalDefId) -> Result<(), Self::Error> {
diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index 52225ea..76ee76a 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -11,9 +11,8 @@
 use rustc::hir::def_id::DefId;
 use rustc::mir::interpret::{ConstEvalErr, ErrorHandled, ScalarMaybeUndef};
 use rustc::mir;
-use rustc::ty::{self, TyCtxt};
+use rustc::ty::{self, Ty, TyCtxt, subst::Subst};
 use rustc::ty::layout::{self, LayoutOf, VariantIdx};
-use rustc::ty::subst::Subst;
 use rustc::traits::Reveal;
 use rustc_data_structures::fx::FxHashMap;
 
@@ -415,7 +414,7 @@
         _bin_op: mir::BinOp,
         _left: ImmTy<'tcx>,
         _right: ImmTy<'tcx>,
-    ) -> InterpResult<'tcx, (Scalar, bool)> {
+    ) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)> {
         Err(
             ConstEvalError::NeedsRfc("pointer arithmetic or comparison".to_string()).into(),
         )
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index ee105fe..4c86c53 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -137,7 +137,7 @@
                 let l = self.read_immediate(args[0])?;
                 let r = self.read_immediate(args[1])?;
                 let is_add = intrinsic_name == "saturating_add";
-                let (val, overflowed) = self.binary_op(if is_add {
+                let (val, overflowed, _ty) = self.overflowing_binary_op(if is_add {
                     BinOp::Add
                 } else {
                     BinOp::Sub
@@ -184,7 +184,7 @@
                     "unchecked_shr" => BinOp::Shr,
                     _ => bug!("Already checked for int ops")
                 };
-                let (val, overflowed) = self.binary_op(bin_op, l, r)?;
+                let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, l, r)?;
                 if overflowed {
                     let layout = self.layout_of(substs.type_at(0))?;
                     let r_val = r.to_scalar()?.to_bits(layout.size)?;
diff --git a/src/librustc_mir/interpret/machine.rs b/src/librustc_mir/interpret/machine.rs
index 33ffb1d..bb74a50 100644
--- a/src/librustc_mir/interpret/machine.rs
+++ b/src/librustc_mir/interpret/machine.rs
@@ -7,7 +7,7 @@
 
 use rustc::hir::def_id::DefId;
 use rustc::mir;
-use rustc::ty::{self, TyCtxt};
+use rustc::ty::{self, Ty, TyCtxt};
 
 use super::{
     Allocation, AllocId, InterpResult, Scalar, AllocationExtra,
@@ -176,7 +176,7 @@
         bin_op: mir::BinOp,
         left: ImmTy<'tcx, Self::PointerTag>,
         right: ImmTy<'tcx, Self::PointerTag>,
-    ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool)>;
+    ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;
 
     /// Heap allocations via the `box` keyword.
     fn box_alloc(
diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index 6771d76..87d36da 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -297,7 +297,7 @@
     /// and `align`. On success, returns `None` for zero-sized accesses (where
     /// nothing else is left to do) and a `Pointer` to use for the actual access otherwise.
     /// Crucially, if the input is a `Pointer`, we will test it for liveness
-    /// *even of* the size is 0.
+    /// *even if* the size is 0.
     ///
     /// Everyone accessing memory based on a `Scalar` should use this method to get the
     /// `Pointer` they need. And even if you already have a `Pointer`, call this method
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index 139a92c..726ae6f 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -108,7 +108,7 @@
 // as input for binary and cast operations.
 #[derive(Copy, Clone, Debug)]
 pub struct ImmTy<'tcx, Tag=()> {
-    pub imm: Immediate<Tag>,
+    pub(crate) imm: Immediate<Tag>,
     pub layout: TyLayout<'tcx>,
 }
 
@@ -155,7 +155,7 @@
 
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub struct OpTy<'tcx, Tag=()> {
-    op: Operand<Tag>,
+    op: Operand<Tag>, // Keep this private, it helps enforce invariants
     pub layout: TyLayout<'tcx>,
 }
 
@@ -187,14 +187,23 @@
     }
 }
 
-impl<'tcx, Tag: Copy> ImmTy<'tcx, Tag>
-{
+impl<'tcx, Tag: Copy> ImmTy<'tcx, Tag> {
     #[inline]
     pub fn from_scalar(val: Scalar<Tag>, layout: TyLayout<'tcx>) -> Self {
         ImmTy { imm: val.into(), layout }
     }
 
     #[inline]
+    pub fn from_uint(i: impl Into<u128>, layout: TyLayout<'tcx>) -> Self {
+        Self::from_scalar(Scalar::from_uint(i, layout.size), layout)
+    }
+
+    #[inline]
+    pub fn from_int(i: impl Into<i128>, layout: TyLayout<'tcx>) -> Self {
+        Self::from_scalar(Scalar::from_int(i, layout.size), layout)
+    }
+
+    #[inline]
     pub fn to_bits(self) -> InterpResult<'tcx, u128> {
         self.to_scalar()?.to_bits(self.layout.size)
     }
diff --git a/src/librustc_mir/interpret/operator.rs b/src/librustc_mir/interpret/operator.rs
index e638ebc..470cc93 100644
--- a/src/librustc_mir/interpret/operator.rs
+++ b/src/librustc_mir/interpret/operator.rs
@@ -1,5 +1,5 @@
 use rustc::mir;
-use rustc::ty::{self, layout::TyLayout};
+use rustc::ty::{self, Ty, layout::{TyLayout, LayoutOf}};
 use syntax::ast::FloatTy;
 use rustc_apfloat::Float;
 use rustc::mir::interpret::{InterpResult, Scalar};
@@ -17,7 +17,12 @@
         right: ImmTy<'tcx, M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> InterpResult<'tcx> {
-        let (val, overflowed) = self.binary_op(op, left, right)?;
+        let (val, overflowed, ty) = self.overflowing_binary_op(op, left, right)?;
+        debug_assert_eq!(
+            self.tcx.intern_tup(&[ty, self.tcx.types.bool]),
+            dest.layout.ty,
+            "type mismatch for result of {:?}", op,
+        );
         let val = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
         self.write_immediate(val, dest)
     }
@@ -31,7 +36,8 @@
         right: ImmTy<'tcx, M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> InterpResult<'tcx> {
-        let (val, _overflowed) = self.binary_op(op, left, right)?;
+        let (val, _overflowed, ty) = self.overflowing_binary_op(op, left, right)?;
+        assert_eq!(ty, dest.layout.ty, "type mismatch for result of {:?}", op);
         self.write_scalar(val, dest)
     }
 }
@@ -42,7 +48,7 @@
         bin_op: mir::BinOp,
         l: char,
         r: char,
-    ) -> (Scalar<M::PointerTag>, bool) {
+    ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
         use rustc::mir::BinOp::*;
 
         let res = match bin_op {
@@ -54,7 +60,7 @@
             Ge => l >= r,
             _ => bug!("Invalid operation on char: {:?}", bin_op),
         };
-        return (Scalar::from_bool(res), false);
+        return (Scalar::from_bool(res), false, self.tcx.types.bool);
     }
 
     fn binary_bool_op(
@@ -62,7 +68,7 @@
         bin_op: mir::BinOp,
         l: bool,
         r: bool,
-    ) -> (Scalar<M::PointerTag>, bool) {
+    ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
         use rustc::mir::BinOp::*;
 
         let res = match bin_op {
@@ -77,32 +83,33 @@
             BitXor => l ^ r,
             _ => bug!("Invalid operation on bool: {:?}", bin_op),
         };
-        return (Scalar::from_bool(res), false);
+        return (Scalar::from_bool(res), false, self.tcx.types.bool);
     }
 
     fn binary_float_op<F: Float + Into<Scalar<M::PointerTag>>>(
         &self,
         bin_op: mir::BinOp,
+        ty: Ty<'tcx>,
         l: F,
         r: F,
-    ) -> (Scalar<M::PointerTag>, bool) {
+    ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
         use rustc::mir::BinOp::*;
 
-        let val = match bin_op {
-            Eq => Scalar::from_bool(l == r),
-            Ne => Scalar::from_bool(l != r),
-            Lt => Scalar::from_bool(l < r),
-            Le => Scalar::from_bool(l <= r),
-            Gt => Scalar::from_bool(l > r),
-            Ge => Scalar::from_bool(l >= r),
-            Add => (l + r).value.into(),
-            Sub => (l - r).value.into(),
-            Mul => (l * r).value.into(),
-            Div => (l / r).value.into(),
-            Rem => (l % r).value.into(),
+        let (val, ty) = match bin_op {
+            Eq => (Scalar::from_bool(l == r), self.tcx.types.bool),
+            Ne => (Scalar::from_bool(l != r), self.tcx.types.bool),
+            Lt => (Scalar::from_bool(l < r), self.tcx.types.bool),
+            Le => (Scalar::from_bool(l <= r), self.tcx.types.bool),
+            Gt => (Scalar::from_bool(l > r), self.tcx.types.bool),
+            Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool),
+            Add => ((l + r).value.into(), ty),
+            Sub => ((l - r).value.into(), ty),
+            Mul => ((l * r).value.into(), ty),
+            Div => ((l / r).value.into(), ty),
+            Rem => ((l % r).value.into(), ty),
             _ => bug!("invalid float op: `{:?}`", bin_op),
         };
-        return (val, false);
+        return (val, false, ty);
     }
 
     fn binary_int_op(
@@ -113,7 +120,7 @@
         left_layout: TyLayout<'tcx>,
         r: u128,
         right_layout: TyLayout<'tcx>,
-    ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool)> {
+    ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
         use rustc::mir::BinOp::*;
 
         // Shift ops can have an RHS with a different numeric type.
@@ -142,7 +149,7 @@
                 }
             };
             let truncated = self.truncate(result, left_layout);
-            return Ok((Scalar::from_uint(truncated, size), oflo));
+            return Ok((Scalar::from_uint(truncated, size), oflo, left_layout.ty));
         }
 
         // For the remaining ops, the types must be the same on both sides
@@ -167,7 +174,7 @@
             if let Some(op) = op {
                 let l = self.sign_extend(l, left_layout) as i128;
                 let r = self.sign_extend(r, right_layout) as i128;
-                return Ok((Scalar::from_bool(op(&l, &r)), false));
+                return Ok((Scalar::from_bool(op(&l, &r)), false, self.tcx.types.bool));
             }
             let op: Option<fn(i128, i128) -> (i128, bool)> = match bin_op {
                 Div if r == 0 => throw_panic!(DivisionByZero),
@@ -187,7 +194,7 @@
                     Rem | Div => {
                         // int_min / -1
                         if r == -1 && l == (1 << (size.bits() - 1)) {
-                            return Ok((Scalar::from_uint(l, size), true));
+                            return Ok((Scalar::from_uint(l, size), true, left_layout.ty));
                         }
                     },
                     _ => {},
@@ -202,25 +209,24 @@
                 // this may be out-of-bounds for the result type, so we have to truncate ourselves
                 let result = result as u128;
                 let truncated = self.truncate(result, left_layout);
-                return Ok((Scalar::from_uint(truncated, size), oflo));
+                return Ok((Scalar::from_uint(truncated, size), oflo, left_layout.ty));
             }
         }
 
         let size = left_layout.size;
 
-        // only ints left
-        let val = match bin_op {
-            Eq => Scalar::from_bool(l == r),
-            Ne => Scalar::from_bool(l != r),
+        let (val, ty) = match bin_op {
+            Eq => (Scalar::from_bool(l == r), self.tcx.types.bool),
+            Ne => (Scalar::from_bool(l != r), self.tcx.types.bool),
 
-            Lt => Scalar::from_bool(l < r),
-            Le => Scalar::from_bool(l <= r),
-            Gt => Scalar::from_bool(l > r),
-            Ge => Scalar::from_bool(l >= r),
+            Lt => (Scalar::from_bool(l < r), self.tcx.types.bool),
+            Le => (Scalar::from_bool(l <= r), self.tcx.types.bool),
+            Gt => (Scalar::from_bool(l > r), self.tcx.types.bool),
+            Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool),
 
-            BitOr => Scalar::from_uint(l | r, size),
-            BitAnd => Scalar::from_uint(l & r, size),
-            BitXor => Scalar::from_uint(l ^ r, size),
+            BitOr => (Scalar::from_uint(l | r, size), left_layout.ty),
+            BitAnd => (Scalar::from_uint(l & r, size), left_layout.ty),
+            BitXor => (Scalar::from_uint(l ^ r, size), left_layout.ty),
 
             Add | Sub | Mul | Rem | Div => {
                 debug_assert!(!left_layout.abi.is_signed());
@@ -236,7 +242,11 @@
                 };
                 let (result, oflo) = op(l, r);
                 let truncated = self.truncate(result, left_layout);
-                return Ok((Scalar::from_uint(truncated, size), oflo || truncated != result));
+                return Ok((
+                    Scalar::from_uint(truncated, size),
+                    oflo || truncated != result,
+                    left_layout.ty,
+                ));
             }
 
             _ => {
@@ -250,17 +260,17 @@
             }
         };
 
-        Ok((val, false))
+        Ok((val, false, ty))
     }
 
-    /// Returns the result of the specified operation and whether it overflowed.
-    #[inline]
-    pub fn binary_op(
+    /// Returns the result of the specified operation, whether it overflowed, and
+    /// the result type.
+    pub fn overflowing_binary_op(
         &self,
         bin_op: mir::BinOp,
         left: ImmTy<'tcx, M::PointerTag>,
         right: ImmTy<'tcx, M::PointerTag>,
-    ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool)> {
+    ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
         trace!("Running binary op {:?}: {:?} ({:?}), {:?} ({:?})",
             bin_op, *left, left.layout.ty, *right, right.layout.ty);
 
@@ -279,11 +289,14 @@
             }
             ty::Float(fty) => {
                 assert_eq!(left.layout.ty, right.layout.ty);
+                let ty = left.layout.ty;
                 let left = left.to_scalar()?;
                 let right = right.to_scalar()?;
                 Ok(match fty {
-                    FloatTy::F32 => self.binary_float_op(bin_op, left.to_f32()?, right.to_f32()?),
-                    FloatTy::F64 => self.binary_float_op(bin_op, left.to_f64()?, right.to_f64()?),
+                    FloatTy::F32 =>
+                        self.binary_float_op(bin_op, ty, left.to_f32()?, right.to_f32()?),
+                    FloatTy::F64 =>
+                        self.binary_float_op(bin_op, ty, left.to_f64()?, right.to_f64()?),
                 })
             }
             _ if left.layout.ty.is_integral() => {
@@ -312,11 +325,23 @@
         }
     }
 
+    /// Typed version of `checked_binary_op`, returning an `ImmTy`. Also ignores overflows.
+    #[inline]
+    pub fn binary_op(
+        &self,
+        bin_op: mir::BinOp,
+        left: ImmTy<'tcx, M::PointerTag>,
+        right: ImmTy<'tcx, M::PointerTag>,
+    ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
+        let (val, _overflow, ty) = self.overflowing_binary_op(bin_op, left, right)?;
+        Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
+    }
+
     pub fn unary_op(
         &self,
         un_op: mir::UnOp,
         val: ImmTy<'tcx, M::PointerTag>,
-    ) -> InterpResult<'tcx, Scalar<M::PointerTag>> {
+    ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
         use rustc::mir::UnOp::*;
 
         let layout = val.layout;
@@ -330,7 +355,7 @@
                     Not => !val,
                     _ => bug!("Invalid bool op {:?}", un_op)
                 };
-                Ok(Scalar::from_bool(res))
+                Ok(ImmTy::from_scalar(Scalar::from_bool(res), self.layout_of(self.tcx.types.bool)?))
             }
             ty::Float(fty) => {
                 let res = match (un_op, fty) {
@@ -338,7 +363,7 @@
                     (Neg, FloatTy::F64) => Scalar::from_f64(-val.to_f64()?),
                     _ => bug!("Invalid float op {:?}", un_op)
                 };
-                Ok(res)
+                Ok(ImmTy::from_scalar(res, layout))
             }
             _ => {
                 assert!(layout.ty.is_integral());
@@ -351,7 +376,7 @@
                     }
                 };
                 // res needs tuncating
-                Ok(Scalar::from_uint(self.truncate(res, layout), layout.size))
+                Ok(ImmTy::from_uint(self.truncate(res, layout), layout))
             }
         }
     }
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index 16686c3..ef9f20d 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -45,7 +45,7 @@
 
 #[derive(Copy, Clone, Debug)]
 pub struct PlaceTy<'tcx, Tag=()> {
-    place: Place<Tag>,
+    place: Place<Tag>, // Keep this private, it helps enforce invariants
     pub layout: TyLayout<'tcx>,
 }
 
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index e558278..b010bf0 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -177,7 +177,8 @@
                 // The operand always has the same type as the result.
                 let val = self.read_immediate(self.eval_operand(operand, Some(dest.layout))?)?;
                 let val = self.unary_op(un_op, val)?;
-                self.write_scalar(val, dest)?;
+                assert_eq!(val.layout, dest.layout, "layout mismatch for result of {:?}", un_op);
+                self.write_immediate(*val, dest)?;
             }
 
             Aggregate(ref kind, ref operands) => {
diff --git a/src/librustc_mir/interpret/terminator.rs b/src/librustc_mir/interpret/terminator.rs
index 1d6b48e..5de2979 100644
--- a/src/librustc_mir/interpret/terminator.rs
+++ b/src/librustc_mir/interpret/terminator.rs
@@ -7,7 +7,7 @@
 use rustc_target::spec::abi::Abi;
 
 use super::{
-    InterpResult, PointerArithmetic, Scalar,
+    InterpResult, PointerArithmetic,
     InterpCx, Machine, OpTy, ImmTy, PlaceTy, MPlaceTy, StackPopCleanup, FnVal,
 };
 
@@ -50,11 +50,10 @@
 
                 for (index, &const_int) in values.iter().enumerate() {
                     // Compare using binary_op, to also support pointer values
-                    let const_int = Scalar::from_uint(const_int, discr.layout.size);
-                    let (res, _) = self.binary_op(mir::BinOp::Eq,
+                    let res = self.overflowing_binary_op(mir::BinOp::Eq,
                         discr,
-                        ImmTy::from_scalar(const_int, discr.layout),
-                    )?;
+                        ImmTy::from_uint(const_int, discr.layout),
+                    )?.0;
                     if res.to_bool()? {
                         target_block = targets[index];
                         break;
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index c3c432d..98d8ca5 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -19,7 +19,7 @@
 use rustc::ty::subst::InternalSubsts;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc::ty::layout::{
-    LayoutOf, TyLayout, LayoutError, HasTyCtxt, TargetDataLayout, HasDataLayout, Size,
+    LayoutOf, TyLayout, LayoutError, HasTyCtxt, TargetDataLayout, HasDataLayout,
 };
 
 use crate::interpret::{
@@ -396,17 +396,10 @@
                 if let ty::Slice(_) = mplace.layout.ty.sty {
                     let len = mplace.meta.unwrap().to_usize(&self.ecx).unwrap();
 
-                    Some(ImmTy {
-                        imm: Immediate::Scalar(
-                            Scalar::from_uint(
-                                len,
-                                Size::from_bits(
-                                    self.tcx.sess.target.usize_ty.bit_width().unwrap() as u64
-                                )
-                            ).into(),
-                        ),
-                        layout: self.tcx.layout_of(self.param_env.and(self.tcx.types.usize)).ok()?,
-                    }.into())
+                    Some(ImmTy::from_uint(
+                        len,
+                        self.tcx.layout_of(self.param_env.and(self.tcx.types.usize)).ok()?,
+                    ).into())
                 } else {
                     trace!("not slice: {:?}", mplace.layout.ty.sty);
                     None
@@ -414,12 +407,10 @@
             },
             Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
                 type_size_of(self.tcx, self.param_env, ty).and_then(|n| Some(
-                    ImmTy {
-                        imm: Immediate::Scalar(
-                            Scalar::from_uint(n, self.tcx.data_layout.pointer_size).into()
-                        ),
-                        layout: self.tcx.layout_of(self.param_env.and(self.tcx.types.usize)).ok()?,
-                    }.into()
+                    ImmTy::from_uint(
+                        n,
+                        self.tcx.layout_of(self.param_env.and(self.tcx.types.usize)).ok()?,
+                    ).into()
                 ))
             }
             Rvalue::UnaryOp(op, ref arg) => {
@@ -452,11 +443,7 @@
                     // Now run the actual operation.
                     this.ecx.unary_op(op, prim)
                 })?;
-                let res = ImmTy {
-                    imm: Immediate::Scalar(val.into()),
-                    layout: place_layout,
-                };
-                Some(res.into())
+                Some(val.into())
             }
             Rvalue::CheckedBinaryOp(op, ref left, ref right) |
             Rvalue::BinaryOp(op, ref left, ref right) => {
@@ -510,8 +497,8 @@
                     this.ecx.read_immediate(left)
                 })?;
                 trace!("const evaluating {:?} for {:?} and {:?}", op, left, right);
-                let (val, overflow) = self.use_ecx(source_info, |this| {
-                    this.ecx.binary_op(op, l, r)
+                let (val, overflow, _ty) = self.use_ecx(source_info, |this| {
+                    this.ecx.overflowing_binary_op(op, l, r)
                 })?;
                 let val = if let Rvalue::CheckedBinaryOp(..) = *rvalue {
                     Immediate::ScalarPair(
diff --git a/src/librustc_resolve/build_reduced_graph.rs b/src/librustc_resolve/build_reduced_graph.rs
index 1510d74..4242845 100644
--- a/src/librustc_resolve/build_reduced_graph.rs
+++ b/src/librustc_resolve/build_reduced_graph.rs
@@ -160,12 +160,25 @@
         Some(ext)
     }
 
+    // FIXME: `extra_placeholders` should be included into the `fragment` as regular placeholders.
     crate fn build_reduced_graph(
-        &mut self, fragment: &AstFragment, parent_scope: ParentScope<'a>
+        &mut self,
+        fragment: &AstFragment,
+        extra_placeholders: &[NodeId],
+        parent_scope: ParentScope<'a>,
     ) -> LegacyScope<'a> {
-        fragment.visit_with(&mut DefCollector::new(&mut self.definitions, parent_scope.expansion));
+        let mut def_collector = DefCollector::new(&mut self.definitions, parent_scope.expansion);
+        fragment.visit_with(&mut def_collector);
+        for placeholder in extra_placeholders {
+            def_collector.visit_macro_invoc(*placeholder);
+        }
+
         let mut visitor = BuildReducedGraphVisitor { r: self, parent_scope };
         fragment.visit_with(&mut visitor);
+        for placeholder in extra_placeholders {
+            visitor.parent_scope.legacy = visitor.visit_invoc(*placeholder);
+        }
+
         visitor.parent_scope.legacy
     }
 
@@ -871,7 +884,7 @@
     }
 
     /// Builds the reduced graph for a single item in an external crate.
-    fn build_reduced_graph_for_external_crate_res(&mut self, child: Export<ast::NodeId>) {
+    fn build_reduced_graph_for_external_crate_res(&mut self, child: Export<NodeId>) {
         let parent = self.parent_scope.module;
         let Export { ident, res, vis, span } = child;
         // FIXME: We shouldn't create the gensym here, it should come from metadata,
@@ -1060,10 +1073,10 @@
         false
     }
 
-    fn visit_invoc(&mut self, id: ast::NodeId) -> LegacyScope<'a> {
+    fn visit_invoc(&mut self, id: NodeId) -> LegacyScope<'a> {
         let invoc_id = id.placeholder_to_expn_id();
 
-        self.parent_scope.module.unresolved_invocations.borrow_mut().insert(invoc_id);
+        self.parent_scope.module.unexpanded_invocations.borrow_mut().insert(invoc_id);
 
         let old_parent_scope = self.r.invocation_parent_scopes.insert(invoc_id, self.parent_scope);
         assert!(old_parent_scope.is_none(), "invocation data is reset for an invocation");
diff --git a/src/librustc_resolve/diagnostics.rs b/src/librustc_resolve/diagnostics.rs
index afdcec1..b79e0c2 100644
--- a/src/librustc_resolve/diagnostics.rs
+++ b/src/librustc_resolve/diagnostics.rs
@@ -169,12 +169,14 @@
                 err
             }
             ResolutionError::NameAlreadyUsedInParameterList(name, first_use_span) => {
-                let mut err = struct_span_err!(self.session,
-                                                span,
-                                                E0403,
-                                                "the name `{}` is already used for a generic \
-                                                parameter in this list of generic parameters",
-                                                name);
+                let mut err = struct_span_err!(
+                    self.session,
+                    span,
+                    E0403,
+                    "the name `{}` is already used for a generic \
+                     parameter in this item's generic parameters",
+                    name,
+                );
                 err.span_label(span, "already used");
                 err.span_label(first_use_span, format!("first use of `{}`", name));
                 err
diff --git a/src/librustc_resolve/error_codes.rs b/src/librustc_resolve/error_codes.rs
index e01f537..1faaf97 100644
--- a/src/librustc_resolve/error_codes.rs
+++ b/src/librustc_resolve/error_codes.rs
@@ -526,15 +526,25 @@
 Erroneous code example:
 
 ```compile_fail,E0403
-fn foo<T, T>(s: T, u: T) {} // error: the name `T` is already used for a type
-                            //        parameter in this type parameter list
+fn f<T, T>(s: T, u: T) {} // error: the name `T` is already used for a generic
+                          //        parameter in this item's generic parameters
 ```
 
 Please verify that none of the type parameters are misspelled, and rename any
 clashing parameters. Example:
 
 ```
-fn foo<T, Y>(s: T, u: Y) {} // ok!
+fn f<T, Y>(s: T, u: Y) {} // ok!
+```
+
+Type parameters in an associated item also cannot shadow parameters from the
+containing item:
+
+```compile_fail,E0403
+trait Foo<T> {
+    fn do_something(&self) -> T;
+    fn do_something_else<T: Clone>(&self, bar: T);
+}
 ```
 "##,
 
diff --git a/src/librustc_resolve/late.rs b/src/librustc_resolve/late.rs
index d8bd866..e15d02a 100644
--- a/src/librustc_resolve/late.rs
+++ b/src/librustc_resolve/late.rs
@@ -111,6 +111,24 @@
     TyParamAsConstParamTy,
 }
 
+impl RibKind<'_> {
+    // Whether this rib kind contains generic parameters, as opposed to local
+    // variables.
+    crate fn contains_params(&self) -> bool {
+        match self {
+            NormalRibKind
+            | FnItemRibKind
+            | ConstantItemRibKind
+            | ModuleRibKind(_)
+            | MacroDefinition(_) => false,
+            AssocItemRibKind
+            | ItemRibKind
+            | ForwardTyParamBanRibKind
+            | TyParamAsConstParamTy => true,
+        }
+    }
+}
+
 /// A single local scope.
 ///
 /// A rib represents a scope names can live in. Note that these appear in many places, not just
@@ -798,6 +816,19 @@
                 let mut function_type_rib = Rib::new(rib_kind);
                 let mut function_value_rib = Rib::new(rib_kind);
                 let mut seen_bindings = FxHashMap::default();
+                // We also can't shadow bindings from the parent item
+                if let AssocItemRibKind = rib_kind {
+                    let mut add_bindings_for_ns = |ns| {
+                        let parent_rib = self.ribs[ns].iter()
+                            .rfind(|rib| if let ItemRibKind = rib.kind { true } else { false })
+                            .expect("associated item outside of an item");
+                        seen_bindings.extend(
+                            parent_rib.bindings.iter().map(|(ident, _)| (*ident, ident.span)),
+                        );
+                    };
+                    add_bindings_for_ns(ValueNS);
+                    add_bindings_for_ns(TypeNS);
+                }
                 for param in &generics.params {
                     match param.kind {
                         GenericParamKind::Lifetime { .. } => {}
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 12c4f5b..2dd0ad1 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -448,7 +448,7 @@
     populate_on_access: Cell<bool>,
 
     // Macro invocations that can expand into items in this module.
-    unresolved_invocations: RefCell<FxHashSet<ExpnId>>,
+    unexpanded_invocations: RefCell<FxHashSet<ExpnId>>,
 
     no_implicit_prelude: bool,
 
@@ -478,7 +478,7 @@
             normal_ancestor_id,
             lazy_resolutions: Default::default(),
             populate_on_access: Cell::new(!normal_ancestor_id.is_local()),
-            unresolved_invocations: Default::default(),
+            unexpanded_invocations: Default::default(),
             no_implicit_prelude: false,
             glob_importers: RefCell::new(Vec::new()),
             globs: RefCell::new(Vec::new()),
@@ -1499,7 +1499,7 @@
             debug!("walk rib\n{:?}", ribs[i].bindings);
             // Use the rib kind to determine whether we are resolving parameters
             // (modern hygiene) or local variables (legacy hygiene).
-            let rib_ident = if let AssocItemRibKind | ItemRibKind = ribs[i].kind {
+            let rib_ident = if ribs[i].kind.contains_params() {
                 modern_ident
             } else {
                 ident
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index 6f49377..01ad672 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -10,7 +10,7 @@
 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
 use rustc::middle::stability;
 use rustc::{ty, lint, span_bug};
-use syntax::ast::{self, Ident};
+use syntax::ast::{self, NodeId, Ident};
 use syntax::attr::StabilityLevel;
 use syntax::edition::Edition;
 use syntax::ext::base::{self, Indeterminate, SpecialDerives};
@@ -26,7 +26,7 @@
 use std::{mem, ptr};
 use rustc_data_structures::sync::Lrc;
 
-type Res = def::Res<ast::NodeId>;
+type Res = def::Res<NodeId>;
 
 /// Binding produced by a `macro_rules` item.
 /// Not modularized, can shadow previous legacy bindings, etc.
@@ -91,11 +91,11 @@
 }
 
 impl<'a> base::Resolver for Resolver<'a> {
-    fn next_node_id(&mut self) -> ast::NodeId {
+    fn next_node_id(&mut self) -> NodeId {
         self.session.next_node_id()
     }
 
-    fn get_module_scope(&mut self, id: ast::NodeId) -> ExpnId {
+    fn get_module_scope(&mut self, id: NodeId) -> ExpnId {
         let expn_id = ExpnId::fresh(Some(ExpnData::default(
             ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, self.session.edition()
         )));
@@ -115,23 +115,18 @@
         });
     }
 
+    // FIXME: `extra_placeholders` should be included into the `fragment` as regular placeholders.
     fn visit_ast_fragment_with_placeholders(
-        &mut self, expansion: ExpnId, fragment: &AstFragment, derives: &[ExpnId]
+        &mut self, expansion: ExpnId, fragment: &AstFragment, extra_placeholders: &[NodeId]
     ) {
-        // Fill in some data for derives if the fragment is from a derive container.
+        // Integrate the new AST fragment into all the definition and module structures.
         // We are inside the `expansion` now, but other parent scope components are still the same.
         let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
-        let parent_def = self.definitions.invocation_parent(expansion);
-        self.invocation_parent_scopes.extend(derives.iter().map(|&derive| (derive, parent_scope)));
-        for &derive_invoc_id in derives {
-            self.definitions.set_invocation_parent(derive_invoc_id, parent_def);
-        }
-        parent_scope.module.unresolved_invocations.borrow_mut().remove(&expansion);
-        parent_scope.module.unresolved_invocations.borrow_mut().extend(derives);
-
-        // Integrate the new AST fragment into all the definition and module structures.
-        let output_legacy_scope = self.build_reduced_graph(fragment, parent_scope);
+        let output_legacy_scope =
+            self.build_reduced_graph(fragment, extra_placeholders, parent_scope);
         self.output_legacy_scopes.insert(expansion, output_legacy_scope);
+
+        parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
     }
 
     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension) {
@@ -485,7 +480,7 @@
                 Scope::MacroUsePrelude => match this.macro_use_prelude.get(&ident.name).cloned() {
                     Some(binding) => Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
                     None => Err(Determinacy::determined(
-                        this.graph_root.unresolved_invocations.borrow().is_empty()
+                        this.graph_root.unexpanded_invocations.borrow().is_empty()
                     ))
                 }
                 Scope::BuiltinAttrs => if is_builtin_attr_name(ident.name) {
@@ -508,7 +503,7 @@
                 Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
                     Some(binding) => Ok((binding, Flags::PRELUDE)),
                     None => Err(Determinacy::determined(
-                        this.graph_root.unresolved_invocations.borrow().is_empty()
+                        this.graph_root.unexpanded_invocations.borrow().is_empty()
                     )),
                 }
                 Scope::ToolPrelude => if KNOWN_TOOLS.contains(&ident.name) {
diff --git a/src/librustc_resolve/resolve_imports.rs b/src/librustc_resolve/resolve_imports.rs
index b49f186..fd222a1 100644
--- a/src/librustc_resolve/resolve_imports.rs
+++ b/src/librustc_resolve/resolve_imports.rs
@@ -202,7 +202,7 @@
                     Err((Determined, Weak::No))
                 } else if let Some(binding) = self.extern_prelude_get(ident, !record_used) {
                     Ok(binding)
-                } else if !self.graph_root.unresolved_invocations.borrow().is_empty() {
+                } else if !self.graph_root.unexpanded_invocations.borrow().is_empty() {
                     // Macro-expanded `extern crate` items can add names to extern prelude.
                     Err((Undetermined, Weak::No))
                 } else {
@@ -348,7 +348,7 @@
         // progress, we have to ignore those potential unresolved invocations from other modules
         // and prohibit access to macro-expanded `macro_export` macros instead (unless restricted
         // shadowing is enabled, see `macro_expanded_macro_export_errors`).
-        let unexpanded_macros = !module.unresolved_invocations.borrow().is_empty();
+        let unexpanded_macros = !module.unexpanded_invocations.borrow().is_empty();
         if let Some(binding) = resolution.binding {
             if !unexpanded_macros || ns == MacroNS || restricted_shadowing {
                 return check_usable(self, binding);
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index b2c0e34..28a1ccd 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -203,7 +203,6 @@
                 fcx.register_wf_obligation(ty, span, code.clone());
             }
             ty::AssocKind::Method => {
-                reject_shadowing_parameters(fcx.tcx, item.def_id);
                 let sig = fcx.tcx.fn_sig(item.def_id);
                 let sig = fcx.normalize_associated_types_in(span, &sig);
                 check_fn_or_method(tcx, fcx, span, sig,
@@ -998,34 +997,6 @@
     err.emit();
 }
 
-fn reject_shadowing_parameters(tcx: TyCtxt<'_>, def_id: DefId) {
-    let generics = tcx.generics_of(def_id);
-    let parent = tcx.generics_of(generics.parent.unwrap());
-    let impl_params: FxHashMap<_, _> = parent.params.iter().flat_map(|param| match param.kind {
-        GenericParamDefKind::Lifetime => None,
-        GenericParamDefKind::Type { .. } | GenericParamDefKind::Const => {
-            Some((param.name, param.def_id))
-        }
-    }).collect();
-
-    for method_param in &generics.params {
-        // Shadowing is checked in `resolve_lifetime`.
-        if let GenericParamDefKind::Lifetime = method_param.kind {
-            continue
-        }
-        if impl_params.contains_key(&method_param.name) {
-            // Tighten up the span to focus on only the shadowing type.
-            let type_span = tcx.def_span(method_param.def_id);
-
-            // The expectation here is that the original trait declaration is
-            // local so it should be okay to just unwrap everything.
-            let trait_def_id = impl_params[&method_param.name];
-            let trait_decl_span = tcx.def_span(trait_def_id);
-            error_194(tcx, type_span, trait_decl_span, &method_param.name.as_str()[..]);
-        }
-    }
-}
-
 /// Feature gates RFC 2056 -- trivial bounds, checking for global bounds that
 /// aren't true.
 fn check_false_global_bounds(fcx: &FnCtxt<'_, '_>, span: Span, id: hir::HirId) {
@@ -1152,12 +1123,3 @@
     err.span_label(span, "unused parameter");
     err
 }
-
-fn error_194(tcx: TyCtxt<'_>, span: Span, trait_decl_span: Span, name: &str) {
-    struct_span_err!(tcx.sess, span, E0194,
-                     "type parameter `{}` shadows another type parameter of the same name",
-                     name)
-        .span_label(span, "shadows another type parameter")
-        .span_label(trait_decl_span, format!("first `{}` declared here", name))
-        .emit();
-}
diff --git a/src/librustc_typeck/error_codes.rs b/src/librustc_typeck/error_codes.rs
index 90118a9..ca9ce3d 100644
--- a/src/librustc_typeck/error_codes.rs
+++ b/src/librustc_typeck/error_codes.rs
@@ -1718,22 +1718,6 @@
 reason to also specify it in a `where` clause.
 "##,
 
-E0194: r##"
-A type parameter was declared which shadows an existing one. An example of this
-error:
-
-```compile_fail,E0194
-trait Foo<T> {
-    fn do_something(&self) -> T;
-    fn do_something_else<T: Clone>(&self, bar: T);
-}
-```
-
-In this example, the trait `Foo` and the trait method `do_something_else` both
-define a type parameter `T`. This is not allowed: if the method wishes to
-define a type parameter, it must use a different name for it.
-"##,
-
 E0195: r##"
 Your method's lifetime parameters do not match the trait declaration.
 Erroneous code example:
@@ -4837,6 +4821,7 @@
 //  E0188, // can not cast an immutable reference to a mutable pointer
 //  E0189, // deprecated: can only cast a boxed pointer to a boxed object
 //  E0190, // deprecated: can only cast a &-pointer to an &-object
+//  E0194, // merged into E0403
 //  E0196, // cannot determine a type for this closure
     E0203, // type parameter has more than one relaxed default bound,
            // and only one is supported
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 3d15782..50e428e 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -5,7 +5,7 @@
 pub use crate::symbol::{Ident, Symbol as Name};
 pub use crate::util::parser::ExprPrecedence;
 
-use crate::ext::hygiene::{ExpnId, SyntaxContext};
+use crate::ext::hygiene::ExpnId;
 use crate::parse::token::{self, DelimToken};
 use crate::print::pprust;
 use crate::ptr::P;
@@ -1787,7 +1787,6 @@
     pub volatile: bool,
     pub alignstack: bool,
     pub dialect: AsmDialect,
-    pub ctxt: SyntaxContext,
 }
 
 /// An argument in a function header.
@@ -2035,7 +2034,6 @@
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug, Copy)]
 pub struct GlobalAsm {
     pub asm: Symbol,
-    pub ctxt: SyntaxContext,
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index fb1bf4d..b0a4a6a 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -1,4 +1,4 @@
-use crate::ast::{self, Attribute, Name, PatKind};
+use crate::ast::{self, NodeId, Attribute, Name, PatKind};
 use crate::attr::{HasAttrs, Stability, Deprecation};
 use crate::source_map::SourceMap;
 use crate::edition::Edition;
@@ -671,13 +671,13 @@
 }
 
 pub trait Resolver {
-    fn next_node_id(&mut self) -> ast::NodeId;
+    fn next_node_id(&mut self) -> NodeId;
 
-    fn get_module_scope(&mut self, id: ast::NodeId) -> ExpnId;
+    fn get_module_scope(&mut self, id: NodeId) -> ExpnId;
 
     fn resolve_dollar_crates(&mut self);
     fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment,
-                                            derives: &[ExpnId]);
+                                            extra_placeholders: &[NodeId]);
     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension);
 
     fn resolve_imports(&mut self);
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index dac4029..c1d52c9 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -291,7 +291,7 @@
         // Unresolved macros produce dummy outputs as a recovery measure.
         invocations.reverse();
         let mut expanded_fragments = Vec::new();
-        let mut derives: FxHashMap<ExpnId, Vec<_>> = FxHashMap::default();
+        let mut all_derive_placeholders: FxHashMap<ExpnId, Vec<_>> = FxHashMap::default();
         let mut undetermined_invocations = Vec::new();
         let (mut progress, mut force) = (false, !self.monotonic);
         loop {
@@ -347,13 +347,14 @@
 
                 let mut item = self.fully_configure(item);
                 item.visit_attrs(|attrs| attrs.retain(|a| a.path != sym::derive));
-                let derives = derives.entry(invoc.expansion_data.id).or_default();
+                let derive_placeholders =
+                    all_derive_placeholders.entry(invoc.expansion_data.id).or_default();
 
-                derives.reserve(traits.len());
+                derive_placeholders.reserve(traits.len());
                 invocations.reserve(traits.len());
                 for path in traits {
                     let expn_id = ExpnId::fresh(None);
-                    derives.push(expn_id);
+                    derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id));
                     invocations.push(Invocation {
                         kind: InvocationKind::Derive { path, item: item.clone() },
                         fragment_kind: invoc.fragment_kind,
@@ -365,7 +366,7 @@
                 }
                 let fragment = invoc.fragment_kind
                     .expect_from_annotatables(::std::iter::once(item));
-                self.collect_invocations(fragment, derives)
+                self.collect_invocations(fragment, derive_placeholders)
             } else {
                 unreachable!()
             };
@@ -384,10 +385,11 @@
         // Finally incorporate all the expanded macros into the input AST fragment.
         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
         while let Some(expanded_fragments) = expanded_fragments.pop() {
-            for (mark, expanded_fragment) in expanded_fragments.into_iter().rev() {
-                let derives = derives.remove(&mark).unwrap_or_else(Vec::new);
-                placeholder_expander.add(NodeId::placeholder_from_expn_id(mark),
-                                         expanded_fragment, derives);
+            for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
+                let derive_placeholders =
+                    all_derive_placeholders.remove(&expn_id).unwrap_or_else(Vec::new);
+                placeholder_expander.add(NodeId::placeholder_from_expn_id(expn_id),
+                                         expanded_fragment, derive_placeholders);
             }
         }
         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
@@ -404,7 +406,7 @@
     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
     /// prepares data for resolving paths of macro invocations.
-    fn collect_invocations(&mut self, mut fragment: AstFragment, derives: &[ExpnId])
+    fn collect_invocations(&mut self, mut fragment: AstFragment, extra_placeholders: &[NodeId])
                            -> (AstFragment, Vec<Invocation>) {
         // Resolve `$crate`s in the fragment for pretty-printing.
         self.cx.resolver.resolve_dollar_crates();
@@ -423,9 +425,10 @@
             collector.invocations
         };
 
+        // FIXME: Merge `extra_placeholders` into the `fragment` as regular placeholders.
         if self.monotonic {
             self.cx.resolver.visit_ast_fragment_with_placeholders(
-                self.cx.current_expansion.id, &fragment, derives);
+                self.cx.current_expansion.id, &fragment, extra_placeholders);
         }
 
         (fragment, invocations)
diff --git a/src/libsyntax/ext/placeholders.rs b/src/libsyntax/ext/placeholders.rs
index 2d05f8f..d800cfe 100644
--- a/src/libsyntax/ext/placeholders.rs
+++ b/src/libsyntax/ext/placeholders.rs
@@ -2,7 +2,6 @@
 use crate::source_map::{DUMMY_SP, dummy_spanned};
 use crate::ext::base::ExtCtxt;
 use crate::ext::expand::{AstFragment, AstFragmentKind};
-use crate::ext::hygiene::ExpnId;
 use crate::tokenstream::TokenStream;
 use crate::mut_visit::*;
 use crate::ptr::P;
@@ -86,11 +85,11 @@
         }
     }
 
-    pub fn add(&mut self, id: ast::NodeId, mut fragment: AstFragment, derives: Vec<ExpnId>) {
+    pub fn add(&mut self, id: ast::NodeId, mut fragment: AstFragment, placeholders: Vec<NodeId>) {
         fragment.mut_visit_with(self);
         if let AstFragment::Items(mut items) = fragment {
-            for derive in derives {
-                match self.remove(NodeId::placeholder_from_expn_id(derive)) {
+            for placeholder in placeholders {
+                match self.remove(placeholder) {
                     AstFragment::Items(derived_items) => items.extend(derived_items),
                     _ => unreachable!(),
                 }
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index b67b461..9785f8e 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -1183,7 +1183,7 @@
         }
         ExprKind::InlineAsm(asm) => {
             let InlineAsm { asm: _, asm_str_style: _, outputs, inputs, clobbers: _, volatile: _,
-                            alignstack: _, dialect: _, ctxt: _ } = asm.deref_mut();
+                            alignstack: _, dialect: _ } = asm.deref_mut();
             for out in outputs {
                 let InlineAsmOutput { constraint: _, expr, is_rw: _, is_indirect: _ } = out;
                 vis.visit_expr(expr);
diff --git a/src/libsyntax_ext/asm.rs b/src/libsyntax_ext/asm.rs
index 950166f..644a44f 100644
--- a/src/libsyntax_ext/asm.rs
+++ b/src/libsyntax_ext/asm.rs
@@ -63,7 +63,7 @@
     MacEager::expr(P(ast::Expr {
         id: ast::DUMMY_NODE_ID,
         node: ast::ExprKind::InlineAsm(P(inline_asm)),
-        span: sp,
+        span: sp.with_ctxt(cx.backtrace()),
         attrs: ThinVec::new(),
     }))
 }
@@ -277,6 +277,5 @@
         volatile,
         alignstack,
         dialect,
-        ctxt: cx.backtrace(),
     }))
 }
diff --git a/src/libsyntax_ext/deriving/cmp/ord.rs b/src/libsyntax_ext/deriving/cmp/ord.rs
index 885cfee..55687c3 100644
--- a/src/libsyntax_ext/deriving/cmp/ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/ord.rs
@@ -43,17 +43,18 @@
 }
 
 
-pub fn ordering_collapsed(cx: &mut ExtCtxt<'_>,
-                          span: Span,
-                          self_arg_tags: &[ast::Ident])
-                          -> P<ast::Expr> {
+pub fn ordering_collapsed(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    self_arg_tags: &[ast::Ident],
+) -> P<ast::Expr> {
     let lft = cx.expr_ident(span, self_arg_tags[0]);
     let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
-    cx.expr_method_call(span, lft, cx.ident_of("cmp"), vec![rgt])
+    cx.expr_method_call(span, lft, ast::Ident::new(sym::cmp, span), vec![rgt])
 }
 
 pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {
-    let test_id = cx.ident_of("cmp").gensym();
+    let test_id = ast::Ident::new(sym::cmp, span);
     let equals_path = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
 
     let cmp_path = cx.std_path(&[sym::cmp, sym::Ord, sym::cmp]);
@@ -75,34 +76,34 @@
             // as the outermost one, and the last as the innermost.
             false,
             |cx, span, old, self_f, other_fs| {
-        // match new {
-        //     ::std::cmp::Ordering::Equal => old,
-        //     cmp => cmp
-        // }
+                // match new {
+                //     ::std::cmp::Ordering::Equal => old,
+                //     cmp => cmp
+                // }
 
-        let new = {
-            let other_f = match other_fs {
-                [o_f] => o_f,
-                _ => cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`"),
-            };
+                let new = {
+                    let other_f = match other_fs {
+                        [o_f] => o_f,
+                        _ => cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`"),
+                    };
 
-            let args = vec![
-                    cx.expr_addr_of(span, self_f),
-                    cx.expr_addr_of(span, other_f.clone()),
-                ];
+                    let args = vec![
+                            cx.expr_addr_of(span, self_f),
+                            cx.expr_addr_of(span, other_f.clone()),
+                        ];
 
-            cx.expr_call_global(span, cmp_path.clone(), args)
-        };
+                    cx.expr_call_global(span, cmp_path.clone(), args)
+                };
 
-        let eq_arm = cx.arm(span,
-                            vec![cx.pat_path(span, equals_path.clone())],
-                            old);
-        let neq_arm = cx.arm(span,
-                             vec![cx.pat_ident(span, test_id)],
-                             cx.expr_ident(span, test_id));
+                let eq_arm = cx.arm(span,
+                                    vec![cx.pat_path(span, equals_path.clone())],
+                                    old);
+                let neq_arm = cx.arm(span,
+                                     vec![cx.pat_ident(span, test_id)],
+                                     cx.expr_ident(span, test_id));
 
-        cx.expr_match(span, new, vec![eq_arm, neq_arm])
-    },
+                cx.expr_match(span, new, vec![eq_arm, neq_arm])
+            },
             cx.expr_path(equals_path.clone()),
             Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
         if self_args.len() != 2 {
diff --git a/src/libsyntax_ext/deriving/cmp/partial_ord.rs b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
index 0ec30f5..740b92a 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
@@ -94,11 +94,12 @@
     GeOp,
 }
 
-pub fn some_ordering_collapsed(cx: &mut ExtCtxt<'_>,
-                               span: Span,
-                               op: OrderingOp,
-                               self_arg_tags: &[ast::Ident])
-                               -> P<ast::Expr> {
+pub fn some_ordering_collapsed(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    op: OrderingOp,
+    self_arg_tags: &[ast::Ident],
+) -> P<ast::Expr> {
     let lft = cx.expr_ident(span, self_arg_tags[0]);
     let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
     let op_str = match op {
@@ -108,11 +109,11 @@
         GtOp => "gt",
         GeOp => "ge",
     };
-    cx.expr_method_call(span, lft, cx.ident_of(op_str), vec![rgt])
+    cx.expr_method_call(span, lft, ast::Ident::from_str_and_span(op_str, span), vec![rgt])
 }
 
 pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {
-    let test_id = cx.ident_of("cmp").gensym();
+    let test_id = ast::Ident::new(sym::cmp, span);
     let ordering = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
     let ordering_expr = cx.expr_path(ordering.clone());
     let equals_expr = cx.expr_some(span, ordering_expr);
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index 1d5234a..4415354 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -62,7 +62,7 @@
     // We want to make sure we have the ctxt set so that we can use unstable methods
     let span = span.with_ctxt(cx.backtrace());
     let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
-    let builder = Ident::from_str("debug_trait_builder").gensym();
+    let builder = Ident::from_str_and_span("debug_trait_builder", span);
     let builder_expr = cx.expr_ident(span, builder.clone());
 
     let fmt = substr.nonself_args[0].clone();
@@ -73,7 +73,7 @@
             // tuple struct/"normal" variant
             let expr =
                 cx.expr_method_call(span, fmt, Ident::from_str("debug_tuple"), vec![name]);
-            stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
+            stmts.push(cx.stmt_let(span, true, builder, expr));
 
             for field in fields {
                 // Use double indirection to make sure this works for unsized types
@@ -82,7 +82,7 @@
 
                 let expr = cx.expr_method_call(span,
                                                 builder_expr.clone(),
-                                                Ident::with_dummy_span(sym::field),
+                                                Ident::new(sym::field, span),
                                                 vec![field]);
 
                 // Use `let _ = expr;` to avoid triggering the
@@ -106,7 +106,7 @@
                 let field = cx.expr_addr_of(field.span, field);
                 let expr = cx.expr_method_call(span,
                                                 builder_expr.clone(),
-                                                Ident::with_dummy_span(sym::field),
+                                                Ident::new(sym::field, span),
                                                 vec![name, field]);
                 stmts.push(stmt_let_undescore(cx, span, expr));
             }
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index 293c5a1..9b6f851 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -1,6 +1,6 @@
-//! The compiler code necessary for `#[derive(Decodable)]`. See encodable.rs for more.
+//! The compiler code necessary for `#[derive(RustcDecodable)]`. See encodable.rs for more.
 
-use crate::deriving::{self, pathvec_std};
+use crate::deriving::pathvec_std;
 use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
@@ -17,7 +17,7 @@
                                        item: &Annotatable,
                                        push: &mut dyn FnMut(Annotatable)) {
     let krate = "rustc_serialize";
-    let typaram = &*deriving::hygienic_type_parameter(item, "__D");
+    let typaram = "__D";
 
     let trait_def = TraitDef {
         span,
diff --git a/src/libsyntax_ext/deriving/encodable.rs b/src/libsyntax_ext/deriving/encodable.rs
index 52e74a7..8b18fb2 100644
--- a/src/libsyntax_ext/deriving/encodable.rs
+++ b/src/libsyntax_ext/deriving/encodable.rs
@@ -1,11 +1,12 @@
-//! The compiler code necessary to implement the `#[derive(Encodable)]`
-//! (and `Decodable`, in `decodable.rs`) extension. The idea here is that
-//! type-defining items may be tagged with `#[derive(Encodable, Decodable)]`.
+//! The compiler code necessary to implement the `#[derive(RustcEncodable)]`
+//! (and `RustcDecodable`, in `decodable.rs`) extension. The idea here is that
+//! type-defining items may be tagged with
+//! `#[derive(RustcEncodable, RustcDecodable)]`.
 //!
 //! For example, a type like:
 //!
 //! ```
-//! #[derive(Encodable, Decodable)]
+//! #[derive(RustcEncodable, RustcDecodable)]
 //! struct Node { id: usize }
 //! ```
 //!
@@ -40,15 +41,17 @@
 //! references other non-built-in types. A type definition like:
 //!
 //! ```
-//! # #[derive(Encodable, Decodable)] struct Span;
-//! #[derive(Encodable, Decodable)]
+//! # #[derive(RustcEncodable, RustcDecodable)]
+//! # struct Span;
+//! #[derive(RustcEncodable, RustcDecodable)]
 //! struct Spanned<T> { node: T, span: Span }
 //! ```
 //!
 //! would yield functions like:
 //!
 //! ```
-//! # #[derive(Encodable, Decodable)] struct Span;
+//! # #[derive(RustcEncodable, RustcDecodable)]
+//! # struct Span;
 //! # struct Spanned<T> { node: T, span: Span }
 //! impl<
 //!     S: Encoder<E>,
@@ -82,7 +85,7 @@
 //! }
 //! ```
 
-use crate::deriving::{self, pathvec_std};
+use crate::deriving::pathvec_std;
 use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
@@ -98,7 +101,7 @@
                                        item: &Annotatable,
                                        push: &mut dyn FnMut(Annotatable)) {
     let krate = "rustc_serialize";
-    let typaram = &*deriving::hygienic_type_parameter(item, "__S");
+    let typaram = "__S";
 
     let trait_def = TraitDef {
         span,
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 55fb767..1475bac 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -890,7 +890,7 @@
 
         for (ty, name) in self.args.iter() {
             let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
-            let ident = cx.ident_of(name).gensym();
+            let ident = ast::Ident::from_str_and_span(name, trait_.span);
             arg_tys.push((ident, ast_ty));
 
             let arg_expr = cx.expr_ident(trait_.span, ident);
@@ -1210,7 +1210,7 @@
         let vi_idents = self_arg_names.iter()
             .map(|name| {
                 let vi_suffix = format!("{}_vi", &name[..]);
-                cx.ident_of(&vi_suffix[..]).gensym()
+                ast::Ident::from_str_and_span(&vi_suffix[..], trait_.span)
             })
             .collect::<Vec<ast::Ident>>();
 
@@ -1387,7 +1387,10 @@
                 let variant_value =
                     deriving::call_intrinsic(cx, sp, "discriminant_value", vec![self_addr]);
 
-                let target_ty = cx.ty_ident(sp, cx.ident_of(target_type_name));
+                let target_ty = cx.ty_ident(
+                    sp,
+                    ast::Ident::from_str_and_span(target_type_name, sp),
+                );
                 let variant_disr = cx.expr_cast(sp, variant_value, target_ty);
                 let let_stmt = cx.stmt_let(sp, false, ident, variant_disr);
                 index_let_stmts.push(let_stmt);
@@ -1588,7 +1591,7 @@
         let mut ident_exprs = Vec::new();
         for (i, struct_field) in struct_def.fields().iter().enumerate() {
             let sp = struct_field.span.with_ctxt(self.span.ctxt());
-            let ident = cx.ident_of(&format!("{}_{}", prefix, i)).gensym();
+            let ident = ast::Ident::from_str_and_span(&format!("{}_{}", prefix, i), self.span);
             paths.push(ident.with_span_pos(sp));
             let val = cx.expr_path(cx.path_ident(sp, ident));
             let val = if use_temporaries {
diff --git a/src/libsyntax_ext/deriving/generic/ty.rs b/src/libsyntax_ext/deriving/generic/ty.rs
index 399829e..7fcf036 100644
--- a/src/libsyntax_ext/deriving/generic/ty.rs
+++ b/src/libsyntax_ext/deriving/generic/ty.rs
@@ -72,7 +72,7 @@
                    self_ty: Ident,
                    self_generics: &Generics)
                    -> ast::Path {
-        let mut idents = self.path.iter().map(|s| cx.ident_of(*s)).collect();
+        let mut idents = self.path.iter().map(|s| Ident::from_str_and_span(*s, span)).collect();
         let lt = mk_lifetimes(cx, span, &self.lifetime);
         let tys: Vec<P<ast::Ty>> =
             self.params.iter().map(|t| t.to_ty(cx, span, self_ty, self_generics)).collect();
@@ -209,7 +209,7 @@
             cx.trait_bound(path)
         })
         .collect();
-    cx.typaram(span, cx.ident_of(name), attrs.to_owned(), bounds, None)
+    cx.typaram(span, ast::Ident::from_str_and_span(name, span), attrs.to_owned(), bounds, None)
 }
 
 fn mk_generics(params: Vec<ast::GenericParam>, span: Span) -> Generics {
diff --git a/src/libsyntax_ext/deriving/hash.rs b/src/libsyntax_ext/deriving/hash.rs
index 9787722..2fc594a 100644
--- a/src/libsyntax_ext/deriving/hash.rs
+++ b/src/libsyntax_ext/deriving/hash.rs
@@ -16,7 +16,7 @@
 
     let path = Path::new_(pathvec_std!(cx, hash::Hash), None, vec![], PathKind::Std);
 
-    let typaram = &*deriving::hygienic_type_parameter(item, "__H");
+    let typaram = "__H";
 
     let arg = Path::new_local(typaram);
     let hash_trait_def = TraitDef {
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index 8cd2853..da68eea 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -54,33 +54,6 @@
     }
 }
 
-/// Construct a name for the inner type parameter that can't collide with any type parameters of
-/// the item. This is achieved by starting with a base and then concatenating the names of all
-/// other type parameters.
-// FIXME(aburka): use real hygiene when that becomes possible
-fn hygienic_type_parameter(item: &Annotatable, base: &str) -> String {
-    let mut typaram = String::from(base);
-    if let Annotatable::Item(ref item) = *item {
-        match item.node {
-            ast::ItemKind::Struct(_, ast::Generics { ref params, .. }) |
-            ast::ItemKind::Enum(_, ast::Generics { ref params, .. }) => {
-                for param in params {
-                    match param.kind {
-                        ast::GenericParamKind::Type { .. } => {
-                            typaram.push_str(&param.ident.as_str());
-                        }
-                        _ => {}
-                    }
-                }
-            }
-
-            _ => {}
-        }
-    }
-
-    typaram
-}
-
 /// Constructs an expression that calls an intrinsic
 fn call_intrinsic(cx: &ExtCtxt<'_>,
                   span: Span,
diff --git a/src/libsyntax_ext/global_asm.rs b/src/libsyntax_ext/global_asm.rs
index 112192f..73ebeae 100644
--- a/src/libsyntax_ext/global_asm.rs
+++ b/src/libsyntax_ext/global_asm.rs
@@ -30,7 +30,7 @@
                 id: ast::DUMMY_NODE_ID,
                 node: ast::ItemKind::GlobalAsm(P(global_asm)),
                 vis: respan(sp.shrink_to_lo(), ast::VisibilityKind::Inherited),
-                span: sp,
+                span: sp.with_ctxt(cx.backtrace()),
                 tokens: None,
             })])
         }
@@ -61,8 +61,5 @@
         None => return Ok(None),
     };
 
-    Ok(Some(ast::GlobalAsm {
-        asm,
-        ctxt: cx.backtrace(),
-    }))
+    Ok(Some(ast::GlobalAsm { asm }))
 }
diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index 87d930f..ebfb076 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -750,15 +750,3 @@
         Ok(ExpnId::root()) // FIXME(jseyfried) intercrate hygiene
     }
 }
-
-impl Encodable for SyntaxContext {
-    fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> {
-        Ok(()) // FIXME(jseyfried) intercrate hygiene
-    }
-}
-
-impl Decodable for SyntaxContext {
-    fn decode<D: Decoder>(_: &mut D) -> Result<Self, D::Error> {
-        Ok(SyntaxContext::root()) // FIXME(jseyfried) intercrate hygiene
-    }
-}
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index 361e017..0b8f16b 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -8,6 +8,7 @@
 use rustc_data_structures::newtype_index;
 use rustc_macros::symbols;
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
+use rustc_serialize::{UseSpecializedDecodable, UseSpecializedEncodable};
 
 use std::cmp::{PartialEq, Ordering, PartialOrd, Ord};
 use std::fmt;
@@ -848,28 +849,9 @@
     }
 }
 
-impl Encodable for Ident {
-    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        if !self.span.modern().from_expansion() {
-            s.emit_str(&self.as_str())
-        } else { // FIXME(jseyfried): intercrate hygiene
-            let mut string = "#".to_owned();
-            string.push_str(&self.as_str());
-            s.emit_str(&string)
-        }
-    }
-}
+impl UseSpecializedEncodable for Ident {}
 
-impl Decodable for Ident {
-    fn decode<D: Decoder>(d: &mut D) -> Result<Ident, D::Error> {
-        let string = d.read_str()?;
-        Ok(if !string.starts_with('#') {
-            Ident::from_str(&string)
-        } else { // FIXME(jseyfried): intercrate hygiene
-            Ident::from_str(&string[1..]).gensym()
-        })
-    }
-}
+impl UseSpecializedDecodable for Ident {}
 
 /// A symbol is an interned or gensymed string. A gensym is a symbol that is
 /// never equal to any other symbol.
diff --git a/src/test/pretty/stmt_expr_attributes.rs b/src/test/pretty/stmt_expr_attributes.rs
index 02d9323..619cce6 100644
--- a/src/test/pretty/stmt_expr_attributes.rs
+++ b/src/test/pretty/stmt_expr_attributes.rs
@@ -259,8 +259,6 @@
     }
 }
 
-/////////////////
-
 fn foo() { }
 fn foo3(_: i32, _: (), _: ()) { }
 fn qux(_: i32) { }
diff --git a/src/test/ui/associated-type/associated-type-projection-from-supertrait.rs b/src/test/ui/associated-type/associated-type-projection-from-supertrait.rs
index 06dfe49..7e05bcd 100644
--- a/src/test/ui/associated-type/associated-type-projection-from-supertrait.rs
+++ b/src/test/ui/associated-type/associated-type-projection-from-supertrait.rs
@@ -12,30 +12,22 @@
     fn chip_paint(&self, c: Self::Color) { }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct Black;
 struct ModelT;
 impl Vehicle for ModelT { type Color = Black; }
 impl Car for ModelT { }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct Blue;
 struct ModelU;
 impl Vehicle for ModelU { type Color = Blue; }
 impl Car for ModelU { }
 
-///////////////////////////////////////////////////////////////////////////
-
 fn dent<C:Car>(c: C, color: C::Color) { c.chip_paint(color) }
 fn a() { dent(ModelT, Black); }
 fn b() { dent(ModelT, Blue); } //~ ERROR mismatched types
 fn c() { dent(ModelU, Black); } //~ ERROR mismatched types
 fn d() { dent(ModelU, Blue); }
 
-///////////////////////////////////////////////////////////////////////////
-
 fn e() { ModelT.chip_paint(Black); }
 fn f() { ModelT.chip_paint(Blue); } //~ ERROR mismatched types
 fn g() { ModelU.chip_paint(Black); } //~ ERROR mismatched types
diff --git a/src/test/ui/associated-type/associated-type-projection-from-supertrait.stderr b/src/test/ui/associated-type/associated-type-projection-from-supertrait.stderr
index 06f1a1c..4ba4925 100644
--- a/src/test/ui/associated-type/associated-type-projection-from-supertrait.stderr
+++ b/src/test/ui/associated-type/associated-type-projection-from-supertrait.stderr
@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/associated-type-projection-from-supertrait.rs:33:23
+  --> $DIR/associated-type-projection-from-supertrait.rs:27:23
    |
 LL | fn b() { dent(ModelT, Blue); }
    |                       ^^^^ expected struct `Black`, found struct `Blue`
@@ -8,7 +8,7 @@
               found type `Blue`
 
 error[E0308]: mismatched types
-  --> $DIR/associated-type-projection-from-supertrait.rs:34:23
+  --> $DIR/associated-type-projection-from-supertrait.rs:28:23
    |
 LL | fn c() { dent(ModelU, Black); }
    |                       ^^^^^ expected struct `Blue`, found struct `Black`
@@ -17,7 +17,7 @@
               found type `Black`
 
 error[E0308]: mismatched types
-  --> $DIR/associated-type-projection-from-supertrait.rs:40:28
+  --> $DIR/associated-type-projection-from-supertrait.rs:32:28
    |
 LL | fn f() { ModelT.chip_paint(Blue); }
    |                            ^^^^ expected struct `Black`, found struct `Blue`
@@ -26,7 +26,7 @@
               found type `Blue`
 
 error[E0308]: mismatched types
-  --> $DIR/associated-type-projection-from-supertrait.rs:41:28
+  --> $DIR/associated-type-projection-from-supertrait.rs:33:28
    |
 LL | fn g() { ModelU.chip_paint(Black); }
    |                            ^^^^^ expected struct `Blue`, found struct `Black`
diff --git a/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs b/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs
index 6531308..6b2bbbe 100644
--- a/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs
+++ b/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs
@@ -11,22 +11,16 @@
     fn honk(&self) { }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct Black;
 struct ModelT;
 impl Vehicle for ModelT { type Color = Black; }
 impl Car for ModelT { }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct Blue;
 struct ModelU;
 impl Vehicle for ModelU { type Color = Blue; }
 impl Car for ModelU { }
 
-///////////////////////////////////////////////////////////////////////////
-
 fn black_car<C:Car<Color=Black>>(c: C) {
 }
 
diff --git a/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.stderr b/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.stderr
index 4b54860..89c48d5 100644
--- a/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.stderr
+++ b/src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.stderr
@@ -1,5 +1,5 @@
 error[E0271]: type mismatch resolving `<ModelT as Vehicle>::Color == Blue`
-  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:37:10
+  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:31:10
    |
 LL | fn b() { blue_car(ModelT); }
    |          ^^^^^^^^ expected struct `Black`, found struct `Blue`
@@ -7,13 +7,13 @@
    = note: expected type `Black`
               found type `Blue`
 note: required by `blue_car`
-  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:33:1
+  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:27:1
    |
 LL | fn blue_car<C:Car<Color=Blue>>(c: C) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0271]: type mismatch resolving `<ModelU as Vehicle>::Color == Black`
-  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:38:10
+  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:32:10
    |
 LL | fn c() { black_car(ModelU); }
    |          ^^^^^^^^^ expected struct `Blue`, found struct `Black`
@@ -21,7 +21,7 @@
    = note: expected type `Blue`
               found type `Black`
 note: required by `black_car`
-  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:30:1
+  --> $DIR/associated-types-binding-to-type-defined-in-supertrait.rs:24:1
    |
 LL | fn black_car<C:Car<Color=Black>>(c: C) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/associated-types/associated-types-ref-from-struct.rs b/src/test/ui/associated-types/associated-types-ref-from-struct.rs
index 3ccba28..c89f604 100644
--- a/src/test/ui/associated-types/associated-types-ref-from-struct.rs
+++ b/src/test/ui/associated-types/associated-types-ref-from-struct.rs
@@ -9,8 +9,6 @@
     fn test(&self, value: &Self::V) -> bool;
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct TesterPair<T:Test> {
     tester: T,
     value: T::V,
@@ -26,8 +24,6 @@
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct EqU32(u32);
 impl Test for EqU32 {
     type V = u32;
diff --git a/src/test/ui/consts/const-eval/ub-nonnull.rs b/src/test/ui/consts/const-eval/ub-nonnull.rs
index 431ff35..9edae19 100644
--- a/src/test/ui/consts/const-eval/ub-nonnull.rs
+++ b/src/test/ui/consts/const-eval/ub-nonnull.rs
@@ -1,5 +1,5 @@
 #![feature(rustc_attrs, const_transmute)]
-#![allow(const_err)] // make sure we cannot allow away the errors tested here
+#![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
 use std::ptr::NonNull;
diff --git a/src/test/ui/consts/const-eval/ub-ref.rs b/src/test/ui/consts/const-eval/ub-ref.rs
index 0d8f301..bbab85c 100644
--- a/src/test/ui/consts/const-eval/ub-ref.rs
+++ b/src/test/ui/consts/const-eval/ub-ref.rs
@@ -1,6 +1,6 @@
 // ignore-tidy-linelength
 #![feature(const_transmute)]
-#![allow(const_err)] // make sure we cannot allow away the errors tested here
+#![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
 
diff --git a/src/test/ui/consts/const-eval/ub-upvars.rs b/src/test/ui/consts/const-eval/ub-upvars.rs
index 0a427cd..baab14d 100644
--- a/src/test/ui/consts/const-eval/ub-upvars.rs
+++ b/src/test/ui/consts/const-eval/ub-upvars.rs
@@ -1,5 +1,5 @@
 #![feature(const_transmute)]
-#![allow(const_err)] // make sure we cannot allow away the errors tested here
+#![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
 
diff --git a/src/test/ui/derives/derive-hygiene.rs b/src/test/ui/derives/derive-hygiene.rs
new file mode 100644
index 0000000..4fa83c4
--- /dev/null
+++ b/src/test/ui/derives/derive-hygiene.rs
@@ -0,0 +1,121 @@
+// Make sure that built-in derives don't rely on the user not declaring certain
+// names to work properly.
+
+// check-pass
+
+#![allow(nonstandard_style)]
+#![feature(decl_macro)]
+
+use std::prelude::v1::test as inline;
+
+static f: () = ();
+static cmp: () = ();
+static other: () = ();
+static state: () = ();
+static __self_0_0: () = ();
+static __self_1_0: () = ();
+static __self_vi: () = ();
+static __arg_1_0: () = ();
+static debug_trait_builder: () = ();
+
+struct isize;
+trait i16 {}
+
+trait MethodsInDerives: Sized {
+    fn debug_tuple(self) {}
+    fn debug_struct(self) {}
+    fn field(self) {}
+    fn finish(self) {}
+    fn clone(self) {}
+    fn cmp(self) {}
+    fn partial_cmp(self) {}
+    fn eq(self) {}
+    fn ne(self) {}
+    fn le(self) {}
+    fn lt(self) {}
+    fn ge(self) {}
+    fn gt(self) {}
+    fn hash(self) {}
+}
+
+trait GenericAny<T, U> {}
+impl<S, T, U> GenericAny<T, U> for S {}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+enum __H { V(i32), }
+
+#[repr(i16)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+enum W { A, B }
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
+struct X<A: GenericAny<A, self::X<i32>>> {
+    A: A,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
+struct Y<B>(B)
+where
+    B: From<B>;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+enum Z<C> {
+    C(C),
+    B { C: C },
+}
+
+// Make sure that we aren't using `self::` in paths, since it doesn't work in
+// non-module scopes.
+const NON_MODULE: () = {
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    enum __H { V(i32), }
+
+    #[repr(i16)]
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    enum W { A, B }
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
+    struct X<A: Fn(A) -> self::X<i32>> {
+        A: A,
+    }
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
+    struct Y<B>(B)
+    where
+        B: From<B>;
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    enum Z<C> {
+        C(C),
+        B { C: C },
+    }
+};
+
+macro m() {
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    enum __H { V(i32), }
+
+    #[repr(i16)]
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    enum W { A, B }
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
+    struct X<A: GenericAny<A, self::X<i32>>> {
+        A: A,
+    }
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
+    struct Y<B>(B)
+    where
+        B: From<B>;
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    enum Z<C> {
+        C(C),
+        B { C: C },
+    }
+}
+
+m!();
+
+fn main() {}
diff --git a/src/test/ui/duplicate/duplicate-type-parameter.stderr b/src/test/ui/duplicate/duplicate-type-parameter.stderr
index 8606479..6754574 100644
--- a/src/test/ui/duplicate/duplicate-type-parameter.stderr
+++ b/src/test/ui/duplicate/duplicate-type-parameter.stderr
@@ -1,4 +1,4 @@
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:1:12
    |
 LL | type Foo<T,T> = Option<T>;
@@ -6,7 +6,7 @@
    |          |
    |          first use of `T`
 
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:4:14
    |
 LL | struct Bar<T,T>(T);
@@ -14,7 +14,7 @@
    |            |
    |            first use of `T`
 
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:7:14
    |
 LL | struct Baz<T,T> {
@@ -22,7 +22,7 @@
    |            |
    |            first use of `T`
 
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:12:12
    |
 LL | enum Boo<T,T> {
@@ -30,7 +30,7 @@
    |          |
    |          first use of `T`
 
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:18:11
    |
 LL | fn quux<T,T>(x: T) {}
@@ -38,7 +38,7 @@
    |         |
    |         first use of `T`
 
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:21:13
    |
 LL | trait Qux<T,T> {}
@@ -46,7 +46,7 @@
    |           |
    |           first use of `T`
 
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/duplicate-type-parameter.rs:24:8
    |
 LL | impl<T,T> Qux<T,T> for Option<T> {}
diff --git a/src/test/ui/error-codes/E0194.rs b/src/test/ui/error-codes/E0194.rs
index 71eff0e..8a43f38 100644
--- a/src/test/ui/error-codes/E0194.rs
+++ b/src/test/ui/error-codes/E0194.rs
@@ -1,7 +1,7 @@
 trait Foo<T> {
     fn do_something(&self) -> T;
     fn do_something_else<T: Clone>(&self, bar: T);
-    //~^ ERROR E0194
+    //~^ ERROR E0403
 }
 
 fn main() {
diff --git a/src/test/ui/error-codes/E0194.stderr b/src/test/ui/error-codes/E0194.stderr
index ab4918a..f2c908e 100644
--- a/src/test/ui/error-codes/E0194.stderr
+++ b/src/test/ui/error-codes/E0194.stderr
@@ -1,12 +1,12 @@
-error[E0194]: type parameter `T` shadows another type parameter of the same name
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/E0194.rs:3:26
    |
 LL | trait Foo<T> {
-   |           - first `T` declared here
+   |           - first use of `T`
 LL |     fn do_something(&self) -> T;
 LL |     fn do_something_else<T: Clone>(&self, bar: T);
-   |                          ^ shadows another type parameter
+   |                          ^ already used
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0194`.
+For more information about this error, try `rustc --explain E0403`.
diff --git a/src/test/ui/error-codes/E0403.stderr b/src/test/ui/error-codes/E0403.stderr
index 2bd7de6..d76a58a 100644
--- a/src/test/ui/error-codes/E0403.stderr
+++ b/src/test/ui/error-codes/E0403.stderr
@@ -1,4 +1,4 @@
-error[E0403]: the name `T` is already used for a generic parameter in this list of generic parameters
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/E0403.rs:1:11
    |
 LL | fn foo<T, T>(s: T, u: T) {}
diff --git a/src/test/ui/higher-rank-trait-bounds/hrtb-type-outlives.rs b/src/test/ui/higher-rank-trait-bounds/hrtb-type-outlives.rs
index a8f3818..88d3961 100644
--- a/src/test/ui/higher-rank-trait-bounds/hrtb-type-outlives.rs
+++ b/src/test/ui/higher-rank-trait-bounds/hrtb-type-outlives.rs
@@ -14,7 +14,6 @@
 {
 }
 
-///////////////////////////////////////////////////////////////////////////
 // Expressed as a where clause
 
 struct SomeStruct<X> {
@@ -30,7 +29,6 @@
     want_foo::<SomeStruct<usize>>();
 }
 
-///////////////////////////////////////////////////////////////////////////
 // Expressed as shorthand
 
 struct AnotherStruct<X> {
diff --git a/src/test/ui/hrtb/hrtb-conflate-regions.rs b/src/test/ui/hrtb/hrtb-conflate-regions.rs
index 3913036..004d62a 100644
--- a/src/test/ui/hrtb/hrtb-conflate-regions.rs
+++ b/src/test/ui/hrtb/hrtb-conflate-regions.rs
@@ -15,7 +15,6 @@
 {
 }
 
-///////////////////////////////////////////////////////////////////////////
 // Expressed as a where clause
 
 struct SomeStruct;
diff --git a/src/test/ui/hrtb/hrtb-conflate-regions.stderr b/src/test/ui/hrtb/hrtb-conflate-regions.stderr
index 3fb6baa..20265d6 100644
--- a/src/test/ui/hrtb/hrtb-conflate-regions.stderr
+++ b/src/test/ui/hrtb/hrtb-conflate-regions.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `for<'a, 'b> SomeStruct: Foo<(&'a isize, &'b isize)>` is not satisfied
-  --> $DIR/hrtb-conflate-regions.rs:28:10
+  --> $DIR/hrtb-conflate-regions.rs:27:10
    |
 LL | fn b() { want_foo2::<SomeStruct>(); }
    |          ^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a, 'b> Foo<(&'a isize, &'b isize)>` is not implemented for `SomeStruct`
diff --git a/src/test/ui/hygiene/auxiliary/codegen-attrs.rs b/src/test/ui/hygiene/auxiliary/codegen-attrs.rs
new file mode 100644
index 0000000..74afedb
--- /dev/null
+++ b/src/test/ui/hygiene/auxiliary/codegen-attrs.rs
@@ -0,0 +1,10 @@
+#![feature(decl_macro)]
+
+macro m($f:ident) {
+    #[export_name = "export_function_name"]
+    pub fn $f() -> i32 {
+        2
+    }
+}
+
+m!(rust_function_name);
diff --git a/src/test/ui/hygiene/cross-crate-codegen-attrs.rs b/src/test/ui/hygiene/cross-crate-codegen-attrs.rs
new file mode 100644
index 0000000..af6b133
--- /dev/null
+++ b/src/test/ui/hygiene/cross-crate-codegen-attrs.rs
@@ -0,0 +1,12 @@
+// Make sure that macro expanded codegen attributes work across crates.
+// We used to gensym the identifiers in attributes, which stopped dependent
+// crates from seeing them, resulting in linker errors in cases like this one.
+
+// run-pass
+// aux-build:codegen-attrs.rs
+
+extern crate codegen_attrs;
+
+fn main() {
+    assert_eq!(codegen_attrs::rust_function_name(), 2);
+}
diff --git a/src/test/ui/impl-trait/bound-normalization-fail.rs b/src/test/ui/impl-trait/bound-normalization-fail.rs
index 9ba7c91..ce15505 100644
--- a/src/test/ui/impl-trait/bound-normalization-fail.rs
+++ b/src/test/ui/impl-trait/bound-normalization-fail.rs
@@ -8,7 +8,6 @@
 
 // See issue 60414
 
-/////////////////////////////////////////////
 // Reduction to `impl Trait`
 
 struct Foo<T>(T);
@@ -33,7 +32,6 @@
     }
 }
 
-/////////////////////////////////////////////
 // Same with lifetimes in the trait
 
 mod lifetimes {
diff --git a/src/test/ui/impl-trait/bound-normalization-fail.stderr b/src/test/ui/impl-trait/bound-normalization-fail.stderr
index b5c8e07..4811b1e 100644
--- a/src/test/ui/impl-trait/bound-normalization-fail.stderr
+++ b/src/test/ui/impl-trait/bound-normalization-fail.stderr
@@ -7,7 +7,7 @@
    = note: `#[warn(incomplete_features)]` on by default
 
 error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as impl_trait::Trait>::Assoc`
-  --> $DIR/bound-normalization-fail.rs:30:32
+  --> $DIR/bound-normalization-fail.rs:29:32
    |
 LL |     fn foo_fail<T: Trait>() -> impl FooLike<Output=T::Assoc> {
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found associated type
@@ -17,13 +17,13 @@
    = note: the return type of a function must have a statically known size
 
 error: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
-  --> $DIR/bound-normalization-fail.rs:47:41
+  --> $DIR/bound-normalization-fail.rs:45:41
    |
 LL |     fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output=T::Assoc> {
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as lifetimes::Trait<'static>>::Assoc`
-  --> $DIR/bound-normalization-fail.rs:47:41
+  --> $DIR/bound-normalization-fail.rs:45:41
    |
 LL |     fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output=T::Assoc> {
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found associated type
diff --git a/src/test/ui/impl-trait/bound-normalization-pass.rs b/src/test/ui/impl-trait/bound-normalization-pass.rs
index 5b634e3..b0ed4be 100644
--- a/src/test/ui/impl-trait/bound-normalization-pass.rs
+++ b/src/test/ui/impl-trait/bound-normalization-pass.rs
@@ -8,7 +8,6 @@
 
 // See issue 60414
 
-/////////////////////////////////////////////
 // Reduction to `impl Trait`
 
 struct Foo<T>(T);
@@ -32,7 +31,6 @@
     }
 }
 
-/////////////////////////////////////////////
 // Same with lifetimes in the trait
 
 mod lifetimes {
@@ -59,7 +57,6 @@
     }
 }
 
-/////////////////////////////////////////////
 // Reduction using `impl Trait` in bindings
 
 mod impl_trait_in_bindings {
@@ -80,7 +77,6 @@
     }
 }
 
-/////////////////////////////////////////////
 // The same applied to `type Foo = impl Bar`s
 
 mod opaque_types {
diff --git a/src/test/ui/issues/issue-12028.rs b/src/test/ui/issues/issue-12028.rs
index d553545..7c2b0d6 100644
--- a/src/test/ui/issues/issue-12028.rs
+++ b/src/test/ui/issues/issue-12028.rs
@@ -17,8 +17,6 @@
     fn stream(&self) -> Self::S;
 }
 
-//////////////////////////////////////////////////////////////////////////////
-
 trait StreamHash<H: StreamHasher>: Hash<H> {
     fn input_stream(&self, stream: &mut H::S);
 }
diff --git a/src/test/ui/issues/issue-12028.stderr b/src/test/ui/issues/issue-12028.stderr
index 64694c7..24aa88c 100644
--- a/src/test/ui/issues/issue-12028.stderr
+++ b/src/test/ui/issues/issue-12028.stderr
@@ -1,5 +1,5 @@
 error[E0284]: type annotations required: cannot resolve `<_ as StreamHasher>::S == <H as StreamHasher>::S`
-  --> $DIR/issue-12028.rs:29:14
+  --> $DIR/issue-12028.rs:27:14
    |
 LL |         self.input_stream(&mut stream);
    |              ^^^^^^^^^^^^
diff --git a/src/test/ui/issues/issue-16739.rs b/src/test/ui/issues/issue-16739.rs
index 54ad8fd..94da2ca 100644
--- a/src/test/ui/issues/issue-16739.rs
+++ b/src/test/ui/issues/issue-16739.rs
@@ -16,8 +16,6 @@
     extern "rust-call" fn call_once(mut self, _: ()) -> u32 { self.call_mut(()) }
 }
 
-/////////////////////////////////////////////////////////////////////////
-
 impl FnMut<(u32,)> for Foo {
     extern "rust-call" fn call_mut(&mut self, (x,): (u32,)) -> u32 { self.foo + x }
 }
@@ -27,8 +25,6 @@
     extern "rust-call" fn call_once(mut self, args: (u32,)) -> u32 { self.call_mut(args) }
 }
 
-/////////////////////////////////////////////////////////////////////////
-
 impl FnMut<(u32,u32)> for Foo {
     extern "rust-call" fn call_mut(&mut self, (x, y): (u32, u32)) -> u32 { self.foo + x + y }
 }
diff --git a/src/test/ui/lint/uninitialized-zeroed.rs b/src/test/ui/lint/uninitialized-zeroed.rs
index d816479..5cf62b8 100644
--- a/src/test/ui/lint/uninitialized-zeroed.rs
+++ b/src/test/ui/lint/uninitialized-zeroed.rs
@@ -2,11 +2,13 @@
 // This test checks that calling `mem::{uninitialized,zeroed}` with certain types results
 // in a lint.
 
-#![feature(never_type)]
+#![feature(never_type, rustc_attrs)]
 #![allow(deprecated)]
 #![deny(invalid_value)]
 
 use std::mem::{self, MaybeUninit};
+use std::ptr::NonNull;
+use std::num::NonZeroU32;
 
 enum Void {}
 
@@ -16,6 +18,11 @@
 struct Wrap<T> { wrapped: T }
 enum WrapEnum<T> { Wrapped(T) }
 
+#[rustc_layout_scalar_valid_range_start(0)]
+#[rustc_layout_scalar_valid_range_end(128)]
+#[repr(transparent)]
+pub(crate) struct NonBig(u64);
+
 #[allow(unused)]
 fn generic<T: 'static>() {
     unsafe {
@@ -29,6 +36,7 @@
 
 fn main() {
     unsafe {
+        // Things that cannot even be zero.
         let _val: ! = mem::zeroed(); //~ ERROR: does not permit zero-initialization
         let _val: ! = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
 
@@ -56,11 +64,28 @@
         let _val: Wrap<(RefPair, i32)> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
         let _val: Wrap<(RefPair, i32)> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
 
-        // Some types that should work just fine.
+        let _val: NonNull<i32> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: NonNull<i32> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        // Things that can be zero, but not uninit.
+        let _val: bool = mem::zeroed();
+        let _val: bool = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Wrap<char> = mem::zeroed();
+        let _val: Wrap<char> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: NonBig = mem::zeroed();
+        let _val: NonBig = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        // Transmute-from-0
+        let _val: &'static i32 = mem::transmute(0usize); //~ ERROR: does not permit zero-initialization
+        let _val: &'static [i32] = mem::transmute((0usize, 0usize)); //~ ERROR: does not permit zero-initialization
+        let _val: NonZeroU32 = mem::transmute(0); //~ ERROR: does not permit zero-initialization
+
+        // Some more types that should work just fine.
         let _val: Option<&'static i32> = mem::zeroed();
         let _val: Option<fn()> = mem::zeroed();
         let _val: MaybeUninit<&'static i32> = mem::zeroed();
-        let _val: bool = mem::zeroed();
         let _val: i32 = mem::zeroed();
     }
 }
diff --git a/src/test/ui/lint/uninitialized-zeroed.stderr b/src/test/ui/lint/uninitialized-zeroed.stderr
index 1b15fc2..a36a32a 100644
--- a/src/test/ui/lint/uninitialized-zeroed.stderr
+++ b/src/test/ui/lint/uninitialized-zeroed.stderr
@@ -1,5 +1,5 @@
 error: the type `&'static T` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:22:32
+  --> $DIR/uninitialized-zeroed.rs:29:32
    |
 LL |         let _val: &'static T = mem::zeroed();
    |                                ^^^^^^^^^^^^^
@@ -15,7 +15,7 @@
    = note: References must be non-null
 
 error: the type `&'static T` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:23:32
+  --> $DIR/uninitialized-zeroed.rs:30:32
    |
 LL |         let _val: &'static T = mem::uninitialized();
    |                                ^^^^^^^^^^^^^^^^^^^^
@@ -26,7 +26,7 @@
    = note: References must be non-null
 
 error: the type `Wrap<&'static T>` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:25:38
+  --> $DIR/uninitialized-zeroed.rs:32:38
    |
 LL |         let _val: Wrap<&'static T> = mem::zeroed();
    |                                      ^^^^^^^^^^^^^
@@ -35,13 +35,13 @@
    |                                      help: use `MaybeUninit<T>` instead
    |
 note: References must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:16:18
+  --> $DIR/uninitialized-zeroed.rs:18:18
    |
 LL | struct Wrap<T> { wrapped: T }
    |                  ^^^^^^^^^^
 
 error: the type `Wrap<&'static T>` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:26:38
+  --> $DIR/uninitialized-zeroed.rs:33:38
    |
 LL |         let _val: Wrap<&'static T> = mem::uninitialized();
    |                                      ^^^^^^^^^^^^^^^^^^^^
@@ -50,13 +50,13 @@
    |                                      help: use `MaybeUninit<T>` instead
    |
 note: References must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:16:18
+  --> $DIR/uninitialized-zeroed.rs:18:18
    |
 LL | struct Wrap<T> { wrapped: T }
    |                  ^^^^^^^^^^
 
 error: the type `!` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:32:23
+  --> $DIR/uninitialized-zeroed.rs:40:23
    |
 LL |         let _val: ! = mem::zeroed();
    |                       ^^^^^^^^^^^^^
@@ -67,7 +67,7 @@
    = note: The never type (`!`) has no valid value
 
 error: the type `!` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:33:23
+  --> $DIR/uninitialized-zeroed.rs:41:23
    |
 LL |         let _val: ! = mem::uninitialized();
    |                       ^^^^^^^^^^^^^^^^^^^^
@@ -78,7 +78,7 @@
    = note: The never type (`!`) has no valid value
 
 error: the type `(i32, !)` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:35:30
+  --> $DIR/uninitialized-zeroed.rs:43:30
    |
 LL |         let _val: (i32, !) = mem::zeroed();
    |                              ^^^^^^^^^^^^^
@@ -89,7 +89,7 @@
    = note: The never type (`!`) has no valid value
 
 error: the type `(i32, !)` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:36:30
+  --> $DIR/uninitialized-zeroed.rs:44:30
    |
 LL |         let _val: (i32, !) = mem::uninitialized();
    |                              ^^^^^^^^^^^^^^^^^^^^
@@ -100,7 +100,7 @@
    = note: The never type (`!`) has no valid value
 
 error: the type `Void` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:38:26
+  --> $DIR/uninitialized-zeroed.rs:46:26
    |
 LL |         let _val: Void = mem::zeroed();
    |                          ^^^^^^^^^^^^^
@@ -111,7 +111,7 @@
    = note: 0-variant enums have no valid value
 
 error: the type `Void` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:39:26
+  --> $DIR/uninitialized-zeroed.rs:47:26
    |
 LL |         let _val: Void = mem::uninitialized();
    |                          ^^^^^^^^^^^^^^^^^^^^
@@ -122,7 +122,7 @@
    = note: 0-variant enums have no valid value
 
 error: the type `&'static i32` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:41:34
+  --> $DIR/uninitialized-zeroed.rs:49:34
    |
 LL |         let _val: &'static i32 = mem::zeroed();
    |                                  ^^^^^^^^^^^^^
@@ -133,7 +133,7 @@
    = note: References must be non-null
 
 error: the type `&'static i32` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:42:34
+  --> $DIR/uninitialized-zeroed.rs:50:34
    |
 LL |         let _val: &'static i32 = mem::uninitialized();
    |                                  ^^^^^^^^^^^^^^^^^^^^
@@ -144,7 +144,7 @@
    = note: References must be non-null
 
 error: the type `Ref` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:44:25
+  --> $DIR/uninitialized-zeroed.rs:52:25
    |
 LL |         let _val: Ref = mem::zeroed();
    |                         ^^^^^^^^^^^^^
@@ -153,13 +153,13 @@
    |                         help: use `MaybeUninit<T>` instead
    |
 note: References must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:13:12
+  --> $DIR/uninitialized-zeroed.rs:15:12
    |
 LL | struct Ref(&'static i32);
    |            ^^^^^^^^^^^^
 
 error: the type `Ref` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:45:25
+  --> $DIR/uninitialized-zeroed.rs:53:25
    |
 LL |         let _val: Ref = mem::uninitialized();
    |                         ^^^^^^^^^^^^^^^^^^^^
@@ -168,13 +168,13 @@
    |                         help: use `MaybeUninit<T>` instead
    |
 note: References must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:13:12
+  --> $DIR/uninitialized-zeroed.rs:15:12
    |
 LL | struct Ref(&'static i32);
    |            ^^^^^^^^^^^^
 
 error: the type `fn()` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:47:26
+  --> $DIR/uninitialized-zeroed.rs:55:26
    |
 LL |         let _val: fn() = mem::zeroed();
    |                          ^^^^^^^^^^^^^
@@ -185,7 +185,7 @@
    = note: Function pointers must be non-null
 
 error: the type `fn()` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:48:26
+  --> $DIR/uninitialized-zeroed.rs:56:26
    |
 LL |         let _val: fn() = mem::uninitialized();
    |                          ^^^^^^^^^^^^^^^^^^^^
@@ -196,7 +196,7 @@
    = note: Function pointers must be non-null
 
 error: the type `Wrap<fn()>` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:50:32
+  --> $DIR/uninitialized-zeroed.rs:58:32
    |
 LL |         let _val: Wrap<fn()> = mem::zeroed();
    |                                ^^^^^^^^^^^^^
@@ -205,13 +205,13 @@
    |                                help: use `MaybeUninit<T>` instead
    |
 note: Function pointers must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:16:18
+  --> $DIR/uninitialized-zeroed.rs:18:18
    |
 LL | struct Wrap<T> { wrapped: T }
    |                  ^^^^^^^^^^
 
 error: the type `Wrap<fn()>` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:51:32
+  --> $DIR/uninitialized-zeroed.rs:59:32
    |
 LL |         let _val: Wrap<fn()> = mem::uninitialized();
    |                                ^^^^^^^^^^^^^^^^^^^^
@@ -220,13 +220,13 @@
    |                                help: use `MaybeUninit<T>` instead
    |
 note: Function pointers must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:16:18
+  --> $DIR/uninitialized-zeroed.rs:18:18
    |
 LL | struct Wrap<T> { wrapped: T }
    |                  ^^^^^^^^^^
 
 error: the type `WrapEnum<fn()>` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:53:36
+  --> $DIR/uninitialized-zeroed.rs:61:36
    |
 LL |         let _val: WrapEnum<fn()> = mem::zeroed();
    |                                    ^^^^^^^^^^^^^
@@ -235,13 +235,13 @@
    |                                    help: use `MaybeUninit<T>` instead
    |
 note: Function pointers must be non-null (in this enum field)
-  --> $DIR/uninitialized-zeroed.rs:17:28
+  --> $DIR/uninitialized-zeroed.rs:19:28
    |
 LL | enum WrapEnum<T> { Wrapped(T) }
    |                            ^
 
 error: the type `WrapEnum<fn()>` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:54:36
+  --> $DIR/uninitialized-zeroed.rs:62:36
    |
 LL |         let _val: WrapEnum<fn()> = mem::uninitialized();
    |                                    ^^^^^^^^^^^^^^^^^^^^
@@ -250,13 +250,13 @@
    |                                    help: use `MaybeUninit<T>` instead
    |
 note: Function pointers must be non-null (in this enum field)
-  --> $DIR/uninitialized-zeroed.rs:17:28
+  --> $DIR/uninitialized-zeroed.rs:19:28
    |
 LL | enum WrapEnum<T> { Wrapped(T) }
    |                            ^
 
 error: the type `Wrap<(RefPair, i32)>` does not permit zero-initialization
-  --> $DIR/uninitialized-zeroed.rs:56:42
+  --> $DIR/uninitialized-zeroed.rs:64:42
    |
 LL |         let _val: Wrap<(RefPair, i32)> = mem::zeroed();
    |                                          ^^^^^^^^^^^^^
@@ -265,13 +265,13 @@
    |                                          help: use `MaybeUninit<T>` instead
    |
 note: References must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:14:16
+  --> $DIR/uninitialized-zeroed.rs:16:16
    |
 LL | struct RefPair((&'static i32, i32));
    |                ^^^^^^^^^^^^^^^^^^^
 
 error: the type `Wrap<(RefPair, i32)>` does not permit being left uninitialized
-  --> $DIR/uninitialized-zeroed.rs:57:42
+  --> $DIR/uninitialized-zeroed.rs:65:42
    |
 LL |         let _val: Wrap<(RefPair, i32)> = mem::uninitialized();
    |                                          ^^^^^^^^^^^^^^^^^^^^
@@ -280,10 +280,102 @@
    |                                          help: use `MaybeUninit<T>` instead
    |
 note: References must be non-null (in this struct field)
-  --> $DIR/uninitialized-zeroed.rs:14:16
+  --> $DIR/uninitialized-zeroed.rs:16:16
    |
 LL | struct RefPair((&'static i32, i32));
    |                ^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 22 previous errors
+error: the type `std::ptr::NonNull<i32>` does not permit zero-initialization
+  --> $DIR/uninitialized-zeroed.rs:67:34
+   |
+LL |         let _val: NonNull<i32> = mem::zeroed();
+   |                                  ^^^^^^^^^^^^^
+   |                                  |
+   |                                  this code causes undefined behavior when executed
+   |                                  help: use `MaybeUninit<T>` instead
+   |
+   = note: std::ptr::NonNull<i32> must be non-null
+
+error: the type `std::ptr::NonNull<i32>` does not permit being left uninitialized
+  --> $DIR/uninitialized-zeroed.rs:68:34
+   |
+LL |         let _val: NonNull<i32> = mem::uninitialized();
+   |                                  ^^^^^^^^^^^^^^^^^^^^
+   |                                  |
+   |                                  this code causes undefined behavior when executed
+   |                                  help: use `MaybeUninit<T>` instead
+   |
+   = note: std::ptr::NonNull<i32> must be non-null
+
+error: the type `bool` does not permit being left uninitialized
+  --> $DIR/uninitialized-zeroed.rs:72:26
+   |
+LL |         let _val: bool = mem::uninitialized();
+   |                          ^^^^^^^^^^^^^^^^^^^^
+   |                          |
+   |                          this code causes undefined behavior when executed
+   |                          help: use `MaybeUninit<T>` instead
+   |
+   = note: Booleans must be `true` or `false`
+
+error: the type `Wrap<char>` does not permit being left uninitialized
+  --> $DIR/uninitialized-zeroed.rs:75:32
+   |
+LL |         let _val: Wrap<char> = mem::uninitialized();
+   |                                ^^^^^^^^^^^^^^^^^^^^
+   |                                |
+   |                                this code causes undefined behavior when executed
+   |                                help: use `MaybeUninit<T>` instead
+   |
+note: Characters must be a valid unicode codepoint (in this struct field)
+  --> $DIR/uninitialized-zeroed.rs:18:18
+   |
+LL | struct Wrap<T> { wrapped: T }
+   |                  ^^^^^^^^^^
+
+error: the type `NonBig` does not permit being left uninitialized
+  --> $DIR/uninitialized-zeroed.rs:78:28
+   |
+LL |         let _val: NonBig = mem::uninitialized();
+   |                            ^^^^^^^^^^^^^^^^^^^^
+   |                            |
+   |                            this code causes undefined behavior when executed
+   |                            help: use `MaybeUninit<T>` instead
+   |
+   = note: NonBig must be initialized inside its custom valid range
+
+error: the type `&'static i32` does not permit zero-initialization
+  --> $DIR/uninitialized-zeroed.rs:81:34
+   |
+LL |         let _val: &'static i32 = mem::transmute(0usize);
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^
+   |                                  |
+   |                                  this code causes undefined behavior when executed
+   |                                  help: use `MaybeUninit<T>` instead
+   |
+   = note: References must be non-null
+
+error: the type `&'static [i32]` does not permit zero-initialization
+  --> $DIR/uninitialized-zeroed.rs:82:36
+   |
+LL |         let _val: &'static [i32] = mem::transmute((0usize, 0usize));
+   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                                    |
+   |                                    this code causes undefined behavior when executed
+   |                                    help: use `MaybeUninit<T>` instead
+   |
+   = note: References must be non-null
+
+error: the type `std::num::NonZeroU32` does not permit zero-initialization
+  --> $DIR/uninitialized-zeroed.rs:83:32
+   |
+LL |         let _val: NonZeroU32 = mem::transmute(0);
+   |                                ^^^^^^^^^^^^^^^^^
+   |                                |
+   |                                this code causes undefined behavior when executed
+   |                                help: use `MaybeUninit<T>` instead
+   |
+   = note: std::num::NonZeroU32 must be non-null
+
+error: aborting due to 30 previous errors
 
diff --git a/src/test/ui/methods/method-projection.rs b/src/test/ui/methods/method-projection.rs
index cf33d53..21d983f 100644
--- a/src/test/ui/methods/method-projection.rs
+++ b/src/test/ui/methods/method-projection.rs
@@ -2,9 +2,6 @@
 // Test that we can use method notation to call methods based on a
 // projection bound from a trait. Issue #20469.
 
-///////////////////////////////////////////////////////////////////////////
-
-
 trait MakeString {
     fn make_string(&self) -> String;
 }
@@ -21,8 +18,6 @@
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 trait Foo {
     type F: MakeString;
 
@@ -33,8 +28,6 @@
     f.get().make_string()
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct SomeStruct {
     field: isize,
 }
@@ -47,8 +40,6 @@
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct SomeOtherStruct {
     field: usize,
 }
diff --git a/src/test/ui/proc-macro/auxiliary/gen-macro-rules.rs b/src/test/ui/proc-macro/auxiliary/gen-macro-rules.rs
new file mode 100644
index 0000000..d4b67d6
--- /dev/null
+++ b/src/test/ui/proc-macro/auxiliary/gen-macro-rules.rs
@@ -0,0 +1,12 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(repro)]
+pub fn proc_macro_hack_expr(_input: TokenStream) -> TokenStream {
+    "macro_rules! m {()=>{}}".parse().unwrap()
+}
diff --git a/src/test/ui/proc-macro/gen-macro-rules.rs b/src/test/ui/proc-macro/gen-macro-rules.rs
new file mode 100644
index 0000000..13ad27f
--- /dev/null
+++ b/src/test/ui/proc-macro/gen-macro-rules.rs
@@ -0,0 +1,13 @@
+// Derive macros can generate `macro_rules` items, regression test for issue #63651.
+
+// check-pass
+// aux-build:gen-macro-rules.rs
+
+extern crate gen_macro_rules as repro;
+
+#[derive(repro::repro)]
+pub struct S;
+
+m!(); // OK
+
+fn main() {}
diff --git a/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.nll.stderr b/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.nll.stderr
index 5028663..eed9934 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.nll.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.nll.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:35:12
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:30:12
    |
 LL | fn with_assoc<'a,'b>() {
    |               -- -- lifetime `'b` defined here
@@ -10,7 +10,7 @@
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'b` must outlive `'a`
 
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:57:12
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:50:12
    |
 LL | fn with_assoc_sub<'a,'b>() {
    |                   -- -- lifetime `'b` defined here
diff --git a/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.stderr b/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.stderr
index d833018..ed58009 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-hrtb.migrate.stderr
@@ -1,33 +1,33 @@
 error[E0491]: in type `&'a WithHrAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:35:12
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:30:12
    |
 LL |     let _: &'a WithHrAssoc<TheType<'b>> = loop { };
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 32:15
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:32:15
+note: the pointer is valid for the lifetime 'a as defined on the function body at 27:15
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:27:15
    |
 LL | fn with_assoc<'a,'b>() {
    |               ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 32:18
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:32:18
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 27:18
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:27:18
    |
 LL | fn with_assoc<'a,'b>() {
    |                  ^^
 
 error[E0491]: in type `&'a WithHrAssocSub<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:57:12
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:50:12
    |
 LL |     let _: &'a WithHrAssocSub<TheType<'b>> = loop { };
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 53:19
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:53:19
+note: the pointer is valid for the lifetime 'a as defined on the function body at 46:19
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:46:19
    |
 LL | fn with_assoc_sub<'a,'b>() {
    |                   ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 53:22
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:53:22
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 46:22
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:46:22
    |
 LL | fn with_assoc_sub<'a,'b>() {
    |                      ^^
diff --git a/src/test/ui/regions/regions-outlives-projection-container-hrtb.nll.stderr b/src/test/ui/regions/regions-outlives-projection-container-hrtb.nll.stderr
index 5028663..eed9934 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-hrtb.nll.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-hrtb.nll.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:35:12
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:30:12
    |
 LL | fn with_assoc<'a,'b>() {
    |               -- -- lifetime `'b` defined here
@@ -10,7 +10,7 @@
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'b` must outlive `'a`
 
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container-hrtb.rs:57:12
+  --> $DIR/regions-outlives-projection-container-hrtb.rs:50:12
    |
 LL | fn with_assoc_sub<'a,'b>() {
    |                   -- -- lifetime `'b` defined here
diff --git a/src/test/ui/regions/regions-outlives-projection-container-hrtb.rs b/src/test/ui/regions/regions-outlives-projection-container-hrtb.rs
index 407a4fd..cee7411 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-hrtb.rs
+++ b/src/test/ui/regions/regions-outlives-projection-container-hrtb.rs
@@ -6,9 +6,6 @@
 
 #![allow(dead_code)]
 
-
-///////////////////////////////////////////////////////////////////////////
-
 pub trait TheTrait<'b> {
     type TheAssocType;
 }
@@ -21,8 +18,6 @@
     type TheAssocType = &'b ();
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 pub struct WithHrAssoc<T>
     where for<'a> T : TheTrait<'a>
 {
@@ -37,8 +32,6 @@
     //[nll]~^^ ERROR lifetime may not live long enough
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 pub trait TheSubTrait : for<'a> TheTrait<'a> {
 }
 
diff --git a/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.nll.stderr b/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.nll.stderr
index 880fe17..8c54d8d 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.nll.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.nll.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container-wc.rs:37:12
+  --> $DIR/regions-outlives-projection-container-wc.rs:33:12
    |
 LL | fn with_assoc<'a,'b>() {
    |               -- -- lifetime `'b` defined here
diff --git a/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.stderr b/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.stderr
index 9e31065..152e6c5 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-wc.migrate.stderr
@@ -1,16 +1,16 @@
 error[E0491]: in type `&'a WithAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container-wc.rs:37:12
+  --> $DIR/regions-outlives-projection-container-wc.rs:33:12
    |
 LL |     let _: &'a WithAssoc<TheType<'b>> = loop { };
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 31:15
-  --> $DIR/regions-outlives-projection-container-wc.rs:31:15
+note: the pointer is valid for the lifetime 'a as defined on the function body at 27:15
+  --> $DIR/regions-outlives-projection-container-wc.rs:27:15
    |
 LL | fn with_assoc<'a,'b>() {
    |               ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 31:18
-  --> $DIR/regions-outlives-projection-container-wc.rs:31:18
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 27:18
+  --> $DIR/regions-outlives-projection-container-wc.rs:27:18
    |
 LL | fn with_assoc<'a,'b>() {
    |                  ^^
diff --git a/src/test/ui/regions/regions-outlives-projection-container-wc.nll.stderr b/src/test/ui/regions/regions-outlives-projection-container-wc.nll.stderr
index 880fe17..8c54d8d 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-wc.nll.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-wc.nll.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container-wc.rs:37:12
+  --> $DIR/regions-outlives-projection-container-wc.rs:33:12
    |
 LL | fn with_assoc<'a,'b>() {
    |               -- -- lifetime `'b` defined here
diff --git a/src/test/ui/regions/regions-outlives-projection-container-wc.rs b/src/test/ui/regions/regions-outlives-projection-container-wc.rs
index 5037ea5..99965f3 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-wc.rs
+++ b/src/test/ui/regions/regions-outlives-projection-container-wc.rs
@@ -8,8 +8,6 @@
 
 #![allow(dead_code)]
 
-///////////////////////////////////////////////////////////////////////////
-
 pub trait TheTrait {
     type TheAssocType;
 }
@@ -22,8 +20,6 @@
     type TheAssocType = &'b ();
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 pub struct WithAssoc<T> where T : TheTrait {
     m: [T; 0]
 }
diff --git a/src/test/ui/regions/regions-outlives-projection-container.nll.stderr b/src/test/ui/regions/regions-outlives-projection-container.nll.stderr
index ef87d02..2cf6e24 100644
--- a/src/test/ui/regions/regions-outlives-projection-container.nll.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container.nll.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container.rs:40:13
+  --> $DIR/regions-outlives-projection-container.rs:36:13
    |
 LL | fn with_assoc<'a,'b>() {
    |               -- -- lifetime `'b` defined here
@@ -10,7 +10,7 @@
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'b` must outlive `'a`
 
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container.rs:58:13
+  --> $DIR/regions-outlives-projection-container.rs:54:13
    |
 LL | fn without_assoc<'a,'b>() {
    |                  -- -- lifetime `'b` defined here
@@ -21,7 +21,7 @@
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'b` must outlive `'a`
 
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container.rs:67:5
+  --> $DIR/regions-outlives-projection-container.rs:63:5
    |
 LL | fn call_with_assoc<'a,'b>() {
    |                    -- -- lifetime `'b` defined here
@@ -32,7 +32,7 @@
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ requires that `'b` must outlive `'a`
 
 error: lifetime may not live long enough
-  --> $DIR/regions-outlives-projection-container.rs:74:5
+  --> $DIR/regions-outlives-projection-container.rs:70:5
    |
 LL | fn call_without_assoc<'a,'b>() {
    |                       -- -- lifetime `'b` defined here
diff --git a/src/test/ui/regions/regions-outlives-projection-container.rs b/src/test/ui/regions/regions-outlives-projection-container.rs
index 78305c0..3afc600 100644
--- a/src/test/ui/regions/regions-outlives-projection-container.rs
+++ b/src/test/ui/regions/regions-outlives-projection-container.rs
@@ -5,8 +5,6 @@
 #![allow(dead_code)]
 #![feature(rustc_attrs)]
 
-///////////////////////////////////////////////////////////////////////////
-
 pub trait TheTrait {
     type TheAssocType;
 }
@@ -19,8 +17,6 @@
     type TheAssocType = &'b ();
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 pub struct WithAssoc<T:TheTrait> {
     m: [T; 0]
 }
diff --git a/src/test/ui/regions/regions-outlives-projection-container.stderr b/src/test/ui/regions/regions-outlives-projection-container.stderr
index b50347a..3c1a98a 100644
--- a/src/test/ui/regions/regions-outlives-projection-container.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container.stderr
@@ -1,67 +1,67 @@
 error[E0491]: in type `&'a WithAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container.rs:40:13
+  --> $DIR/regions-outlives-projection-container.rs:36:13
    |
 LL |     let _x: &'a WithAssoc<TheType<'b>> = loop { };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 32:15
-  --> $DIR/regions-outlives-projection-container.rs:32:15
+note: the pointer is valid for the lifetime 'a as defined on the function body at 28:15
+  --> $DIR/regions-outlives-projection-container.rs:28:15
    |
 LL | fn with_assoc<'a,'b>() {
    |               ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 32:18
-  --> $DIR/regions-outlives-projection-container.rs:32:18
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 28:18
+  --> $DIR/regions-outlives-projection-container.rs:28:18
    |
 LL | fn with_assoc<'a,'b>() {
    |                  ^^
 
 error[E0491]: in type `&'a WithoutAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container.rs:58:13
+  --> $DIR/regions-outlives-projection-container.rs:54:13
    |
 LL |     let _x: &'a WithoutAssoc<TheType<'b>> = loop { };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 54:18
-  --> $DIR/regions-outlives-projection-container.rs:54:18
+note: the pointer is valid for the lifetime 'a as defined on the function body at 50:18
+  --> $DIR/regions-outlives-projection-container.rs:50:18
    |
 LL | fn without_assoc<'a,'b>() {
    |                  ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 54:21
-  --> $DIR/regions-outlives-projection-container.rs:54:21
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 50:21
+  --> $DIR/regions-outlives-projection-container.rs:50:21
    |
 LL | fn without_assoc<'a,'b>() {
    |                     ^^
 
 error[E0491]: in type `&'a WithAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container.rs:67:12
+  --> $DIR/regions-outlives-projection-container.rs:63:12
    |
 LL |     call::<&'a WithAssoc<TheType<'b>>>();
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 62:20
-  --> $DIR/regions-outlives-projection-container.rs:62:20
+note: the pointer is valid for the lifetime 'a as defined on the function body at 58:20
+  --> $DIR/regions-outlives-projection-container.rs:58:20
    |
 LL | fn call_with_assoc<'a,'b>() {
    |                    ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 62:23
-  --> $DIR/regions-outlives-projection-container.rs:62:23
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 58:23
+  --> $DIR/regions-outlives-projection-container.rs:58:23
    |
 LL | fn call_with_assoc<'a,'b>() {
    |                       ^^
 
 error[E0491]: in type `&'a WithoutAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container.rs:74:12
+  --> $DIR/regions-outlives-projection-container.rs:70:12
    |
 LL |     call::<&'a WithoutAssoc<TheType<'b>>>();
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: the pointer is valid for the lifetime 'a as defined on the function body at 71:23
-  --> $DIR/regions-outlives-projection-container.rs:71:23
+note: the pointer is valid for the lifetime 'a as defined on the function body at 67:23
+  --> $DIR/regions-outlives-projection-container.rs:67:23
    |
 LL | fn call_without_assoc<'a,'b>() {
    |                       ^^
-note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 71:26
-  --> $DIR/regions-outlives-projection-container.rs:71:26
+note: but the referenced data is only valid for the lifetime 'b as defined on the function body at 67:26
+  --> $DIR/regions-outlives-projection-container.rs:67:26
    |
 LL | fn call_without_assoc<'a,'b>() {
    |                          ^^
diff --git a/src/test/ui/rfc1598-generic-associated-types/shadowing.rs b/src/test/ui/rfc1598-generic-associated-types/shadowing.rs
index 0349263..f5197fd 100644
--- a/src/test/ui/rfc1598-generic-associated-types/shadowing.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/shadowing.rs
@@ -1,12 +1,9 @@
+#![allow(incomplete_features)]
 #![feature(generic_associated_types)]
 
-//FIXME(#44265): The lifetime shadowing and type parameter shadowing
-// should cause an error. Now it compiles (erroneously) and this will be addressed
-// by a future PR. Then remove the following:
-// build-pass (FIXME(62277): could be check-pass?)
-
 trait Shadow<'a> {
-    type Bar<'a>; // Error: shadowed lifetime
+    //FIXME(#44265): The lifetime parameter shadowing should cause an error.
+    type Bar<'a>;
 }
 
 trait NoShadow<'a> {
@@ -14,11 +11,12 @@
 }
 
 impl<'a> NoShadow<'a> for &'a u32 {
-    type Bar<'a> = i32; // Error: shadowed lifetime
+    //FIXME(#44265): The lifetime parameter shadowing should cause an error.
+    type Bar<'a> = i32;
 }
 
 trait ShadowT<T> {
-    type Bar<T>; // Error: shadowed type parameter
+    type Bar<T>; //~ ERROR the name `T` is already used
 }
 
 trait NoShadowT<T> {
@@ -26,7 +24,7 @@
 }
 
 impl<T> NoShadowT<T> for Option<T> {
-    type Bar<T> = i32; // Error: shadowed type parameter
+    type Bar<T> = i32; //~ ERROR the name `T` is already used
 }
 
 fn main() {}
diff --git a/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr b/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr
index 9526df2..a06c635 100644
--- a/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr
@@ -1,8 +1,19 @@
-warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
-  --> $DIR/shadowing.rs:1:12
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
+  --> $DIR/shadowing.rs:19:14
    |
-LL | #![feature(generic_associated_types)]
-   |            ^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `#[warn(incomplete_features)]` on by default
+LL | trait ShadowT<T> {
+   |               - first use of `T`
+LL |     type Bar<T>;
+   |              ^ already used
 
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
+  --> $DIR/shadowing.rs:27:14
+   |
+LL | impl<T> NoShadowT<T> for Option<T> {
+   |      - first use of `T`
+LL |     type Bar<T> = i32;
+   |              ^ already used
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0403`.
diff --git a/src/test/ui/shadowed/shadowed-type-parameter.rs b/src/test/ui/shadowed/shadowed-type-parameter.rs
index ba9f3ab..e74620f 100644
--- a/src/test/ui/shadowed/shadowed-type-parameter.rs
+++ b/src/test/ui/shadowed/shadowed-type-parameter.rs
@@ -6,7 +6,7 @@
 
 impl<T> Foo<T> {
     fn shadow_in_method<T>(&self) {}
-    //~^ ERROR type parameter `T` shadows another type parameter
+    //~^ ERROR the name `T` is already used
 
     fn not_shadow_in_item<U>(&self) {
         struct Bar<T, U>(T,U); // not a shadow, separate item
@@ -18,10 +18,10 @@
     fn dummy(&self) -> T;
 
     fn shadow_in_required<T>(&self);
-    //~^ ERROR type parameter `T` shadows another type parameter
+    //~^ ERROR the name `T` is already used
 
     fn shadow_in_provided<T>(&self) {}
-    //~^ ERROR type parameter `T` shadows another type parameter
+    //~^ ERROR the name `T` is already used
 
     fn not_shadow_in_required<U>(&self);
     fn not_shadow_in_provided<U>(&self) {}
diff --git a/src/test/ui/shadowed/shadowed-type-parameter.stderr b/src/test/ui/shadowed/shadowed-type-parameter.stderr
index 6b4d1fa..0ea82f9 100644
--- a/src/test/ui/shadowed/shadowed-type-parameter.stderr
+++ b/src/test/ui/shadowed/shadowed-type-parameter.stderr
@@ -1,29 +1,29 @@
-error[E0194]: type parameter `T` shadows another type parameter of the same name
-  --> $DIR/shadowed-type-parameter.rs:20:27
-   |
-LL | trait Bar<T> {
-   |           - first `T` declared here
-...
-LL |     fn shadow_in_required<T>(&self);
-   |                           ^ shadows another type parameter
-
-error[E0194]: type parameter `T` shadows another type parameter of the same name
-  --> $DIR/shadowed-type-parameter.rs:23:27
-   |
-LL | trait Bar<T> {
-   |           - first `T` declared here
-...
-LL |     fn shadow_in_provided<T>(&self) {}
-   |                           ^ shadows another type parameter
-
-error[E0194]: type parameter `T` shadows another type parameter of the same name
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
   --> $DIR/shadowed-type-parameter.rs:8:25
    |
 LL | impl<T> Foo<T> {
-   |      - first `T` declared here
+   |      - first use of `T`
 LL |     fn shadow_in_method<T>(&self) {}
-   |                         ^ shadows another type parameter
+   |                         ^ already used
+
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
+  --> $DIR/shadowed-type-parameter.rs:20:27
+   |
+LL | trait Bar<T> {
+   |           - first use of `T`
+...
+LL |     fn shadow_in_required<T>(&self);
+   |                           ^ already used
+
+error[E0403]: the name `T` is already used for a generic parameter in this item's generic parameters
+  --> $DIR/shadowed-type-parameter.rs:23:27
+   |
+LL | trait Bar<T> {
+   |           - first use of `T`
+...
+LL |     fn shadow_in_provided<T>(&self) {}
+   |                           ^ already used
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0194`.
+For more information about this error, try `rustc --explain E0403`.
diff --git a/src/test/ui/specialization/defaultimpl/specialization-no-default.rs b/src/test/ui/specialization/defaultimpl/specialization-no-default.rs
index 7ea79a9..37005f83 100644
--- a/src/test/ui/specialization/defaultimpl/specialization-no-default.rs
+++ b/src/test/ui/specialization/defaultimpl/specialization-no-default.rs
@@ -3,9 +3,7 @@
 // Check a number of scenarios in which one impl tries to override another,
 // without correctly using `default`.
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 1: one layer of specialization, multiple methods, missing `default`
-////////////////////////////////////////////////////////////////////////////////
 
 trait Foo {
     fn foo(&self);
@@ -25,9 +23,7 @@
     fn bar(&self) {} //~ ERROR E0520
 }
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 2: one layer of specialization, missing `default` on associated type
-////////////////////////////////////////////////////////////////////////////////
 
 trait Bar {
     type T;
@@ -41,9 +37,7 @@
     type T = (); //~ ERROR E0520
 }
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 3a: multiple layers of specialization, missing interior `default`
-////////////////////////////////////////////////////////////////////////////////
 
 trait Baz {
     fn baz(&self);
@@ -61,10 +55,8 @@
     fn baz(&self) {} //~ ERROR E0520
 }
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 3b: multiple layers of specialization, missing interior `default`,
 // redundant `default` in bottom layer.
-////////////////////////////////////////////////////////////////////////////////
 
 trait Redundant {
     fn redundant(&self);
diff --git a/src/test/ui/specialization/defaultimpl/specialization-no-default.stderr b/src/test/ui/specialization/defaultimpl/specialization-no-default.stderr
index 91690f6..13636b2 100644
--- a/src/test/ui/specialization/defaultimpl/specialization-no-default.stderr
+++ b/src/test/ui/specialization/defaultimpl/specialization-no-default.stderr
@@ -1,5 +1,5 @@
 error[E0520]: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:22:5
+  --> $DIR/specialization-no-default.rs:20:5
    |
 LL | / impl<T> Foo for T {
 LL | |     fn foo(&self) {}
@@ -13,7 +13,7 @@
    = note: to specialize, `foo` in the parent `impl` must be marked `default`
 
 error[E0520]: `bar` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:25:5
+  --> $DIR/specialization-no-default.rs:23:5
    |
 LL | / impl<T> Foo for T {
 LL | |     fn foo(&self) {}
@@ -27,7 +27,7 @@
    = note: to specialize, `bar` in the parent `impl` must be marked `default`
 
 error[E0520]: `T` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:41:5
+  --> $DIR/specialization-no-default.rs:37:5
    |
 LL | / impl<T> Bar for T {
 LL | |     type T = u8;
@@ -40,7 +40,7 @@
    = note: to specialize, `T` in the parent `impl` must be marked `default`
 
 error[E0520]: `baz` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:61:5
+  --> $DIR/specialization-no-default.rs:55:5
    |
 LL | / impl<T: Clone> Baz for T {
 LL | |     fn baz(&self) {}
@@ -53,7 +53,7 @@
    = note: to specialize, `baz` in the parent `impl` must be marked `default`
 
 error[E0520]: `redundant` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:82:5
+  --> $DIR/specialization-no-default.rs:74:5
    |
 LL | / impl<T: Clone> Redundant for T {
 LL | |     fn redundant(&self) {}
diff --git a/src/test/ui/specialization/specialization-no-default.rs b/src/test/ui/specialization/specialization-no-default.rs
index 29afbbd9..57346b2 100644
--- a/src/test/ui/specialization/specialization-no-default.rs
+++ b/src/test/ui/specialization/specialization-no-default.rs
@@ -3,9 +3,7 @@
 // Check a number of scenarios in which one impl tries to override another,
 // without correctly using `default`.
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 1: one layer of specialization, multiple methods, missing `default`
-////////////////////////////////////////////////////////////////////////////////
 
 trait Foo {
     fn foo(&self);
@@ -25,9 +23,7 @@
     fn bar(&self) {} //~ ERROR E0520
 }
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 2: one layer of specialization, missing `default` on associated type
-////////////////////////////////////////////////////////////////////////////////
 
 trait Bar {
     type T;
@@ -41,9 +37,7 @@
     type T = (); //~ ERROR E0520
 }
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 3a: multiple layers of specialization, missing interior `default`
-////////////////////////////////////////////////////////////////////////////////
 
 trait Baz {
     fn baz(&self);
@@ -61,10 +55,8 @@
     fn baz(&self) {} //~ ERROR E0520
 }
 
-////////////////////////////////////////////////////////////////////////////////
 // Test 3b: multiple layers of specialization, missing interior `default`,
 // redundant `default` in bottom layer.
-////////////////////////////////////////////////////////////////////////////////
 
 trait Redundant {
     fn redundant(&self);
diff --git a/src/test/ui/specialization/specialization-no-default.stderr b/src/test/ui/specialization/specialization-no-default.stderr
index c39986d..992e9ab 100644
--- a/src/test/ui/specialization/specialization-no-default.stderr
+++ b/src/test/ui/specialization/specialization-no-default.stderr
@@ -1,5 +1,5 @@
 error[E0520]: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:22:5
+  --> $DIR/specialization-no-default.rs:20:5
    |
 LL | / impl<T> Foo for T {
 LL | |     fn foo(&self) {}
@@ -13,7 +13,7 @@
    = note: to specialize, `foo` in the parent `impl` must be marked `default`
 
 error[E0520]: `bar` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:25:5
+  --> $DIR/specialization-no-default.rs:23:5
    |
 LL | / impl<T> Foo for T {
 LL | |     fn foo(&self) {}
@@ -27,7 +27,7 @@
    = note: to specialize, `bar` in the parent `impl` must be marked `default`
 
 error[E0520]: `T` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:41:5
+  --> $DIR/specialization-no-default.rs:37:5
    |
 LL | / impl<T> Bar for T {
 LL | |     type T = u8;
@@ -40,7 +40,7 @@
    = note: to specialize, `T` in the parent `impl` must be marked `default`
 
 error[E0520]: `baz` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:61:5
+  --> $DIR/specialization-no-default.rs:55:5
    |
 LL | / impl<T: Clone> Baz for T {
 LL | |     fn baz(&self) {}
@@ -53,7 +53,7 @@
    = note: to specialize, `baz` in the parent `impl` must be marked `default`
 
 error[E0520]: `redundant` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:82:5
+  --> $DIR/specialization-no-default.rs:74:5
    |
 LL | / impl<T: Clone> Redundant for T {
 LL | |     fn redundant(&self) {}
diff --git a/src/test/ui/traits/traits-conditional-model-fn.rs b/src/test/ui/traits/traits-conditional-model-fn.rs
index 27ce6d9..afdfb96 100644
--- a/src/test/ui/traits/traits-conditional-model-fn.rs
+++ b/src/test/ui/traits/traits-conditional-model-fn.rs
@@ -14,8 +14,6 @@
 use std::rc::Rc;
 use std::cell::Cell;
 
-///////////////////////////////////////////////////////////////////////////
-
 struct SomeGoableThing {
     counter: Rc<Cell<isize>>
 }
@@ -26,8 +24,6 @@
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 struct SomeGoOnceableThing {
     counter: Rc<Cell<isize>>
 }
@@ -38,8 +34,6 @@
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-
 fn main() {
     let counter = Rc::new(Cell::new(0));
     let mut x = SomeGoableThing { counter: counter.clone() };