eddyb's changes for DST coercions

+ lots of rebasing

Author: Nick Cameron

src/liballoc/boxed.rs

@@ -62,6 +62,11 @@ use core::ops::{Deref, DerefMut};
 use core::ptr::{Unique};
 use core::raw::{TraitObject};
 
+#[cfg(not(stage0))] // SNAP c64d671
+use core::marker::Unsize;
+#[cfg(not(stage0))] // SNAP c64d671
+use core::ops::CoerceUnsized;
+
 /// A value that represents the heap. This is the default place that the `box`
 /// keyword allocates into when no place is supplied.
 ///
@@ -390,3 +395,6 @@ impl<'a,A,R> FnOnce<A> for Box<FnBox<A,Output=R>+Send+'a> {
         self.call_box(args)
     }
 }
+
+#[cfg(not(stage0))] // SNAP c64d671
+impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<Box<U>> for Box<T> {}

src/liballoc/rc.rs

@@ -173,9 +173,9 @@ use core::intrinsics::assume;
 use heap::deallocate;
 
 struct RcBox<T> {
-    value: T,
     strong: Cell<usize>,
-    weak: Cell<usize>
+    weak: Cell<usize>,
+    value: T
 }
 
 /// A reference-counted pointer type over an immutable value.

src/libcore/intrinsics.rs

@@ -193,6 +193,13 @@ extern "rust-intrinsic" {
     pub fn min_align_of<T>() -> usize;
     pub fn pref_align_of<T>() -> usize;
 
+    #[cfg(not(stage0))]
+    pub fn size_of_val<T: ?Sized>(_: &T) -> usize;
+    #[cfg(not(stage0))]
+    pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
+    #[cfg(not(stage0))]
+    pub fn drop_in_place<T: ?Sized>(_: *mut T);
+
     /// Gets a static string slice containing the name of a type.
     pub fn type_name<T: ?Sized>() -> &'static str;
 

src/libcore/marker.rs

@@ -53,6 +53,14 @@ pub trait Sized {
     // Empty.
 }
 
+/// Types that can be "unsized" to a dynamically sized type.
+#[unstable(feature = "core")]
+#[cfg(not(stage0))] // SNAP c64d671
+#[lang="unsize"]
+pub trait Unsize<T> {
+    // Empty.
+}
+
 /// Types that can be copied by simply copying bits (i.e. `memcpy`).
 ///
 /// By default, variable bindings have 'move semantics.' In other

src/libcore/mem.rs

@@ -86,6 +86,22 @@ pub fn size_of<T>() -> usize {
     unsafe { intrinsics::size_of::<T>() }
 }
 
+/// Returns the size of the type that `val` points to in bytes.
+///
+/// # Examples
+///
+/// ```
+/// use std::mem;
+///
+/// assert_eq!(4, mem::size_of_val(&5i32));
+/// ```
+#[cfg(not(stage0))] // SNAP c64d671
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn size_of_val<T: ?Sized>(val: &T) -> usize {
+    unsafe { intrinsics::size_of_val(val) }
+}
+
 /// Returns the size of the type that `_val` points to in bytes.
 ///
 /// # Examples
@@ -95,6 +111,7 @@ pub fn size_of<T>() -> usize {
 ///
 /// assert_eq!(4, mem::size_of_val(&5i32));
 /// ```
+#[cfg(stage0)] // SNAP c64d671
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn size_of_val<T>(_val: &T) -> usize {
@@ -118,6 +135,22 @@ pub fn min_align_of<T>() -> usize {
     unsafe { intrinsics::min_align_of::<T>() }
 }
 
+/// Returns the ABI-required minimum alignment of the type of the value that `val` points to
+///
+/// # Examples
+///
+/// ```
+/// use std::mem;
+///
+/// assert_eq!(4, mem::min_align_of_val(&5i32));
+/// ```
+#[cfg(not(stage0))] // SNAP c64d671
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn min_align_of_val<T: ?Sized>(val: &T) -> usize {
+    unsafe { intrinsics::min_align_of_val(val) }
+}
+
 /// Returns the ABI-required minimum alignment of the type of the value that `_val` points to
 ///
 /// # Examples
@@ -127,6 +160,7 @@ pub fn min_align_of<T>() -> usize {
 ///
 /// assert_eq!(4, mem::min_align_of_val(&5i32));
 /// ```
+#[cfg(stage0)] // SNAP c64d671
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn min_align_of_val<T>(_val: &T) -> usize {

src/libcore/nonzero.rs

@@ -12,6 +12,8 @@
 
 use marker::Sized;
 use ops::Deref;
+#[cfg(not(stage0))] // SNAP c64d671
+use ops::CoerceUnsized;
 
 /// Unsafe trait to indicate what types are usable with the NonZero struct
 pub unsafe trait Zeroable {}
@@ -54,3 +56,6 @@ impl<T: Zeroable> Deref for NonZero<T> {
         inner
     }
 }
+
+#[cfg(not(stage0))] // SNAP c64d671
+impl<T: Zeroable+CoerceUnsized<U>, U: Zeroable> CoerceUnsized<NonZero<U>> for NonZero<T> {}

src/libcore/ops.rs

@@ -70,6 +70,9 @@
 use marker::Sized;
 use fmt;
 
+#[cfg(not(stage0))] // SNAP c64d671
+use marker::Unsize;
+
 /// The `Drop` trait is used to run some code when a value goes out of scope. This
 /// is sometimes called a 'destructor'.
 ///
@@ -1207,3 +1210,34 @@ mod impls {
         }
     }
 }
+
+/// Trait that indicates that this is a pointer or a wrapper for one,
+/// where unsizing can be performed on the pointee.
+#[unstable(feature = "core")]
+#[cfg(not(stage0))] // SNAP c64d671
+#[lang="coerce_unsized"]
+pub trait CoerceUnsized<T> {
+    // Empty.
+}
+
+#[cfg(not(stage0))] // SNAP c64d671
+impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a mut U> for &'a mut T {}
+#[cfg(not(stage0))] // SNAP c64d671
+impl<'a, 'b: 'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b mut T {}
+#[cfg(not(stage0))] // SNAP c64d671
+impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for &'a mut T {}
+#[cfg(not(stage0))] // SNAP c64d671
+impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a mut T {}
+
+#[cfg(not(stage0))] // SNAP c64d671
+impl<'a, 'b: 'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
+#[cfg(not(stage0))] // SNAP c64d671
+impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a T {}
+
+#[cfg(not(stage0))] // SNAP c64d671
+impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
+#[cfg(not(stage0))] // SNAP c64d671
+impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *mut T {}
+
+#[cfg(not(stage0))] // SNAP c64d671
+impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}

src/librustc/diagnostics.rs

@@ -807,6 +807,9 @@ register_diagnostics! {
     E0017,
     E0019,
     E0022,
+    E0038,
+    E0079, // enum variant: expected signed integer constant
+    E0080, // enum variant: constant evaluation error
     E0109,
     E0110,
     E0134,

src/librustc/metadata/common.rs

@@ -259,3 +259,5 @@ pub const tag_codemap_filemap: usize = 0xa2;
 pub const tag_item_super_predicates: usize = 0xa3;
 
 pub const tag_defaulted_trait: usize = 0xa4;
+
+pub const tag_impl_coerce_unsized_kind: usize = 0xa5;

src/librustc/metadata/csearch.rs

@@ -279,6 +279,14 @@ pub fn get_impl_polarity<'tcx>(tcx: &ty::ctxt<'tcx>,
     decoder::get_impl_polarity(&*cdata, def.node)
 }
 
+pub fn get_custom_coerce_unsized_kind<'tcx>(tcx: &ty::ctxt<'tcx>,
+                                            def: ast::DefId)
+                                            -> Option<ty::CustomCoerceUnsized> {
+    let cstore = &tcx.sess.cstore;
+    let cdata = cstore.get_crate_data(def.krate);
+    decoder::get_custom_coerce_unsized_kind(&*cdata, def.node)
+}
+
 // Given a def_id for an impl, return the trait it implements,
 // if there is one.
 pub fn get_impl_trait<'tcx>(tcx: &ty::ctxt<'tcx>,