rollup merge of #22286: nikomatsakis/variance-4b

Conflicts:
	src/librustc/middle/infer/combine.rs
	src/librustc_typeck/check/wf.rs

4 files changed, 52 insertions, 33 deletions

diff --git a/src/libstd/collections/hash/state.rs b/src/libstd/collections/hash/state.rs
index 79e01304fb8..7e6dd45b51e 100644
--- a/src/libstd/collections/hash/state.rs
+++ b/src/libstd/collections/hash/state.rs
@@ -11,6 +11,7 @@
 use clone::Clone;
 use default::Default;
 use hash;
+use marker;
 
 /// A trait representing stateful hashes which can be used to hash keys in a
 /// `HashMap`.
@@ -37,7 +38,7 @@ pub trait HashState {
 ///
 /// This struct has is 0-sized and does not need construction.
 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
-pub struct DefaultState<H>;
+pub struct DefaultState<H>(marker::PhantomData<H>);
 
 impl<H: Default + hash::Hasher> HashState for DefaultState<H> {
     type Hasher = H;
@@ -45,9 +46,9 @@ impl<H: Default + hash::Hasher> HashState for DefaultState<H> {
 }
 
 impl<H> Clone for DefaultState<H> {
-    fn clone(&self) -> DefaultState<H> { DefaultState }
+    fn clone(&self) -> DefaultState<H> { DefaultState(marker::PhantomData) }
 }
 
 impl<H> Default for DefaultState<H> {
-    fn default() -> DefaultState<H> { DefaultState }
+    fn default() -> DefaultState<H> { DefaultState(marker::PhantomData) }
 }
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index 7114da93ea0..f301f6db92f 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -23,8 +23,8 @@ use num::{Int, UnsignedInt};
 use ops::{Deref, DerefMut, Drop};
 use option::Option;
 use option::Option::{Some, None};
-use ptr::{self, PtrExt, copy_nonoverlapping_memory, zero_memory};
-use rt::heap::{allocate, deallocate};
+use ptr::{self, PtrExt, copy_nonoverlapping_memory, Unique, zero_memory};
+use rt::heap::{allocate, deallocate, EMPTY};
 use collections::hash_state::HashState;
 
 const EMPTY_BUCKET: u64 = 0u64;
@@ -69,10 +69,11 @@ const EMPTY_BUCKET: u64 = 0u64;
 pub struct RawTable<K, V> {
     capacity: usize,
     size:     usize,
-    hashes:   *mut u64,
+    hashes:   Unique<u64>,
+
     // Because K/V do not appear directly in any of the types in the struct,
     // inform rustc that in fact instances of K and V are reachable from here.
-    marker:   marker::CovariantType<(K,V)>,
+    marker:   marker::PhantomData<(K,V)>,
 }
 
 unsafe impl<K: Send, V: Send> Send for RawTable<K, V> {}
@@ -81,7 +82,8 @@ unsafe impl<K: Sync, V: Sync> Sync for RawTable<K, V> {}
 struct RawBucket<K, V> {
     hash: *mut u64,
     key:  *mut K,
-    val:  *mut V
+    val:  *mut V,
+    _marker: marker::PhantomData<(K,V)>,
 }
 
 impl<K,V> Copy for RawBucket<K,V> {}
@@ -187,11 +189,12 @@ fn can_alias_safehash_as_u64() {
 }
 
 impl<K, V> RawBucket<K, V> {
-    unsafe fn offset(self, count: int) -> RawBucket<K, V> {
+    unsafe fn offset(self, count: isize) -> RawBucket<K, V> {
         RawBucket {
             hash: self.hash.offset(count),
             key:  self.key.offset(count),
             val:  self.val.offset(count),
+            _marker: marker::PhantomData,
         }
     }
 }
@@ -584,10 +587,11 @@ impl<K, V> RawTable<K, V> {
             return RawTable {
                 size: 0,
                 capacity: 0,
-                hashes: ptr::null_mut(),
-                marker: marker::CovariantType,
+                hashes: Unique::new(EMPTY as *mut u64),
+                marker: marker::PhantomData,
             };
         }
+
         // No need for `checked_mul` before a more restrictive check performed
         // later in this method.
         let hashes_size = capacity * size_of::<u64>();
@@ -623,8 +627,8 @@ impl<K, V> RawTable<K, V> {
         RawTable {
             capacity: capacity,
             size:     0,
-            hashes:   hashes,
-            marker:   marker::CovariantType,
+            hashes:   Unique::new(hashes),
+            marker:   marker::PhantomData,
         }
     }
 
@@ -632,16 +636,17 @@ impl<K, V> RawTable<K, V> {
         let hashes_size = self.capacity * size_of::<u64>();
         let keys_size = self.capacity * size_of::<K>();
 
-        let buffer = self.hashes as *mut u8;
+        let buffer = *self.hashes as *mut u8;
         let (keys_offset, vals_offset) = calculate_offsets(hashes_size,
                                                            keys_size, min_align_of::<K>(),
                                                            min_align_of::<V>());
 
         unsafe {
             RawBucket {
-                hash: self.hashes,
+                hash: *self.hashes,
                 key:  buffer.offset(keys_offset as isize) as *mut K,
-                val:  buffer.offset(vals_offset as isize) as *mut V
+                val:  buffer.offset(vals_offset as isize) as *mut V,
+                _marker: marker::PhantomData,
             }
         }
     }
@@ -651,7 +656,7 @@ impl<K, V> RawTable<K, V> {
     pub fn new(capacity: usize) -> RawTable<K, V> {
         unsafe {
             let ret = RawTable::new_uninitialized(capacity);
-            zero_memory(ret.hashes, capacity);
+            zero_memory(*ret.hashes, capacity);
             ret
         }
     }
@@ -673,7 +678,7 @@ impl<K, V> RawTable<K, V> {
             hashes_end: unsafe {
                 self.hashes.offset(self.capacity as isize)
             },
-            marker: marker::ContravariantLifetime,
+            marker: marker::PhantomData,
         }
     }
 
@@ -698,7 +703,7 @@ impl<K, V> RawTable<K, V> {
             iter: RawBuckets {
                 raw: raw,
                 hashes_end: hashes_end,
-                marker: marker::ContravariantLifetime,
+                marker: marker::PhantomData,
             },
             table: self,
         }
@@ -711,7 +716,7 @@ impl<K, V> RawTable<K, V> {
             iter: RawBuckets {
                 raw: raw,
                 hashes_end: hashes_end,
-                marker: marker::ContravariantLifetime::<'static>,
+                marker: marker::PhantomData,
             },
             table: self,
         }
@@ -725,7 +730,7 @@ impl<K, V> RawTable<K, V> {
             raw: raw_bucket.offset(self.capacity as isize),
             hashes_end: raw_bucket.hash,
             elems_left: self.size,
-            marker:     marker::ContravariantLifetime,
+            marker:     marker::PhantomData,
         }
     }
 }
@@ -735,7 +740,13 @@ impl<K, V> RawTable<K, V> {
 struct RawBuckets<'a, K, V> {
     raw: RawBucket<K, V>,
     hashes_end: *mut u64,
-    marker: marker::ContravariantLifetime<'a>,
+
+    // Strictly speaking, this should be &'a (K,V), but that would
+    // require that K:'a, and we often use RawBuckets<'static...> for
+    // move iterations, so that messes up a lot of other things. So
+    // just use `&'a (K,V)` as this is not a publicly exposed type
+    // anyway.
+    marker: marker::PhantomData<&'a ()>,
 }
 
 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
@@ -744,7 +755,7 @@ impl<'a, K, V> Clone for RawBuckets<'a, K, V> {
         RawBuckets {
             raw: self.raw,
             hashes_end: self.hashes_end,
-            marker: marker::ContravariantLifetime,
+            marker: marker::PhantomData,
         }
     }
 }
@@ -776,7 +787,11 @@ struct RevMoveBuckets<'a, K, V> {
     raw: RawBucket<K, V>,
     hashes_end: *mut u64,
     elems_left: usize,
-    marker: marker::ContravariantLifetime<'a>,
+
+    // As above, `&'a (K,V)` would seem better, but we often use
+    // 'static for the lifetime, and this is not a publicly exposed
+    // type.
+    marker: marker::PhantomData<&'a ()>,
 }
 
 impl<'a, K, V> Iterator for RevMoveBuckets<'a, K, V> {
@@ -983,9 +998,10 @@ impl<K: Clone, V: Clone> Clone for RawTable<K, V> {
 #[unsafe_destructor]
 impl<K, V> Drop for RawTable<K, V> {
     fn drop(&mut self) {
-        if self.hashes.is_null() {
+        if self.capacity == 0 {
             return;
         }
+
         // This is done in reverse because we've likely partially taken
         // some elements out with `.into_iter()` from the front.
         // Check if the size is 0, so we don't do a useless scan when
@@ -1003,7 +1019,7 @@ impl<K, V> Drop for RawTable<K, V> {
                                                     vals_size, min_align_of::<V>());
 
         unsafe {
-            deallocate(self.hashes as *mut u8, size, align);
+            deallocate(*self.hashes as *mut u8, size, align);
             // Remember how everything was allocated out of one buffer
             // during initialization? We only need one call to free here.
         }
diff --git a/src/libstd/old_io/mod.rs b/src/libstd/old_io/mod.rs
index 21282a0c28a..fc3deb67f41 100644
--- a/src/libstd/old_io/mod.rs
+++ b/src/libstd/old_io/mod.rs
@@ -252,7 +252,7 @@ use error::Error;
 use fmt;
 use isize;
 use iter::{Iterator, IteratorExt};
-use marker::Sized;
+use marker::{PhantomFn, Sized};
 use mem::transmute;
 use ops::FnOnce;
 use option::Option;
@@ -433,7 +433,7 @@ pub enum IoErrorKind {
 }
 
 /// A trait that lets you add a `detail` to an IoError easily
-trait UpdateIoError<T> {
+trait UpdateIoError {
     /// Returns an IoError with updated description and detail
     fn update_err<D>(self, desc: &'static str, detail: D) -> Self where
         D: FnOnce(&IoError) -> String;
@@ -446,7 +446,7 @@ trait UpdateIoError<T> {
     fn update_desc(self, desc: &'static str) -> Self;
 }
 
-impl<T> UpdateIoError<T> for IoResult<T> {
+impl<T> UpdateIoError for IoResult<T> {
     fn update_err<D>(self, desc: &'static str, detail: D) -> IoResult<T> where
         D: FnOnce(&IoError) -> String,
     {
@@ -1572,7 +1572,9 @@ pub trait Seek {
 /// connections.
 ///
 /// Doing so produces some sort of Acceptor.
-pub trait Listener<T, A: Acceptor<T>> {
+pub trait Listener<T, A: Acceptor<T>>
+    : PhantomFn<T,T> // FIXME should be an assoc type anyhow
+{
     /// Spin up the listener and start queuing incoming connections
     ///
     /// # Error
diff --git a/src/libstd/thread.rs b/src/libstd/thread.rs
index 3137d779c40..3653e7e31d5 100644
--- a/src/libstd/thread.rs
+++ b/src/libstd/thread.rs
@@ -153,7 +153,7 @@ use any::Any;
 use cell::UnsafeCell;
 use fmt;
 use io;
-use marker;
+use marker::PhantomData;
 use old_io::stdio;
 use rt::{self, unwind};
 use sync::{Mutex, Condvar, Arc};
@@ -260,7 +260,7 @@ impl Builder {
         T: Send + 'a, F: FnOnce() -> T, F: Send + 'a
     {
         self.spawn_inner(Thunk::new(f)).map(|inner| {
-            JoinGuard { inner: inner, _marker: marker::CovariantType }
+            JoinGuard { inner: inner, _marker: PhantomData }
         })
     }
 
@@ -642,7 +642,7 @@ impl Drop for JoinHandle {
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct JoinGuard<'a, T: 'a> {
     inner: JoinInner<T>,
-    _marker: marker::CovariantType<&'a T>,
+    _marker: PhantomData<&'a T>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]