move DropArena -> libarena

src/libarena/lib.rs

@@ -488,5 +488,86 @@ impl DroplessArena {
     }
 }
 
+/// Calls the destructor for an object when dropped.
+struct DropType {
+    drop_fn: unsafe fn(*mut u8),
+    obj: *mut u8,
+}
+
+unsafe fn drop_for_type<T>(to_drop: *mut u8) {
+    std::ptr::drop_in_place(to_drop as *mut T)
+}
+
+impl Drop for DropType {
+    fn drop(&mut self) {
+        unsafe { (self.drop_fn)(self.obj) }
+    }
+}
+
+/// An arena which can be used to allocate any type.
+/// Allocating in this arena is unsafe since the type system
+/// doesn't know which types it contains. In order to
+/// allocate safely, you must store a PhantomData<T>
+/// alongside this arena for each type T you allocate.
+#[derive(Default)]
+pub struct DropArena {
+    /// A list of destructors to run when the arena drops.
+    /// Ordered so `destructors` gets dropped before the arena
+    /// since its destructor can reference memory in the arena.
+    destructors: RefCell<Vec<DropType>>,
+    arena: DroplessArena,
+}
+
+impl DropArena {
+    #[inline]
+    pub unsafe fn alloc<T>(&self, object: T) -> &mut T {
+        let mem =
+            self.arena.alloc_raw(mem::size_of::<T>(), mem::align_of::<T>()) as *mut _ as *mut T;
+        // Write into uninitialized memory.
+        ptr::write(mem, object);
+        let result = &mut *mem;
+        // Record the destructor after doing the allocation as that may panic
+        // and would cause `object`'s destuctor to run twice if it was recorded before
+        self.destructors
+            .borrow_mut()
+            .push(DropType { drop_fn: drop_for_type::<T>, obj: result as *mut T as *mut u8 });
+        result
+    }
+
+    #[inline]
+    pub unsafe fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] {
+        let mut vec: SmallVec<[_; 8]> = iter.into_iter().collect();
+        if vec.is_empty() {
+            return &mut [];
+        }
+        let len = vec.len();
+
+        let start_ptr = self
+            .arena
+            .alloc_raw(len.checked_mul(mem::size_of::<T>()).unwrap(), mem::align_of::<T>())
+            as *mut _ as *mut T;
+
+        let mut destructors = self.destructors.borrow_mut();
+        // Reserve space for the destructors so we can't panic while adding them
+        destructors.reserve(len);
+
+        // Move the content to the arena by copying it and then forgetting
+        // the content of the SmallVec
+        vec.as_ptr().copy_to_nonoverlapping(start_ptr, len);
+        mem::forget(vec.drain(..));
+
+        // Record the destructors after doing the allocation as that may panic
+        // and would cause `object`'s destuctor to run twice if it was recorded before
+        for i in 0..len {
+            destructors.push(DropType {
+                drop_fn: drop_for_type::<T>,
+                obj: start_ptr.offset(i as isize) as *mut u8,
+            });
+        }
+
+        slice::from_raw_parts_mut(start_ptr, len)
+    }
+}
+
 #[cfg(test)]
 mod tests;

src/librustc/arena.rs

@@ -1,10 +1,6 @@
-use arena::{DroplessArena, TypedArena};
-use smallvec::SmallVec;
-use std::cell::RefCell;
+use arena::{DropArena, DroplessArena, TypedArena};
 use std::marker::PhantomData;
 use std::mem;
-use std::ptr;
-use std::slice;
 
 /// This declares a list of types which can be allocated by `Arena`.
 ///
@@ -275,84 +271,3 @@ impl<'tcx> Arena<'tcx> {
         }
     }
 }
-
-/// Calls the destructor for an object when dropped.
-struct DropType {
-    drop_fn: unsafe fn(*mut u8),
-    obj: *mut u8,
-}
-
-unsafe fn drop_for_type<T>(to_drop: *mut u8) {
-    std::ptr::drop_in_place(to_drop as *mut T)
-}
-
-impl Drop for DropType {
-    fn drop(&mut self) {
-        unsafe { (self.drop_fn)(self.obj) }
-    }
-}
-
-/// An arena which can be used to allocate any type.
-/// Allocating in this arena is unsafe since the type system
-/// doesn't know which types it contains. In order to
-/// allocate safely, you must store a PhantomData<T>
-/// alongside this arena for each type T you allocate.
-#[derive(Default)]
-struct DropArena {
-    /// A list of destructors to run when the arena drops.
-    /// Ordered so `destructors` gets dropped before the arena
-    /// since its destructor can reference memory in the arena.
-    destructors: RefCell<Vec<DropType>>,
-    arena: DroplessArena,
-}
-
-impl DropArena {
-    #[inline]
-    unsafe fn alloc<T>(&self, object: T) -> &mut T {
-        let mem =
-            self.arena.alloc_raw(mem::size_of::<T>(), mem::align_of::<T>()) as *mut _ as *mut T;
-        // Write into uninitialized memory.
-        ptr::write(mem, object);
-        let result = &mut *mem;
-        // Record the destructor after doing the allocation as that may panic
-        // and would cause `object`'s destuctor to run twice if it was recorded before
-        self.destructors
-            .borrow_mut()
-            .push(DropType { drop_fn: drop_for_type::<T>, obj: result as *mut T as *mut u8 });
-        result
-    }
-
-    #[inline]
-    unsafe fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] {
-        let mut vec: SmallVec<[_; 8]> = iter.into_iter().collect();
-        if vec.is_empty() {
-            return &mut [];
-        }
-        let len = vec.len();
-
-        let start_ptr = self
-            .arena
-            .alloc_raw(len.checked_mul(mem::size_of::<T>()).unwrap(), mem::align_of::<T>())
-            as *mut _ as *mut T;
-
-        let mut destructors = self.destructors.borrow_mut();
-        // Reserve space for the destructors so we can't panic while adding them
-        destructors.reserve(len);
-
-        // Move the content to the arena by copying it and then forgetting
-        // the content of the SmallVec
-        vec.as_ptr().copy_to_nonoverlapping(start_ptr, len);
-        mem::forget(vec.drain(..));
-
-        // Record the destructors after doing the allocation as that may panic
-        // and would cause `object`'s destuctor to run twice if it was recorded before
-        for i in 0..len {
-            destructors.push(DropType {
-                drop_fn: drop_for_type::<T>,
-                obj: start_ptr.offset(i as isize) as *mut u8,
-            });
-        }
-
-        slice::from_raw_parts_mut(start_ptr, len)
-    }
-}