Replace the forget intrinsic with ManuallyDrop

less intrinsics = better life

Author: nagisa

src/libcore/intrinsics.rs

@@ -691,9 +691,6 @@ extern "rust-intrinsic" {
     /// initialize memory previous set to the result of `uninit`.
     pub fn uninit<T>() -> T;
 
-    /// Moves a value out of scope without running drop glue.
-    pub fn forget<T>(_: T) -> ();
-
     /// Reinterprets the bits of a value of one type as another type.
     ///
     /// Both types must have the same size. Neither the original, nor the result,

src/libcore/mem.rs

@@ -171,7 +171,7 @@ pub use intrinsics::transmute;
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn forget<T>(t: T) {
-    unsafe { intrinsics::forget(t) }
+    ManuallyDrop::new(t);
 }
 
 /// Returns the size of a type in bytes.
@@ -780,12 +780,14 @@ pub union ManuallyDrop<T>{ value: T }
 impl<T> ManuallyDrop<T> {
     /// Wrap a value to be manually dropped.
     #[unstable(feature = "manually_drop", issue = "40673")]
+    #[inline]
     pub fn new(value: T) -> ManuallyDrop<T> {
         ManuallyDrop { value: value }
     }
 
     /// Extract the value from the ManuallyDrop container.
     #[unstable(feature = "manually_drop", issue = "40673")]
+    #[inline]
     pub fn into_inner(self) -> T {
         unsafe {
             self.value
@@ -800,6 +802,7 @@ impl<T> ManuallyDrop<T> {
     /// now represents uninitialized data. It is up to the user of this method to ensure the
     /// uninitialized data is not actually used.
     #[unstable(feature = "manually_drop", issue = "40673")]
+    #[inline]
     pub unsafe fn drop(slot: &mut ManuallyDrop<T>) {
         ptr::drop_in_place(&mut slot.value)
     }
@@ -808,6 +811,7 @@ impl<T> ManuallyDrop<T> {
 #[unstable(feature = "manually_drop", issue = "40673")]
 impl<T> ::ops::Deref for ManuallyDrop<T> {
     type Target = T;
+    #[inline]
     fn deref(&self) -> &Self::Target {
         unsafe {
             &self.value
@@ -817,6 +821,7 @@ impl<T> ::ops::Deref for ManuallyDrop<T> {
 
 #[unstable(feature = "manually_drop", issue = "40673")]
 impl<T> ::ops::DerefMut for ManuallyDrop<T> {
+    #[inline]
     fn deref_mut(&mut self) -> &mut Self::Target {
         unsafe {
             &mut self.value

src/librustc_trans/intrinsic.rs

@@ -188,7 +188,7 @@ pub fn trans_intrinsic_call<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
             C_nil(ccx)
         }
         // Effectively no-ops
-        "uninit" | "forget" => {
+        "uninit" => {
             C_nil(ccx)
         }
         "needs_drop" => {

src/librustc_typeck/check/intrinsic.rs

@@ -124,7 +124,6 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             "rustc_peek" => (1, vec![param(0)], param(0)),
             "init" => (1, Vec::new(), param(0)),
             "uninit" => (1, Vec::new(), param(0)),
-            "forget" => (1, vec![ param(0) ], tcx.mk_nil()),
             "transmute" => (2, vec![ param(0) ], param(1)),
             "move_val_init" => {
                 (1,