Auto merge of #46925 - arielb1:make-the-trains-run-on-time, r=arielb1

Bounce out the layout refactor from beta

@eddyb's #45225 was supposed to get into get into 1.24, but due to an ordering mistake, it had snuck into 1.23.

That wide-effect translation-changing PR had poked LLVM's weak corners and caused many regressions (3 of them have fixes I include here, but also #46897, #46845, #46449, #46371). I don't think it is a good idea to land it in the beta (1.23) because there are bound to be some regressions we didn't patch.

Therefore, I am reverting it in time for stable, along with its related regression fixes.

r? @michaelwoerister (I think)

Author: bors

src/liballoc/boxed.rs

@@ -151,7 +151,7 @@ impl<T> Place<T> for IntermediateBox<T> {
 unsafe fn finalize<T>(b: IntermediateBox<T>) -> Box<T> {
     let p = b.ptr as *mut T;
     mem::forget(b);
-    Box::from_raw(p)
+    mem::transmute(p)
 }
 
 fn make_place<T>() -> IntermediateBox<T> {
@@ -300,10 +300,7 @@ impl<T: ?Sized> Box<T> {
                issue = "27730")]
     #[inline]
     pub unsafe fn from_unique(u: Unique<T>) -> Self {
-        #[cfg(stage0)]
-        return mem::transmute(u);
-        #[cfg(not(stage0))]
-        return Box(u);
+        mem::transmute(u)
     }
 
     /// Consumes the `Box`, returning the wrapped raw pointer.
@@ -365,14 +362,7 @@ impl<T: ?Sized> Box<T> {
                issue = "27730")]
     #[inline]
     pub fn into_unique(b: Box<T>) -> Unique<T> {
-        #[cfg(stage0)]
-        return unsafe { mem::transmute(b) };
-        #[cfg(not(stage0))]
-        return {
-            let unique = b.0;
-            mem::forget(b);
-            unique
-        };
+        unsafe { mem::transmute(b) }
     }
 }
 
@@ -637,7 +627,7 @@ impl Box<Any + Send> {
     pub fn downcast<T: Any>(self) -> Result<Box<T>, Box<Any + Send>> {
         <Box<Any>>::downcast(self).map_err(|s| unsafe {
             // reapply the Send marker
-            Box::from_raw(Box::into_raw(s) as *mut (Any + Send))
+            mem::transmute::<Box<Any>, Box<Any + Send>>(s)
         })
     }
 }

src/librustc/lib.rs

@@ -46,13 +46,11 @@
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]
-#![feature(i128)]
 #![feature(i128_type)]
-#![feature(inclusive_range)]
+#![feature(match_default_bindings)]
 #![feature(inclusive_range_syntax)]
 #![cfg_attr(windows, feature(libc))]
 #![feature(macro_vis_matcher)]
-#![feature(match_default_bindings)]
 #![feature(never_type)]
 #![feature(nonzero)]
 #![feature(quote)]