Rollup merge of #63793 - oli-obk:🧹, r=dtolnay

Have tidy ensure that we document all `unsafe` blocks in libcore

cc @rust-lang/libs

I documented a few and added ignore flags on the other files. We can incrementally document the files, but won't regress any files this way.

2 files changed, 20 insertions, 1 deletions

diff --git a/src/libcore/mem/maybe_uninit.rs b/src/libcore/mem/maybe_uninit.rs
index 03093139bc2..4b3dc1c83c4 100644
--- a/src/libcore/mem/maybe_uninit.rs
+++ b/src/libcore/mem/maybe_uninit.rs
@@ -1,6 +1,8 @@
 use crate::intrinsics;
 use crate::mem::ManuallyDrop;
 
+// ignore-tidy-undocumented-unsafe
+
 /// A wrapper type to construct uninitialized instances of `T`.
 ///
 /// # Initialization invariant
diff --git a/src/libcore/mem/mod.rs b/src/libcore/mem/mod.rs
index c7da56aad30..26909be9496 100644
--- a/src/libcore/mem/mod.rs
+++ b/src/libcore/mem/mod.rs
@@ -93,6 +93,8 @@ pub fn forget<T>(t: T) {
 #[inline]
 #[unstable(feature = "forget_unsized", issue = "0")]
 pub fn forget_unsized<T: ?Sized>(t: T) {
+    // SAFETY: the forget intrinsic could be safe, but there's no point in making it safe since
+    // we'll be implementing this function soon via `ManuallyDrop`
     unsafe { intrinsics::forget(t) }
 }
 
@@ -266,7 +268,11 @@ pub const fn size_of<T>() -> usize {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn size_of_val<T: ?Sized>(val: &T) -> usize {
+    #[cfg(bootstrap)]
+    // SAFETY: going away soon
     unsafe { intrinsics::size_of_val(val) }
+    #[cfg(not(bootstrap))]
+    intrinsics::size_of_val(val)
 }
 
 /// Returns the [ABI]-required minimum alignment of a type.
@@ -310,7 +316,11 @@ pub fn min_align_of<T>() -> usize {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_deprecated(reason = "use `align_of_val` instead", since = "1.2.0")]
 pub fn min_align_of_val<T: ?Sized>(val: &T) -> usize {
+    #[cfg(bootstrap)]
+    // SAFETY: going away soon
     unsafe { intrinsics::min_align_of_val(val) }
+    #[cfg(not(bootstrap))]
+    intrinsics::min_align_of_val(val)
 }
 
 /// Returns the [ABI]-required minimum alignment of a type.
@@ -350,8 +360,9 @@ pub const fn align_of<T>() -> usize {
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[allow(deprecated)]
 pub fn align_of_val<T: ?Sized>(val: &T) -> usize {
-    unsafe { intrinsics::min_align_of_val(val) }
+    min_align_of_val(val)
 }
 
 /// Returns `true` if dropping values of type `T` matters.
@@ -508,6 +519,8 @@ pub unsafe fn uninitialized<T>() -> T {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn swap<T>(x: &mut T, y: &mut T) {
+    // SAFETY: the raw pointers have been created from safe mutable references satisfying all the
+    // constraints on `ptr::swap_nonoverlapping_one`
     unsafe {
         ptr::swap_nonoverlapping_one(x, y);
     }
@@ -822,7 +835,11 @@ impl<T> fmt::Debug for Discriminant<T> {
 /// ```
 #[stable(feature = "discriminant_value", since = "1.21.0")]
 pub fn discriminant<T>(v: &T) -> Discriminant<T> {
+    #[cfg(bootstrap)]
+    // SAFETY: going away soon
     unsafe {
         Discriminant(intrinsics::discriminant_value(v), PhantomData)
     }
+    #[cfg(not(bootstrap))]
+    Discriminant(intrinsics::discriminant_value(v), PhantomData)
 }