Merging upstream version 1.74.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 23 insertions, 7 deletions

diff --git a/library/core/src/ops/deref.rs b/library/core/src/ops/deref.rs
index 08c35b6da..911761c6e 100644
--- a/library/core/src/ops/deref.rs
+++ b/library/core/src/ops/deref.rs
@@ -14,6 +14,11 @@
 /// For similar reasons, **this trait should never fail**. Failure during
 /// dereferencing can be extremely confusing when `Deref` is invoked implicitly.
 ///
+/// Violating these requirements is a logic error. The behavior resulting from a logic error is not
+/// specified, but users of the trait must ensure that such logic errors do *not* result in
+/// undefined behavior. This means that `unsafe` code **must not** rely on the correctness of this
+/// method.
+///
 /// # More on `Deref` coercion
 ///
 /// If `T` implements `Deref<Target = U>`, and `x` is a value of type `T`, then:
@@ -114,6 +119,11 @@ impl<T: ?Sized> Deref for &mut T {
 /// dereferencing can be extremely confusing when `DerefMut` is invoked
 /// implicitly.
 ///
+/// Violating these requirements is a logic error. The behavior resulting from a logic error is not
+/// specified, but users of the trait must ensure that such logic errors do *not* result in
+/// undefined behavior. This means that `unsafe` code **must not** rely on the correctness of this
+/// method.
+///
 /// # More on `Deref` coercion
 ///
 /// If `T` implements `DerefMut<Target = U>`, and `x` is a value of type `T`,
diff --git a/library/core/src/ops/drop.rs b/library/core/src/ops/drop.rs
index 9ebf426be..34dfa9e4c 100644
--- a/library/core/src/ops/drop.rs
+++ b/library/core/src/ops/drop.rs
@@ -202,7 +202,7 @@
 /// [nomicon]: ../../nomicon/phantom-data.html#an-exception-the-special-case-of-the-standard-library-and-its-unstable-may_dangle
 #[lang = "drop"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait Drop {
     /// Executes the destructor for this type.
     ///
@@ -217,8 +217,13 @@ pub trait Drop {
     ///
     /// # Panics
     ///
-    /// Given that a [`panic!`] will call `drop` as it unwinds, any [`panic!`]
-    /// in a `drop` implementation will likely abort.
+    /// Implementations should generally avoid [`panic!`]ing, because `drop()` may itself be called
+    /// during unwinding due to a panic, and if the `drop()` panics in that situation (a “double
+    /// panic”), this will likely abort the program. It is possible to check [`panicking()`] first,
+    /// which may be desirable for a `Drop` implementation that is reporting a bug of the kind
+    /// “you didn't finish using this before it was dropped”; but most types should simply clean up
+    /// their owned allocations or other resources and return normally from `drop()`, regardless of
+    /// what state they are in.
     ///
     /// Note that even if this panics, the value is considered to be dropped;
     /// you must not cause `drop` to be called again. This is normally automatically
@@ -227,6 +232,7 @@ pub trait Drop {
     ///
     /// [E0040]: ../../error_codes/E0040.html
     /// [`panic!`]: crate::panic!
+    /// [`panicking()`]: ../../std/thread/fn.panicking.html
     /// [`mem::drop`]: drop
     /// [`ptr::drop_in_place`]: crate::ptr::drop_in_place
     #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/core/src/ops/function.rs b/library/core/src/ops/function.rs
index 67c8245f0..20f0bba4c 100644
--- a/library/core/src/ops/function.rs
+++ b/library/core/src/ops/function.rs
@@ -72,7 +72,7 @@ use crate::marker::Tuple;
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait Fn<Args: Tuple>: FnMut<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -159,7 +159,7 @@ pub trait Fn<Args: Tuple>: FnMut<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait FnMut<Args: Tuple>: FnOnce<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -238,7 +238,7 @@ pub trait FnMut<Args: Tuple>: FnOnce<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait FnOnce<Args: Tuple> {
     /// The returned type after the call operator is used.
     #[lang = "fn_once_output"]
diff --git a/library/core/src/ops/range.rs b/library/core/src/ops/range.rs
index ba5e6ddc7..cc596293c 100644
--- a/library/core/src/ops/range.rs
+++ b/library/core/src/ops/range.rs
@@ -11,7 +11,7 @@ use crate::hash::Hash;
 /// The `..` syntax is a `RangeFull`:
 ///
 /// ```
-/// assert_eq!((..), std::ops::RangeFull);
+/// assert_eq!(.., std::ops::RangeFull);
 /// ```
 ///
 /// It does not have an [`IntoIterator`] implementation, so you can't use it in