Merge pull request #291 from ehuss/2024-initial-docs

Add some more initial stub docs for 2024.

src/rust-2024/cargo-remove-implicit-features.md

@@ -2,6 +2,9 @@
 
 🚧 The 2024 Edition has not yet been released and hence this section is still "under construction".
 
+This feature has not yet been implemented.
+More information may be found in the tracking issue at <https://github.com/rust-lang/cargo/issues/12826>.
+
 ## Summary
 
 ## Details

src/rust-2024/public-private-dependencies.md

@@ -2,6 +2,9 @@
 
 🚧 The 2024 Edition has not yet been released and hence this section is still "under construction".
 
+This feature is only partially implemented, and not yet ready for testing.
+More information may be found in the tracking issue at <https://github.com/rust-lang/rust/issues/44663>.
+
 ## Summary
 
 ## Details

src/rust-2024/rpit-lifetime-capture.md

@@ -2,6 +2,9 @@
 
 🚧 The 2024 Edition has not yet been released and hence this section is still "under construction".
 
+This feature is partially implemented, and not yet ready for testing.
+More information may be found in the tracking issue at <https://github.com/rust-lang/rust/issues/117587>.
+
 ## Summary
 
 ## Details

src/rust-2024/rustfmt-overflow-delimited-expr.md

@@ -2,6 +2,9 @@
 
 🚧 The 2024 Edition has not yet been released and hence this section is still "under construction".
 
+This feature is not yet implemented.
+More information may be found in <https://github.com/rust-lang/rust/pull/114764>.
+
 ## Summary
 
 ## Details

src/rust-2024/static-mut-reference.md

@@ -4,6 +4,37 @@
 
 ## Summary
 
+- The [`static_mut_ref`] lint is now a hard error that cannot be disabled.
+  This prevents taking a shared or mutable reference to a `static mut`.
+
+[`static_mut_ref`]: ../../rustc/lints/listing/warn-by-default.html#static-mut-ref
+
 ## Details
 
+Taking a reference to a [`static mut`] is no longer allowed:
+
+<!-- edition2024,E0796 -->
+```rust
+static mut X: i32 = 23;
+static mut Y: i32 = 24;
+
+unsafe {
+    let y = &X;             // ERROR: reference of mutable static
+    let ref x = X;          // ERROR: reference of mutable static
+    let (x, y) = (&X, &Y);  // ERROR: reference of mutable static
+}
+```
+
+Shared or mutable references of mutable static are almost always a mistake and can lead to undefined behavior and various other problems in your code.
+For example, another thread writing to the `static mut` will cause an aliasing violation and incur [Undefined Behavior].
+
+<!-- TODO: Discuss possible alternatives. -->
+
+[Undefined Behavior]: ../../reference/behavior-considered-undefined.html
+[`static mut`]: ../../reference/items/static-items.html#mutable-statics
+
 ## Migration
+
+🚧 The automatic migration for this has not yet been implemented.
+
+<!-- TODO: Discuss alternatives around rewriting your code. -->

src/rust-2024/unsafe-op-in-unsafe-fn.md

@@ -4,6 +4,55 @@
 
 ## Summary
 
+- The [`unsafe_op_in_unsafe_fn`] lint now warns by default.
+  This warning detects calls to unsafe operations in unsafe functions without an explicit unsafe block.
+
+[`unsafe_op_in_unsafe_fn`]: ../../rustc/lints/listing/allowed-by-default.html#unsafe-op-in-unsafe-fn
+
 ## Details
 
+The [`unsafe_op_in_unsafe_fn`] lint will fire if there are [unsafe operations] in an unsafe function without an explicit [`unsafe {}` block][unsafe-block].
+
+```rust
+# #![warn(unsafe_op_in_unsafe_fn)]
+unsafe fn get_unchecked<T>(x: &[T], i: usize) -> &T {
+  x.get_unchecked(i) // WARNING: requires unsafe block
+}
+```
+
+The solution is to wrap any unsafe operations in an `unsafe` block:
+
+```rust
+# #![deny(unsafe_op_in_unsafe_fn)]
+unsafe fn get_unchecked<T>(x: &[T], i: usize) -> &T {
+  unsafe { x.get_unchecked(i) }
+}
+```
+
+This change is intended to help protect against accidental use of unsafe operations in an unsafe function.
+The `unsafe` function keyword was performing two roles.
+One was to declare that *calling* the function requires unsafe, and that the caller is responsible to uphold additional safety requirements.
+The other role was to allow the use of unsafe operations inside of the function.
+This second role was determined to be too risky without explicit `unsafe` blocks.
+
+More information and motivation may be found in [RFC #2585].
+
+[unsafe operations]: ../../reference/unsafety.html
+[unsafe-block]: ../../reference/expressions/block-expr.html#unsafe-blocks
+[RFC #2585]: https://rust-lang.github.io/rfcs/2585-unsafe-block-in-unsafe-fn.html
+
 ## Migration
+
+The [`unsafe_op_in_unsafe_fn`] lint is part of the `rust-2024-compatibility` lint group.
+In order to migrate your code to be Rust 2024 Edition compatible, run:
+
+```sh
+cargo fix --edition
+```
+
+Alternatively, you can manually enable the lint to find places where unsafe blocks need to be added, or switch it to `allow` to silence the lint completely.
+
+```rust
+// Add this to the root of your crate to do a manual migration.
+#![warn(unsafe_op_in_unsafe_fn)]
+```