Stabilize `&mut`, `*mut`, `&Cell`, and `*const Cell` in const.

• Changed paragraphs: 6.1.2:12, 6.1.2:17, 6.1.2:29

Allow creating references to statics in `const` initializers.

• No change: This previous restriction is not specified in the FLS

Implement raw lifetimes and labels (`’r#ident`).

• Changed syntax: Lifetime

Define behavior when atomic and non-atomic reads race.

• No change: Already covered by the definition of data race.

Non-exhaustive structs may now be empty.

• Removed paragraph: Paragraph fls_2CWUWbYT9KcT

• Changed paragraph: 4.12.6:8, 4.12.6:11

Disallow implicit coercions from places of type `!`

• No change: The FLS does not specify type inference to such a degree

`const extern` functions can now be defined for other calling conventions.

• No change: This previous restriction is not specified in the FLS

Stabilize `expr_2021` macro fragment specifier in all editions.

• Changed syntax: MacroFragmentSpecifier

• Changed paragraphs: 20.4.1.2:6, 20.1.1:6

The `non_local_definitions` lint now fires on less code and warns by default.

• No change: Lints are not part of the FLS

Don’t make statement nonterminals match pattern nonterminals

• No change: Exact parsing behavior of non-terminals within declarative macros is not specified

Patterns matching empty types can now be omitted in common cases

• New section: Visible Emptiness

• Changed paragraphs: 5.1:2, 5.1:3, 5.1.4:8, 5.1.4:9, 5.1.6:2, 5.2:8

Enforce supertrait outlives obligations when using trait impls

• No change: the concrete type inference resolution is not part of the FLS

`addr_of(_mut)!` macros and the newly stabilized `&raw (const|mut)` are now safe to use with all static items

• No change: addr_of is not specified as it is a library defined macro, &raw (const|mut) appears as a new feature separately below

size_of_val_raw: for length 0 this is safe to call

• No change: size_of_val_raw is a library defined function

Reorder trait bound modifiers *after* `for<…>` binder in trait bounds

• Changed syntax: TraitBound

Stabilize opaque type precise capturing (RFC 3617)

• Changed syntax: ImplTraitTypeSpecification, ImplTraitTypeSpecificationOneBound

• New syntax: UseCaptures, UseCapturesGenericArgs, UseCapturesGenericArg

• New paragraphs: 4.8.1:7, 4.8.1:8, 4.8.1:9, 4.8.1:10

Stabilize `&raw const` and `&raw mut` operators (RFC 2582)

• New section: Raw Borrow Expression

• New paragraphs: 6.1.4:23

Stabilize unsafe extern blocks (RFC 3484)

• New syntax: ItemSafety

• Changed syntax: WeakKeyword, FunctionQualifierList, StaticDeclaration

• New paragraphs: 21.2:2, 7.2:5, 9:33

• Changed paragraphs: 2.6.3:5, 9:32, 21.2:1, 21.3:2, 21.4:3

• Removed paragraph Paragraph fls_iaimuqcclstl

Stabilize nested field access in `offset_of!`

• No change: offset_of is a library defined macro

Do not require `T` to be live when dropping `[T; 0]`

• No change: The drop interaction with the borrow checker is not specified as the borrow checker is not specified in the FLS

Stabilize `const` operands in inline assembly

• Note: These changes affect content that is informational.

• New syntax: ConstRegisterExpression

• New paragraphs: 22.3:13, 22.3:16, 22.3:17

Stabilize floating-point arithmetic in `const fn`

• New paragraph: 6.5:2

• Removed paragraph: Paragraph fls_9mrrosm8jnn7

Stabilize explicit opt-in to unsafe attributes

• New section: Attribute unsafe

Document NaN bit patterns guarantees

• New paragraph: 4.3.3.1:3

Abort on uncaught panics in `extern “C”` functions.

• No change: unwinding is not specified in the FLS

Fix ambiguous cases of multiple `&` in elided self lifetimes.

• Changed paragraph: 4.14.3.1:15

• New paragraph: 4.14.3.1:6

Stabilize `#[expect]` for lints (RFC 2383), like `#[allow]` with a warning if the lint is _not_ fulfilled.

• New paragraph: 13.2:21

Change method resolution to constrain hidden types instead of rejecting method candidates.

• No change: the concrete type inference resolution is not part of the FLS

Bump `elided_lifetimes_in_associated_constant` to deny.

• No change: lints are not part of the FLS

`offset_from`: always allow pointers to point to the same address.

• No change: this previous restriction is not specified in the FLS

Allow constraining opaque types during subtyping in the trait system.

• No change: the concrete type inference resolution is not part of the FLS

Allow constraining opaque types during various unsizing casts.

• No change: the concrete type inference resolution is not part of the FLS

Deny keyword lifetimes pre-expansion.

• No change: the FLS already specifies this restriction in Lifetime

Document maximum allocation size

• New paragraphs: 7:2, 7:3, 7:4, 7:11, 7:12, 7:13

Allow zero-byte offsets and ZST read/writes on arbitrary pointers

• No change: this previous restriction is not specified in the FLS

Support C23’s variadics without a named parameter

• No change: this previous restriction is not specified in the FLS

Stabilize `exclusive_range_pattern` feature

• Changed syntax: RangePattern

• New syntax: ExclusiveRangePattern

• Changed paragraph: 5.1.5:16

• New paragraphs: 5.1.5:4, 5.1.5:11, 5.4.5:4

Stabilize inline `const {}` expressions.

• New section: Const Blocks

Prevent opaque types being instantiated twice with different regions within the same function.

• No change: already described in 4.12.2:51

Stabilize WebAssembly target features that are in phase 4 and 5.

• No change: cfg and cfg_attr configuration predicates are not part of the FLS

Add the `redundant_lifetimes` lint to detect lifetimes which are semantically redundant.

• No change: lints are not part of the FLS

Stabilize the `unnameable_types` lint for public types that can’t be named.

• No change: lints are not part of the FLS

Enable debuginfo in macros, and stabilize `-C collapse-macro-debuginfo` and `#[collapse_debuginfo]`.

• New section: Attribute collapse_debuginfo

Propagate temporary lifetime extension into `if` and `match` expressions.

• New paragraphs: 15.8.1:9, 15.8.1:10, 15.8.1:11

Restrict promotion of `const fn` calls.

• No change: already described in 7.4.1:6

Warn against refining impls of crate-private traits with `refining_impl_trait` lint.

• No change: lints are not part of the FLS

Stabilize associated type bounds (RFC 2289).

• New paragraph: 12.3:5

Stabilize importing `main` from other modules or crates.

• No change: this lifted restriction was not previously described in the FLS

• While updating the FLS to account for this feature, we realized that the way the FLS described crate types was incorrect. We rectified this:

  • New section: Program Entry Point

  • New glossary entry: crate type

  • New paragraphs: 18.3:2, 18.3:3, 18.3:4, 18.3:6

  • Updated glossary entries: binary crate, library crate, proc-macro crate

  • Updated paragraphs: 18.3:5, 18.3:9, 18.3:8

  • Moved paragraph: 18.7:2

Check return types of function types for well-formedness

• No change: the exact trait resolution implementation is not part of the FLS

Rework `impl Trait` lifetime inference

• New paragraphs: 4.8.1:3, 4.8.1:4, 4.8.1:5

Change inductive trait solver cycles to be ambiguous

• No change: the exact trait solver is not part of the FLS

Stabilize `#[cfg(target_abi = …)]`

• No change: cfg and cfg_attr configuration predicates are not part of the FLS

Stabilize the `#[diagnostic]` namespace and `#[diagnostic::on_unimplemented]` attribute

• No change: tool attributes are not part of the FLS

Make async-fn-in-trait implementable with concrete signatures

• No change: no paragraph in the FLS forbids this prior incompatability

Make matching on NaN a hard error, and remove the rest of `illegal_floating_point_literal_pattern`

• New paragraph: 5.1.2:3

static mut: allow mutable reference to arbitrary types, not just slices and arrays

• No change: this lifted restriction was not previously described in the FLS

Extend `invalid_reference_casting` to include references casting to bigger memory layout

• No change: lints are not part of the FLS

Add `non_contiguous_range_endpoints` lint for singleton gaps after exclusive ranges

• No change: lints are not part of the FLS

Add `wasm_c_abi` lint for use of older wasm-bindgen versions

• No change: lints are not part of the FLS

Update `indirect_structural_match` and `pointer_structural_match` lints to match RFC

• No change: lints are not part of the FLS

Make non-`PartialEq`-typed consts as patterns a hard error

• No change: already described in 5.1.4:4

Split `refining_impl_trait` lint into `_reachable`, `_internal` variants

• No change: lints are not part of the FLS

Remove unnecessary type inference when using associated types inside of higher ranked `where`-bounds

• No change: the FLS does not specify type inference to such a degree

Weaken eager detection of cyclic types during type inference

• No change: the FLS does not specify type inference to such a degree

`trait Trait: Auto {}`: allow upcasting from `dyn Trait` to `dyn Trait + Auto`

• New paragraph: 4.12.3:29

Reveal opaque types within the defining body for exhaustiveness checking.

• No change: the FLS does not specify introspection of the concrete type of the match expression scrutinee to such a degree

Stabilize C-string literals.

• New section: C String Literals

Stabilize THIR unsafeck.

• No change: not a language change

Add lint `static_mut_refs` to warn on references to mutable statics.

• No change: lints are not part of the FLS

Support async recursive calls (as long as they have indirection).

• No change: this lifted restriction was not previously described in the FLS

Undeprecate lint `unstable_features` and make use of it in the compiler.

• No change: lints are not part of the FLS

Make inductive cycles in coherence ambiguous always.

• No change: the FLS does not describe the trait solver to such a degree

Get rid of type-driven traversal in const-eval interning, only as a future compatibility lint for now.

• No change: this lifted restriction was not previously described in the FLS

Deny braced macro invocations in let-else.

• New paragraph: 8.1:4