rustc_feature/unstable.rs
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//! List of the unstable feature gates.
use rustc_data_structures::fx::FxHashSet;
use rustc_span::Span;
use rustc_span::symbol::{Symbol, sym};
use super::{Feature, to_nonzero};
#[derive(PartialEq)]
enum FeatureStatus {
Default,
Incomplete,
Internal,
}
macro_rules! status_to_enum {
(unstable) => {
FeatureStatus::Default
};
(incomplete) => {
FeatureStatus::Incomplete
};
(internal) => {
FeatureStatus::Internal
};
}
/// A set of features to be used by later passes.
///
/// There are two ways to check if a language feature `foo` is enabled:
/// - Directly with the `foo` method, e.g. `if tcx.features().foo() { ... }`.
/// - With the `enabled` method, e.g. `if tcx.features.enabled(sym::foo) { ... }`.
///
/// The former is preferred. `enabled` should only be used when the feature symbol is not a
/// constant, e.g. a parameter, or when the feature is a library feature.
#[derive(Clone, Default, Debug)]
pub struct Features {
/// `#![feature]` attrs for language features, for error reporting.
enabled_lang_features: Vec<EnabledLangFeature>,
/// `#![feature]` attrs for non-language (library) features.
enabled_lib_features: Vec<EnabledLibFeature>,
/// `enabled_lang_features` + `enabled_lib_features`.
enabled_features: FxHashSet<Symbol>,
}
/// Information about an enabled language feature.
#[derive(Debug, Copy, Clone)]
pub struct EnabledLangFeature {
/// Name of the feature gate guarding the language feature.
pub gate_name: Symbol,
/// Span of the `#[feature(...)]` attribute.
pub attr_sp: Span,
/// If the lang feature is stable, the version number when it was stabilized.
pub stable_since: Option<Symbol>,
}
/// Information about an enabled library feature.
#[derive(Debug, Copy, Clone)]
pub struct EnabledLibFeature {
pub gate_name: Symbol,
pub attr_sp: Span,
}
impl Features {
/// `since` should be set for stable features that are nevertheless enabled with a `#[feature]`
/// attribute, indicating since when they are stable.
pub fn set_enabled_lang_feature(&mut self, lang_feat: EnabledLangFeature) {
self.enabled_lang_features.push(lang_feat);
self.enabled_features.insert(lang_feat.gate_name);
}
pub fn set_enabled_lib_feature(&mut self, lib_feat: EnabledLibFeature) {
self.enabled_lib_features.push(lib_feat);
self.enabled_features.insert(lib_feat.gate_name);
}
/// Returns a list of [`EnabledLangFeature`] with info about:
///
/// - Feature gate name.
/// - The span of the `#[feature]` attribute.
/// - For stable language features, version info for when it was stabilized.
pub fn enabled_lang_features(&self) -> &Vec<EnabledLangFeature> {
&self.enabled_lang_features
}
pub fn enabled_lib_features(&self) -> &Vec<EnabledLibFeature> {
&self.enabled_lib_features
}
pub fn enabled_features(&self) -> &FxHashSet<Symbol> {
&self.enabled_features
}
/// Is the given feature enabled (via `#[feature(...)]`)?
pub fn enabled(&self, feature: Symbol) -> bool {
self.enabled_features.contains(&feature)
}
}
macro_rules! declare_features {
($(
$(#[doc = $doc:tt])* ($status:ident, $feature:ident, $ver:expr, $issue:expr),
)+) => {
/// Unstable language features that are being implemented or being
/// considered for acceptance (stabilization) or removal.
pub const UNSTABLE_LANG_FEATURES: &[Feature] = &[
$(Feature {
name: sym::$feature,
since: $ver,
issue: to_nonzero($issue),
}),+
];
impl Features {
$(
pub fn $feature(&self) -> bool {
self.enabled_features.contains(&sym::$feature)
}
)*
/// Some features are known to be incomplete and using them is likely to have
/// unanticipated results, such as compiler crashes. We warn the user about these
/// to alert them.
pub fn incomplete(&self, feature: Symbol) -> bool {
match feature {
$(
sym::$feature => status_to_enum!($status) == FeatureStatus::Incomplete,
)*
_ if self.enabled_features.contains(&feature) => {
// Accepted/removed features and library features aren't in this file but
// are never incomplete.
false
}
_ => panic!("`{}` was not listed in `declare_features`", feature),
}
}
/// Some features are internal to the compiler and standard library and should not
/// be used in normal projects. We warn the user about these to alert them.
pub fn internal(&self, feature: Symbol) -> bool {
match feature {
$(
sym::$feature => status_to_enum!($status) == FeatureStatus::Internal,
)*
_ if self.enabled_features.contains(&feature) => {
// This could be accepted/removed, or a libs feature.
// Accepted/removed features aren't in this file but are never internal
// (a removed feature might have been internal, but that's now irrelevant).
// Libs features are internal if they end in `_internal` or `_internals`.
// As a special exception we also consider `core_intrinsics` internal;
// renaming that age-old feature is just not worth the hassle.
// We just always test the name; it's not a big deal if we accidentally hit
// an accepted/removed lang feature that way.
let name = feature.as_str();
name == "core_intrinsics" || name.ends_with("_internal") || name.ends_with("_internals")
}
_ => panic!("`{}` was not listed in `declare_features`", feature),
}
}
}
};
}
// See https://rustc-dev-guide.rust-lang.org/feature-gates.html#feature-gates for more
// documentation about handling feature gates.
//
// If you change this, please modify `src/doc/unstable-book` as well.
//
// Don't ever remove anything from this list; move them to `accepted.rs` if
// accepted or `removed.rs` if removed.
//
// The version numbers here correspond to the version in which the current status
// was set.
//
// Note that the features are grouped into internal/user-facing and then
// sorted alphabetically inside those groups. This is enforced with tidy.
//
// N.B., `tools/tidy/src/features.rs` parses this information directly out of the
// source, so take care when modifying it.
#[rustfmt::skip]
declare_features! (
// -------------------------------------------------------------------------
// feature-group-start: internal feature gates (no tracking issue)
// -------------------------------------------------------------------------
// no-tracking-issue-start
/// Allows using the `unadjusted` ABI; perma-unstable.
(internal, abi_unadjusted, "1.16.0", None),
/// Allows using `#![needs_allocator]`, an implementation detail of `#[global_allocator]`.
(internal, allocator_internals, "1.20.0", None),
/// Allows using `#[allow_internal_unsafe]`. This is an
/// attribute on `macro_rules!` and can't use the attribute handling
/// below (it has to be checked before expansion possibly makes
/// macros disappear).
(internal, allow_internal_unsafe, "1.0.0", None),
/// Allows using `#[allow_internal_unstable]`. This is an
/// attribute on `macro_rules!` and can't use the attribute handling
/// below (it has to be checked before expansion possibly makes
/// macros disappear).
(internal, allow_internal_unstable, "1.0.0", None),
/// Allows using anonymous lifetimes in argument-position impl-trait.
(unstable, anonymous_lifetime_in_impl_trait, "1.63.0", None),
/// Allows identifying the `compiler_builtins` crate.
(internal, compiler_builtins, "1.13.0", None),
/// Allows writing custom MIR
(internal, custom_mir, "1.65.0", None),
/// Outputs useful `assert!` messages
(unstable, generic_assert, "1.63.0", None),
/// Allows using the `rust-intrinsic`'s "ABI".
(internal, intrinsics, "1.0.0", None),
/// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
(internal, lang_items, "1.0.0", None),
/// Changes `impl Trait` to capture all lifetimes in scope.
(unstable, lifetime_capture_rules_2024, "1.76.0", None),
/// Allows `#[link(..., cfg(..))]`; perma-unstable per #37406
(internal, link_cfg, "1.14.0", None),
/// Allows using `?Trait` trait bounds in more contexts.
(internal, more_maybe_bounds, "1.82.0", None),
/// Allows the `multiple_supertrait_upcastable` lint.
(unstable, multiple_supertrait_upcastable, "1.69.0", None),
/// Allow negative trait bounds. This is an internal-only feature for testing the trait solver!
(internal, negative_bounds, "1.71.0", None),
/// Allows using `#[omit_gdb_pretty_printer_section]`.
(internal, omit_gdb_pretty_printer_section, "1.5.0", None),
/// Set the maximum pattern complexity allowed (not limited by default).
(internal, pattern_complexity, "1.78.0", None),
/// Allows using pattern types.
(internal, pattern_types, "1.79.0", Some(123646)),
/// Allows using `#[prelude_import]` on glob `use` items.
(internal, prelude_import, "1.2.0", None),
/// Used to identify crates that contain the profiler runtime.
(internal, profiler_runtime, "1.18.0", None),
/// Allows using `rustc_*` attributes (RFC 572).
(internal, rustc_attrs, "1.0.0", None),
/// Allows using the `#[stable]` and `#[unstable]` attributes.
(internal, staged_api, "1.0.0", None),
/// Added for testing unstable lints; perma-unstable.
(internal, test_unstable_lint, "1.60.0", None),
/// Helps with formatting for `group_imports = "StdExternalCrate"`.
(unstable, unqualified_local_imports, "1.83.0", None),
/// Use for stable + negative coherence and strict coherence depending on trait's
/// rustc_strict_coherence value.
(unstable, with_negative_coherence, "1.60.0", None),
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// no-tracking-issue-end
// -------------------------------------------------------------------------
// feature-group-end: internal feature gates (no tracking issue)
// -------------------------------------------------------------------------
// -------------------------------------------------------------------------
// feature-group-start: internal feature gates
// -------------------------------------------------------------------------
/// Allows using the `vectorcall` ABI.
(unstable, abi_vectorcall, "1.7.0", Some(124485)),
/// Allows features specific to auto traits.
/// Renamed from `optin_builtin_traits`.
(unstable, auto_traits, "1.50.0", Some(13231)),
/// Allows using `box` in patterns (RFC 469).
(unstable, box_patterns, "1.0.0", Some(29641)),
/// Allows builtin # foo() syntax
(internal, builtin_syntax, "1.71.0", Some(110680)),
/// Allows `#[doc(notable_trait)]`.
/// Renamed from `doc_spotlight`.
(unstable, doc_notable_trait, "1.52.0", Some(45040)),
/// Allows using the `may_dangle` attribute (RFC 1327).
(unstable, dropck_eyepatch, "1.10.0", Some(34761)),
/// Allows making `dyn Trait` well-formed even if `Trait` is not dyn-compatible[^1].
/// In that case, `dyn Trait: Trait` does not hold. Moreover, coercions and
/// casts in safe Rust to `dyn Trait` for such a `Trait` is also forbidden.
///
/// Renamed from `object_safe_for_dispatch`.
///
/// [^1]: Formerly known as "object safe".
(unstable, dyn_compatible_for_dispatch, "1.83.0", Some(43561)),
/// Allows using the `#[fundamental]` attribute.
(unstable, fundamental, "1.0.0", Some(29635)),
/// Allows using `#[link_name="llvm.*"]`.
(internal, link_llvm_intrinsics, "1.0.0", Some(29602)),
/// Allows using the `#[linkage = ".."]` attribute.
(unstable, linkage, "1.0.0", Some(29603)),
/// Allows declaring with `#![needs_panic_runtime]` that a panic runtime is needed.
(internal, needs_panic_runtime, "1.10.0", Some(32837)),
/// Allows using the `#![panic_runtime]` attribute.
(internal, panic_runtime, "1.10.0", Some(32837)),
/// Allows using `#[rustc_allow_const_fn_unstable]`.
/// This is an attribute on `const fn` for the same
/// purpose as `#[allow_internal_unstable]`.
(internal, rustc_allow_const_fn_unstable, "1.49.0", Some(69399)),
/// Allows using compiler's own crates.
(unstable, rustc_private, "1.0.0", Some(27812)),
/// Allows using internal rustdoc features like `doc(keyword)`.
(internal, rustdoc_internals, "1.58.0", Some(90418)),
/// Allows using the `rustdoc::missing_doc_code_examples` lint
(unstable, rustdoc_missing_doc_code_examples, "1.31.0", Some(101730)),
/// Allows using `#[start]` on a function indicating that it is the program entrypoint.
(unstable, start, "1.0.0", Some(29633)),
/// Allows using `#[structural_match]` which indicates that a type is structurally matchable.
/// FIXME: Subsumed by trait `StructuralPartialEq`, cannot move to removed until a library
/// feature with the same name exists.
(unstable, structural_match, "1.8.0", Some(31434)),
/// Allows using the `rust-call` ABI.
(unstable, unboxed_closures, "1.0.0", Some(29625)),
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// -------------------------------------------------------------------------
// feature-group-end: internal feature gates
// -------------------------------------------------------------------------
// -------------------------------------------------------------------------
// feature-group-start: actual feature gates (target features)
// -------------------------------------------------------------------------
// FIXME: Document these and merge with the list below.
// Unstable `#[target_feature]` directives.
(unstable, aarch64_unstable_target_feature, "1.82.0", Some(44839)),
(unstable, aarch64_ver_target_feature, "1.27.0", Some(44839)),
(unstable, arm_target_feature, "1.27.0", Some(44839)),
(unstable, avx512_target_feature, "1.27.0", Some(44839)),
(unstable, bpf_target_feature, "1.54.0", Some(44839)),
(unstable, csky_target_feature, "1.73.0", Some(44839)),
(unstable, ermsb_target_feature, "1.49.0", Some(44839)),
(unstable, hexagon_target_feature, "1.27.0", Some(44839)),
(unstable, lahfsahf_target_feature, "1.78.0", Some(44839)),
(unstable, loongarch_target_feature, "1.73.0", Some(44839)),
(unstable, mips_target_feature, "1.27.0", Some(44839)),
(unstable, powerpc_target_feature, "1.27.0", Some(44839)),
(unstable, prfchw_target_feature, "1.78.0", Some(44839)),
(unstable, riscv_target_feature, "1.45.0", Some(44839)),
(unstable, rtm_target_feature, "1.35.0", Some(44839)),
(unstable, s390x_target_feature, "1.82.0", Some(44839)),
(unstable, sparc_target_feature, "CURRENT_RUSTC_VERSION", Some(132783)),
(unstable, sse4a_target_feature, "1.27.0", Some(44839)),
(unstable, tbm_target_feature, "1.27.0", Some(44839)),
(unstable, wasm_target_feature, "1.30.0", Some(44839)),
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// -------------------------------------------------------------------------
// feature-group-end: actual feature gates (target features)
// -------------------------------------------------------------------------
// -------------------------------------------------------------------------
// feature-group-start: actual feature gates
// -------------------------------------------------------------------------
/// Allows `extern "avr-interrupt" fn()` and `extern "avr-non-blocking-interrupt" fn()`.
(unstable, abi_avr_interrupt, "1.45.0", Some(69664)),
/// Allows `extern "C-cmse-nonsecure-call" fn()`.
(unstable, abi_c_cmse_nonsecure_call, "1.51.0", Some(81391)),
/// Allows `extern "msp430-interrupt" fn()`.
(unstable, abi_msp430_interrupt, "1.16.0", Some(38487)),
/// Allows `extern "ptx-*" fn()`.
(unstable, abi_ptx, "1.15.0", Some(38788)),
/// Allows `extern "riscv-interrupt-m" fn()` and `extern "riscv-interrupt-s" fn()`.
(unstable, abi_riscv_interrupt, "1.73.0", Some(111889)),
/// Allows `extern "x86-interrupt" fn()`.
(unstable, abi_x86_interrupt, "1.17.0", Some(40180)),
/// Allows additional const parameter types, such as `[u8; 10]` or user defined types
(unstable, adt_const_params, "1.56.0", Some(95174)),
/// Allows defining an `#[alloc_error_handler]`.
(unstable, alloc_error_handler, "1.29.0", Some(51540)),
/// Allows inherent and trait methods with arbitrary self types.
(unstable, arbitrary_self_types, "1.23.0", Some(44874)),
/// Allows inherent and trait methods with arbitrary self types that are raw pointers.
(unstable, arbitrary_self_types_pointers, "1.83.0", Some(44874)),
/// Enables experimental inline assembly support for additional architectures.
(unstable, asm_experimental_arch, "1.58.0", Some(93335)),
/// Allows using `label` operands in inline assembly.
(unstable, asm_goto, "1.78.0", Some(119364)),
/// Allows the `may_unwind` option in inline assembly.
(unstable, asm_unwind, "1.58.0", Some(93334)),
/// Allows users to enforce equality of associated constants `TraitImpl<AssocConst=3>`.
(unstable, associated_const_equality, "1.58.0", Some(92827)),
/// Allows associated type defaults.
(unstable, associated_type_defaults, "1.2.0", Some(29661)),
/// Allows `async || body` closures.
(unstable, async_closure, "1.37.0", Some(62290)),
/// Allows `#[track_caller]` on async functions.
(unstable, async_fn_track_caller, "1.73.0", Some(110011)),
/// Allows `for await` loops.
(unstable, async_for_loop, "1.77.0", Some(118898)),
/// Allows using C-variadics.
(unstable, c_variadic, "1.34.0", Some(44930)),
/// Allows the use of `#[cfg(<true/false>)]`.
(unstable, cfg_boolean_literals, "1.83.0", Some(131204)),
/// Allows the use of `#[cfg(overflow_checks)` to check if integer overflow behaviour.
(unstable, cfg_overflow_checks, "1.71.0", Some(111466)),
/// Provides the relocation model information as cfg entry
(unstable, cfg_relocation_model, "1.73.0", Some(114929)),
/// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
(unstable, cfg_sanitize, "1.41.0", Some(39699)),
/// Allows `cfg(sanitizer_cfi_generalize_pointers)` and `cfg(sanitizer_cfi_normalize_integers)`.
(unstable, cfg_sanitizer_cfi, "1.77.0", Some(89653)),
/// Allows `cfg(target(abi = "..."))`.
(unstable, cfg_target_compact, "1.63.0", Some(96901)),
/// Allows `cfg(target_has_atomic_load_store = "...")`.
(unstable, cfg_target_has_atomic, "1.60.0", Some(94039)),
/// Allows `cfg(target_has_atomic_equal_alignment = "...")`.
(unstable, cfg_target_has_atomic_equal_alignment, "1.60.0", Some(93822)),
/// Allows `cfg(target_thread_local)`.
(unstable, cfg_target_thread_local, "1.7.0", Some(29594)),
/// Allows the use of `#[cfg(ub_checks)` to check if UB checks are enabled.
(unstable, cfg_ub_checks, "1.79.0", Some(123499)),
/// Allow conditional compilation depending on rust version
(unstable, cfg_version, "1.45.0", Some(64796)),
/// Allows to use the `#[cfi_encoding = ""]` attribute.
(unstable, cfi_encoding, "1.71.0", Some(89653)),
/// Allows `for<...>` on closures and coroutines.
(unstable, closure_lifetime_binder, "1.64.0", Some(97362)),
/// Allows `#[track_caller]` on closures and coroutines.
(unstable, closure_track_caller, "1.57.0", Some(87417)),
/// Allows `extern "C-cmse-nonsecure-entry" fn()`.
(unstable, cmse_nonsecure_entry, "1.48.0", Some(75835)),
/// Allows `async {}` expressions in const contexts.
(unstable, const_async_blocks, "1.53.0", Some(85368)),
/// Allows `const || {}` closures in const contexts.
(incomplete, const_closures, "1.68.0", Some(106003)),
/// Allows `for _ in _` loops in const contexts.
(unstable, const_for, "1.56.0", Some(87575)),
/// Be more precise when looking for live drops in a const context.
(unstable, const_precise_live_drops, "1.46.0", Some(73255)),
/// Allows `impl const Trait for T` syntax.
(unstable, const_trait_impl, "1.42.0", Some(67792)),
/// Allows the `?` operator in const contexts.
(unstable, const_try, "1.56.0", Some(74935)),
/// Allows coroutines to be cloned.
(unstable, coroutine_clone, "1.65.0", Some(95360)),
/// Allows defining coroutines.
(unstable, coroutines, "1.21.0", Some(43122)),
/// Allows function attribute `#[coverage(on/off)]`, to control coverage
/// instrumentation of that function.
(unstable, coverage_attribute, "1.74.0", Some(84605)),
/// Allows non-builtin attributes in inner attribute position.
(unstable, custom_inner_attributes, "1.30.0", Some(54726)),
/// Allows custom test frameworks with `#![test_runner]` and `#[test_case]`.
(unstable, custom_test_frameworks, "1.30.0", Some(50297)),
/// Allows declarative macros 2.0 (`macro`).
(unstable, decl_macro, "1.17.0", Some(39412)),
/// Allows using `#[deprecated_safe]` to deprecate the safeness of a function or trait
(unstable, deprecated_safe, "1.61.0", Some(94978)),
/// Allows having using `suggestion` in the `#[deprecated]` attribute.
(unstable, deprecated_suggestion, "1.61.0", Some(94785)),
/// Allows deref patterns.
(incomplete, deref_patterns, "1.79.0", Some(87121)),
/// Controls errors in trait implementations.
(unstable, do_not_recommend, "1.67.0", Some(51992)),
/// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
(unstable, doc_auto_cfg, "1.58.0", Some(43781)),
/// Allows `#[doc(cfg(...))]`.
(unstable, doc_cfg, "1.21.0", Some(43781)),
/// Allows `#[doc(cfg_hide(...))]`.
(unstable, doc_cfg_hide, "1.57.0", Some(43781)),
/// Allows `#[doc(masked)]`.
(unstable, doc_masked, "1.21.0", Some(44027)),
/// Allows `dyn* Trait` objects.
(incomplete, dyn_star, "1.65.0", Some(102425)),
/// Allows exhaustive pattern matching on types that contain uninhabited types.
(unstable, exhaustive_patterns, "1.13.0", Some(51085)),
/// Allows explicit tail calls via `become` expression.
(incomplete, explicit_tail_calls, "1.72.0", Some(112788)),
/// Allows using `efiapi`, `sysv64` and `win64` as calling convention
/// for functions with varargs.
(unstable, extended_varargs_abi_support, "1.65.0", Some(100189)),
/// Allows defining `extern type`s.
(unstable, extern_types, "1.23.0", Some(43467)),
/// Allow using 128-bit (quad precision) floating point numbers.
(unstable, f128, "1.78.0", Some(116909)),
/// Allow using 16-bit (half precision) floating point numbers.
(unstable, f16, "1.78.0", Some(116909)),
/// Allows the use of `#[ffi_const]` on foreign functions.
(unstable, ffi_const, "1.45.0", Some(58328)),
/// Allows the use of `#[ffi_pure]` on foreign functions.
(unstable, ffi_pure, "1.45.0", Some(58329)),
/// Controlling the behavior of fmt::Debug
(unstable, fmt_debug, "1.82.0", Some(129709)),
/// Allows using `#[repr(align(...))]` on function items
(unstable, fn_align, "1.53.0", Some(82232)),
/// Support delegating implementation of functions to other already implemented functions.
(incomplete, fn_delegation, "1.76.0", Some(118212)),
/// Allows impls for the Freeze trait.
(internal, freeze_impls, "1.78.0", Some(121675)),
/// Allows defining gen blocks and `gen fn`.
(unstable, gen_blocks, "1.75.0", Some(117078)),
/// Infer generic args for both consts and types.
(unstable, generic_arg_infer, "1.55.0", Some(85077)),
/// An extension to the `generic_associated_types` feature, allowing incomplete features.
(incomplete, generic_associated_types_extended, "1.61.0", Some(95451)),
/// Allows non-trivial generic constants which have to have wfness manually propagated to callers
(incomplete, generic_const_exprs, "1.56.0", Some(76560)),
/// Allows generic parameters and where-clauses on free & associated const items.
(incomplete, generic_const_items, "1.73.0", Some(113521)),
/// Allows registering static items globally, possibly across crates, to iterate over at runtime.
(unstable, global_registration, "1.80.0", Some(125119)),
/// Allows using `..=X` as a patterns in slices.
(unstable, half_open_range_patterns_in_slices, "1.66.0", Some(67264)),
/// Allows `if let` guard in match arms.
(unstable, if_let_guard, "1.47.0", Some(51114)),
/// Allows `impl Trait` to be used inside associated types (RFC 2515).
(unstable, impl_trait_in_assoc_type, "1.70.0", Some(63063)),
/// Allows `impl Trait` as output type in `Fn` traits in return position of functions.
(unstable, impl_trait_in_fn_trait_return, "1.64.0", Some(99697)),
/// Allows associated types in inherent impls.
(incomplete, inherent_associated_types, "1.52.0", Some(8995)),
/// Allow anonymous constants from an inline `const` block in pattern position
(unstable, inline_const_pat, "1.58.0", Some(76001)),
/// Allows using `pointer` and `reference` in intra-doc links
(unstable, intra_doc_pointers, "1.51.0", Some(80896)),
// Allows setting the threshold for the `large_assignments` lint.
(unstable, large_assignments, "1.52.0", Some(83518)),
/// Allow to have type alias types for inter-crate use.
(incomplete, lazy_type_alias, "1.72.0", Some(112792)),
/// Allows `if/while p && let q = r && ...` chains.
(unstable, let_chains, "1.37.0", Some(53667)),
/// Allows using `#[link(kind = "link-arg", name = "...")]`
/// to pass custom arguments to the linker.
(unstable, link_arg_attribute, "1.76.0", Some(99427)),
/// Give access to additional metadata about declarative macro meta-variables.
(unstable, macro_metavar_expr, "1.61.0", Some(83527)),
/// Provides a way to concatenate identifiers using metavariable expressions.
(unstable, macro_metavar_expr_concat, "1.81.0", Some(124225)),
/// Allows `#[marker]` on certain traits allowing overlapping implementations.
(unstable, marker_trait_attr, "1.30.0", Some(29864)),
/// Enables the generic const args MVP (only bare paths, not arbitrary computation).
(incomplete, min_generic_const_args, "CURRENT_RUSTC_VERSION", Some(132980)),
/// A minimal, sound subset of specialization intended to be used by the
/// standard library until the soundness issues with specialization
/// are fixed.
(unstable, min_specialization, "1.7.0", Some(31844)),
/// Allows qualified paths in struct expressions, struct patterns and tuple struct patterns.
(unstable, more_qualified_paths, "1.54.0", Some(86935)),
/// Allows the `#[must_not_suspend]` attribute.
(unstable, must_not_suspend, "1.57.0", Some(83310)),
/// Allows `mut ref` and `mut ref mut` identifier patterns.
(incomplete, mut_ref, "1.79.0", Some(123076)),
/// Allows using `#[naked]` on functions.
(unstable, naked_functions, "1.9.0", Some(90957)),
/// Allows specifying the as-needed link modifier
(unstable, native_link_modifiers_as_needed, "1.53.0", Some(81490)),
/// Allow negative trait implementations.
(unstable, negative_impls, "1.44.0", Some(68318)),
/// Allows the `!` pattern.
(incomplete, never_patterns, "1.76.0", Some(118155)),
/// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
(unstable, never_type, "1.13.0", Some(35121)),
/// Allows diverging expressions to fall back to `!` rather than `()`.
(unstable, never_type_fallback, "1.41.0", Some(65992)),
/// Allows `#![no_core]`.
(unstable, no_core, "1.3.0", Some(29639)),
/// Allows the use of `no_sanitize` attribute.
(unstable, no_sanitize, "1.42.0", Some(39699)),
/// Allows using the `non_exhaustive_omitted_patterns` lint.
(unstable, non_exhaustive_omitted_patterns_lint, "1.57.0", Some(89554)),
/// Allows `for<T>` binders in where-clauses
(incomplete, non_lifetime_binders, "1.69.0", Some(108185)),
/// Allows using enums in offset_of!
(unstable, offset_of_enum, "1.75.0", Some(120141)),
/// Allows using fields with slice type in offset_of!
(unstable, offset_of_slice, "1.81.0", Some(126151)),
/// Allows using `#[optimize(X)]`.
(unstable, optimize_attribute, "1.34.0", Some(54882)),
/// Allows specifying nop padding on functions for dynamic patching.
(unstable, patchable_function_entry, "1.81.0", Some(123115)),
/// Experimental features that make `Pin` more ergonomic.
(incomplete, pin_ergonomics, "1.83.0", Some(130494)),
/// Allows postfix match `expr.match { ... }`
(unstable, postfix_match, "1.79.0", Some(121618)),
/// Allows `use<..>` precise capturign on impl Trait in traits.
(unstable, precise_capturing_in_traits, "1.83.0", Some(130044)),
/// Allows macro attributes on expressions, statements and non-inline modules.
(unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
/// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
(incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),
/// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024—structural variant
(incomplete, ref_pat_eat_one_layer_2024_structural, "1.81.0", Some(123076)),
/// Allows using the `#[register_tool]` attribute.
(unstable, register_tool, "1.41.0", Some(66079)),
/// Allows the `#[repr(i128)]` attribute for enums.
(incomplete, repr128, "1.16.0", Some(56071)),
/// Allows `repr(simd)` and importing the various simd intrinsics.
(unstable, repr_simd, "1.4.0", Some(27731)),
/// Allows bounding the return type of AFIT/RPITIT.
(unstable, return_type_notation, "1.70.0", Some(109417)),
/// Allows `extern "rust-cold"`.
(unstable, rust_cold_cc, "1.63.0", Some(97544)),
/// Allows use of x86 SHA512, SM3 and SM4 target-features and intrinsics
(unstable, sha512_sm_x86, "1.82.0", Some(126624)),
/// Allows the use of SIMD types in functions declared in `extern` blocks.
(unstable, simd_ffi, "1.0.0", Some(27731)),
/// Allows specialization of implementations (RFC 1210).
(incomplete, specialization, "1.7.0", Some(31844)),
/// Allows attributes on expressions and non-item statements.
(unstable, stmt_expr_attributes, "1.6.0", Some(15701)),
/// Allows lints part of the strict provenance effort.
(unstable, strict_provenance_lints, "1.61.0", Some(130351)),
/// Allows string patterns to dereference values to match them.
(unstable, string_deref_patterns, "1.67.0", Some(87121)),
/// Allows the use of `#[target_feature]` on safe functions.
(unstable, target_feature_11, "1.45.0", Some(69098)),
/// Allows using `#[thread_local]` on `static` items.
(unstable, thread_local, "1.0.0", Some(29594)),
/// Allows defining `trait X = A + B;` alias items.
(unstable, trait_alias, "1.24.0", Some(41517)),
/// Allows dyn upcasting trait objects via supertraits.
/// Dyn upcasting is casting, e.g., `dyn Foo -> dyn Bar` where `Foo: Bar`.
(unstable, trait_upcasting, "1.56.0", Some(65991)),
/// Allows for transmuting between arrays with sizes that contain generic consts.
(unstable, transmute_generic_consts, "1.70.0", Some(109929)),
/// Allows #[repr(transparent)] on unions (RFC 2645).
(unstable, transparent_unions, "1.37.0", Some(60405)),
/// Allows inconsistent bounds in where clauses.
(unstable, trivial_bounds, "1.28.0", Some(48214)),
/// Allows using `try {...}` expressions.
(unstable, try_blocks, "1.29.0", Some(31436)),
/// Allows `impl Trait` to be used inside type aliases (RFC 2515).
(unstable, type_alias_impl_trait, "1.38.0", Some(63063)),
/// Allows creation of instances of a struct by moving fields that have
/// not changed from prior instances of the same struct (RFC #2528)
(unstable, type_changing_struct_update, "1.58.0", Some(86555)),
/// Allows const generic parameters to be defined with types that
/// are not `Sized`, e.g. `fn foo<const N: [u8]>() {`.
(incomplete, unsized_const_params, "1.82.0", Some(95174)),
/// Allows unsized fn parameters.
(internal, unsized_fn_params, "1.49.0", Some(48055)),
/// Allows unsized rvalues at arguments and parameters.
(incomplete, unsized_locals, "1.30.0", Some(48055)),
/// Allows unsized tuple coercion.
(unstable, unsized_tuple_coercion, "1.20.0", Some(42877)),
/// Allows using the `#[used(linker)]` (or `#[used(compiler)]`) attribute.
(unstable, used_with_arg, "1.60.0", Some(93798)),
/// Allows use of x86 `AMX` target-feature attributes and intrinsics
(unstable, x86_amx_intrinsics, "1.81.0", Some(126622)),
/// Allows use of the `xop` target-feature
(unstable, xop_target_feature, "1.81.0", Some(127208)),
/// Allows `do yeet` expressions
(unstable, yeet_expr, "1.62.0", Some(96373)),
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
// !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
// -------------------------------------------------------------------------
// feature-group-end: actual feature gates
// -------------------------------------------------------------------------
);
/// Some features are not allowed to be used together at the same time, if
/// the two are present, produce an error.
///
/// Currently empty, but we will probably need this again in the future,
/// so let's keep it in for now.
pub const INCOMPATIBLE_FEATURES: &[(Symbol, Symbol)] = &[];