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//! List of the active feature gates.
use super::{Feature, State};
use rustc_span::edition::Edition;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
macro_rules! set {
($field: ident) => {{
fn f(features: &mut Features, _: Span) {
features.$field = true;
f as fn(&mut Features, Span)
macro_rules! declare_features {
$(#[doc = $doc:tt])* (active, $feature:ident, $ver:expr, $issue:expr, $edition:expr),
)+) => {
/// Represents active features that are currently being implemented or
/// currently being considered for addition/removal.
&[Feature] =
// (sym::$feature, $ver, $issue, $edition, set!($feature))
Feature {
state: State::Active { set: set!($feature) },
name: sym::$feature,
since: $ver,
issue: $issue,
edition: $edition,
description: concat!($($doc,)*),
/// A set of features to be used by later passes.
#[derive(Clone, Default)]
pub struct Features {
/// `#![feature]` attrs for language features, for error reporting.
pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
/// `#![feature]` attrs for non-language (library) features.
pub declared_lib_features: Vec<(Symbol, Span)>,
$(#[doc = $doc])*
pub $feature: bool
impl Features {
pub fn walk_feature_fields(&self, mut f: impl FnMut(&str, bool)) {
$(f(stringify!($feature), self.$feature);)+
/// Is the given feature enabled?
/// Panics if the symbol doesn't correspond to a declared feature.
pub fn enabled(&self, feature: Symbol) -> bool {
match feature {
$( sym::$feature => self.$feature, )*
_ => panic!("`{}` was not listed in `declare_features`", feature),
impl Feature {
/// Sets this feature in `Features`. Panics if called on a non-active feature.
pub fn set(&self, features: &mut Features, span: Span) {
match self.state {
State::Active { set } => set(features, span),
_ => panic!("called `set` on feature `{}` which is not `active`",,
// If you change this, please modify `src/doc/unstable-book` as well.
// Don't ever remove anything from this list; move them to ``.
// The version numbers here correspond to the version in which the current status
// was set. This is most important for knowing when a particular feature became
// stable (active).
// Note that the features are grouped into internal/user-facing and then
// sorted by version inside those groups. This is enforced with tidy.
// N.B., `tools/tidy/src/` parses this information directly out of the
// source, so take care when modifying it.
declare_features! (
// -------------------------------------------------------------------------
// feature-group-start: internal feature gates
// -------------------------------------------------------------------------
// no-tracking-issue-start
/// Allows using `rustc_*` attributes (RFC 572).
(active, rustc_attrs, "1.0.0", None, None),
/// Allows using compiler's own crates.
(active, rustc_private, "1.0.0", Some(27812), None),
/// Allows using the `rust-intrinsic`'s "ABI".
(active, intrinsics, "1.0.0", None, None),
/// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
(active, lang_items, "1.0.0", None, None),
/// Allows using the `#[stable]` and `#[unstable]` attributes.
(active, staged_api, "1.0.0", None, 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).
(active, allow_internal_unstable, "1.0.0", None, 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).
(active, allow_internal_unsafe, "1.0.0", None, None),
/// no-tracking-issue-end
/// Allows using `#[link_name="llvm.*"]`.
(active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
/// Allows using the `box $expr` syntax.
(active, box_syntax, "1.0.0", Some(49733), None),
/// Allows using `#[main]` to replace the entrypoint `#[lang = "start"]` calls.
(active, main, "1.0.0", Some(29634), None),
/// Allows using `#[start]` on a function indicating that it is the program entrypoint.
(active, start, "1.0.0", Some(29633), None),
/// Allows using the `#[fundamental]` attribute.
(active, fundamental, "1.0.0", Some(29635), None),
/// Allows using the `rust-call` ABI.
(active, unboxed_closures, "1.0.0", Some(29625), None),
/// Allows using the `#[linkage = ".."]` attribute.
(active, linkage, "1.0.0", Some(29603), None),
/// Allows features specific to OIBIT (auto traits).
(active, optin_builtin_traits, "1.0.0", Some(13231), None),
/// Allows using `box` in patterns (RFC 469).
(active, box_patterns, "1.0.0", Some(29641), None),
// no-tracking-issue-start
/// Allows using `#[prelude_import]` on glob `use` items.
(active, prelude_import, "1.2.0", None, None),
// no-tracking-issue-end
// no-tracking-issue-start
/// Allows using `#[omit_gdb_pretty_printer_section]`.
(active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
/// Allows using the `vectorcall` ABI.
(active, abi_vectorcall, "1.7.0", None, None),
// no-tracking-issue-end
/// 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.
(active, structural_match, "1.8.0", Some(31434), None),
/// Allows using the `may_dangle` attribute (RFC 1327).
(active, dropck_eyepatch, "1.10.0", Some(34761), None),
/// Allows using the `#![panic_runtime]` attribute.
(active, panic_runtime, "1.10.0", Some(32837), None),
/// Allows declaring with `#![needs_panic_runtime]` that a panic runtime is needed.
(active, needs_panic_runtime, "1.10.0", Some(32837), None),
// no-tracking-issue-start
/// Allows identifying the `compiler_builtins` crate.
(active, compiler_builtins, "1.13.0", None, None),
/// Allows using the `unadjusted` ABI; perma-unstable.
(active, abi_unadjusted, "1.16.0", None, None),
/// Used to identify crates that contain the profiler runtime.
(active, profiler_runtime, "1.18.0", None, None),
/// Allows using the `thiscall` ABI.
(active, abi_thiscall, "1.19.0", None, None),
/// Allows using `#![needs_allocator]`, an implementation detail of `#[global_allocator]`.
(active, allocator_internals, "1.20.0", None, None),
/// Added for testing E0705; perma-unstable.
(active, test_2018_feature, "1.31.0", None, Some(Edition::Edition2018)),
/// Allows `#[repr(no_niche)]` (an implementation detail of `rustc`,
/// it is not on path for eventual stabilization).
(active, no_niche, "1.42.0", None, None),
// no-tracking-issue-end
// -------------------------------------------------------------------------
// 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.
(active, arm_target_feature, "1.27.0", Some(44839), None),
(active, aarch64_target_feature, "1.27.0", Some(44839), None),
(active, hexagon_target_feature, "1.27.0", Some(44839), None),
(active, powerpc_target_feature, "1.27.0", Some(44839), None),
(active, mips_target_feature, "1.27.0", Some(44839), None),
(active, avx512_target_feature, "1.27.0", Some(44839), None),
(active, mmx_target_feature, "1.27.0", Some(44839), None),
(active, sse4a_target_feature, "1.27.0", Some(44839), None),
(active, tbm_target_feature, "1.27.0", Some(44839), None),
(active, wasm_target_feature, "1.30.0", Some(44839), None),
(active, adx_target_feature, "1.32.0", Some(44839), None),
(active, cmpxchg16b_target_feature, "1.32.0", Some(44839), None),
(active, movbe_target_feature, "1.34.0", Some(44839), None),
(active, rtm_target_feature, "1.35.0", Some(44839), None),
(active, f16c_target_feature, "1.36.0", Some(44839), None),
(active, riscv_target_feature, "1.45.0", Some(44839), None),
// -------------------------------------------------------------------------
// feature-group-end: actual feature gates (target features)
// -------------------------------------------------------------------------
// -------------------------------------------------------------------------
// feature-group-start: actual feature gates
// -------------------------------------------------------------------------
/// Allows using the `#[link_args]` attribute.
(active, link_args, "1.0.0", Some(29596), None),
/// Allows defining identifiers beyond ASCII.
(active, non_ascii_idents, "1.0.0", Some(55467), None),
/// Allows using `#[plugin_registrar]` on functions.
(active, plugin_registrar, "1.0.0", Some(29597), None),
/// Allows using `#![plugin(myplugin)]`.
(active, plugin, "1.0.0", Some(29597), None),
/// Allows using `#[thread_local]` on `static` items.
(active, thread_local, "1.0.0", Some(29594), None),
/// Allows the use of SIMD types in functions declared in `extern` blocks.
(active, simd_ffi, "1.0.0", Some(27731), None),
/// Allows using non lexical lifetimes (RFC 2094).
(active, nll, "1.0.0", Some(43234), None),
/// Allows the definition of `const` functions with some advanced features.
(active, const_fn, "1.2.0", Some(57563), None),
/// Allows associated type defaults.
(active, associated_type_defaults, "1.2.0", Some(29661), None),
/// Allows `#![no_core]`.
(active, no_core, "1.3.0", Some(29639), None),
/// Allows default type parameters to influence type inference.
(active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
/// Allows `repr(simd)` and importing the various simd intrinsics.
(active, repr_simd, "1.4.0", Some(27731), None),
/// Allows `extern "platform-intrinsic" { ... }`.
(active, platform_intrinsics, "1.4.0", Some(27731), None),
/// Allows `#[unwind(..)]`.
/// Permits specifying whether a function should permit unwinding or abort on unwind.
(active, unwind_attributes, "1.4.0", Some(58760), None),
/// Allows attributes on expressions and non-item statements.
(active, stmt_expr_attributes, "1.6.0", Some(15701), None),
/// Allows the use of type ascription in expressions.
(active, type_ascription, "1.6.0", Some(23416), None),
/// Allows `cfg(target_thread_local)`.
(active, cfg_target_thread_local, "1.7.0", Some(29594), None),
/// Allows specialization of implementations (RFC 1210).
(active, specialization, "1.7.0", Some(31844), None),
/// A minimal, sound subset of specialization intended to be used by the
/// standard library until the soundness issues with specialization
/// are fixed.
(active, min_specialization, "1.7.0", Some(31844), None),
/// Allows using `#[naked]` on functions.
(active, naked_functions, "1.9.0", Some(32408), None),
/// Allows `cfg(target_has_atomic = "...")`.
(active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
/// Allows `X..Y` patterns.
(active, exclusive_range_pattern, "1.11.0", Some(37854), None),
/// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
(active, never_type, "1.13.0", Some(35121), None),
/// Allows exhaustive pattern matching on types that contain uninhabited types.
(active, exhaustive_patterns, "1.13.0", Some(51085), None),
/// Allows `union`s to implement `Drop`. Moreover, `union`s may now include fields
/// that don't implement `Copy` as long as they don't have any drop glue.
/// This is checked recursively. On encountering type variable where no progress can be made,
/// `T: Copy` is used as a substitute for "no drop glue".
/// NOTE: A limited form of `union U { ... }` was accepted in 1.19.0.
(active, untagged_unions, "1.13.0", Some(55149), None),
/// Allows `#[link(..., cfg(..))]`.
(active, link_cfg, "1.14.0", Some(37406), None),
/// Allows `extern "ptx-*" fn()`.
(active, abi_ptx, "1.15.0", Some(38788), None),
/// Allows the `#[repr(i128)]` attribute for enums.
(active, repr128, "1.16.0", Some(56071), None),
/// Allows `#[link(kind="static-nobundle"...)]`.
(active, static_nobundle, "1.16.0", Some(37403), None),
/// Allows `extern "msp430-interrupt" fn()`.
(active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
/// Allows declarative macros 2.0 (`macro`).
(active, decl_macro, "1.17.0", Some(39412), None),
/// Allows `extern "x86-interrupt" fn()`.
(active, abi_x86_interrupt, "1.17.0", Some(40180), None),
/// Allows a test to fail without failing the whole suite.
(active, allow_fail, "1.19.0", Some(46488), None),
/// Allows unsized tuple coercion.
(active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
/// Allows defining generators.
(active, generators, "1.21.0", Some(43122), None),
/// Allows `#[doc(cfg(...))]`.
(active, doc_cfg, "1.21.0", Some(43781), None),
/// Allows `#[doc(masked)]`.
(active, doc_masked, "1.21.0", Some(44027), None),
/// Allows `#[doc(include = "some-file")]`.
(active, external_doc, "1.22.0", Some(44732), None),
/// Allows using `crate` as visibility modifier, synonymous with `pub(crate)`.
(active, crate_visibility_modifier, "1.23.0", Some(53120), None),
/// Allows defining `extern type`s.
(active, extern_types, "1.23.0", Some(43467), None),
/// Allows trait methods with arbitrary self types.
(active, arbitrary_self_types, "1.23.0", Some(44874), None),
/// Allows in-band quantification of lifetime bindings (e.g., `fn foo(x: &'a u8) -> &'a u8`).
(active, in_band_lifetimes, "1.23.0", Some(44524), None),
/// Allows associated types to be generic, e.g., `type Foo<T>;` (RFC 1598).
(active, generic_associated_types, "1.23.0", Some(44265), None),
/// Allows defining `trait X = A + B;` alias items.
(active, trait_alias, "1.24.0", Some(41517), None),
/// Allows inferring `'static` outlives requirements (RFC 2093).
(active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
/// Allows accessing fields of unions inside `const` functions.
(active, const_fn_union, "1.27.0", Some(51909), None),
/// Allows casting raw pointers to `usize` during const eval.
(active, const_raw_ptr_to_usize_cast, "1.27.0", Some(51910), None),
/// Allows dereferencing raw pointers during const eval.
(active, const_raw_ptr_deref, "1.27.0", Some(51911), None),
/// Allows `#[doc(alias = "...")]`.
(active, doc_alias, "1.27.0", Some(50146), None),
/// Allows inconsistent bounds in where clauses.
(active, trivial_bounds, "1.28.0", Some(48214), None),
/// Allows `'a: { break 'a; }`.
(active, label_break_value, "1.28.0", Some(48594), None),
/// Allows using `#[doc(keyword = "...")]`.
(active, doc_keyword, "1.28.0", Some(51315), None),
/// Allows using `try {...}` expressions.
(active, try_blocks, "1.29.0", Some(31436), None),
/// Allows defining an `#[alloc_error_handler]`.
(active, alloc_error_handler, "1.29.0", Some(51540), None),
/// Allows using the `amdgpu-kernel` ABI.
(active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
/// Allows panicking during const eval (producing compile-time errors).
(active, const_panic, "1.30.0", Some(51999), None),
/// Allows `#[marker]` on certain traits allowing overlapping implementations.
(active, marker_trait_attr, "1.30.0", Some(29864), None),
/// Allows macro attributes on expressions, statements and non-inline modules.
(active, proc_macro_hygiene, "1.30.0", Some(54727), None),
/// Allows unsized rvalues at arguments and parameters.
(active, unsized_locals, "1.30.0", Some(48055), None),
/// Allows custom test frameworks with `#![test_runner]` and `#[test_case]`.
(active, custom_test_frameworks, "1.30.0", Some(50297), None),
/// Allows non-builtin attributes in inner attribute position.
(active, custom_inner_attributes, "1.30.0", Some(54726), None),
/// Allows `impl Trait` in bindings (`let`, `const`, `static`).
(active, impl_trait_in_bindings, "1.30.0", Some(63065), None),
/// Allows using `reason` in lint attributes and the `#[expect(lint)]` lint check.
(active, lint_reasons, "1.31.0", Some(54503), None),
/// Allows exhaustive integer pattern matching on `usize` and `isize`.
(active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
/// Allows using `#[ffi_returns_twice]` on foreign functions.
(active, ffi_returns_twice, "1.34.0", Some(58314), None),
/// Allows const generic types (e.g. `struct Foo<const N: usize>(...);`).
(active, const_generics, "1.34.0", Some(44580), None),
/// Allows using `#[optimize(X)]`.
(active, optimize_attribute, "1.34.0", Some(54882), None),
/// Allows using C-variadics.
(active, c_variadic, "1.34.0", Some(44930), None),
/// Allows the user of associated type bounds.
(active, associated_type_bounds, "1.34.0", Some(52662), None),
/// Allows `if/while p && let q = r && ...` chains.
(active, let_chains, "1.37.0", Some(53667), None),
/// Allows #[repr(transparent)] on unions (RFC 2645).
(active, transparent_unions, "1.37.0", Some(60405), None),
/// Allows explicit discriminants on non-unit enum variants.
(active, arbitrary_enum_discriminant, "1.37.0", Some(60553), None),
/// Allows `impl Trait` with multiple unrelated lifetimes.
(active, member_constraints, "1.37.0", Some(61997), None),
/// Allows `async || body` closures.
(active, async_closure, "1.37.0", Some(62290), None),
/// Allows `[x; N]` where `x` is a constant (RFC 2203).
(active, const_in_array_repeat_expressions, "1.37.0", Some(49147), None),
/// Allows `impl Trait` to be used inside type aliases (RFC 2515).
(active, type_alias_impl_trait, "1.38.0", Some(63063), None),
/// Allows the use of or-patterns (e.g., `0 | 1`).
(active, or_patterns, "1.38.0", Some(54883), None),
/// Allows the definition of `const extern fn` and `const unsafe extern fn`.
(active, const_extern_fn, "1.40.0", Some(64926), None),
/// Allows the use of raw-dylibs (RFC 2627).
(active, raw_dylib, "1.40.0", Some(58713), None),
/// Allows making `dyn Trait` well-formed even if `Trait` is not object safe.
/// 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.
(active, object_safe_for_dispatch, "1.40.0", Some(43561), None),
/// Allows using the `efiapi` ABI.
(active, abi_efiapi, "1.40.0", Some(65815), None),
/// Allows `&raw const $place_expr` and `&raw mut $place_expr` expressions.
(active, raw_ref_op, "1.41.0", Some(64490), None),
/// Allows diverging expressions to fall back to `!` rather than `()`.
(active, never_type_fallback, "1.41.0", Some(65992), None),
/// Allows using the `#[register_attr]` attribute.
(active, register_attr, "1.41.0", Some(66080), None),
/// Allows using the `#[register_tool]` attribute.
(active, register_tool, "1.41.0", Some(66079), None),
/// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
(active, cfg_sanitize, "1.41.0", Some(39699), None),
/// Allows using `..X`, `..=X`, `...X`, and `X..` as a pattern.
(active, half_open_range_patterns, "1.41.0", Some(67264), None),
/// Allows using `&mut` in constant functions.
(active, const_mut_refs, "1.41.0", Some(57349), None),
/// Allows bindings in the subpattern of a binding pattern.
/// For example, you can write `x @ Some(y)`.
(active, bindings_after_at, "1.41.0", Some(65490), None),
/// Allows patterns with concurrent by-move and by-ref bindings.
/// For example, you can write `Foo(a, ref b)` where `a` is by-move and `b` is by-ref.
(active, move_ref_pattern, "1.42.0", Some(68354), None),
/// Allows `impl const Trait for T` syntax.
(active, const_trait_impl, "1.42.0", Some(67792), None),
/// Allows `T: ?const Trait` syntax in bounds.
(active, const_trait_bound_opt_out, "1.42.0", Some(67794), None),
/// Allows the use of `no_sanitize` attribute.
(active, no_sanitize, "1.42.0", Some(39699), None),
// Allows limiting the evaluation steps of const expressions
(active, const_eval_limit, "1.43.0", Some(67217), None),
/// Allow negative trait implementations.
(active, negative_impls, "1.44.0", Some(68318), None),
/// Allows the use of `#[target_feature]` on safe functions.
(active, target_feature_11, "1.45.0", Some(69098), None),
/// Allow conditional compilation depending on rust version
(active, cfg_version, "1.45.0", Some(64796), None),
/// Allows the use of `#[ffi_pure]` on foreign functions.
(active, ffi_pure, "1.45.0", Some(58329), None),
/// Allows the use of `#[ffi_const]` on foreign functions.
(active, ffi_const, "1.45.0", Some(58328), None),
/// No longer treat an unsafe function as an unsafe block.
(active, unsafe_block_in_unsafe_fn, "1.45.0", Some(71668), None),
/// Allows `extern "avr-interrupt" fn()` and `extern "avr-non-blocking-interrupt" fn()`.
(active, abi_avr_interrupt, "1.45.0", Some(69664), None),
/// Be more precise when looking for live drops in a const context.
(active, const_precise_live_drops, "1.46.0", Some(73255), None),
/// Allows capturing variables in scope using format_args!
(active, format_args_capture, "1.46.0", Some(67984), None),
/// Lazily evaluate constants. This allows constants to depend on type parameters.
(active, lazy_normalization_consts, "1.46.0", Some(72219), None),
/// Alloc calling `transmute` in const fn
(active, const_fn_transmute, "1.46.0", Some(53605), None),
// -------------------------------------------------------------------------
// feature-group-end: actual feature gates
// -------------------------------------------------------------------------
/// 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 const INCOMPLETE_FEATURES: &[Symbol] = &[