src/librustc_feature/active.rs

   1 //! List of the active feature gates.
   2
   3 use super::{State, Feature};
   4
   5 use syntax_pos::edition::Edition;
   6 use syntax_pos::Span;
   7 use syntax_pos::symbol::{Symbol, sym};
   8
   9 macro_rules! set {
  10     ($field: ident) => {{
  11         fn f(features: &mut Features, _: Span) {
  12             features.$field = true;
  13         }
  14         f as fn(&mut Features, Span)
  15     }}
  16 }
  17
  18 macro_rules! declare_features {
  19     ($(
  20         $(#[doc = $doc:tt])* (active, $feature:ident, $ver:expr, $issue:expr, $edition:expr),
  21     )+) => {
  22         /// Represents active features that are currently being implemented or
  23         /// currently being considered for addition/removal.
  24         pub const ACTIVE_FEATURES:
  25             &[Feature] =
  26             &[$(
  27                 // (sym::$feature, $ver, $issue, $edition, set!($feature))
  28                 Feature {
  29                     state: State::Active { set: set!($feature) },
  30                     name: sym::$feature,
  31                     since: $ver,
  32                     issue: $issue,
  33                     edition: $edition,
  34                     description: concat!($($doc,)*),
  35                 }
  36             ),+];
  37
  38         /// A set of features to be used by later passes.
  39         #[derive(Clone, Default)]
  40         pub struct Features {
  41             /// `#![feature]` attrs for language features, for error reporting.
  42             pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
  43             /// `#![feature]` attrs for non-language (library) features.
  44             pub declared_lib_features: Vec<(Symbol, Span)>,
  45             $(
  46                 $(#[doc = $doc])*
  47                 pub $feature: bool
  48             ),+
  49         }
  50
  51         impl Features {
  52             pub fn walk_feature_fields(&self, mut f: impl FnMut(&str, bool)) {
  53                 $(f(stringify!($feature), self.$feature);)+
  54             }
  55
  56             /// Is the given feature enabled?
  57             ///
  58             /// Panics if the symbol doesn't correspond to a declared feature.
  59             pub fn enabled(&self, feature: Symbol) -> bool {
  60                 match feature {
  61                     $( sym::$feature => self.$feature, )*
  62
  63                     _ => panic!("`{}` was not listed in `declare_features`", feature),
  64                 }
  65             }
  66         }
  67     };
  68 }
  69
  70 impl Feature {
  71     /// Sets this feature in `Features`. Panics if called on a non-active feature.
  72     pub fn set(&self, features: &mut Features, span: Span) {
  73         match self.state {
  74             State::Active { set } => set(features, span),
  75             _ => panic!("called `set` on feature `{}` which is not `active`", self.name)
  76         }
  77     }
  78 }
  79
  80 // If you change this, please modify `src/doc/unstable-book` as well.
  81 //
  82 // Don't ever remove anything from this list; move them to `removed.rs`.
  83 //
  84 // The version numbers here correspond to the version in which the current status
  85 // was set. This is most important for knowing when a particular feature became
  86 // stable (active).
  87 //
  88 // Note that the features are grouped into internal/user-facing and then
  89 // sorted by version inside those groups. This is enforced with tidy.
  90 //
  91 // N.B., `tools/tidy/src/features.rs` parses this information directly out of the
  92 // source, so take care when modifying it.
  93
  94 declare_features! (
  95     // -------------------------------------------------------------------------
  96     // feature-group-start: internal feature gates
  97     // -------------------------------------------------------------------------
  98
  99     // no-tracking-issue-start
 100
 101     /// Allows using compiler's own crates.
 102     (active, rustc_private, "1.0.0", Some(27812), None),
 103
 104     /// Allows using the `rust-intrinsic`'s "ABI".
 105     (active, intrinsics, "1.0.0", None, None),
 106
 107     /// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
 108     (active, lang_items, "1.0.0", None, None),
 109
 110     /// Allows using the `#[stable]` and `#[unstable]` attributes.
 111     (active, staged_api, "1.0.0", None, None),
 112
 113     /// Allows using `#[allow_internal_unstable]`. This is an
 114     /// attribute on `macro_rules!` and can't use the attribute handling
 115     /// below (it has to be checked before expansion possibly makes
 116     /// macros disappear).
 117     (active, allow_internal_unstable, "1.0.0", None, None),
 118
 119     /// Allows using `#[allow_internal_unsafe]`. This is an
 120     /// attribute on `macro_rules!` and can't use the attribute handling
 121     /// below (it has to be checked before expansion possibly makes
 122     /// macros disappear).
 123     (active, allow_internal_unsafe, "1.0.0", None, None),
 124
 125     /// no-tracking-issue-end
 126
 127     /// Allows using `#[link_name="llvm.*"]`.
 128     (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
 129
 130     /// Allows using `rustc_*` attributes (RFC 572).
 131     (active, rustc_attrs, "1.0.0", Some(29642), None),
 132
 133     /// Allows using the `box $expr` syntax.
 134     (active, box_syntax, "1.0.0", Some(49733), None),
 135
 136     /// Allows using `#[main]` to replace the entrypoint `#[lang = "start"]` calls.
 137     (active, main, "1.0.0", Some(29634), None),
 138
 139     /// Allows using `#[start]` on a function indicating that it is the program entrypoint.
 140     (active, start, "1.0.0", Some(29633), None),
 141
 142     /// Allows using the `#[fundamental]` attribute.
 143     (active, fundamental, "1.0.0", Some(29635), None),
 144
 145     /// Allows using the `rust-call` ABI.
 146     (active, unboxed_closures, "1.0.0", Some(29625), None),
 147
 148     /// Allows using the `#[linkage = ".."]` attribute.
 149     (active, linkage, "1.0.0", Some(29603), None),
 150
 151     /// Allows features specific to OIBIT (auto traits).
 152     (active, optin_builtin_traits, "1.0.0", Some(13231), None),
 153
 154     /// Allows using `box` in patterns (RFC 469).
 155     (active, box_patterns, "1.0.0", Some(29641), None),
 156
 157     // no-tracking-issue-start
 158
 159     /// Allows using `#[prelude_import]` on glob `use` items.
 160     (active, prelude_import, "1.2.0", None, None),
 161
 162     // no-tracking-issue-end
 163
 164     // no-tracking-issue-start
 165
 166     /// Allows using `#[omit_gdb_pretty_printer_section]`.
 167     (active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
 168
 169     /// Allows using the `vectorcall` ABI.
 170     (active, abi_vectorcall, "1.7.0", None, None),
 171
 172     // no-tracking-issue-end
 173
 174     /// Allows using `#[structural_match]` which indicates that a type is structurally matchable.
 175     (active, structural_match, "1.8.0", Some(31434), None),
 176
 177     /// Allows using the `may_dangle` attribute (RFC 1327).
 178     (active, dropck_eyepatch, "1.10.0", Some(34761), None),
 179
 180     /// Allows using the `#![panic_runtime]` attribute.
 181     (active, panic_runtime, "1.10.0", Some(32837), None),
 182
 183     /// Allows declaring with `#![needs_panic_runtime]` that a panic runtime is needed.
 184     (active, needs_panic_runtime, "1.10.0", Some(32837), None),
 185
 186     // no-tracking-issue-start
 187
 188     /// Allows identifying the `compiler_builtins` crate.
 189     (active, compiler_builtins, "1.13.0", None, None),
 190
 191     /// Allows using the `unadjusted` ABI; perma-unstable.
 192     (active, abi_unadjusted, "1.16.0", None, None),
 193
 194     /// Allows identifying crates that contain sanitizer runtimes.
 195     (active, sanitizer_runtime, "1.17.0", None, None),
 196
 197     /// Used to identify crates that contain the profiler runtime.
 198     (active, profiler_runtime, "1.18.0", None, None),
 199
 200     /// Allows using the `thiscall` ABI.
 201     (active, abi_thiscall, "1.19.0", None, None),
 202
 203     /// Allows using `#![needs_allocator]`, an implementation detail of `#[global_allocator]`.
 204     (active, allocator_internals, "1.20.0", None, None),
 205
 206     /// Added for testing E0705; perma-unstable.
 207     (active, test_2018_feature, "1.31.0", None, Some(Edition::Edition2018)),
 208
 209     // no-tracking-issue-end
 210
 211     // -------------------------------------------------------------------------
 212     // feature-group-end: internal feature gates
 213     // -------------------------------------------------------------------------
 214
 215     // -------------------------------------------------------------------------
 216     // feature-group-start: actual feature gates (target features)
 217     // -------------------------------------------------------------------------
 218
 219     // FIXME: Document these and merge with the list below.
 220
 221     // Unstable `#[target_feature]` directives.
 222     (active, arm_target_feature, "1.27.0", Some(44839), None),
 223     (active, aarch64_target_feature, "1.27.0", Some(44839), None),
 224     (active, hexagon_target_feature, "1.27.0", Some(44839), None),
 225     (active, powerpc_target_feature, "1.27.0", Some(44839), None),
 226     (active, mips_target_feature, "1.27.0", Some(44839), None),
 227     (active, avx512_target_feature, "1.27.0", Some(44839), None),
 228     (active, mmx_target_feature, "1.27.0", Some(44839), None),
 229     (active, sse4a_target_feature, "1.27.0", Some(44839), None),
 230     (active, tbm_target_feature, "1.27.0", Some(44839), None),
 231     (active, wasm_target_feature, "1.30.0", Some(44839), None),
 232     (active, adx_target_feature, "1.32.0", Some(44839), None),
 233     (active, cmpxchg16b_target_feature, "1.32.0", Some(44839), None),
 234     (active, movbe_target_feature, "1.34.0", Some(44839), None),
 235     (active, rtm_target_feature, "1.35.0", Some(44839), None),
 236     (active, f16c_target_feature, "1.36.0", Some(44839), None),
 237
 238     // -------------------------------------------------------------------------
 239     // feature-group-end: actual feature gates (target features)
 240     // -------------------------------------------------------------------------
 241
 242     // -------------------------------------------------------------------------
 243     // feature-group-start: actual feature gates
 244     // -------------------------------------------------------------------------
 245
 246     /// Allows using the `#[link_args]` attribute.
 247     (active, link_args, "1.0.0", Some(29596), None),
 248
 249     /// Allows defining identifiers beyond ASCII.
 250     (active, non_ascii_idents, "1.0.0", Some(55467), None),
 251
 252     /// Allows using `#[plugin_registrar]` on functions.
 253     (active, plugin_registrar, "1.0.0", Some(29597), None),
 254
 255     /// Allows using `#![plugin(myplugin)]`.
 256     (active, plugin, "1.0.0", Some(29597), None),
 257
 258     /// Allows using `#[thread_local]` on `static` items.
 259     (active, thread_local, "1.0.0", Some(29594), None),
 260
 261     /// Allows the use of SIMD types in functions declared in `extern` blocks.
 262     (active, simd_ffi, "1.0.0", Some(27731), None),
 263
 264     /// Allows using non lexical lifetimes (RFC 2094).
 265     (active, nll, "1.0.0", Some(43234), None),
 266
 267     /// Allows using slice patterns.
 268     (active, slice_patterns, "1.0.0", Some(62254), None),
 269
 270     /// Allows the definition of `const` functions with some advanced features.
 271     (active, const_fn, "1.2.0", Some(57563), None),
 272
 273     /// Allows associated type defaults.
 274     (active, associated_type_defaults, "1.2.0", Some(29661), None),
 275
 276     /// Allows `#![no_core]`.
 277     (active, no_core, "1.3.0", Some(29639), None),
 278
 279     /// Allows default type parameters to influence type inference.
 280     (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
 281
 282     /// Allows `repr(simd)` and importing the various simd intrinsics.
 283     (active, repr_simd, "1.4.0", Some(27731), None),
 284
 285     /// Allows `extern "platform-intrinsic" { ... }`.
 286     (active, platform_intrinsics, "1.4.0", Some(27731), None),
 287
 288     /// Allows `#[unwind(..)]`.
 289     ///
 290     /// Permits specifying whether a function should permit unwinding or abort on unwind.
 291     (active, unwind_attributes, "1.4.0", Some(58760), None),
 292
 293     /// Allows `#[no_debug]`.
 294     (active, no_debug, "1.5.0", Some(29721), None),
 295
 296     /// Allows attributes on expressions and non-item statements.
 297     (active, stmt_expr_attributes, "1.6.0", Some(15701), None),
 298
 299     /// Allows the use of type ascription in expressions.
 300     (active, type_ascription, "1.6.0", Some(23416), None),
 301
 302     /// Allows `cfg(target_thread_local)`.
 303     (active, cfg_target_thread_local, "1.7.0", Some(29594), None),
 304
 305     /// Allows specialization of implementations (RFC 1210).
 306     (active, specialization, "1.7.0", Some(31844), None),
 307
 308     /// Allows using `#[naked]` on functions.
 309     (active, naked_functions, "1.9.0", Some(32408), None),
 310
 311     /// Allows `cfg(target_has_atomic = "...")`.
 312     (active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
 313
 314     /// Allows `X..Y` patterns.
 315     (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
 316
 317     /// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
 318     (active, never_type, "1.13.0", Some(35121), None),
 319
 320     /// Allows exhaustive pattern matching on types that contain uninhabited types.
 321     (active, exhaustive_patterns, "1.13.0", Some(51085), None),
 322
 323     /// Allows `union`s to implement `Drop`. Moreover, `union`s may now include fields
 324     /// that don't implement `Copy` as long as they don't have any drop glue.
 325     /// This is checked recursively. On encountering type variable where no progress can be made,
 326     /// `T: Copy` is used as a substitute for "no drop glue".
 327     ///
 328     /// NOTE: A limited form of `union U { ... }` was accepted in 1.19.0.
 329     (active, untagged_unions, "1.13.0", Some(55149), None),
 330
 331     /// Allows `#[link(..., cfg(..))]`.
 332     (active, link_cfg, "1.14.0", Some(37406), None),
 333
 334     /// Allows `extern "ptx-*" fn()`.
 335     (active, abi_ptx, "1.15.0", Some(38788), None),
 336
 337     /// Allows the `#[repr(i128)]` attribute for enums.
 338     (active, repr128, "1.16.0", Some(35118), None),
 339
 340     /// Allows `#[link(kind="static-nobundle"...)]`.
 341     (active, static_nobundle, "1.16.0", Some(37403), None),
 342
 343     /// Allows `extern "msp430-interrupt" fn()`.
 344     (active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
 345
 346     /// Allows declarative macros 2.0 (`macro`).
 347     (active, decl_macro, "1.17.0", Some(39412), None),
 348
 349     /// Allows `extern "x86-interrupt" fn()`.
 350     (active, abi_x86_interrupt, "1.17.0", Some(40180), None),
 351
 352     /// Allows overlapping impls of marker traits.
 353     (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
 354
 355     /// Allows a test to fail without failing the whole suite.
 356     (active, allow_fail, "1.19.0", Some(46488), None),
 357
 358     /// Allows unsized tuple coercion.
 359     (active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
 360
 361     /// Allows defining generators.
 362     (active, generators, "1.21.0", Some(43122), None),
 363
 364     /// Allows `#[doc(cfg(...))]`.
 365     (active, doc_cfg, "1.21.0", Some(43781), None),
 366
 367     /// Allows `#[doc(masked)]`.
 368     (active, doc_masked, "1.21.0", Some(44027), None),
 369
 370     /// Allows `#[doc(spotlight)]`.
 371     (active, doc_spotlight, "1.22.0", Some(45040), None),
 372
 373     /// Allows `#[doc(include = "some-file")]`.
 374     (active, external_doc, "1.22.0", Some(44732), None),
 375
 376     /// Allows using `crate` as visibility modifier, synonymous with `pub(crate)`.
 377     (active, crate_visibility_modifier, "1.23.0", Some(53120), None),
 378
 379     /// Allows defining `extern type`s.
 380     (active, extern_types, "1.23.0", Some(43467), None),
 381
 382     /// Allows trait methods with arbitrary self types.
 383     (active, arbitrary_self_types, "1.23.0", Some(44874), None),
 384
 385     /// Allows in-band quantification of lifetime bindings (e.g., `fn foo(x: &'a u8) -> &'a u8`).
 386     (active, in_band_lifetimes, "1.23.0", Some(44524), None),
 387
 388     /// Allows associated types to be generic, e.g., `type Foo<T>;` (RFC 1598).
 389     (active, generic_associated_types, "1.23.0", Some(44265), None),
 390
 391     /// Allows defining `trait X = A + B;` alias items.
 392     (active, trait_alias, "1.24.0", Some(41517), None),
 393
 394     /// Allows infering `'static` outlives requirements (RFC 2093).
 395     (active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
 396
 397     /// Allows accessing fields of unions inside `const` functions.
 398     (active, const_fn_union, "1.27.0", Some(51909), None),
 399
 400     /// Allows casting raw pointers to `usize` during const eval.
 401     (active, const_raw_ptr_to_usize_cast, "1.27.0", Some(51910), None),
 402
 403     /// Allows dereferencing raw pointers during const eval.
 404     (active, const_raw_ptr_deref, "1.27.0", Some(51911), None),
 405
 406     /// Allows comparing raw pointers during const eval.
 407     (active, const_compare_raw_pointers, "1.27.0", Some(53020), None),
 408
 409     /// Allows `#[doc(alias = "...")]`.
 410     (active, doc_alias, "1.27.0", Some(50146), None),
 411
 412     /// Allows inconsistent bounds in where clauses.
 413     (active, trivial_bounds, "1.28.0", Some(48214), None),
 414
 415     /// Allows `'a: { break 'a; }`.
 416     (active, label_break_value, "1.28.0", Some(48594), None),
 417
 418     /// Allows using `#[doc(keyword = "...")]`.
 419     (active, doc_keyword, "1.28.0", Some(51315), None),
 420
 421     /// Allows using `try {...}` expressions.
 422     (active, try_blocks, "1.29.0", Some(31436), None),
 423
 424     /// Allows defining an `#[alloc_error_handler]`.
 425     (active, alloc_error_handler, "1.29.0", Some(51540), None),
 426
 427     /// Allows using the `amdgpu-kernel` ABI.
 428     (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
 429
 430     /// Allows panicking during const eval (producing compile-time errors).
 431     (active, const_panic, "1.30.0", Some(51999), None),
 432
 433     /// Allows `#[marker]` on certain traits allowing overlapping implementations.
 434     (active, marker_trait_attr, "1.30.0", Some(29864), None),
 435
 436     /// Allows macro invocations on modules expressions and statements and
 437     /// procedural macros to expand to non-items.
 438     (active, proc_macro_hygiene, "1.30.0", Some(54727), None),
 439
 440     /// Allows unsized rvalues at arguments and parameters.
 441     (active, unsized_locals, "1.30.0", Some(48055), None),
 442
 443     /// Allows custom test frameworks with `#![test_runner]` and `#[test_case]`.
 444     (active, custom_test_frameworks, "1.30.0", Some(50297), None),
 445
 446     /// Allows non-builtin attributes in inner attribute position.
 447     (active, custom_inner_attributes, "1.30.0", Some(54726), None),
 448
 449     /// Allows `impl Trait` in bindings (`let`, `const`, `static`).
 450     (active, impl_trait_in_bindings, "1.30.0", Some(63065), None),
 451
 452     /// Allows using `reason` in lint attributes and the `#[expect(lint)]` lint check.
 453     (active, lint_reasons, "1.31.0", Some(54503), None),
 454
 455     /// Allows exhaustive integer pattern matching on `usize` and `isize`.
 456     (active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
 457
 458     /// Allows using `#[ffi_returns_twice]` on foreign functions.
 459     (active, ffi_returns_twice, "1.34.0", Some(58314), None),
 460
 461     /// Allows const generic types (e.g. `struct Foo<const N: usize>(...);`).
 462     (active, const_generics, "1.34.0", Some(44580), None),
 463
 464     /// Allows using `#[optimize(X)]`.
 465     (active, optimize_attribute, "1.34.0", Some(54882), None),
 466
 467     /// Allows using C-variadics.
 468     (active, c_variadic, "1.34.0", Some(44930), None),
 469
 470     /// Allows the user of associated type bounds.
 471     (active, associated_type_bounds, "1.34.0", Some(52662), None),
 472
 473     /// Allows `if/while p && let q = r && ...` chains.
 474     (active, let_chains, "1.37.0", Some(53667), None),
 475
 476     /// Allows #[repr(transparent)] on enums (RFC 2645).
 477     (active, transparent_enums, "1.37.0", Some(60405), None),
 478
 479     /// Allows #[repr(transparent)] on unions (RFC 2645).
 480     (active, transparent_unions, "1.37.0", Some(60405), None),
 481
 482     /// Allows explicit discriminants on non-unit enum variants.
 483     (active, arbitrary_enum_discriminant, "1.37.0", Some(60553), None),
 484
 485     /// Allows `impl Trait` with multiple unrelated lifetimes.
 486     (active, member_constraints, "1.37.0", Some(61977), None),
 487
 488     /// Allows `async || body` closures.
 489     (active, async_closure, "1.37.0", Some(62290), None),
 490
 491     /// Allows `[x; N]` where `x` is a constant (RFC 2203).
 492     (active, const_in_array_repeat_expressions, "1.37.0", Some(49147), None),
 493
 494     /// Allows `impl Trait` to be used inside type aliases (RFC 2515).
 495     (active, type_alias_impl_trait, "1.38.0", Some(63063), None),
 496
 497     /// Allows the use of or-patterns (e.g., `0 | 1`).
 498     (active, or_patterns, "1.38.0", Some(54883), None),
 499
 500     /// Allows the definition of `const extern fn` and `const unsafe extern fn`.
 501     (active, const_extern_fn, "1.40.0", Some(64926), None),
 502
 503     /// Allows the use of raw-dylibs (RFC 2627).
 504     (active, raw_dylib, "1.40.0", Some(58713), None),
 505
 506     /// Allows `#[track_caller]` to be used which provides
 507     /// accurate caller location reporting during panic (RFC 2091).
 508     (active, track_caller, "1.40.0", Some(47809), None),
 509
 510     /// Allows making `dyn Trait` well-formed even if `Trait` is not object safe.
 511     /// In that case, `dyn Trait: Trait` does not hold. Moreover, coercions and
 512     /// casts in safe Rust to `dyn Trait` for such a `Trait` is also forbidden.
 513     (active, object_safe_for_dispatch, "1.40.0", Some(43561), None),
 514
 515     /// Allows using the `efiapi` ABI.
 516     (active, abi_efiapi, "1.40.0", Some(65815), None),
 517
 518     /// Allows `&raw const $place_expr` and `&raw mut $place_expr` expressions.
 519     (active, raw_ref_op, "1.41.0", Some(64490), None),
 520
 521     /// Allows diverging expressions to fall back to `!` rather than `()`.
 522     (active, never_type_fallback, "1.41.0", Some(65992), None),
 523
 524     /// Allows using the `#[register_attr]` attribute.
 525     (active, register_attr, "1.41.0", Some(66080), None),
 526
 527     /// Allows using the `#[register_tool]` attribute.
 528     (active, register_tool, "1.41.0", Some(66079), None),
 529
 530     /// Allows the use of `if` and `match` in constants.
 531     (active, const_if_match, "1.41.0", Some(49146), None),
 532
 533     /// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
 534     (active, cfg_sanitize, "1.41.0", Some(39699), None),
 535
 536     /// Allows using `&mut` in constant functions.
 537     (active, const_mut_refs, "1.41.0", Some(57349), None),
 538
 539     /// Allows the use of `loop` and `while` in constants.
 540     (active, const_loop, "1.41.0", Some(52000), None),
 541
 542     // -------------------------------------------------------------------------
 543     // feature-group-end: actual feature gates
 544     // -------------------------------------------------------------------------
 545 );
 546
 547 /// Some features are known to be incomplete and using them is likely to have
 548 /// unanticipated results, such as compiler crashes. We warn the user about these
 549 /// to alert them.
 550 pub const INCOMPLETE_FEATURES: &[Symbol] = &[
 551     sym::impl_trait_in_bindings,
 552     sym::generic_associated_types,
 553     sym::const_generics,
 554     sym::or_patterns,
 555     sym::let_chains,
 556     sym::raw_dylib,
 557 ];