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- //! # Feature gating
- //!
- //! This module implements the gating necessary for preventing certain compiler
- //! features from being used by default. This module will crawl a pre-expanded
- //! AST to ensure that there are no features which are used that are not
- //! enabled.
- //!
- //! Features are enabled in programs via the crate-level attributes of
- //! `#![feature(...)]` with a comma-separated list of features.
- //!
- //! For the purpose of future feature-tracking, once code for detection of feature
- //! gate usage is added, *do not remove it again* even once the feature
- //! becomes stable.
- use AttributeType::*;
- use AttributeGate::*;
- use crate::ast::{self, NodeId, GenericParam, GenericParamKind, PatKind, RangeEnd};
- use crate::attr;
- use crate::early_buffered_lints::BufferedEarlyLintId;
- use crate::source_map::Spanned;
- use crate::edition::{ALL_EDITIONS, Edition};
- use crate::visit::{self, FnKind, Visitor};
- use crate::parse::{token, ParseSess};
- use crate::symbol::{Symbol, keywords, sym};
- use crate::tokenstream::TokenTree;
- use errors::{DiagnosticBuilder, Handler};
- use rustc_data_structures::fx::FxHashMap;
- use rustc_target::spec::abi::Abi;
- use syntax_pos::{Span, DUMMY_SP};
- use log::debug;
- use lazy_static::lazy_static;
- use std::env;
- macro_rules! set {
- ($field: ident) => {{
- fn f(features: &mut Features, _: Span) {
- features.$field = true;
- }
- f as fn(&mut Features, Span)
- }}
- }
- macro_rules! declare_features {
- ($((active, $feature: ident, $ver: expr, $issue: expr, $edition: expr),)+) => {
- /// Represents active features that are currently being implemented or
- /// currently being considered for addition/removal.
- const ACTIVE_FEATURES:
- &[(Symbol, &str, Option<u32>, Option<Edition>, fn(&mut Features, Span))] =
- &[$((sym::$feature, $ver, $issue, $edition, set!($feature))),+];
- /// A set of features to be used by later passes.
- #[derive(Clone)]
- 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)>,
- $(pub $feature: bool),+
- }
- impl Features {
- pub fn new() -> Features {
- Features {
- declared_lang_features: Vec::new(),
- declared_lib_features: Vec::new(),
- $($feature: false),+
- }
- }
- pub fn walk_feature_fields<F>(&self, mut f: F)
- where F: FnMut(&str, bool)
- {
- $(f(stringify!($feature), self.$feature);)+
- }
- }
- };
- ($((removed, $feature: ident, $ver: expr, $issue: expr, None, $reason: expr),)+) => {
- /// Represents unstable features which have since been removed (it was once Active)
- const REMOVED_FEATURES: &[(Symbol, &str, Option<u32>, Option<&str>)] = &[
- $((sym::$feature, $ver, $issue, $reason)),+
- ];
- };
- ($((stable_removed, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
- /// Represents stable features which have since been removed (it was once Accepted)
- const STABLE_REMOVED_FEATURES: &[(Symbol, &str, Option<u32>, Option<&str>)] = &[
- $((sym::$feature, $ver, $issue, None)),+
- ];
- };
- ($((accepted, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
- /// Those language feature has since been Accepted (it was once Active)
- const ACCEPTED_FEATURES: &[(Symbol, &str, Option<u32>, Option<&str>)] = &[
- $((sym::$feature, $ver, $issue, None)),+
- ];
- }
- }
- // If you change this, please modify `src/doc/unstable-book` as well.
- //
- // Don't ever remove anything from this list; set them to 'Removed'.
- //
- // 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 inforced with tidy.
- //
- // N.B., `tools/tidy/src/features.rs` 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 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),
- // Allows using the macros:
- // + `__diagnostic_used`
- // + `__register_diagnostic`
- // +`__build_diagnostic_array`
- (active, rustc_diagnostic_macros, "1.0.0", None, None),
- // Allows using `#[rustc_const_unstable(feature = "foo", ..)]` which
- // lets a function to be `const` when opted into with `#![feature(foo)]`.
- (active, rustc_const_unstable, "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 `rustc_*` attributes (RFC 572).
- (active, rustc_attrs, "1.0.0", Some(29642), None),
- // Allows using `#[on_unimplemented(..)]` on traits.
- (active, on_unimplemented, "1.0.0", Some(29628), 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
- // Allows using `#[unsafe_destructor_blind_to_params]` (RFC 1238).
- (active, dropck_parametricity, "1.3.0", Some(28498), None),
- // 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.
- (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),
- // Allows identifying crates that contain sanitizer runtimes.
- (active, sanitizer_runtime, "1.17.0", 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),
- // Allows using the `format_args_nl` macro.
- (active, format_args_nl, "1.29.0", None, None),
- // no-tracking-issue-end
- // Added for testing E0705; perma-unstable.
- (active, test_2018_feature, "1.31.0", Some(0), Some(Edition::Edition2018)),
- // -------------------------------------------------------------------------
- // 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),
- // -------------------------------------------------------------------------
- // feature-group-end: actual feature gates (target features)
- // -------------------------------------------------------------------------
- // -------------------------------------------------------------------------
- // feature-group-start: actual feature gates
- // -------------------------------------------------------------------------
- // Allows using `asm!` macro with which inline assembly can be embedded.
- (active, asm, "1.0.0", Some(29722), None),
- // Allows using the `concat_idents!` macro with which identifiers can be concatenated.
- (active, concat_idents, "1.0.0", Some(29599), None),
- // 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 using the `log_syntax!` macro.
- (active, log_syntax, "1.0.0", Some(29598), None),
- // Allows using the `trace_macros!` macro.
- (active, trace_macros, "1.0.0", Some(29598), None),
- // Allows the use of SIMD types in functions declared in `extern` blocks.
- (active, simd_ffi, "1.0.0", Some(27731), None),
- // Allows using custom attributes (RFC 572).
- (active, custom_attribute, "1.0.0", Some(29642), None),
- // Allows using non lexical lifetimes (RFC 2094).
- (active, nll, "1.0.0", Some(43234), None),
- // Allows using slice patterns.
- (active, slice_patterns, "1.0.0", Some(23121), 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 `#[no_debug]`.
- (active, no_debug, "1.5.0", Some(29721), 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),
- // 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 untagged unions `union U { ... }`.
- (active, untagged_unions, "1.13.0", Some(32836), 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(35118), 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 module-level inline assembly by way of `global_asm!()`.
- (active, global_asm, "1.18.0", Some(35119), None),
- // Allows overlapping impls of marker traits.
- (active, overlapping_marker_traits, "1.18.0", Some(29864), 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(spotlight)]`.
- (active, doc_spotlight, "1.22.0", Some(45040), None),
- // Allows `#[doc(include = "some-file")]`.
- (active, external_doc, "1.22.0", Some(44732), None),
- // Allows future-proofing enums/structs with the `#[non_exhaustive]` attribute (RFC 2008).
- (active, non_exhaustive, "1.22.0", Some(44109), 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 infering `'static` outlives requirements (RFC 2093).
- (active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
- // Allows macro invocations in `extern {}` blocks.
- (active, macros_in_extern, "1.27.0", Some(49476), 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 comparing raw pointers during const eval.
- (active, const_compare_raw_pointers, "1.27.0", Some(53020), None),
- // Allows `#[doc(alias = "...")]`.
- (active, doc_alias, "1.27.0", Some(50146), None),
- // Allows defining `existential type`s.
- (active, existential_type, "1.28.0", Some(34511), 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 async and await syntax.
- (active, async_await, "1.28.0", Some(50547), None),
- // Allows await! macro-like syntax.
- // This will likely be removed prior to stabilization of async/await.
- (active, await_macro, "1.28.0", Some(50547), None),
- // Allows reinterpretation of the bits of a value of one type as another type during const eval.
- (active, const_transmute, "1.29.0", Some(53605), 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 invocations on modules expressions and statements and
- // procedural macros to expand to non-items.
- (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 mixing bind-by-move in patterns and references to those identifiers in guards.
- (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
- // Allows `impl Trait` in bindings (`let`, `const`, `static`).
- (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
- // Allows `const _: TYPE = VALUE`.
- (active, underscore_const_names, "1.31.0", Some(54912), None),
- // Allows using `reason` in lint attributes and the `#[expect(lint)]` lint check.
- (active, lint_reasons, "1.31.0", Some(54503), None),
- // Allows paths to enum variants on type aliases.
- (active, type_alias_enum_variants, "1.31.0", Some(49683), None),
- // Allows exhaustive integer pattern matching on `usize` and `isize`.
- (active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
- // Allows relaxing the coherence rules such that
- // `impl<T> ForeignTrait<LocalType> for ForeignType<T> is permitted.
- (active, re_rebalance_coherence, "1.32.0", Some(55437), 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 `#[repr(align(X))]` on enums.
- (active, repr_align_enum, "1.34.0", Some(57996), None),
- // Allows using C-variadics.
- (active, c_variadic, "1.34.0", Some(44930), 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.
- const INCOMPLETE_FEATURES: &[Symbol] = &[
- sym::impl_trait_in_bindings,
- sym::generic_associated_types,
- sym::const_generics
- ];
- declare_features! (
- // -------------------------------------------------------------------------
- // feature-group-start: removed features
- // -------------------------------------------------------------------------
- (removed, import_shadowing, "1.0.0", None, None, None),
- (removed, managed_boxes, "1.0.0", None, None, None),
- // Allows use of unary negate on unsigned integers, e.g., -e for e: u8
- (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
- (removed, reflect, "1.0.0", Some(27749), None, None),
- // A way to temporarily opt out of opt in copy. This will *never* be accepted.
- (removed, opt_out_copy, "1.0.0", None, None, None),
- (removed, quad_precision_float, "1.0.0", None, None, None),
- (removed, struct_inherit, "1.0.0", None, None, None),
- (removed, test_removed_feature, "1.0.0", None, None, None),
- (removed, visible_private_types, "1.0.0", None, None, None),
- (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
- // Allows using items which are missing stability attributes
- (removed, unmarked_api, "1.0.0", None, None, None),
- (removed, allocator, "1.0.0", None, None, None),
- (removed, simd, "1.0.0", Some(27731), None,
- Some("removed in favor of `#[repr(simd)]`")),
- (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
- Some("merged into `#![feature(slice_patterns)]`")),
- (removed, macro_reexport, "1.0.0", Some(29638), None,
- Some("subsumed by `pub use`")),
- (removed, pushpop_unsafe, "1.2.0", None, None, None),
- (removed, needs_allocator, "1.4.0", Some(27389), None,
- Some("subsumed by `#![feature(allocator_internals)]`")),
- (removed, proc_macro_mod, "1.27.0", Some(54727), None,
- Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
- (removed, proc_macro_expr, "1.27.0", Some(54727), None,
- Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
- (removed, proc_macro_non_items, "1.27.0", Some(54727), None,
- Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
- (removed, proc_macro_gen, "1.27.0", Some(54727), None,
- Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
- (removed, panic_implementation, "1.28.0", Some(44489), None,
- Some("subsumed by `#[panic_handler]`")),
- // Allows the use of `#[derive(Anything)]` as sugar for `#[derive_Anything]`.
- (removed, custom_derive, "1.32.0", Some(29644), None,
- Some("subsumed by `#[proc_macro_derive]`")),
- // Paths of the form: `extern::foo::bar`
- (removed, extern_in_paths, "1.33.0", Some(55600), None,
- Some("subsumed by `::foo::bar` paths")),
- (removed, quote, "1.33.0", Some(29601), None, None),
- // -------------------------------------------------------------------------
- // feature-group-end: removed features
- // -------------------------------------------------------------------------
- );
- declare_features! (
- (stable_removed, no_stack_check, "1.0.0", None, None),
- );
- declare_features! (
- // -------------------------------------------------------------------------
- // feature-group-start: for testing purposes
- // -------------------------------------------------------------------------
- // A temporary feature gate used to enable parser extensions needed
- // to bootstrap fix for #5723.
- (accepted, issue_5723_bootstrap, "1.0.0", None, None),
- // These are used to test this portion of the compiler,
- // they don't actually mean anything.
- (accepted, test_accepted_feature, "1.0.0", None, None),
- // -------------------------------------------------------------------------
- // feature-group-end: for testing purposes
- // -------------------------------------------------------------------------
- // -------------------------------------------------------------------------
- // feature-group-start: accepted features
- // -------------------------------------------------------------------------
- // Allows using associated `type`s in `trait`s.
- (accepted, associated_types, "1.0.0", None, None),
- // Allows using assigning a default type to type parameters in algebraic data type definitions.
- (accepted, default_type_params, "1.0.0", None, None),
- // FIXME: explain `globs`.
- (accepted, globs, "1.0.0", None, None),
- // Allows `macro_rules!` items.
- (accepted, macro_rules, "1.0.0", None, None),
- // Allows use of `&foo[a..b]` as a slicing syntax.
- (accepted, slicing_syntax, "1.0.0", None, None),
- // Allows struct variants `Foo { baz: u8, .. }` in enums (RFC 418).
- (accepted, struct_variant, "1.0.0", None, None),
- // Allows indexing tuples.
- (accepted, tuple_indexing, "1.0.0", None, None),
- // Allows the use of `if let` expressions.
- (accepted, if_let, "1.0.0", None, None),
- // Allows the use of `while let` expressions.
- (accepted, while_let, "1.0.0", None, None),
- // Allows using `#![no_std]`.
- (accepted, no_std, "1.6.0", None, None),
- // Allows overloading augmented assignment operations like `a += b`.
- (accepted, augmented_assignments, "1.8.0", Some(28235), None),
- // Allows empty structs and enum variants with braces.
- (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
- // Allows `#[deprecated]` attribute.
- (accepted, deprecated, "1.9.0", Some(29935), None),
- // Allows macros to appear in the type position.
- (accepted, type_macros, "1.13.0", Some(27245), None),
- // Allows use of the postfix `?` operator in expressions.
- (accepted, question_mark, "1.13.0", Some(31436), None),
- // Allows `..` in tuple (struct) patterns.
- (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
- // Allows some increased flexibility in the name resolution rules,
- // especially around globs and shadowing (RFC 1560).
- (accepted, item_like_imports, "1.15.0", Some(35120), None),
- // Allows using `Self` and associated types in struct expressions and patterns.
- (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
- // Allows elision of `'static` lifetimes in `static`s and `const`s.
- (accepted, static_in_const, "1.17.0", Some(35897), None),
- // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
- (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
- // Allows the definition recursive static items.
- (accepted, static_recursion, "1.17.0", Some(29719), None),
- // Allows `pub(restricted)` visibilities (RFC 1422).
- (accepted, pub_restricted, "1.18.0", Some(32409), None),
- // Allows `#![windows_subsystem]`.
- (accepted, windows_subsystem, "1.18.0", Some(37499), None),
- // Allows `break {expr}` with a value inside `loop`s.
- (accepted, loop_break_value, "1.19.0", Some(37339), None),
- // Allows numeric fields in struct expressions and patterns.
- (accepted, relaxed_adts, "1.19.0", Some(35626), None),
- // Allows coercing non capturing closures to function pointers.
- (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
- // Allows attributes on struct literal fields.
- (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
- // Allows the definition of associated constants in `trait` or `impl` blocks.
- (accepted, associated_consts, "1.20.0", Some(29646), None),
- // Allows usage of the `compile_error!` macro.
- (accepted, compile_error, "1.20.0", Some(40872), None),
- // Allows code like `let x: &'static u32 = &42` to work (RFC 1414).
- (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
- // Allows `Drop` types in constants (RFC 1440).
- (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
- // Allows the sysV64 ABI to be specified on all platforms
- // instead of just the platforms on which it is the C ABI.
- (accepted, abi_sysv64, "1.24.0", Some(36167), None),
- // Allows `repr(align(16))` struct attribute (RFC 1358).
- (accepted, repr_align, "1.25.0", Some(33626), None),
- // Allows '|' at beginning of match arms (RFC 1925).
- (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
- // Allows nested groups in `use` items (RFC 2128).
- (accepted, use_nested_groups, "1.25.0", Some(44494), None),
- // Allows indexing into constant arrays.
- (accepted, const_indexing, "1.26.0", Some(29947), None),
- // Allows using `a..=b` and `..=b` as inclusive range syntaxes.
- (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
- // Allows `..=` in patterns (RFC 1192).
- (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
- // Allows `fn main()` with return types which implements `Termination` (RFC 1937).
- (accepted, termination_trait, "1.26.0", Some(43301), None),
- // Allows implementing `Clone` for closures where possible (RFC 2132).
- (accepted, clone_closures, "1.26.0", Some(44490), None),
- // Allows implementing `Copy` for closures where possible (RFC 2132).
- (accepted, copy_closures, "1.26.0", Some(44490), None),
- // Allows `impl Trait` in function arguments.
- (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
- // Allows `impl Trait` in function return types.
- (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
- // Allows using the `u128` and `i128` types.
- (accepted, i128_type, "1.26.0", Some(35118), None),
- // Allows default match binding modes (RFC 2005).
- (accepted, match_default_bindings, "1.26.0", Some(42640), None),
- // Allows `'_` placeholder lifetimes.
- (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
- // Allows attributes on lifetime/type formal parameters in generics (RFC 1327).
- (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
- // Allows `cfg(target_feature = "...")`.
- (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
- // Allows `#[target_feature(...)]`.
- (accepted, target_feature, "1.27.0", None, None),
- // Allows using `dyn Trait` as a syntax for trait objects.
- (accepted, dyn_trait, "1.27.0", Some(44662), None),
- // Allows `#[must_use]` on functions, and introduces must-use operators (RFC 1940).
- (accepted, fn_must_use, "1.27.0", Some(43302), None),
- // Allows use of the `:lifetime` macro fragment specifier.
- (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
- // Allows `#[test]` functions where the return type implements `Termination` (RFC 1937).
- (accepted, termination_trait_test, "1.27.0", Some(48854), None),
- // Allows the `#[global_allocator]` attribute.
- (accepted, global_allocator, "1.28.0", Some(27389), None),
- // Allows `#[repr(transparent)]` attribute on newtype structs.
- (accepted, repr_transparent, "1.28.0", Some(43036), None),
- // Allows procedural macros in `proc-macro` crates.
- (accepted, proc_macro, "1.29.0", Some(38356), None),
- // Allows `foo.rs` as an alternative to `foo/mod.rs`.
- (accepted, non_modrs_mods, "1.30.0", Some(44660), None),
- // Allows use of the `:vis` macro fragment specifier
- (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
- // Allows importing and reexporting macros with `use`,
- // enables macro modularization in general.
- (accepted, use_extern_macros, "1.30.0", Some(35896), None),
- // Allows keywords to be escaped for use as identifiers.
- (accepted, raw_identifiers, "1.30.0", Some(48589), None),
- // Allows attributes scoped to tools.
- (accepted, tool_attributes, "1.30.0", Some(44690), None),
- // Allows multi-segment paths in attributes and derives.
- (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
- // Allows all literals in attribute lists and values of key-value pairs.
- (accepted, attr_literals, "1.30.0", Some(34981), None),
- // Allows inferring outlives requirements (RFC 2093).
- (accepted, infer_outlives_requirements, "1.30.0", Some(44493), None),
- // Allows annotating functions conforming to `fn(&PanicInfo) -> !` with `#[panic_handler]`.
- // This defines the behavior of panics.
- (accepted, panic_handler, "1.30.0", Some(44489), None),
- // Allows `#[used]` to preserve symbols (see llvm.used).
- (accepted, used, "1.30.0", Some(40289), None),
- // Allows `crate` in paths.
- (accepted, crate_in_paths, "1.30.0", Some(45477), None),
- // Allows resolving absolute paths as paths from other crates.
- (accepted, extern_absolute_paths, "1.30.0", Some(44660), None),
- // Allows access to crate names passed via `--extern` through prelude.
- (accepted, extern_prelude, "1.30.0", Some(44660), None),
- // Allows parentheses in patterns.
- (accepted, pattern_parentheses, "1.31.0", Some(51087), None),
- // Allows the definition of `const fn` functions.
- (accepted, min_const_fn, "1.31.0", Some(53555), None),
- // Allows scoped lints.
- (accepted, tool_lints, "1.31.0", Some(44690), None),
- // Allows lifetime elision in `impl` headers. For example:
- // + `impl<I:Iterator> Iterator for &mut Iterator`
- // + `impl Debug for Foo<'_>`
- (accepted, impl_header_lifetime_elision, "1.31.0", Some(15872), None),
- // Allows `extern crate foo as bar;`. This puts `bar` into extern prelude.
- (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
- // Allows use of the `:literal` macro fragment specifier (RFC 1576).
- (accepted, macro_literal_matcher, "1.32.0", Some(35625), None),
- // Allows use of `?` as the Kleene "at most one" operator in macros.
- (accepted, macro_at_most_once_rep, "1.32.0", Some(48075), None),
- // Allows `Self` struct constructor (RFC 2302).
- (accepted, self_struct_ctor, "1.32.0", Some(51994), None),
- // Allows `Self` in type definitions (RFC 2300).
- (accepted, self_in_typedefs, "1.32.0", Some(49303), None),
- // Allows `use x::y;` to search `x` in the current scope.
- (accepted, uniform_paths, "1.32.0", Some(53130), None),
- // Allows integer match exhaustiveness checking (RFC 2591).
- (accepted, exhaustive_integer_patterns, "1.33.0", Some(50907), None),
- // Allows `use path as _;` and `extern crate c as _;`.
- (accepted, underscore_imports, "1.33.0", Some(48216), None),
- // Allows `#[repr(packed(N))]` attribute on structs.
- (accepted, repr_packed, "1.33.0", Some(33158), None),
- // Allows irrefutable patterns in `if let` and `while let` statements (RFC 2086).
- (accepted, irrefutable_let_patterns, "1.33.0", Some(44495), None),
- // Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
- (accepted, min_const_unsafe_fn, "1.33.0", Some(55607), None),
- // Allows let bindings, assignments and destructuring in `const` functions and constants.
- // As long as control flow is not implemented in const eval, `&&` and `||` may not be used
- // at the same time as let bindings.
- (accepted, const_let, "1.33.0", Some(48821), None),
- // Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
- (accepted, cfg_attr_multi, "1.33.0", Some(54881), None),
- // Allows top level or-patterns (`p | q`) in `if let` and `while let`.
- (accepted, if_while_or_patterns, "1.33.0", Some(48215), None),
- // Allows `cfg(target_vendor = "...")`.
- (accepted, cfg_target_vendor, "1.33.0", Some(29718), None),
- // Allows `extern crate self as foo;`.
- // This puts local crate root into extern prelude under name `foo`.
- (accepted, extern_crate_self, "1.34.0", Some(56409), None),
- // Allows arbitrary delimited token streams in non-macro attributes.
- (accepted, unrestricted_attribute_tokens, "1.34.0", Some(55208), None),
- // -------------------------------------------------------------------------
- // feature-group-end: accepted features
- // -------------------------------------------------------------------------
- );
- // If you change this, please modify `src/doc/unstable-book` as well. You must
- // move that documentation into the relevant place in the other docs, and
- // remove the chapter on the flag.
- #[derive(Copy, Clone, PartialEq, Debug)]
- pub enum AttributeType {
- /// Normal, builtin attribute that is consumed
- /// by the compiler before the unused_attribute check
- Normal,
- /// Builtin attribute that may not be consumed by the compiler
- /// before the unused_attribute check. These attributes
- /// will be ignored by the unused_attribute lint
- Whitelisted,
- /// Builtin attribute that is only allowed at the crate level
- CrateLevel,
- }
- pub enum AttributeGate {
- /// Is gated by a given feature gate, reason
- /// and function to check if enabled
- Gated(Stability, Symbol, &'static str, fn(&Features) -> bool),
- /// Ungated attribute, can be used on all release channels
- Ungated,
- }
- /// A template that the attribute input must match.
- /// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
- #[derive(Clone, Copy)]
- pub struct AttributeTemplate {
- word: bool,
- list: Option<&'static str>,
- name_value_str: Option<&'static str>,
- }
- impl AttributeTemplate {
- /// Checks that the given meta-item is compatible with this template.
- fn compatible(&self, meta_item_kind: &ast::MetaItemKind) -> bool {
- match meta_item_kind {
- ast::MetaItemKind::Word => self.word,
- ast::MetaItemKind::List(..) => self.list.is_some(),
- ast::MetaItemKind::NameValue(lit) if lit.node.is_str() => self.name_value_str.is_some(),
- ast::MetaItemKind::NameValue(..) => false,
- }
- }
- }
- /// A convenience macro for constructing attribute templates.
- /// E.g., `template!(Word, List: "description")` means that the attribute
- /// supports forms `#[attr]` and `#[attr(description)]`.
- macro_rules! template {
- (Word) => { template!(@ true, None, None) };
- (List: $descr: expr) => { template!(@ false, Some($descr), None) };
- (NameValueStr: $descr: expr) => { template!(@ false, None, Some($descr)) };
- (Word, List: $descr: expr) => { template!(@ true, Some($descr), None) };
- (Word, NameValueStr: $descr: expr) => { template!(@ true, None, Some($descr)) };
- (List: $descr1: expr, NameValueStr: $descr2: expr) => {
- template!(@ false, Some($descr1), Some($descr2))
- };
- (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
- template!(@ true, Some($descr1), Some($descr2))
- };
- (@ $word: expr, $list: expr, $name_value_str: expr) => { AttributeTemplate {
- word: $word, list: $list, name_value_str: $name_value_str
- } };
- }
- impl AttributeGate {
- fn is_deprecated(&self) -> bool {
- match *self {
- Gated(Stability::Deprecated(_, _), ..) => true,
- _ => false,
- }
- }
- }
- #[derive(Copy, Clone, Debug)]
- pub enum Stability {
- Unstable,
- // First argument is tracking issue link; second argument is an optional
- // help message, which defaults to "remove this attribute"
- Deprecated(&'static str, Option<&'static str>),
- }
- // fn() is not Debug
- impl std::fmt::Debug for AttributeGate {
- fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
- match *self {
- Gated(ref stab, name, expl, _) =>
- write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
- Ungated => write!(fmt, "Ungated")
- }
- }
- }
- macro_rules! cfg_fn {
- ($field: ident) => {{
- fn f(features: &Features) -> bool {
- features.$field
- }
- f as fn(&Features) -> bool
- }}
- }
- pub fn deprecated_attributes() -> Vec<&'static (Symbol, AttributeType,
- AttributeTemplate, AttributeGate)> {
- BUILTIN_ATTRIBUTES.iter().filter(|(.., gate)| gate.is_deprecated()).collect()
- }
- pub fn is_builtin_attr_name(name: ast::Name) -> bool {
- BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
- }
- pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
- attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).is_some()
- }
- /// Attributes that have a special meaning to rustc or rustdoc
- pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
- // Normal attributes
- (
- sym::warn,
- Normal,
- template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
- Ungated
- ),
- (
- sym::allow,
- Normal,
- template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
- Ungated
- ),
- (
- sym::forbid,
- Normal,
- template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
- Ungated
- ),
- (
- sym::deny,
- Normal,
- template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
- Ungated
- ),
- (sym::macro_use, Normal, template!(Word, List: "name1, name2, ..."), Ungated),
- (sym::macro_export, Normal, template!(Word, List: "local_inner_macros"), Ungated),
- (sym::plugin_registrar, Normal, template!(Word), Ungated),
- (sym::cfg, Normal, template!(List: "predicate"), Ungated),
- (sym::cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ..."), Ungated),
- (sym::main, Normal, template!(Word), Ungated),
- (sym::start, Normal, template!(Word), Ungated),
- (sym::repr, Normal, template!(List: "C, packed, ..."), Ungated),
- (sym::path, Normal, template!(NameValueStr: "file"), Ungated),
- (sym::automatically_derived, Normal, template!(Word), Ungated),
- (sym::no_mangle, Normal, template!(Word), Ungated),
- (sym::no_link, Normal, template!(Word), Ungated),
- (sym::derive, Normal, template!(List: "Trait1, Trait2, ..."), Ungated),
- (
- sym::should_panic,
- Normal,
- template!(Word, List: r#"expected = "reason"#, NameValueStr: "reason"),
- Ungated
- ),
- (sym::ignore, Normal, template!(Word, NameValueStr: "reason"), Ungated),
- (sym::no_implicit_prelude, Normal, template!(Word), Ungated),
- (sym::reexport_test_harness_main, Normal, template!(NameValueStr: "name"), Ungated),
- (sym::link_args, Normal, template!(NameValueStr: "args"), Gated(Stability::Unstable,
- sym::link_args,
- "the `link_args` attribute is experimental and not \
- portable across platforms, it is recommended to \
- use `#[link(name = \"foo\")] instead",
- cfg_fn!(link_args))),
- (sym::macro_escape, Normal, template!(Word), Ungated),
- // RFC #1445.
- (sym::structural_match, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::structural_match,
- "the semantics of constant patterns is \
- not yet settled",
- cfg_fn!(structural_match))),
- // RFC #2008
- (sym::non_exhaustive, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::non_exhaustive,
- "non exhaustive is an experimental feature",
- cfg_fn!(non_exhaustive))),
- // RFC #1268
- (sym::marker, Normal, template!(Word), Gated(Stability::Unstable,
- sym::marker_trait_attr,
- "marker traits is an experimental feature",
- cfg_fn!(marker_trait_attr))),
- (sym::plugin, CrateLevel, template!(List: "name|name(args)"), Gated(Stability::Unstable,
- sym::plugin,
- "compiler plugins are experimental \
- and possibly buggy",
- cfg_fn!(plugin))),
- (sym::no_std, CrateLevel, template!(Word), Ungated),
- (sym::no_core, CrateLevel, template!(Word), Gated(Stability::Unstable,
- sym::no_core,
- "no_core is experimental",
- cfg_fn!(no_core))),
- (sym::lang, Normal, template!(NameValueStr: "name"), Gated(Stability::Unstable,
- sym::lang_items,
- "language items are subject to change",
- cfg_fn!(lang_items))),
- (sym::linkage, Whitelisted, template!(NameValueStr: "external|internal|..."),
- Gated(Stability::Unstable,
- sym::linkage,
- "the `linkage` attribute is experimental \
- and not portable across platforms",
- cfg_fn!(linkage))),
- (sym::thread_local, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::thread_local,
- "`#[thread_local]` is an experimental feature, and does \
- not currently handle destructors",
- cfg_fn!(thread_local))),
- (sym::rustc_on_unimplemented, Whitelisted, template!(List:
- r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
- NameValueStr: "message"),
- Gated(Stability::Unstable,
- sym::on_unimplemented,
- "the `#[rustc_on_unimplemented]` attribute \
- is an experimental feature",
- cfg_fn!(on_unimplemented))),
- (sym::rustc_const_unstable, Normal, template!(List: r#"feature = "name""#),
- Gated(Stability::Unstable,
- sym::rustc_const_unstable,
- "the `#[rustc_const_unstable]` attribute \
- is an internal feature",
- cfg_fn!(rustc_const_unstable))),
- (sym::global_allocator, Normal, template!(Word), Ungated),
- (sym::default_lib_allocator, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::allocator_internals,
- "the `#[default_lib_allocator]` \
- attribute is an experimental feature",
- cfg_fn!(allocator_internals))),
- (sym::needs_allocator, Normal, template!(Word), Gated(Stability::Unstable,
- sym::allocator_internals,
- "the `#[needs_allocator]` \
- attribute is an experimental \
- feature",
- cfg_fn!(allocator_internals))),
- (sym::panic_runtime, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::panic_runtime,
- "the `#[panic_runtime]` attribute is \
- an experimental feature",
- cfg_fn!(panic_runtime))),
- (sym::needs_panic_runtime, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::needs_panic_runtime,
- "the `#[needs_panic_runtime]` \
- attribute is an experimental \
- feature",
- cfg_fn!(needs_panic_runtime))),
- (sym::rustc_outlives, Normal, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_outlives]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_variance, Normal, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_variance]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_layout, Normal, template!(List: "field1, field2, ..."),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_layout]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_layout_scalar_valid_range_start, Whitelisted, template!(List: "value"),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_layout_scalar_valid_range_start]` attribute \
- is just used to enable niche optimizations in libcore \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_layout_scalar_valid_range_end, Whitelisted, template!(List: "value"),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_layout_scalar_valid_range_end]` attribute \
- is just used to enable niche optimizations in libcore \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_regions, Normal, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_regions]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_error, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_error]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_dump_user_substs, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "this attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_if_this_changed, Whitelisted, template!(Word, List: "DepNode"),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_if_this_changed]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_then_this_would_need, Whitelisted, template!(List: "DepNode"),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_if_this_changed]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_dirty, Whitelisted, template!(List: r#"cfg = "...", /*opt*/ label = "...",
- /*opt*/ except = "...""#),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_dirty]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_clean, Whitelisted, template!(List: r#"cfg = "...", /*opt*/ label = "...",
- /*opt*/ except = "...""#),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_clean]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (
- sym::rustc_partition_reused,
- Whitelisted,
- template!(List: r#"cfg = "...", module = "...""#),
- Gated(
- Stability::Unstable,
- sym::rustc_attrs,
- "this attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs)
- )
- ),
- (
- sym::rustc_partition_codegened,
- Whitelisted,
- template!(List: r#"cfg = "...", module = "...""#),
- Gated(
- Stability::Unstable,
- sym::rustc_attrs,
- "this attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs),
- )
- ),
- (sym::rustc_expected_cgu_reuse, Whitelisted, template!(List: r#"cfg = "...", module = "...",
- kind = "...""#),
- Gated(Stability::Unstable,
- sym::rustc_attrs,
- "this attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_synthetic, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "this attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_symbol_name, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "internal rustc attributes will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_def_path, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "internal rustc attributes will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_mir, Whitelisted, template!(List: "arg1, arg2, ..."), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_mir]` attribute \
- is just used for rustc unit tests \
- and will never be stable",
- cfg_fn!(rustc_attrs))),
- (
- sym::rustc_inherit_overflow_checks,
- Whitelisted,
- template!(Word),
- Gated(
- Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_inherit_overflow_checks]` \
- attribute is just used to control \
- overflow checking behavior of several \
- libcore functions that are inlined \
- across crates and will never be stable",
- cfg_fn!(rustc_attrs),
- )
- ),
- (sym::rustc_dump_program_clauses, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_dump_program_clauses]` \
- attribute is just used for rustc unit \
- tests and will never be stable",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_test_marker, Normal, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "the `#[rustc_test_marker]` attribute \
- is used internally to track tests",
- cfg_fn!(rustc_attrs))),
- (sym::rustc_transparent_macro, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "used internally for testing macro hygiene",
- cfg_fn!(rustc_attrs))),
- (sym::compiler_builtins, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::compiler_builtins,
- "the `#[compiler_builtins]` attribute is used to \
- identify the `compiler_builtins` crate which \
- contains compiler-rt intrinsics and will never be \
- stable",
- cfg_fn!(compiler_builtins))),
- (sym::sanitizer_runtime, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::sanitizer_runtime,
- "the `#[sanitizer_runtime]` attribute is used to \
- identify crates that contain the runtime of a \
- sanitizer and will never be stable",
- cfg_fn!(sanitizer_runtime))),
- (sym::profiler_runtime, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::profiler_runtime,
- "the `#[profiler_runtime]` attribute is used to \
- identify the `profiler_builtins` crate which \
- contains the profiler runtime and will never be \
- stable",
- cfg_fn!(profiler_runtime))),
- (sym::allow_internal_unstable, Normal, template!(Word, List: "feat1, feat2, ..."),
- Gated(Stability::Unstable,
- sym::allow_internal_unstable,
- EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
- cfg_fn!(allow_internal_unstable))),
- (sym::allow_internal_unsafe, Normal, template!(Word), Gated(Stability::Unstable,
- sym::allow_internal_unsafe,
- EXPLAIN_ALLOW_INTERNAL_UNSAFE,
- cfg_fn!(allow_internal_unsafe))),
- (sym::fundamental, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::fundamental,
- "the `#[fundamental]` attribute \
- is an experimental feature",
- cfg_fn!(fundamental))),
- (sym::proc_macro_derive, Normal, template!(List: "TraitName, \
- /*opt*/ attributes(name1, name2, ...)"),
- Ungated),
- (sym::rustc_copy_clone_marker, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "internal implementation detail",
- cfg_fn!(rustc_attrs))),
- // FIXME: #14408 whitelist docs since rustdoc looks at them
- (
- sym::doc,
- Whitelisted,
- template!(List: "hidden|inline|...", NameValueStr: "string"),
- Ungated
- ),
- // FIXME: #14406 these are processed in codegen, which happens after the
- // lint pass
- (sym::cold, Whitelisted, template!(Word), Ungated),
- (sym::naked, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::naked_functions,
- "the `#[naked]` attribute \
- is an experimental feature",
- cfg_fn!(naked_functions))),
- (sym::ffi_returns_twice, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::ffi_returns_twice,
- "the `#[ffi_returns_twice]` attribute \
- is an experimental feature",
- cfg_fn!(ffi_returns_twice))),
- (sym::target_feature, Whitelisted, template!(List: r#"enable = "name""#), Ungated),
- (sym::export_name, Whitelisted, template!(NameValueStr: "name"), Ungated),
- (sym::inline, Whitelisted, template!(Word, List: "always|never"), Ungated),
- (sym::link, Whitelisted, template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...",
- /*opt*/ cfg = "...""#), Ungated),
- (sym::link_name, Whitelisted, template!(NameValueStr: "name"), Ungated),
- (sym::link_section, Whitelisted, template!(NameValueStr: "name"), Ungated),
- (sym::no_builtins, Whitelisted, template!(Word), Ungated),
- (sym::no_debug, Whitelisted, template!(Word), Gated(
- Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
- sym::no_debug,
- "the `#[no_debug]` attribute was an experimental feature that has been \
- deprecated due to lack of demand",
- cfg_fn!(no_debug))),
- (
- sym::omit_gdb_pretty_printer_section,
- Whitelisted,
- template!(Word),
- Gated(
- Stability::Unstable,
- sym::omit_gdb_pretty_printer_section,
- "the `#[omit_gdb_pretty_printer_section]` \
- attribute is just used for the Rust test \
- suite",
- cfg_fn!(omit_gdb_pretty_printer_section)
- )
- ),
- (sym::unsafe_destructor_blind_to_params,
- Normal,
- template!(Word),
- Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761",
- Some("replace this attribute with `#[may_dangle]`")),
- sym::dropck_parametricity,
- "unsafe_destructor_blind_to_params has been replaced by \
- may_dangle and will be removed in the future",
- cfg_fn!(dropck_parametricity))),
- (sym::may_dangle,
- Normal,
- template!(Word),
- Gated(Stability::Unstable,
- sym::dropck_eyepatch,
- "may_dangle has unstable semantics and may be removed in the future",
- cfg_fn!(dropck_eyepatch))),
- (sym::unwind, Whitelisted, template!(List: "allowed|aborts"), Gated(Stability::Unstable,
- sym::unwind_attributes,
- "#[unwind] is experimental",
- cfg_fn!(unwind_attributes))),
- (sym::used, Whitelisted, template!(Word), Ungated),
- // used in resolve
- (sym::prelude_import, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::prelude_import,
- "`#[prelude_import]` is for use by rustc only",
- cfg_fn!(prelude_import))),
- // FIXME: #14407 these are only looked at on-demand so we can't
- // guarantee they'll have already been checked
- (
- sym::rustc_deprecated,
- Whitelisted,
- template!(List: r#"since = "version", reason = "...""#),
- Ungated
- ),
- (sym::must_use, Whitelisted, template!(Word, NameValueStr: "reason"), Ungated),
- (
- sym::stable,
- Whitelisted,
- template!(List: r#"feature = "name", since = "version""#),
- Ungated
- ),
- (
- sym::unstable,
- Whitelisted,
- template!(List: r#"feature = "name", reason = "...", issue = "N""#),
- Ungated
- ),
- (sym::deprecated,
- Normal,
- template!(
- Word,
- List: r#"/*opt*/ since = "version", /*opt*/ note = "reason"#,
- NameValueStr: "reason"
- ),
- Ungated
- ),
- (sym::rustc_paren_sugar, Normal, template!(Word), Gated(Stability::Unstable,
- sym::unboxed_closures,
- "unboxed_closures are still evolving",
- cfg_fn!(unboxed_closures))),
- (sym::windows_subsystem, Whitelisted, template!(NameValueStr: "windows|console"), Ungated),
- (sym::proc_macro_attribute, Normal, template!(Word), Ungated),
- (sym::proc_macro, Normal, template!(Word), Ungated),
- (sym::rustc_proc_macro_decls, Normal, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "used internally by rustc",
- cfg_fn!(rustc_attrs))),
- (sym::allow_fail, Normal, template!(Word), Gated(Stability::Unstable,
- sym::allow_fail,
- "allow_fail attribute is currently unstable",
- cfg_fn!(allow_fail))),
- (sym::rustc_std_internal_symbol, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "this is an internal attribute that will \
- never be stable",
- cfg_fn!(rustc_attrs))),
- // whitelists "identity-like" conversion methods to suggest on type mismatch
- (sym::rustc_conversion_suggestion, Whitelisted, template!(Word), Gated(Stability::Unstable,
- sym::rustc_attrs,
- "this is an internal attribute that will \
- never be stable",
- cfg_fn!(rustc_attrs))),
- (
- sym::rustc_args_required_const,
- Whitelisted,
- template!(List: "N"),
- Gated(Stability::Unstable, sym::rustc_attrs, "never will be stable",
- cfg_fn!(rustc_attrs))
- ),
- // RFC 2070
- (sym::panic_handler, Normal, template!(Word), Ungated),
- (sym::alloc_error_handler, Normal, template!(Word), Gated(Stability::Unstable,
- sym::alloc_error_handler,
- "#[alloc_error_handler] is an unstable feature",
- cfg_fn!(alloc_error_handler))),
- // RFC 2412
- (sym::optimize, Whitelisted, template!(List: "size|speed"), Gated(Stability::Unstable,
- sym::optimize_attribute,
- "#[optimize] attribute is an unstable feature",
- cfg_fn!(optimize_attribute))),
- // Crate level attributes
- (sym::crate_name, CrateLevel, template!(NameValueStr: "name"), Ungated),
- (sym::crate_type, CrateLevel, template!(NameValueStr: "bin|lib|..."), Ungated),
- (sym::crate_id, CrateLevel, template!(NameValueStr: "ignored"), Ungated),
- (sym::feature, CrateLevel, template!(List: "name1, name1, ..."), Ungated),
- (sym::no_start, CrateLevel, template!(Word), Ungated),
- (sym::no_main, CrateLevel, template!(Word), Ungated),
- (sym::recursion_limit, CrateLevel, template!(NameValueStr: "N"), Ungated),
- (sym::type_length_limit, CrateLevel, template!(NameValueStr: "N"), Ungated),
- (sym::test_runner, CrateLevel, template!(List: "path"), Gated(Stability::Unstable,
- sym::custom_test_frameworks,
- EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
- cfg_fn!(custom_test_frameworks))),
- ];
- pub type BuiltinAttribute = (Symbol, AttributeType, AttributeTemplate, AttributeGate);
- lazy_static! {
- pub static ref BUILTIN_ATTRIBUTE_MAP: FxHashMap<Symbol, &'static BuiltinAttribute> = {
- let mut map = FxHashMap::default();
- for attr in BUILTIN_ATTRIBUTES.iter() {
- if map.insert(attr.0, attr).is_some() {
- panic!("duplicate builtin attribute `{}`", attr.0);
- }
- }
- map
- };
- }
- // cfg(...)'s that are feature gated
- const GATED_CFGS: &[(Symbol, Symbol, fn(&Features) -> bool)] = &[
- // (name in cfg, feature, function to check if the feature is enabled)
- (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
- (sym::target_has_atomic, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
- (sym::rustdoc, sym::doc_cfg, cfg_fn!(doc_cfg)),
- ];
- #[derive(Debug)]
- pub struct GatedCfg {
- span: Span,
- index: usize,
- }
- impl GatedCfg {
- pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
- GATED_CFGS.iter()
- .position(|info| cfg.check_name(info.0))
- .map(|idx| {
- GatedCfg {
- span: cfg.span,
- index: idx
- }
- })
- }
- pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
- let (cfg, feature, has_feature) = GATED_CFGS[self.index];
- if !has_feature(features) && !self.span.allows_unstable(feature) {
- let explain = format!("`cfg({})` is experimental and subject to change", cfg);
- emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
- }
- }
- }
- struct Context<'a> {
- features: &'a Features,
- parse_sess: &'a ParseSess,
- plugin_attributes: &'a [(Symbol, AttributeType)],
- }
- macro_rules! gate_feature_fn {
- ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
- let (cx, has_feature, span,
- name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
- let has_feature: bool = has_feature(&$cx.features);
- debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
- if !has_feature && !span.allows_unstable($name) {
- leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
- .emit();
- }
- }}
- }
- macro_rules! gate_feature {
- ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
- gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
- sym::$feature, $explain, GateStrength::Hard)
- };
- ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
- gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
- sym::$feature, $explain, $level)
- };
- }
- impl<'a> Context<'a> {
- fn check_attribute(
- &self,
- attr: &ast::Attribute,
- attr_info: Option<&BuiltinAttribute>,
- is_macro: bool
- ) {
- debug!("check_attribute(attr = {:?})", attr);
- if let Some(&(name, ty, _template, ref gateage)) = attr_info {
- if let Gated(_, name, desc, ref has_feature) = *gateage {
- if !attr.span.allows_unstable(name) {
- gate_feature_fn!(
- self, has_feature, attr.span, name, desc, GateStrength::Hard
- );
- }
- } else if name == sym::doc {
- if let Some(content) = attr.meta_item_list() {
- if content.iter().any(|c| c.check_name(sym::include)) {
- gate_feature!(self, external_doc, attr.span,
- "#[doc(include = \"...\")] is experimental"
- );
- }
- }
- }
- debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
- return;
- }
- for &(n, ty) in self.plugin_attributes {
- if attr.path == n {
- // Plugins can't gate attributes, so we don't check for it
- // unlike the code above; we only use this loop to
- // short-circuit to avoid the checks below.
- debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
- return;
- }
- }
- if !attr::is_known(attr) {
- if attr.name_or_empty().as_str().starts_with("rustc_") {
- let msg = "unless otherwise specified, attributes with the prefix `rustc_` \
- are reserved for internal compiler diagnostics";
- gate_feature!(self, rustc_attrs, attr.span, msg);
- } else if !is_macro {
- // Only run the custom attribute lint during regular feature gate
- // checking. Macro gating runs before the plugin attributes are
- // registered, so we skip this in that case.
- let msg = format!("The attribute `{}` is currently unknown to the compiler and \
- may have meaning added to it in the future", attr.path);
- gate_feature!(self, custom_attribute, attr.span, &msg);
- }
- }
- }
- }
- pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
- let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
- cx.check_attribute(
- attr,
- attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name).map(|a| *a)),
- true
- );
- }
- fn find_lang_feature_issue(feature: Symbol) -> Option<u32> {
- if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
- let issue = info.2;
- // FIXME (#28244): enforce that active features have issue numbers
- // assert!(issue.is_some())
- issue
- } else {
- // search in Accepted, Removed, or Stable Removed features
- let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
- .find(|t| t.0 == feature);
- match found {
- Some(&(_, _, issue, _)) => issue,
- None => panic!("Feature `{}` is not declared anywhere", feature),
- }
- }
- }
- pub enum GateIssue {
- Language,
- Library(Option<u32>)
- }
- #[derive(Debug, Copy, Clone, PartialEq)]
- pub enum GateStrength {
- /// A hard error. (Most feature gates should use this.)
- Hard,
- /// Only a warning. (Use this only as backwards-compatibility demands.)
- Soft,
- }
- pub fn emit_feature_err(
- sess: &ParseSess,
- feature: Symbol,
- span: Span,
- issue: GateIssue,
- explain: &str,
- ) {
- feature_err(sess, feature, span, issue, explain).emit();
- }
- pub fn feature_err<'a>(
- sess: &'a ParseSess,
- feature: Symbol,
- span: Span,
- issue: GateIssue,
- explain: &str,
- ) -> DiagnosticBuilder<'a> {
- leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
- }
- fn leveled_feature_err<'a>(
- sess: &'a ParseSess,
- feature: Symbol,
- span: Span,
- issue: GateIssue,
- explain: &str,
- level: GateStrength,
- ) -> DiagnosticBuilder<'a> {
- let diag = &sess.span_diagnostic;
- let issue = match issue {
- GateIssue::Language => find_lang_feature_issue(feature),
- GateIssue::Library(lib) => lib,
- };
- let mut err = match level {
- GateStrength::Hard => {
- diag.struct_span_err_with_code(span, explain, stringify_error_code!(E0658))
- }
- GateStrength::Soft => diag.struct_span_warn(span, explain),
- };
- match issue {
- None | Some(0) => {} // We still accept `0` as a stand-in for backwards compatibility
- Some(n) => {
- err.note(&format!(
- "for more information, see https://github.com/rust-lang/rust/issues/{}",
- n,
- ));
- }
- }
- // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
- if sess.unstable_features.is_nightly_build() {
- err.help(&format!("add #![feature({})] to the crate attributes to enable", feature));
- }
- // If we're on stable and only emitting a "soft" warning, add a note to
- // clarify that the feature isn't "on" (rather than being on but
- // warning-worthy).
- if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
- err.help("a nightly build of the compiler is required to enable this feature");
- }
- err
- }
- const EXPLAIN_BOX_SYNTAX: &str =
- "box expression syntax is experimental; you can call `Box::new` instead";
- pub const EXPLAIN_STMT_ATTR_SYNTAX: &str =
- "attributes on expressions are experimental";
- pub const EXPLAIN_ASM: &str =
- "inline assembly is not stable enough for use and is subject to change";
- pub const EXPLAIN_GLOBAL_ASM: &str =
- "`global_asm!` is not stable enough for use and is subject to change";
- pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &str =
- "custom test frameworks are an unstable feature";
- pub const EXPLAIN_LOG_SYNTAX: &str =
- "`log_syntax!` is not stable enough for use and is subject to change";
- pub const EXPLAIN_CONCAT_IDENTS: &str =
- "`concat_idents` is not stable enough for use and is subject to change";
- pub const EXPLAIN_FORMAT_ARGS_NL: &str =
- "`format_args_nl` is only for internal language use and is subject to change";
- pub const EXPLAIN_TRACE_MACROS: &str =
- "`trace_macros` is not stable enough for use and is subject to change";
- pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &str =
- "allow_internal_unstable side-steps feature gating and stability checks";
- pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &str =
- "allow_internal_unsafe side-steps the unsafe_code lint";
- pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &str =
- "unsized tuple coercion is not stable enough for use and is subject to change";
- struct PostExpansionVisitor<'a> {
- context: &'a Context<'a>,
- builtin_attributes: &'static FxHashMap<Symbol, &'static BuiltinAttribute>,
- }
- macro_rules! gate_feature_post {
- ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
- let (cx, span) = ($cx, $span);
- if !span.allows_unstable(sym::$feature) {
- gate_feature!(cx.context, $feature, span, $explain)
- }
- }};
- ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
- let (cx, span) = ($cx, $span);
- if !span.allows_unstable(sym::$feature) {
- gate_feature!(cx.context, $feature, span, $explain, $level)
- }
- }}
- }
- impl<'a> PostExpansionVisitor<'a> {
- fn check_abi(&self, abi: Abi, span: Span) {
- match abi {
- Abi::RustIntrinsic => {
- gate_feature_post!(&self, intrinsics, span,
- "intrinsics are subject to change");
- },
- Abi::PlatformIntrinsic => {
- gate_feature_post!(&self, platform_intrinsics, span,
- "platform intrinsics are experimental and possibly buggy");
- },
- Abi::Vectorcall => {
- gate_feature_post!(&self, abi_vectorcall, span,
- "vectorcall is experimental and subject to change");
- },
- Abi::Thiscall => {
- gate_feature_post!(&self, abi_thiscall, span,
- "thiscall is experimental and subject to change");
- },
- Abi::RustCall => {
- gate_feature_post!(&self, unboxed_closures, span,
- "rust-call ABI is subject to change");
- },
- Abi::PtxKernel => {
- gate_feature_post!(&self, abi_ptx, span,
- "PTX ABIs are experimental and subject to change");
- },
- Abi::Unadjusted => {
- gate_feature_post!(&self, abi_unadjusted, span,
- "unadjusted ABI is an implementation detail and perma-unstable");
- },
- Abi::Msp430Interrupt => {
- gate_feature_post!(&self, abi_msp430_interrupt, span,
- "msp430-interrupt ABI is experimental and subject to change");
- },
- Abi::X86Interrupt => {
- gate_feature_post!(&self, abi_x86_interrupt, span,
- "x86-interrupt ABI is experimental and subject to change");
- },
- Abi::AmdGpuKernel => {
- gate_feature_post!(&self, abi_amdgpu_kernel, span,
- "amdgpu-kernel ABI is experimental and subject to change");
- },
- // Stable
- Abi::Cdecl |
- Abi::Stdcall |
- Abi::Fastcall |
- Abi::Aapcs |
- Abi::Win64 |
- Abi::SysV64 |
- Abi::Rust |
- Abi::C |
- Abi::System => {}
- }
- }
- fn check_builtin_attribute(&mut self, attr: &ast::Attribute, name: Symbol,
- template: AttributeTemplate) {
- // Some special attributes like `cfg` must be checked
- // before the generic check, so we skip them here.
- let should_skip = |name| name == sym::cfg;
- // Some of previously accepted forms were used in practice,
- // report them as warnings for now.
- let should_warn = |name| name == sym::doc || name == sym::ignore ||
- name == sym::inline || name == sym::link;
- match attr.parse_meta(self.context.parse_sess) {
- Ok(meta) => if !should_skip(name) && !template.compatible(&meta.node) {
- let mut msg = "attribute must be of the form ".to_owned();
- let mut first = true;
- if template.word {
- first = false;
- msg.push_str(&format!("`#[{}{}]`", name, ""));
- }
- if let Some(descr) = template.list {
- if !first {
- msg.push_str(" or ");
- }
- first = false;
- msg.push_str(&format!("`#[{}({})]`", name, descr));
- }
- if let Some(descr) = template.name_value_str {
- if !first {
- msg.push_str(" or ");
- }
- msg.push_str(&format!("`#[{} = \"{}\"]`", name, descr));
- }
- if should_warn(name) {
- self.context.parse_sess.buffer_lint(
- BufferedEarlyLintId::IllFormedAttributeInput,
- meta.span,
- ast::CRATE_NODE_ID,
- &msg,
- );
- } else {
- self.context.parse_sess.span_diagnostic.span_err(meta.span, &msg);
- }
- }
- Err(mut err) => err.emit(),
- }
- }
- }
- impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
- fn visit_attribute(&mut self, attr: &ast::Attribute) {
- let attr_info = attr.ident().and_then(|ident| {
- self.builtin_attributes.get(&ident.name).map(|a| *a)
- });
- // check for gated attributes
- self.context.check_attribute(attr, attr_info, false);
- if attr.check_name(sym::doc) {
- if let Some(content) = attr.meta_item_list() {
- if content.len() == 1 && content[0].check_name(sym::cfg) {
- gate_feature_post!(&self, doc_cfg, attr.span,
- "#[doc(cfg(...))] is experimental"
- );
- } else if content.iter().any(|c| c.check_name(sym::masked)) {
- gate_feature_post!(&self, doc_masked, attr.span,
- "#[doc(masked)] is experimental"
- );
- } else if content.iter().any(|c| c.check_name(sym::spotlight)) {
- gate_feature_post!(&self, doc_spotlight, attr.span,
- "#[doc(spotlight)] is experimental"
- );
- } else if content.iter().any(|c| c.check_name(sym::alias)) {
- gate_feature_post!(&self, doc_alias, attr.span,
- "#[doc(alias = \"...\")] is experimental"
- );
- } else if content.iter().any(|c| c.check_name(sym::keyword)) {
- gate_feature_post!(&self, doc_keyword, attr.span,
- "#[doc(keyword = \"...\")] is experimental"
- );
- }
- }
- }
- match attr_info {
- Some(&(name, _, template, _)) => self.check_builtin_attribute(
- attr,
- name,
- template
- ),
- None => if let Some(TokenTree::Token(_, token::Eq)) = attr.tokens.trees().next() {
- // All key-value attributes are restricted to meta-item syntax.
- attr.parse_meta(self.context.parse_sess).map_err(|mut err| err.emit()).ok();
- }
- }
- }
- fn visit_name(&mut self, sp: Span, name: ast::Name) {
- if !name.as_str().is_ascii() {
- gate_feature_post!(
- &self,
- non_ascii_idents,
- self.context.parse_sess.source_map().def_span(sp),
- "non-ascii idents are not fully supported"
- );
- }
- }
- fn visit_item(&mut self, i: &'a ast::Item) {
- match i.node {
- ast::ItemKind::Const(_,_) => {
- if i.ident.name == keywords::Underscore.name() {
- gate_feature_post!(&self, underscore_const_names, i.span,
- "naming constants with `_` is unstable");
- }
- }
- ast::ItemKind::ForeignMod(ref foreign_module) => {
- self.check_abi(foreign_module.abi, i.span);
- }
- ast::ItemKind::Fn(..) => {
- if attr::contains_name(&i.attrs[..], sym::plugin_registrar) {
- gate_feature_post!(&self, plugin_registrar, i.span,
- "compiler plugins are experimental and possibly buggy");
- }
- if attr::contains_name(&i.attrs[..], sym::start) {
- gate_feature_post!(&self, start, i.span,
- "a #[start] function is an experimental \
- feature whose signature may change \
- over time");
- }
- if attr::contains_name(&i.attrs[..], sym::main) {
- gate_feature_post!(&self, main, i.span,
- "declaration of a nonstandard #[main] \
- function may change over time, for now \
- a top-level `fn main()` is required");
- }
- }
- ast::ItemKind::Struct(..) => {
- for attr in attr::filter_by_name(&i.attrs[..], sym::repr) {
- for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
- if item.check_name(sym::simd) {
- gate_feature_post!(&self, repr_simd, attr.span,
- "SIMD types are experimental and possibly buggy");
- }
- }
- }
- }
- ast::ItemKind::Enum(..) => {
- for attr in attr::filter_by_name(&i.attrs[..], sym::repr) {
- for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
- if item.check_name(sym::align) {
- gate_feature_post!(&self, repr_align_enum, attr.span,
- "`#[repr(align(x))]` on enums is experimental");
- }
- }
- }
- }
- ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
- if polarity == ast::ImplPolarity::Negative {
- gate_feature_post!(&self, optin_builtin_traits,
- i.span,
- "negative trait bounds are not yet fully implemented; \
- use marker types for now");
- }
- if let ast::Defaultness::Default = defaultness {
- gate_feature_post!(&self, specialization,
- i.span,
- "specialization is unstable");
- }
- }
- ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
- gate_feature_post!(&self, optin_builtin_traits,
- i.span,
- "auto traits are experimental and possibly buggy");
- }
- ast::ItemKind::TraitAlias(..) => {
- gate_feature_post!(
- &self,
- trait_alias,
- i.span,
- "trait aliases are experimental"
- );
- }
- ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
- let msg = "`macro` is experimental";
- gate_feature_post!(&self, decl_macro, i.span, msg);
- }
- ast::ItemKind::Existential(..) => {
- gate_feature_post!(
- &self,
- existential_type,
- i.span,
- "existential types are unstable"
- );
- }
- _ => {}
- }
- visit::walk_item(self, i);
- }
- fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
- match i.node {
- ast::ForeignItemKind::Fn(..) |
- ast::ForeignItemKind::Static(..) => {
- let link_name = attr::first_attr_value_str_by_name(&i.attrs, sym::link_name);
- let links_to_llvm = match link_name {
- Some(val) => val.as_str().starts_with("llvm."),
- _ => false
- };
- if links_to_llvm {
- gate_feature_post!(&self, link_llvm_intrinsics, i.span,
- "linking to LLVM intrinsics is experimental");
- }
- }
- ast::ForeignItemKind::Ty => {
- gate_feature_post!(&self, extern_types, i.span,
- "extern types are experimental");
- }
- ast::ForeignItemKind::Macro(..) => {}
- }
- visit::walk_foreign_item(self, i)
- }
- fn visit_ty(&mut self, ty: &'a ast::Ty) {
- match ty.node {
- ast::TyKind::BareFn(ref bare_fn_ty) => {
- self.check_abi(bare_fn_ty.abi, ty.span);
- }
- ast::TyKind::Never => {
- gate_feature_post!(&self, never_type, ty.span,
- "The `!` type is experimental");
- }
- _ => {}
- }
- visit::walk_ty(self, ty)
- }
- fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
- if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
- if let ast::TyKind::Never = output_ty.node {
- // Do nothing
- } else {
- self.visit_ty(output_ty)
- }
- }
- }
- fn visit_expr(&mut self, e: &'a ast::Expr) {
- match e.node {
- ast::ExprKind::Box(_) => {
- gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
- }
- ast::ExprKind::Type(..) => {
- // To avoid noise about type ascription in common syntax errors, only emit if it
- // is the *only* error.
- if self.context.parse_sess.span_diagnostic.err_count() == 0 {
- gate_feature_post!(&self, type_ascription, e.span,
- "type ascription is experimental");
- }
- }
- ast::ExprKind::ObsoleteInPlace(..) => {
- // these get a hard error in ast-validation
- }
- ast::ExprKind::Yield(..) => {
- gate_feature_post!(&self, generators,
- e.span,
- "yield syntax is experimental");
- }
- ast::ExprKind::TryBlock(_) => {
- gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
- }
- ast::ExprKind::Block(_, opt_label) => {
- if let Some(label) = opt_label {
- gate_feature_post!(&self, label_break_value, label.ident.span,
- "labels on blocks are unstable");
- }
- }
- ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
- gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
- }
- ast::ExprKind::Async(..) => {
- gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
- }
- ast::ExprKind::Await(origin, _) => {
- match origin {
- ast::AwaitOrigin::FieldLike =>
- gate_feature_post!(&self, async_await, e.span, "async/await is unstable"),
- ast::AwaitOrigin::MacroLike =>
- gate_feature_post!(
- &self,
- await_macro,
- e.span,
- "`await!(<expr>)` macro syntax is unstable, and will soon be removed \
- in favor of `<expr>.await` syntax."
- ),
- }
- }
- _ => {}
- }
- visit::walk_expr(self, e);
- }
- fn visit_arm(&mut self, arm: &'a ast::Arm) {
- visit::walk_arm(self, arm)
- }
- fn visit_pat(&mut self, pattern: &'a ast::Pat) {
- match pattern.node {
- PatKind::Slice(_, Some(ref subslice), _) => {
- gate_feature_post!(&self, slice_patterns,
- subslice.span,
- "syntax for subslices in slice patterns is not yet stabilized");
- }
- PatKind::Box(..) => {
- gate_feature_post!(&self, box_patterns,
- pattern.span,
- "box pattern syntax is experimental");
- }
- PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
- gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
- "exclusive range pattern syntax is experimental");
- }
- _ => {}
- }
- visit::walk_pat(self, pattern)
- }
- fn visit_fn(&mut self,
- fn_kind: FnKind<'a>,
- fn_decl: &'a ast::FnDecl,
- span: Span,
- _node_id: NodeId) {
- if let Some(header) = fn_kind.header() {
- // Check for const fn and async fn declarations.
- if header.asyncness.node.is_async() {
- gate_feature_post!(&self, async_await, span, "async fn is unstable");
- }
- // Stability of const fn methods are covered in
- // `visit_trait_item` and `visit_impl_item` below; this is
- // because default methods don't pass through this point.
- self.check_abi(header.abi, span);
- }
- if fn_decl.c_variadic {
- gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
- }
- visit::walk_fn(self, fn_kind, fn_decl, span);
- }
- fn visit_generic_param(&mut self, param: &'a GenericParam) {
- if let GenericParamKind::Const { .. } = param.kind {
- gate_feature_post!(&self, const_generics, param.ident.span,
- "const generics are unstable");
- }
- visit::walk_generic_param(self, param);
- }
- fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
- match ti.node {
- ast::TraitItemKind::Method(ref sig, ref block) => {
- if block.is_none() {
- self.check_abi(sig.header.abi, ti.span);
- }
- if sig.header.asyncness.node.is_async() {
- gate_feature_post!(&self, async_await, ti.span, "async fn is unstable");
- }
- if sig.decl.c_variadic {
- gate_feature_post!(&self, c_variadic, ti.span,
- "C-variadic functions are unstable");
- }
- if sig.header.constness.node == ast::Constness::Const {
- gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
- }
- }
- ast::TraitItemKind::Type(_, ref default) => {
- // We use three if statements instead of something like match guards so that all
- // of these errors can be emitted if all cases apply.
- if default.is_some() {
- gate_feature_post!(&self, associated_type_defaults, ti.span,
- "associated type defaults are unstable");
- }
- if !ti.generics.params.is_empty() {
- gate_feature_post!(&self, generic_associated_types, ti.span,
- "generic associated types are unstable");
- }
- if !ti.generics.where_clause.predicates.is_empty() {
- gate_feature_post!(&self, generic_associated_types, ti.span,
- "where clauses on associated types are unstable");
- }
- }
- _ => {}
- }
- visit::walk_trait_item(self, ti);
- }
- fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
- if ii.defaultness == ast::Defaultness::Default {
- gate_feature_post!(&self, specialization,
- ii.span,
- "specialization is unstable");
- }
- match ii.node {
- ast::ImplItemKind::Method(..) => {}
- ast::ImplItemKind::Existential(..) => {
- gate_feature_post!(
- &self,
- existential_type,
- ii.span,
- "existential types are unstable"
- );
- }
- ast::ImplItemKind::Type(_) => {
- if !ii.generics.params.is_empty() {
- gate_feature_post!(&self, generic_associated_types, ii.span,
- "generic associated types are unstable");
- }
- if !ii.generics.where_clause.predicates.is_empty() {
- gate_feature_post!(&self, generic_associated_types, ii.span,
- "where clauses on associated types are unstable");
- }
- }
- _ => {}
- }
- visit::walk_impl_item(self, ii);
- }
- fn visit_vis(&mut self, vis: &'a ast::Visibility) {
- if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
- gate_feature_post!(&self, crate_visibility_modifier, vis.span,
- "`crate` visibility modifier is experimental");
- }
- visit::walk_vis(self, vis);
- }
- }
- pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
- crate_edition: Edition, allow_features: &Option<Vec<String>>) -> Features {
- fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
- let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
- if let Some(reason) = reason {
- err.span_note(span, reason);
- }
- err.emit();
- }
- let mut features = Features::new();
- let mut edition_enabled_features = FxHashMap::default();
- for &edition in ALL_EDITIONS {
- if edition <= crate_edition {
- // The `crate_edition` implies its respective umbrella feature-gate
- // (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
- edition_enabled_features.insert(edition.feature_name(), edition);
- }
- }
- for &(name, .., f_edition, set) in ACTIVE_FEATURES {
- if let Some(f_edition) = f_edition {
- if f_edition <= crate_edition {
- set(&mut features, DUMMY_SP);
- edition_enabled_features.insert(name, crate_edition);
- }
- }
- }
- // Process the edition umbrella feature-gates first, to ensure
- // `edition_enabled_features` is completed before it's queried.
- for attr in krate_attrs {
- if !attr.check_name(sym::feature) {
- continue
- }
- let list = match attr.meta_item_list() {
- Some(list) => list,
- None => continue,
- };
- for mi in list {
- if !mi.is_word() {
- continue;
- }
- let name = mi.name_or_empty();
- if INCOMPLETE_FEATURES.iter().any(|f| name == *f) {
- span_handler.struct_span_warn(
- mi.span(),
- &format!(
- "the feature `{}` is incomplete and may cause the compiler to crash",
- name
- )
- ).emit();
- }
- if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
- if *edition <= crate_edition {
- continue;
- }
- for &(name, .., f_edition, set) in ACTIVE_FEATURES {
- if let Some(f_edition) = f_edition {
- if f_edition <= *edition {
- // FIXME(Manishearth) there is currently no way to set
- // lib features by edition
- set(&mut features, DUMMY_SP);
- edition_enabled_features.insert(name, *edition);
- }
- }
- }
- }
- }
- }
- for attr in krate_attrs {
- if !attr.check_name(sym::feature) {
- continue
- }
- let list = match attr.meta_item_list() {
- Some(list) => list,
- None => continue,
- };
- for mi in list {
- let name = match mi.ident() {
- Some(ident) if mi.is_word() => ident.name,
- _ => {
- span_err!(span_handler, mi.span(), E0556,
- "malformed feature, expected just one word");
- continue
- }
- };
- if let Some(edition) = edition_enabled_features.get(&name) {
- struct_span_warn!(
- span_handler,
- mi.span(),
- E0705,
- "the feature `{}` is included in the Rust {} edition",
- name,
- edition,
- ).emit();
- continue;
- }
- if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
- // Handled in the separate loop above.
- continue;
- }
- let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
- let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
- if let Some((.., reason)) = removed.or(stable_removed) {
- feature_removed(span_handler, mi.span(), *reason);
- continue;
- }
- if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
- let since = Some(Symbol::intern(since));
- features.declared_lang_features.push((name, mi.span(), since));
- continue;
- }
- if let Some(allowed) = allow_features.as_ref() {
- if allowed.iter().find(|f| *f == name.as_str()).is_none() {
- span_err!(span_handler, mi.span(), E0725,
- "the feature `{}` is not in the list of allowed features",
- name);
- continue;
- }
- }
- if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
- set(&mut features, mi.span());
- features.declared_lang_features.push((name, mi.span(), None));
- continue;
- }
- features.declared_lib_features.push((name, mi.span()));
- }
- }
- features
- }
- pub fn check_crate(krate: &ast::Crate,
- sess: &ParseSess,
- features: &Features,
- plugin_attributes: &[(Symbol, AttributeType)],
- unstable: UnstableFeatures) {
- maybe_stage_features(&sess.span_diagnostic, krate, unstable);
- let ctx = Context {
- features,
- parse_sess: sess,
- plugin_attributes,
- };
- let visitor = &mut PostExpansionVisitor {
- context: &ctx,
- builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP,
- };
- visit::walk_crate(visitor, krate);
- }
- #[derive(Clone, Copy, Hash)]
- pub enum UnstableFeatures {
- /// Hard errors for unstable features are active, as on beta/stable channels.
- Disallow,
- /// Allow features to be activated, as on nightly.
- Allow,
- /// Errors are bypassed for bootstrapping. This is required any time
- /// during the build that feature-related lints are set to warn or above
- /// because the build turns on warnings-as-errors and uses lots of unstable
- /// features. As a result, this is always required for building Rust itself.
- Cheat
- }
- impl UnstableFeatures {
- pub fn from_environment() -> UnstableFeatures {
- // Whether this is a feature-staged build, i.e., on the beta or stable channel
- let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
- // Whether we should enable unstable features for bootstrapping
- let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
- match (disable_unstable_features, bootstrap) {
- (_, true) => UnstableFeatures::Cheat,
- (true, _) => UnstableFeatures::Disallow,
- (false, _) => UnstableFeatures::Allow
- }
- }
- pub fn is_nightly_build(&self) -> bool {
- match *self {
- UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
- _ => false,
- }
- }
- }
- fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
- unstable: UnstableFeatures) {
- let allow_features = match unstable {
- UnstableFeatures::Allow => true,
- UnstableFeatures::Disallow => false,
- UnstableFeatures::Cheat => true
- };
- if !allow_features {
- for attr in &krate.attrs {
- if attr.check_name(sym::feature) {
- let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
- span_err!(span_handler, attr.span, E0554,
- "#![feature] may not be used on the {} release channel",
- release_channel);
- }
- }
- }
- }
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