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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, AssocTyConstraint, AssocTyConstraintKind, 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::parse::parser::Parser;
use crate::symbol::{Symbol, sym};
use crate::tokenstream::TokenTree;
use errors::{Applicability, DiagnosticBuilder, Handler};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lock;
use rustc_target::spec::abi::Abi;
use syntax_pos::{Span, DUMMY_SP, MultiSpan};
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
// 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", Some(0), 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(62254), 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 using `reason` in lint attributes and the `#[expect(lint)]` lint check.
(active, lint_reasons, "1.31.0", Some(54503), None),
// Allows exhaustive integer pattern matching on `usize` and `isize`.
(active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
// Allows 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 C-variadics.
(active, c_variadic, "1.34.0", Some(44930), None),
// Allows the user of associated type bounds.
(active, associated_type_bounds, "1.34.0", Some(52662), None),
// Attributes on formal function params.
(active, param_attrs, "1.36.0", Some(60406), None),
// Allows calling constructor functions in `const fn`.
(active, const_constructor, "1.37.0", Some(61456), None),
// Allows `if/while p && let q = r && ...` chains.
(active, let_chains, "1.37.0", Some(53667), None),
// #[repr(transparent)] on enums.
(active, transparent_enums, "1.37.0", Some(60405), None),
// #[repr(transparent)] on unions.
(active, transparent_unions, "1.37.0", Some(60405), None),
// Allows explicit discriminants on non-unit enum variants.
(active, arbitrary_enum_discriminant, "1.37.0", Some(60553), None),
// Allows `impl Trait` with multiple unrelated lifetimes.
(active, member_constraints, "1.37.0", Some(61977), None),
// Allows `async || body` closures.
(active, async_closure, "1.37.0", Some(62290), None),
// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests
(active, cfg_doctest, "1.37.0", Some(62210), 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,
sym::let_chains,
];
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(62254), 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),
// Allows using `#[unsafe_destructor_blind_to_params]` (RFC 1238).
(removed, dropck_parametricity, "1.38.0", Some(28498), 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),
// Allows paths to enum variants on type aliases including `Self`.
(accepted, type_alias_enum_variants, "1.37.0", Some(49683), None),
// Allows using `#[repr(align(X))]` on enums with equivalent semantics
// to wrapping an enum in a wrapper struct with `#[repr(align(X))]`.
(accepted, repr_align_enum, "1.37.0", Some(57996), None),
// Allows `const _: TYPE = VALUE`.
(accepted, underscore_const_names, "1.37.0", Some(54912), 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, Whitelisted, 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_nonnull_optimization_guaranteed, Whitelisted, template!(Word),
Gated(Stability::Unstable,
sym::rustc_attrs,
"the `#[rustc_nonnull_optimization_guaranteed]` 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_dump_env_program_clauses, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"the `#[rustc_dump_env_program_clauses]` \
attribute is just used for rustc unit \
tests and will never be stable",
cfg_fn!(rustc_attrs))),
(sym::rustc_object_lifetime_default, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"the `#[rustc_object_lifetime_default]` \
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_macro_transparency, Whitelisted, template!(NameValueStr:
"transparent|semitransparent|opaque"),
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))),
(sym::rustc_allocator, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"internal implementation detail",
cfg_fn!(rustc_attrs))),
(sym::rustc_allocator_nounwind, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"internal implementation detail",
cfg_fn!(rustc_attrs))),
(sym::rustc_builtin_macro, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"internal implementation detail",
cfg_fn!(rustc_attrs))),
(sym::rustc_promotable, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"internal implementation detail",
cfg_fn!(rustc_attrs))),
(sym::rustc_allow_const_fn_ptr, Whitelisted, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"internal implementation detail",
cfg_fn!(rustc_attrs))),
(sym::rustc_dummy, Normal, template!(Word /* doesn't matter*/), Gated(Stability::Unstable,
sym::rustc_attrs,
"used by the test suite",
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::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,
"custom test frameworks are an unstable feature",
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)),
(sym::doctest, sym::cfg_doctest, cfg_fn!(cfg_doctest)),
];
#[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;
} else {
for segment in &attr.path.segments {
if segment.ident.as_str().starts_with("rustc") {
let msg = "attributes starting with `rustc` are \
reserved for use by the `rustc` compiler";
gate_feature!(self, rustc_attrs, segment.ident.span, msg);
}
}
}
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 !is_macro && !attr::is_known(attr) {
// 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, 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, S: Into<MultiSpan>>(
sess: &'a ParseSess,
feature: Symbol,
span: S,
issue: GateIssue,
explain: &str,
) -> DiagnosticBuilder<'a> {
leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
}
fn leveled_feature_err<'a, S: Into<MultiSpan>>(
sess: &'a ParseSess,
feature: Symbol,
span: S,
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_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 error_msg = format!("malformed `{}` attribute input", name);
let mut msg = "attribute must be of the form ".to_owned();
let mut suggestions = vec![];
let mut first = true;
if template.word {
first = false;
let code = format!("#[{}]", name);
msg.push_str(&format!("`{}`", &code));
suggestions.push(code);
}
if let Some(descr) = template.list {
if !first {
msg.push_str(" or ");
}
first = false;
let code = format!("#[{}({})]", name, descr);
msg.push_str(&format!("`{}`", &code));
suggestions.push(code);
}
if let Some(descr) = template.name_value_str {
if !first {
msg.push_str(" or ");
}
let code = format!("#[{} = \"{}\"]", name, descr);
msg.push_str(&format!("`{}`", &code));
suggestions.push(code);
}
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.struct_span_err(meta.span, &error_msg)
.span_suggestions(
meta.span,
if suggestions.len() == 1 {
"must be of the form"
} else {
"the following are the possible correct uses"
},
suggestions.into_iter(),
Applicability::HasPlaceholders,
).emit();
}
}
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 {
// `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
Some(&(name, _, template, _)) if name != sym::rustc_dummy =>
self.check_builtin_attribute(attr, name, template),
_ => if let Some(TokenTree::Token(token)) = attr.tokens.trees().next() {
if token == token::Eq {
// 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::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 non-standard `#[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(ast::EnumDef{ref variants, ..}, ..) => {
for variant in variants {
match (&variant.node.data, &variant.node.disr_expr) {
(ast::VariantData::Unit(..), _) => {},
(_, Some(disr_expr)) =>
gate_feature_post!(
&self,
arbitrary_enum_discriminant,
disr_expr.value.span,
"discriminants on non-unit variants are experimental"),
_ => {},
}
}
let has_feature = self.context.features.arbitrary_enum_discriminant;
if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
Parser::maybe_report_invalid_custom_discriminants(
self.context.parse_sess,
&variants,
);
}
}
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::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::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) {
match param.kind {
GenericParamKind::Const { .. } =>
gate_feature_post!(&self, const_generics, param.ident.span,
"const generics are unstable"),
_ => {}
}
visit::walk_generic_param(self, param)
}
fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
match constraint.kind {
AssocTyConstraintKind::Bound { .. } =>
gate_feature_post!(&self, associated_type_bounds, constraint.span,
"associated type bounds are unstable"),
_ => {}
}
visit::walk_assoc_ty_constraint(self, constraint)
}
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);
} else {
err.span_label(span, "feature has been removed");
}
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,
};
let bad_input = |span| {
struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
};
for mi in list {
let name = match mi.ident() {
Some(ident) if mi.is_word() => ident.name,
Some(ident) => {
bad_input(mi.span()).span_suggestion(
mi.span(),
"expected just one word",
format!("{}", ident.name),
Applicability::MaybeIncorrect,
).emit();
continue
}
None => {
bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
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
}
fn for_each_in_lock<T>(vec: &Lock<Vec<T>>, f: impl Fn(&T)) {
vec.borrow().iter().for_each(f);
}
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,
};
for_each_in_lock(&sess.param_attr_spans, |span| gate_feature!(
&ctx,
param_attrs,
*span,
"attributes on function parameters are unstable"
));
for_each_in_lock(&sess.let_chains_spans, |span| gate_feature!(
&ctx,
let_chains,
*span,
"`let` expressions in this position are experimental"
));
for_each_in_lock(&sess.async_closure_spans, |span| gate_feature!(
&ctx,
async_closure,
*span,
"async closures are unstable"
));
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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