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rust/src/libsyntax/feature_gate.rs
bors e1d7e4ae82 Auto merge of #63248 - petrochenkov:nomarker, r=matthewjasper 
Move special treatment of `derive(Copy, PartialEq, Eq)` from expansion infrastructure to elsewhere

As described in https://github.com/rust-lang/rust/pull/62086#issuecomment-515195477.

Reminder:
- `derive(PartialEq, Eq)` makes the type it applied to a "structural match" type, so constants of this type can be used in patterns (and const generics in the future).
- `derive(Copy)` notifies other derives that the type it applied to implements `Copy`, so `derive(Clone)` can generate optimized code and other derives can generate code working with `packed` types and types with `rustc_layout_scalar_valid_range` attributes.

First, the special behavior is now enabled after properly resolving the derives, rather than after textually comparing them with `"Copy"`, `"PartialEq"` and `"Eq"` in `fn add_derived_markers`.

The markers are no longer kept as attributes in AST since derives cannot modify items and previously did it through hacks in the expansion infra.
Instead, the markers are now kept in a "global context" available from all the necessary places, namely - resolver.

For `derive(PartialEq, Eq)` the markers are created by the derive macros themselves and then consumed during HIR lowering to add the `#[structural_match]` attribute in HIR.
This is still a hack, but now it's a hack local to two specific macros rather than affecting the whole expansion infra.
Ideally we should find the way to put `#[structural_match]` on the impls rather than on the original item, and then consume it in `rustc_mir`, then no hacks in expansion and lowering will be required.
(I'll make an issue about this for someone else to solve, after this PR lands.)

The marker for `derive(Copy)` cannot be emitted by the `Copy` macro itself because we need to know it *before* the `Copy` macro is expanded for expanding other macros.
So we have to do it in resolve and block expansion of any derives in a `derive(...)` container until we know for sure whether this container has `Copy` in it or not.
Nasty stuff.

r? @eddyb or @matthewjasper
2019-08-05 04:36:51 +00:00

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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::{self, check_builtin_attribute, AttributeTemplate};
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 compiler's own crates.
(active, rustc_private, "1.0.0", Some(27812), None),
// Allows using the `rust-intrinsic`'s "ABI".
(active, intrinsics, "1.0.0", None, None),
// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
(active, lang_items, "1.0.0", None, None),
// Allows using the `#[stable]` and `#[unstable]` attributes.
(active, staged_api, "1.0.0", None, None),
// Allows using `#[allow_internal_unstable]`. This is an
// attribute on `macro_rules!` and can't use the attribute handling
// below (it has to be checked before expansion possibly makes
// macros disappear).
(active, allow_internal_unstable, "1.0.0", None, None),
// Allows using `#[allow_internal_unsafe]`. This is an
// attribute on `macro_rules!` and can't use the attribute handling
// below (it has to be checked before expansion possibly makes
// macros disappear).
(active, allow_internal_unsafe, "1.0.0", None, None),
// 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),
// 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 the `#[link_args]` attribute.
(active, link_args, "1.0.0", Some(29596), None),
// Allows defining identifiers beyond ASCII.
(active, non_ascii_idents, "1.0.0", Some(55467), None),
// Allows using `#[plugin_registrar]` on functions.
(active, plugin_registrar, "1.0.0", Some(29597), None),
// Allows using `#![plugin(myplugin)]`.
(active, plugin, "1.0.0", Some(29597), None),
// Allows using `#[thread_local]` on `static` items.
(active, thread_local, "1.0.0", Some(29594), None),
// Allows the use of SIMD types in functions declared in `extern` blocks.
(active, simd_ffi, "1.0.0", Some(27731), None),
// Allows using 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 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 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 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(63065), None),
// Allows using `reason` in lint attributes and the `#[expect(lint)]` lint check.
(active, lint_reasons, "1.31.0", Some(54503), None),
// Allows exhaustive integer pattern matching on `usize` and `isize`.
(active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
// Allows 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),
// Allows #[repr(transparent)] on enums (RFC 2645).
(active, transparent_enums, "1.37.0", Some(60405), None),
// Allows #[repr(transparent)] on unions (RFC 2645).
(active, transparent_unions, "1.37.0", Some(60405), None),
// Allows explicit discriminants on non-unit enum variants.
(active, arbitrary_enum_discriminant, "1.37.0", Some(60553), None),
// Allows `impl Trait` with multiple unrelated lifetimes.
(active, member_constraints, "1.37.0", Some(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),
// Allows `[x; N]` where `x` is a constant (RFC 2203).
(active, const_in_array_repeat_expressions, "1.37.0", Some(49147), None),
// Allows `impl Trait` to be used inside type aliases (RFC 2515).
(active, type_alias_impl_trait, "1.38.0", Some(63063), None),
// -------------------------------------------------------------------------
// feature-group-end: actual feature gates
// -------------------------------------------------------------------------
);
/// Some features are known to be incomplete and using them is likely to have
/// unanticipated results, such as compiler crashes. We warn the user about these
/// to alert them.
pub const INCOMPLETE_FEATURES: &[Symbol] = &[
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),
(removed, await_macro, "1.38.0", Some(50547), None,
Some("subsumed by `.await` syntax")),
// Allows defining `existential type`s.
(removed, existential_type, "1.38.0", Some(63063), None,
Some("removed in favor of `#![feature(type_alias_impl_trait)]`")),
// -------------------------------------------------------------------------
// 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 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::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_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 => {}
}
}
}
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 =>
check_builtin_attribute(self.context.parse_sess, 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::OpaqueTy(..) => {
gate_feature_post!(
&self,
type_alias_impl_trait,
i.span,
"`impl Trait` in type aliases is 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(_) => {
gate_feature_post!(&self, async_await, e.span, "async/await is unstable");
}
_ => {}
}
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(pats) => {
for pat in &*pats {
let span = pat.span;
let inner_pat = match &pat.node {
PatKind::Ident(.., Some(pat)) => pat,
_ => pat,
};
if inner_pat.is_rest() {
gate_feature_post!(
&self,
slice_patterns,
span,
"subslice patterns are unstable"
);
}
}
}
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::OpaqueTy(..) => {
gate_feature_post!(
&self,
type_alias_impl_trait,
ii.span,
"`impl Trait` in type aliases is unstable"
);
}
ast::ImplItemKind::TyAlias(_) => {
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 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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