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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! 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 self::AttributeType::*;
use self::AttributeGate::*;
use rustc_data_structures::fx::FxHashMap;
use rustc_target::spec::abi::Abi;
use ast::{self, NodeId, PatKind, RangeEnd};
use attr;
use codemap::Spanned;
use edition::{ALL_EDITIONS, Edition};
use syntax_pos::{Span, DUMMY_SP};
use errors::{DiagnosticBuilder, Handler};
use visit::{self, FnKind, Visitor};
use parse::ParseSess;
use symbol::{keywords, Symbol};
use std::{env, path};
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, $edition: expr),)+) => {
/// Represents active features that are currently being implemented or
/// currently being considered for addition/removal.
const ACTIVE_FEATURES:
&'static [(&'static str, &'static str, Option<u32>,
Option<Edition>, fn(&mut Features, Span))] =
&[$((stringify!($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: &[(&str, &str, Option<u32>, Option<&str>)] = &[
$((stringify!($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: &[(&str, &str, Option<u32>, Option<&str>)] = &[
$((stringify!($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: &[(&str, &str, Option<u32>, Option<&str>)] = &[
$((stringify!($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).
//
// NB: tools/tidy/src/features.rs parses this information directly out of the
// source, so take care when modifying it.
declare_features! (
(active, asm, "1.0.0", Some(29722), None),
(active, concat_idents, "1.0.0", Some(29599), None),
(active, link_args, "1.0.0", Some(29596), None),
(active, log_syntax, "1.0.0", Some(29598), None),
(active, non_ascii_idents, "1.0.0", Some(28979), None),
(active, plugin_registrar, "1.0.0", Some(29597), None),
(active, thread_local, "1.0.0", Some(29594), None),
(active, trace_macros, "1.0.0", Some(29598), None),
// rustc internal, for now:
(active, intrinsics, "1.0.0", None, None),
(active, lang_items, "1.0.0", None, None),
(active, format_args_nl, "1.29.0", None, None),
(active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
(active, linkage, "1.0.0", Some(29603), None),
(active, quote, "1.0.0", Some(29601), None),
// rustc internal
(active, rustc_diagnostic_macros, "1.0.0", None, None),
(active, rustc_const_unstable, "1.0.0", None, None),
(active, box_syntax, "1.0.0", Some(49733), None),
(active, unboxed_closures, "1.0.0", Some(29625), None),
(active, fundamental, "1.0.0", Some(29635), None),
(active, main, "1.0.0", Some(29634), None),
(active, needs_allocator, "1.4.0", Some(27389), None),
(active, on_unimplemented, "1.0.0", Some(29628), None),
(active, plugin, "1.0.0", Some(29597), None),
(active, simd_ffi, "1.0.0", Some(27731), None),
(active, start, "1.0.0", Some(29633), None),
(active, structural_match, "1.8.0", Some(31434), None),
(active, panic_runtime, "1.10.0", Some(32837), None),
(active, needs_panic_runtime, "1.10.0", Some(32837), None),
// OIBIT specific features
(active, optin_builtin_traits, "1.0.0", Some(13231), None),
// Allows use of #[staged_api]
// rustc internal
(active, staged_api, "1.0.0", None, None),
// Allows using #![no_core]
(active, no_core, "1.3.0", Some(29639), None),
// Allows using `box` in patterns; RFC 469
(active, box_patterns, "1.0.0", Some(29641), None),
// Allows using the unsafe_destructor_blind_to_params attribute;
// RFC 1238
(active, dropck_parametricity, "1.3.0", Some(28498), None),
// Allows using the may_dangle attribute; RFC 1327
(active, dropck_eyepatch, "1.10.0", Some(34761), None),
// Allows the use of custom attributes; RFC 572
(active, custom_attribute, "1.0.0", Some(29642), None),
// Allows the use of #[derive(Anything)] as sugar for
// #[derive_Anything].
(active, custom_derive, "1.0.0", Some(29644), None),
// Allows the use of rustc_* attributes; RFC 572
(active, rustc_attrs, "1.0.0", Some(29642), None),
// Allows the use of non lexical lifetimes; RFC 2094
(active, nll, "1.0.0", Some(43234), None),
// Allows the use of #[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).
//
// rustc internal
(active, allow_internal_unstable, "1.0.0", None, None),
// Allows the use of #[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).
//
// rustc internal
(active, allow_internal_unsafe, "1.0.0", None, None),
// #23121. Array patterns have some hazards yet.
(active, slice_patterns, "1.0.0", Some(23121), None),
// Allows the definition of `const fn` functions.
(active, const_fn, "1.2.0", Some(24111), None),
// Allows let bindings and destructuring in `const fn` functions and constants.
(active, const_let, "1.22.1", Some(48821), None),
// Allows accessing fields of unions inside const fn
(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 using #[prelude_import] on glob `use` items.
//
// rustc internal
(active, prelude_import, "1.2.0", None, None),
// Allows default type parameters to influence type inference.
(active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
// Allows associated type defaults
(active, associated_type_defaults, "1.2.0", Some(29661), None),
// allow `repr(simd)`, and importing the various simd intrinsics
(active, repr_simd, "1.4.0", Some(27731), None),
// allow `extern "platform-intrinsic" { ... }`
(active, platform_intrinsics, "1.4.0", Some(27731), None),
// allow `#[unwind(..)]`
// rustc internal for rust runtime
(active, unwind_attributes, "1.4.0", None, None),
// allow the use of `#[naked]` on functions.
(active, naked_functions, "1.9.0", Some(32408), None),
// allow `#[no_debug]`
(active, no_debug, "1.5.0", Some(29721), None),
// allow `#[omit_gdb_pretty_printer_section]`
// rustc internal.
(active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
// Allows cfg(target_vendor = "...").
(active, cfg_target_vendor, "1.5.0", Some(29718), None),
// Allow attributes on expressions and non-item statements
(active, stmt_expr_attributes, "1.6.0", Some(15701), None),
// allow using 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),
// rustc internal
(active, abi_vectorcall, "1.7.0", None, None),
// X..Y patterns
(active, exclusive_range_pattern, "1.11.0", Some(37854), None),
// impl specialization (RFC 1210)
(active, specialization, "1.7.0", Some(31844), None),
// Allows cfg(target_has_atomic = "...").
(active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
// 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 all literals in attribute lists and values of key-value pairs.
(active, attr_literals, "1.13.0", Some(34981), None),
// Allows untagged unions `union U { ... }`
(active, untagged_unions, "1.13.0", Some(32836), None),
// Used to identify the `compiler_builtins` crate
// rustc internal
(active, compiler_builtins, "1.13.0", None, None),
// Allows #[link(..., cfg(..))]
(active, link_cfg, "1.14.0", Some(37406), None),
// `extern "ptx-*" fn()`
(active, abi_ptx, "1.15.0", Some(38788), None),
// The `repr(i128)` annotation for enums
(active, repr128, "1.16.0", Some(35118), None),
// The `unadjusted` ABI. Perma unstable.
// rustc internal
(active, abi_unadjusted, "1.16.0", None, None),
// Declarative macros 2.0 (`macro`).
(active, decl_macro, "1.17.0", Some(39412), None),
// Allows #[link(kind="static-nobundle"...)]
(active, static_nobundle, "1.16.0", Some(37403), None),
// `extern "msp430-interrupt" fn()`
(active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
// Used to identify crates that contain sanitizer runtimes
// rustc internal
(active, sanitizer_runtime, "1.17.0", None, None),
// Used to identify crates that contain the profiler runtime
// rustc internal
(active, profiler_runtime, "1.18.0", None, None),
// `extern "x86-interrupt" fn()`
(active, abi_x86_interrupt, "1.17.0", Some(40180), None),
// Allows the `catch {...}` expression
(active, catch_expr, "1.17.0", Some(31436), None),
// Used to preserve symbols (see llvm.used)
(active, used, "1.18.0", Some(40289), 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 use of the :vis macro fragment specifier
(active, macro_vis_matcher, "1.18.0", Some(41022), None),
// rustc internal
(active, abi_thiscall, "1.19.0", None, None),
// Allows a test to fail without failing the whole suite
(active, allow_fail, "1.19.0", Some(42219), None),
// Allows unsized tuple coercion.
(active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
// Generators
(active, generators, "1.21.0", Some(43122), None),
// Trait aliases
(active, trait_alias, "1.24.0", Some(41517), None),
// rustc internal
(active, allocator_internals, "1.20.0", None, None),
// #[doc(cfg(...))]
(active, doc_cfg, "1.21.0", Some(43781), None),
// #[doc(masked)]
(active, doc_masked, "1.21.0", Some(44027), None),
// #[doc(spotlight)]
(active, doc_spotlight, "1.22.0", Some(45040), None),
// #[doc(include="some-file")]
(active, external_doc, "1.22.0", Some(44732), None),
// Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
(active, non_exhaustive, "1.22.0", Some(44109), None),
// `crate` as visibility modifier, synonymous to `pub(crate)`
(active, crate_visibility_modifier, "1.23.0", Some(45388), Some(Edition::Edition2018)),
// extern types
(active, extern_types, "1.23.0", Some(43467), None),
// Allow trait methods with arbitrary self types
(active, arbitrary_self_types, "1.23.0", Some(44874), None),
// `crate` in paths
(active, crate_in_paths, "1.23.0", Some(45477), Some(Edition::Edition2018)),
// In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
(active, in_band_lifetimes, "1.23.0", Some(44524), None),
// generic associated types (RFC 1598)
(active, generic_associated_types, "1.23.0", Some(44265), None),
// Resolve absolute paths as paths from other crates
(active, extern_absolute_paths, "1.24.0", Some(44660), Some(Edition::Edition2018)),
// `foo.rs` as an alternative to `foo/mod.rs`
(active, non_modrs_mods, "1.24.0", Some(44660), Some(Edition::Edition2018)),
// `extern` in paths
(active, extern_in_paths, "1.23.0", Some(44660), None),
// Use `?` as the Kleene "at most one" operator
(active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
// Infer outlives requirements; RFC 2093
(active, infer_outlives_requirements, "1.26.0", Some(44493), None),
// Infer static outlives requirements; RFC 2093
(active, infer_static_outlives_requirements, "1.26.0", Some(44493), None),
// Multiple patterns with `|` in `if let` and `while let`
(active, if_while_or_patterns, "1.26.0", Some(48215), None),
// Parentheses in patterns
(active, pattern_parentheses, "1.26.0", Some(51087), None),
// Allows `#[repr(packed)]` attribute on structs
(active, repr_packed, "1.26.0", Some(33158), None),
// `use path as _;` and `extern crate c as _;`
(active, underscore_imports, "1.26.0", Some(48216), None),
// Allows keywords to be escaped for use as identifiers
(active, raw_identifiers, "1.26.0", Some(48589), Some(Edition::Edition2018)),
// Allows macro invocations in `extern {}` blocks
(active, macros_in_extern, "1.27.0", Some(49476), None),
// `existential type`
(active, existential_type, "1.28.0", Some(34511), None),
// 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),
// Allows macro invocations of the form `#[foo::bar]`
(active, proc_macro_path_invoc, "1.27.0", Some(38356), None),
// Allows macro invocations on modules expressions and statements and
// procedural macros to expand to non-items.
(active, proc_macro_mod, "1.27.0", Some(38356), None),
(active, proc_macro_expr, "1.27.0", Some(38356), None),
(active, proc_macro_non_items, "1.27.0", Some(38356), None),
(active, proc_macro_gen, "1.27.0", Some(38356), None),
// #[doc(alias = "...")]
(active, doc_alias, "1.27.0", Some(50146), None),
// Access to crate names passed via `--extern` through prelude
(active, extern_prelude, "1.27.0", Some(44660), Some(Edition::Edition2018)),
// Scoped attributes
(active, tool_attributes, "1.25.0", Some(44690), None),
// Scoped lints
(active, tool_lints, "1.28.0", Some(44690), None),
// allow irrefutable patterns in if-let and while-let statements (RFC 2086)
(active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
// Allows use of the :literal macro fragment specifier (RFC 1576)
(active, macro_literal_matcher, "1.27.0", Some(35625), None),
// inconsistent bounds in where clauses
(active, trivial_bounds, "1.28.0", Some(48214), None),
// 'a: { break 'a; }
(active, label_break_value, "1.28.0", Some(48594), None),
// #[panic_implementation]
(active, panic_implementation, "1.28.0", Some(44489), None),
// #[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),
// #[alloc_error_handler]
(active, alloc_error_handler, "1.29.0", Some(51540), None),
(active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
// impl<I:Iterator> Iterator for &mut Iterator
// impl Debug for Foo<'_>
(active, impl_header_lifetime_elision, "1.30.0", Some(15872), Some(Edition::Edition2018)),
// Support for arbitrary delimited token streams in non-macro attributes.
(active, unrestricted_attribute_tokens, "1.30.0", Some(44690), None),
// Allows `use x::y;` to resolve through `self::x`, not just `::x`.
(active, uniform_paths, "1.30.0", Some(53130), None),
);
declare_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
// rustc internal
(removed, unmarked_api, "1.0.0", None, None, None),
(removed, pushpop_unsafe, "1.2.0", None, None, None),
(removed, allocator, "1.0.0", None, None, None),
(removed, simd, "1.0.0", Some(27731), None,
Some("removed in favor of `#[repr(simd)]`")),
(removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
Some("merged into `#![feature(slice_patterns)]`")),
(removed, macro_reexport, "1.0.0", Some(29638), None,
Some("subsumed by `pub use`")),
);
declare_features! (
(stable_removed, no_stack_check, "1.0.0", None, None),
);
declare_features! (
(accepted, associated_types, "1.0.0", None, None),
// allow overloading augmented assignment operations like `a += b`
(accepted, augmented_assignments, "1.8.0", Some(28235), None),
// allow empty structs and enum variants with braces
(accepted, braced_empty_structs, "1.8.0", Some(29720), None),
// Allows indexing into constant arrays.
(accepted, const_indexing, "1.26.0", Some(29947), None),
(accepted, default_type_params, "1.0.0", None, None),
(accepted, globs, "1.0.0", None, None),
(accepted, if_let, "1.0.0", None, None),
// A temporary feature gate used to enable parser extensions needed
// to bootstrap fix for #5723.
(accepted, issue_5723_bootstrap, "1.0.0", None, None),
(accepted, macro_rules, "1.0.0", None, None),
// Allows using #![no_std]
(accepted, no_std, "1.6.0", None, None),
(accepted, slicing_syntax, "1.0.0", None, None),
(accepted, struct_variant, "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),
(accepted, tuple_indexing, "1.0.0", None, None),
// Allows macros to appear in the type position.
(accepted, type_macros, "1.13.0", Some(27245), None),
(accepted, while_let, "1.0.0", None, None),
// Allows `#[deprecated]` attribute
(accepted, deprecated, "1.9.0", Some(29935), None),
// `expr?`
(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),
(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),
// elide `'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),
// pub(restricted) visibilities (RFC 1422)
(accepted, pub_restricted, "1.18.0", Some(32409), None),
// The #![windows_subsystem] attribute
(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),
// Permits numeric fields in struct expressions and patterns.
(accepted, relaxed_adts, "1.19.0", Some(35626), None),
// Coerces 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),
// Usage of the `compile_error!` macro
(accepted, compile_error, "1.20.0", Some(40872), None),
// See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
(accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
// Allow 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),
// allow '|' at beginning of match arms (RFC 1925)
(accepted, match_beginning_vert, "1.25.0", Some(44101), None),
// Nested groups in `use` (RFC 2128)
(accepted, use_nested_groups, "1.25.0", Some(44494), None),
// a..=b and ..=b
(accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
// allow `..=` in patterns (RFC 1192)
(accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
// Termination trait in main (RFC 1937)
(accepted, termination_trait, "1.26.0", Some(43301), None),
// Copy/Clone closures (RFC 2132)
(accepted, clone_closures, "1.26.0", Some(44490), None),
(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),
// The `i128` type
(accepted, i128_type, "1.26.0", Some(35118), None),
// Default match binding modes (RFC 2005)
(accepted, match_default_bindings, "1.26.0", Some(42640), None),
// allow `'_` 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),
// Trait object syntax with `dyn` prefix
(accepted, dyn_trait, "1.27.0", Some(44662), None),
// allow `#[must_use]` on functions; and, 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),
// Termination trait in tests (RFC 1937)
(accepted, termination_trait_test, "1.27.0", Some(48854), None),
// 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),
// Defining procedural macros in `proc-macro` crates
(accepted, proc_macro, "1.29.0", Some(38356), None),
// Allows importing and reexporting macros with `use`,
// enables macro modularization in general.
(accepted, use_extern_macros, "1.30.0", Some(35896), None),
);
// 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, &'static str, &'static str, fn(&Features) -> bool),
/// Ungated attribute, can be used on all release channels
Ungated,
}
impl AttributeGate {
fn is_deprecated(&self) -> bool {
match *self {
Gated(Stability::Deprecated(_), ..) => true,
_ => false,
}
}
}
#[derive(Copy, Clone, Debug)]
pub enum Stability {
Unstable,
// Argument is tracking issue link.
Deprecated(&'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 (&'static str, AttributeType, AttributeGate)> {
BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
}
pub fn is_builtin_attr_name(name: ast::Name) -> bool {
BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
}
pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
}
// Attributes that have a special meaning to rustc or rustdoc
pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
// Normal attributes
("warn", Normal, Ungated),
("allow", Normal, Ungated),
("forbid", Normal, Ungated),
("deny", Normal, Ungated),
("macro_use", Normal, Ungated),
("macro_export", Normal, Ungated),
("plugin_registrar", Normal, Ungated),
("cfg", Normal, Ungated),
("cfg_attr", Normal, Ungated),
("main", Normal, Ungated),
("start", Normal, Ungated),
("test", Normal, Ungated),
("bench", Normal, Ungated),
("repr", Normal, Ungated),
("path", Normal, Ungated),
("abi", Normal, Ungated),
("automatically_derived", Normal, Ungated),
("no_mangle", Normal, Ungated),
("no_link", Normal, Ungated),
("derive", Normal, Ungated),
("should_panic", Normal, Ungated),
("ignore", Normal, Ungated),
("no_implicit_prelude", Normal, Ungated),
("reexport_test_harness_main", Normal, Ungated),
("link_args", Normal, Gated(Stability::Unstable,
"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))),
("macro_escape", Normal, Ungated),
// RFC #1445.
("structural_match", Whitelisted, Gated(Stability::Unstable,
"structural_match",
"the semantics of constant patterns is \
not yet settled",
cfg_fn!(structural_match))),
// RFC #2008
("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
"non_exhaustive",
"non exhaustive is an experimental feature",
cfg_fn!(non_exhaustive))),
("plugin", CrateLevel, Gated(Stability::Unstable,
"plugin",
"compiler plugins are experimental \
and possibly buggy",
cfg_fn!(plugin))),
("no_std", CrateLevel, Ungated),
("no_core", CrateLevel, Gated(Stability::Unstable,
"no_core",
"no_core is experimental",
cfg_fn!(no_core))),
("lang", Normal, Gated(Stability::Unstable,
"lang_items",
"language items are subject to change",
cfg_fn!(lang_items))),
("linkage", Whitelisted, Gated(Stability::Unstable,
"linkage",
"the `linkage` attribute is experimental \
and not portable across platforms",
cfg_fn!(linkage))),
("thread_local", Whitelisted, Gated(Stability::Unstable,
"thread_local",
"`#[thread_local]` is an experimental feature, and does \
not currently handle destructors.",
cfg_fn!(thread_local))),
("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
"on_unimplemented",
"the `#[rustc_on_unimplemented]` attribute \
is an experimental feature",
cfg_fn!(on_unimplemented))),
("rustc_const_unstable", Normal, Gated(Stability::Unstable,
"rustc_const_unstable",
"the `#[rustc_const_unstable]` attribute \
is an internal feature",
cfg_fn!(rustc_const_unstable))),
("global_allocator", Normal, Ungated),
("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
"allocator_internals",
"the `#[default_lib_allocator]` \
attribute is an experimental feature",
cfg_fn!(allocator_internals))),
("needs_allocator", Normal, Gated(Stability::Unstable,
"allocator_internals",
"the `#[needs_allocator]` \
attribute is an experimental \
feature",
cfg_fn!(allocator_internals))),
("panic_runtime", Whitelisted, Gated(Stability::Unstable,
"panic_runtime",
"the `#[panic_runtime]` attribute is \
an experimental feature",
cfg_fn!(panic_runtime))),
("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
"needs_panic_runtime",
"the `#[needs_panic_runtime]` \
attribute is an experimental \
feature",
cfg_fn!(needs_panic_runtime))),
("rustc_outlives", Normal, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_outlives]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_variance", Normal, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_variance]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_regions", Normal, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_regions]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_error", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_error]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_if_this_changed]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_if_this_changed]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_dirty]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_clean", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_clean]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"this attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"this attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"this attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"internal rustc attributes will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"internal rustc attributes will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_mir", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_mir]` attribute \
is just used for rustc unit tests \
and will never be stable",
cfg_fn!(rustc_attrs))),
("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
"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))),
("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"the `#[rustc_dump_program_clauses]` \
attribute is just used for rustc unit \
tests and will never be stable",
cfg_fn!(rustc_attrs))),
// RFC #2094
("nll", Whitelisted, Gated(Stability::Unstable,
"nll",
"Non lexical lifetimes",
cfg_fn!(nll))),
("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
"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))),
("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
"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))),
("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
"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))),
("allow_internal_unstable", Normal, Gated(Stability::Unstable,
"allow_internal_unstable",
EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
cfg_fn!(allow_internal_unstable))),
("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
"allow_internal_unsafe",
EXPLAIN_ALLOW_INTERNAL_UNSAFE,
cfg_fn!(allow_internal_unsafe))),
("fundamental", Whitelisted, Gated(Stability::Unstable,
"fundamental",
"the `#[fundamental]` attribute \
is an experimental feature",
cfg_fn!(fundamental))),
("proc_macro_derive", Normal, Ungated),
("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"internal implementation detail",
cfg_fn!(rustc_attrs))),
// FIXME: #14408 whitelist docs since rustdoc looks at them
("doc", Whitelisted, Ungated),
// FIXME: #14406 these are processed in codegen, which happens after the
// lint pass
("cold", Whitelisted, Ungated),
("naked", Whitelisted, Gated(Stability::Unstable,
"naked_functions",
"the `#[naked]` attribute \
is an experimental feature",
cfg_fn!(naked_functions))),
("target_feature", Whitelisted, Ungated),
("export_name", Whitelisted, Ungated),
("inline", Whitelisted, Ungated),
("link", Whitelisted, Ungated),
("link_name", Whitelisted, Ungated),
("link_section", Whitelisted, Ungated),
("no_builtins", Whitelisted, Ungated),
("no_mangle", Whitelisted, Ungated),
("no_debug", Whitelisted, Gated(
Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
"no_debug",
"the `#[no_debug]` attribute was an experimental feature that has been \
deprecated due to lack of demand",
cfg_fn!(no_debug))),
("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
"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))),
("unsafe_destructor_blind_to_params",
Normal,
Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761"),
"dropck_parametricity",
"unsafe_destructor_blind_to_params has been replaced by \
may_dangle and will be removed in the future",
cfg_fn!(dropck_parametricity))),
("may_dangle",
Normal,
Gated(Stability::Unstable,
"dropck_eyepatch",
"may_dangle has unstable semantics and may be removed in the future",
cfg_fn!(dropck_eyepatch))),
("unwind", Whitelisted, Gated(Stability::Unstable,
"unwind_attributes",
"#[unwind] is experimental",
cfg_fn!(unwind_attributes))),
("used", Whitelisted, Gated(
Stability::Unstable, "used",
"the `#[used]` attribute is an experimental feature",
cfg_fn!(used))),
// used in resolve
("prelude_import", Whitelisted, Gated(Stability::Unstable,
"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
("rustc_deprecated", Whitelisted, Ungated),
("must_use", Whitelisted, Ungated),
("stable", Whitelisted, Ungated),
("unstable", Whitelisted, Ungated),
("deprecated", Normal, Ungated),
("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
"unboxed_closures",
"unboxed_closures are still evolving",
cfg_fn!(unboxed_closures))),
("windows_subsystem", Whitelisted, Ungated),
("proc_macro_attribute", Normal, Ungated),
("proc_macro", Normal, Ungated),
("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
"rustc_derive_registrar",
"used internally by rustc",
cfg_fn!(rustc_attrs))),
("allow_fail", Normal, Gated(Stability::Unstable,
"allow_fail",
"allow_fail attribute is currently unstable",
cfg_fn!(allow_fail))),
("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
"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
("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"this is an internal attribute that will \
never be stable",
cfg_fn!(rustc_attrs))),
("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
"rustc_attrs",
"never will be stable",
cfg_fn!(rustc_attrs))),
// RFC #2093
("infer_outlives_requirements", Normal, Gated(Stability::Unstable,
"infer_outlives_requirements",
"infer outlives requirements is an experimental feature",
cfg_fn!(infer_outlives_requirements))),
// RFC #2093
("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
"infer_static_outlives_requirements",
"infer 'static lifetime requirements",
cfg_fn!(infer_static_outlives_requirements))),
// RFC 2070
("panic_implementation", Normal, Gated(Stability::Unstable,
"panic_implementation",
"#[panic_implementation] is an unstable feature",
cfg_fn!(panic_implementation))),
("alloc_error_handler", Normal, Gated(Stability::Unstable,
"alloc_error_handler",
"#[alloc_error_handler] is an unstable feature",
cfg_fn!(alloc_error_handler))),
// Crate level attributes
("crate_name", CrateLevel, Ungated),
("crate_type", CrateLevel, Ungated),
("crate_id", CrateLevel, Ungated),
("feature", CrateLevel, Ungated),
("no_start", CrateLevel, Ungated),
("no_main", CrateLevel, Ungated),
("no_builtins", CrateLevel, Ungated),
("recursion_limit", CrateLevel, Ungated),
("type_length_limit", CrateLevel, Ungated),
];
// cfg(...)'s that are feature gated
const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
// (name in cfg, feature, function to check if the feature is enabled)
("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
];
#[derive(Debug)]
pub struct GatedCfg {
span: Span,
index: usize,
}
impl GatedCfg {
pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
let name = cfg.name().as_str();
GATED_CFGS.iter()
.position(|info| info.0 == name)
.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() {
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 [(String, 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() {
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, $span,
stringify!($feature), $explain, GateStrength::Hard)
};
($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
stringify!($feature), $explain, $level)
};
}
impl<'a> Context<'a> {
fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
debug!("check_attribute(attr = {:?})", attr);
let name = attr.name().as_str();
for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
if name == n {
if let Gated(_, name, desc, ref has_feature) = *gateage {
gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
} else if name == "doc" {
if let Some(content) = attr.meta_item_list() {
if content.iter().any(|c| c.check_name("include")) {
gate_feature!(self, external_doc, attr.span,
"#[doc(include = \"...\")] is experimental"
);
}
}
}
debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
return;
}
}
for &(ref n, ref 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 name.starts_with("rustc_") {
gate_feature!(self, rustc_attrs, attr.span,
"unless otherwise specified, attributes \
with the prefix `rustc_` \
are reserved for internal compiler diagnostics");
} else if name.starts_with("derive_") {
gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
} else if !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 then
if !is_macro {
let msg = format!("The attribute `{}` is currently unknown to the compiler and \
may have meaning added to it in the future", attr.path);
gate_feature!(self, custom_attribute, attr.span, &msg);
}
}
}
}
pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
cx.check_attribute(attr, true);
}
fn find_lang_feature_issue(feature: &str) -> 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: &str, span: Span, issue: GateIssue,
explain: &str) {
feature_err(sess, feature, span, issue, explain).emit();
}
pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
explain: &str) -> DiagnosticBuilder<'a> {
leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
}
fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
let diag = &sess.span_diagnostic;
let issue = match issue {
GateIssue::Language => find_lang_feature_issue(feature),
GateIssue::Library(lib) => lib,
};
let explanation = match issue {
None | Some(0) => explain.to_owned(),
Some(n) => format!("{} (see issue #{})", explain, n)
};
let mut err = match level {
GateStrength::Hard => {
diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
}
GateStrength::Soft => diag.struct_span_warn(span, &explanation),
};
// #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: &'static str =
"box expression syntax is experimental; you can call `Box::new` instead.";
pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
"attributes on expressions are experimental.";
pub const EXPLAIN_ASM: &'static str =
"inline assembly is not stable enough for use and is subject to change";
pub const EXPLAIN_GLOBAL_ASM: &'static str =
"`global_asm!` is not stable enough for use and is subject to change";
pub const EXPLAIN_LOG_SYNTAX: &'static str =
"`log_syntax!` is not stable enough for use and is subject to change";
pub const EXPLAIN_CONCAT_IDENTS: &'static str =
"`concat_idents` is not stable enough for use and is subject to change";
pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
"`format_args_nl` is only for internal language use and is subject to change";
pub const EXPLAIN_TRACE_MACROS: &'static str =
"`trace_macros` is not stable enough for use and is subject to change";
pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
"allow_internal_unstable side-steps feature gating and stability checks";
pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
"allow_internal_unsafe side-steps the unsafe_code lint";
pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
"`#[derive]` for custom traits is deprecated and will be removed in the future.";
pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
"`#[derive]` for custom traits is deprecated and will be removed in the future. \
Prefer using procedural macro custom derive.";
pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
"attributes of the form `#[derive_*]` are reserved for the compiler";
pub const EXPLAIN_VIS_MATCHER: &'static str =
":vis fragment specifier is experimental and subject to change";
pub const EXPLAIN_LITERAL_MATCHER: &'static str =
":literal fragment specifier is experimental and subject to change";
pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
"unsized tuple coercion is not stable enough for use and is subject to change";
pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
"using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
struct PostExpansionVisitor<'a> {
context: &'a Context<'a>,
}
macro_rules! gate_feature_post {
($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
let (cx, span) = ($cx, $span);
if !span.allows_unstable() {
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() {
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 contains_novel_literal(item: &ast::MetaItem) -> bool {
use ast::MetaItemKind::*;
use ast::NestedMetaItemKind::*;
match item.node {
Word => false,
NameValue(ref lit) => !lit.node.is_str(),
List(ref list) => list.iter().any(|li| {
match li.node {
MetaItem(ref mi) => contains_novel_literal(mi),
Literal(_) => true,
}
}),
}
}
impl<'a> PostExpansionVisitor<'a> {
fn whole_crate_feature_gates(&mut self, _krate: &ast::Crate) {
for &(ident, span) in &*self.context.parse_sess.non_modrs_mods.borrow() {
if !span.allows_unstable() {
let cx = &self.context;
let level = GateStrength::Hard;
let has_feature = cx.features.non_modrs_mods;
let name = "non_modrs_mods";
debug!("gate_feature(feature = {:?}, span = {:?}); has? {}",
name, span, has_feature);
if !has_feature && !span.allows_unstable() {
leveled_feature_err(
cx.parse_sess, name, span, GateIssue::Language,
"mod statements in non-mod.rs files are unstable", level
)
.help(&format!("on stable builds, rename this file to {}{}mod.rs",
ident, path::MAIN_SEPARATOR))
.emit();
}
}
}
}
}
impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
fn visit_attribute(&mut self, attr: &ast::Attribute) {
if !attr.span.allows_unstable() {
// check for gated attributes
self.context.check_attribute(attr, false);
}
if attr.check_name("doc") {
if let Some(content) = attr.meta_item_list() {
if content.len() == 1 && content[0].check_name("cfg") {
gate_feature_post!(&self, doc_cfg, attr.span,
"#[doc(cfg(...))] is experimental"
);
} else if content.iter().any(|c| c.check_name("masked")) {
gate_feature_post!(&self, doc_masked, attr.span,
"#[doc(masked)] is experimental"
);
} else if content.iter().any(|c| c.check_name("spotlight")) {
gate_feature_post!(&self, doc_spotlight, attr.span,
"#[doc(spotlight)] is experimental"
);
} else if content.iter().any(|c| c.check_name("alias")) {
gate_feature_post!(&self, doc_alias, attr.span,
"#[doc(alias = \"...\")] is experimental"
);
} else if content.iter().any(|c| c.check_name("keyword")) {
gate_feature_post!(&self, doc_keyword, attr.span,
"#[doc(keyword = \"...\")] is experimental"
);
}
}
}
if !self.context.features.unrestricted_attribute_tokens {
// Unfortunately, `parse_meta` cannot be called speculatively because it can report
// errors by itself, so we have to call it only if the feature is disabled.
match attr.parse_meta(self.context.parse_sess) {
Ok(meta) => {
// allow attr_literals in #[repr(align(x))] and #[repr(packed(n))]
let mut allow_attr_literal = false;
if attr.path == "repr" {
if let Some(content) = meta.meta_item_list() {
allow_attr_literal = content.iter().any(
|c| c.check_name("align") || c.check_name("packed"));
}
}
if !allow_attr_literal && contains_novel_literal(&meta) {
gate_feature_post!(&self, attr_literals, attr.span,
"non-string literals in attributes, or string \
literals in top-level positions, are experimental");
}
}
Err(mut err) => {
err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
}
}
}
}
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.codemap().def_span(sp),
"non-ascii idents are not fully supported.");
}
}
fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
if ident.name == "_" {
gate_feature_post!(&self, underscore_imports, use_tree.span,
"renaming imports with `_` is unstable");
}
}
visit::walk_use_tree(self, use_tree, id);
}
fn visit_item(&mut self, i: &'a ast::Item) {
match i.node {
ast::ItemKind::ExternCrate(_) => {
if i.ident.name == "_" {
gate_feature_post!(&self, underscore_imports, i.span,
"renaming extern crates with `_` is unstable");
}
}
ast::ItemKind::ForeignMod(ref foreign_module) => {
self.check_abi(foreign_module.abi, i.span);
}
ast::ItemKind::Fn(..) => {
if attr::contains_name(&i.attrs[..], "plugin_registrar") {
gate_feature_post!(&self, plugin_registrar, i.span,
"compiler plugins are experimental and possibly buggy");
}
if attr::contains_name(&i.attrs[..], "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[..], "main") {
gate_feature_post!(&self, main, i.span,
"declaration of a nonstandard #[main] \
function may change over time, for now \
a top-level `fn main()` is required");
}
}
ast::ItemKind::Struct(..) => {
if let Some(attr) = attr::find_by_name(&i.attrs[..], "repr") {
for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
if item.check_name("simd") {
gate_feature_post!(&self, repr_simd, attr.span,
"SIMD types are experimental and possibly buggy");
}
if let Some((name, _)) = item.name_value_literal() {
if name == "packed" {
gate_feature_post!(&self, repr_packed, attr.span,
"the `#[repr(packed(n))]` attribute \
is experimental");
}
}
}
}
}
ast::ItemKind::TraitAlias(..) => {
gate_feature_post!(&self, trait_alias,
i.span,
"trait aliases are not yet fully implemented");
}
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::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, "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(..) => {
gate_feature_post!(&self, type_ascription, e.span,
"type ascription is experimental");
}
ast::ExprKind::ObsoleteInPlace(..) => {
// these get a hard error in ast-validation
}
ast::ExprKind::Yield(..) => {
gate_feature_post!(&self, generators,
e.span,
"yield syntax is experimental");
}
ast::ExprKind::Catch(_) => {
gate_feature_post!(&self, catch_expr, e.span, "`catch` expression is experimental");
}
ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
if pats.len() > 1 {
gate_feature_post!(&self, if_while_or_patterns, e.span,
"multiple patterns in `if let` and `while let` are unstable");
}
}
ast::ExprKind::Block(_, opt_label) => {
if let Some(label) = opt_label {
gate_feature_post!(&self, label_break_value, label.ident.span,
"labels on blocks are unstable");
}
}
ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
}
ast::ExprKind::Async(..) => {
gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
}
_ => {}
}
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");
}
PatKind::Paren(..) => {
gate_feature_post!(&self, pattern_parentheses, pattern.span,
"parentheses in patterns are unstable");
}
_ => {}
}
visit::walk_pat(self, pattern)
}
fn visit_fn(&mut self,
fn_kind: FnKind<'a>,
fn_decl: &'a ast::FnDecl,
span: Span,
_node_id: NodeId) {
match fn_kind {
FnKind::ItemFn(_, header, _, _) => {
// check for const fn and async fn declarations
if header.asyncness.is_async() {
gate_feature_post!(&self, async_await, span, "async fn is unstable");
}
if header.constness.node == ast::Constness::Const {
gate_feature_post!(&self, const_fn, span, "const 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);
}
FnKind::Method(_, sig, _, _) => {
self.check_abi(sig.header.abi, span);
}
_ => {}
}
visit::walk_fn(self, fn_kind, fn_decl, span);
}
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.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(ref sig, _) => {
if sig.header.constness.node == ast::Constness::Const {
gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable");
}
}
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");
}
_ => {}
}
visit::walk_impl_item(self, ii);
}
fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
for segment in &path.segments {
// Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
// For such macros identifiers must have empty context, because this context is
// used during name resolution and produced names must be unhygienic for compatibility.
// On the other hand, we need the actual non-empty context for feature gate checking
// because it's hygienic even for legacy macros. As previously stated, such context
// cannot be kept in identifiers, so it's kept in paths instead and we take it from
// there while keeping location info from the ident span.
let span = segment.ident.span.with_ctxt(path.span.ctxt());
if segment.ident.name == keywords::Crate.name() {
gate_feature_post!(&self, crate_in_paths, span,
"`crate` in paths is experimental");
} else if segment.ident.name == keywords::Extern.name() {
gate_feature_post!(&self, extern_in_paths, span,
"`extern` in paths is experimental");
}
}
visit::walk_path(self, path);
}
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) -> Features {
fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
if let Some(reason) = reason {
err.span_note(span, reason);
}
err.emit();
}
// 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.
let incomplete_features = ["generic_associated_types"];
let mut features = Features::new();
let mut edition_enabled_features = FxHashMap();
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(Symbol::intern(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(Symbol::intern(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("feature") {
continue
}
let list = match attr.meta_item_list() {
Some(list) => list,
None => continue,
};
for mi in list {
let name = if let Some(word) = mi.word() {
word.name()
} else {
continue
};
if incomplete_features.iter().any(|f| *f == name.as_str()) {
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(Symbol::intern(name), *edition);
}
}
}
}
}
}
for attr in krate_attrs {
if !attr.check_name("feature") {
continue
}
let list = match attr.meta_item_list() {
Some(list) => list,
None => {
span_err!(span_handler, attr.span, E0555,
"malformed feature attribute, expected #![feature(...)]");
continue
}
};
for mi in list {
let name = if let Some(word) = mi.word() {
word.name()
} else {
span_err!(span_handler, mi.span, E0556,
"malformed feature, expected just one word");
continue
};
if let Some(edition) = edition_enabled_features.get(&name) {
struct_span_warn!(
span_handler,
mi.span,
E0705,
"the feature `{}` is included in the Rust {} edition",
name,
edition,
).emit();
continue;
}
if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
// Handled in the separate loop above.
continue;
}
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
}
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
}
features.declared_lib_features.push((name, mi.span));
}
}
features
}
pub fn check_crate(krate: &ast::Crate,
sess: &ParseSess,
features: &Features,
plugin_attributes: &[(String, AttributeType)],
unstable: UnstableFeatures) {
maybe_stage_features(&sess.span_diagnostic, krate, unstable);
let ctx = Context {
features,
parse_sess: sess,
plugin_attributes,
};
if !features.raw_identifiers {
for &span in sess.raw_identifier_spans.borrow().iter() {
if !span.allows_unstable() {
gate_feature!(&ctx, raw_identifiers, span,
"raw identifiers are experimental and subject to change"
);
}
}
}
let visitor = &mut PostExpansionVisitor { context: &ctx };
visitor.whole_crate_feature_gates(krate);
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("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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