// 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 or the MIT license // , 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 abi::Abi; use ast::{self, NodeId, PatKind, RangeEnd}; use attr; use codemap::Spanned; use syntax_pos::Span; use errors::{DiagnosticBuilder, Handler, FatalError}; use visit::{self, FnKind, Visitor}; use parse::ParseSess; use symbol::Symbol; use std::ascii::AsciiExt; use std::env; macro_rules! setter { ($field: ident) => {{ fn f(features: &mut Features) -> &mut bool { &mut features.$field } f as fn(&mut Features) -> &mut bool }} } macro_rules! declare_features { ($((active, $feature: ident, $ver: expr, $issue: 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, fn(&mut Features) -> &mut bool)] = &[ $((stringify!($feature), $ver, $issue, setter!($feature))),+ ]; /// A set of features to be used by later passes. pub struct Features { /// #![feature] attrs for stable language features, for error reporting pub declared_stable_lang_features: Vec<(Symbol, Span)>, /// #![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_stable_lang_features: Vec::new(), declared_lib_features: Vec::new(), $($feature: false),+ } } } }; ($((removed, $feature: ident, $ver: expr, $issue: expr),)+) => { /// Represents unstable features which have since been removed (it was once Active) const REMOVED_FEATURES: &'static [(&'static str, &'static str, Option)] = &[ $((stringify!($feature), $ver, $issue)),+ ]; }; ($((stable_removed, $feature: ident, $ver: expr, $issue: expr),)+) => { /// Represents stable features which have since been removed (it was once Accepted) const STABLE_REMOVED_FEATURES: &'static [(&'static str, &'static str, Option)] = &[ $((stringify!($feature), $ver, $issue)),+ ]; }; ($((accepted, $feature: ident, $ver: expr, $issue: expr),)+) => { /// Those language feature has since been Accepted (it was once Active) const ACCEPTED_FEATURES: &'static [(&'static str, &'static str, Option)] = &[ $((stringify!($feature), $ver, $issue)),+ ]; } } // 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: The featureck.py script parses this information directly out of the source // so take care when modifying it. declare_features! ( (active, asm, "1.0.0", Some(29722)), (active, concat_idents, "1.0.0", Some(29599)), (active, link_args, "1.0.0", Some(29596)), (active, log_syntax, "1.0.0", Some(29598)), (active, non_ascii_idents, "1.0.0", Some(28979)), (active, plugin_registrar, "1.0.0", Some(29597)), (active, thread_local, "1.0.0", Some(29594)), (active, trace_macros, "1.0.0", Some(29598)), // rustc internal, for now: (active, intrinsics, "1.0.0", None), (active, lang_items, "1.0.0", None), (active, link_llvm_intrinsics, "1.0.0", Some(29602)), (active, linkage, "1.0.0", Some(29603)), (active, quote, "1.0.0", Some(29601)), (active, simd, "1.0.0", Some(27731)), // rustc internal (active, rustc_diagnostic_macros, "1.0.0", None), (active, advanced_slice_patterns, "1.0.0", Some(23121)), (active, box_syntax, "1.0.0", Some(27779)), (active, placement_in_syntax, "1.0.0", Some(27779)), (active, unboxed_closures, "1.0.0", Some(29625)), (active, allocator, "1.0.0", Some(27389)), (active, fundamental, "1.0.0", Some(29635)), (active, main, "1.0.0", Some(29634)), (active, needs_allocator, "1.4.0", Some(27389)), (active, on_unimplemented, "1.0.0", Some(29628)), (active, plugin, "1.0.0", Some(29597)), (active, simd_ffi, "1.0.0", Some(27731)), (active, start, "1.0.0", Some(29633)), (active, structural_match, "1.8.0", Some(31434)), (active, panic_runtime, "1.10.0", Some(32837)), (active, needs_panic_runtime, "1.10.0", Some(32837)), // OIBIT specific features (active, optin_builtin_traits, "1.0.0", Some(13231)), // macro reexport needs more discussion and stabilization (active, macro_reexport, "1.0.0", Some(29638)), // Allows use of #[staged_api] // rustc internal (active, staged_api, "1.0.0", None), // Allows using #![no_core] (active, no_core, "1.3.0", Some(29639)), // Allows using `box` in patterns; RFC 469 (active, box_patterns, "1.0.0", Some(29641)), // Allows using the unsafe_destructor_blind_to_params attribute; // RFC 1238 (active, dropck_parametricity, "1.3.0", Some(28498)), // Allows using the may_dangle attribute; RFC 1327 (active, dropck_eyepatch, "1.10.0", Some(34761)), // Allows the use of custom attributes; RFC 572 (active, custom_attribute, "1.0.0", Some(29642)), // Allows the use of #[derive(Anything)] as sugar for // #[derive_Anything]. (active, custom_derive, "1.0.0", Some(29644)), // Allows the use of rustc_* attributes; RFC 572 (active, rustc_attrs, "1.0.0", Some(29642)), // 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), // #23121. Array patterns have some hazards yet. (active, slice_patterns, "1.0.0", Some(23121)), // Allows the definition of associated constants in `trait` or `impl` // blocks. (active, associated_consts, "1.0.0", Some(29646)), // Allows the definition of `const fn` functions. (active, const_fn, "1.2.0", Some(24111)), // Allows indexing into constant arrays. (active, const_indexing, "1.4.0", Some(29947)), // Allows using #[prelude_import] on glob `use` items. // // rustc internal (active, prelude_import, "1.2.0", None), // Allows default type parameters to influence type inference. (active, default_type_parameter_fallback, "1.3.0", Some(27336)), // Allows associated type defaults (active, associated_type_defaults, "1.2.0", Some(29661)), // allow `repr(simd)`, and importing the various simd intrinsics (active, repr_simd, "1.4.0", Some(27731)), // Allows cfg(target_feature = "..."). (active, cfg_target_feature, "1.4.0", Some(29717)), // allow `extern "platform-intrinsic" { ... }` (active, platform_intrinsics, "1.4.0", Some(27731)), // allow `#[unwind]` // rust runtime internal (active, unwind_attributes, "1.4.0", None), // allow the use of `#[naked]` on functions. (active, naked_functions, "1.9.0", Some(32408)), // allow `#[no_debug]` (active, no_debug, "1.5.0", Some(29721)), // allow `#[omit_gdb_pretty_printer_section]` // rustc internal. (active, omit_gdb_pretty_printer_section, "1.5.0", None), // Allows cfg(target_vendor = "..."). (active, cfg_target_vendor, "1.5.0", Some(29718)), // Allow attributes on expressions and non-item statements (active, stmt_expr_attributes, "1.6.0", Some(15701)), // allow using type ascription in expressions (active, type_ascription, "1.6.0", Some(23416)), // Allows cfg(target_thread_local) (active, cfg_target_thread_local, "1.7.0", Some(29594)), // rustc internal (active, abi_vectorcall, "1.7.0", None), // a...b and ...b (active, inclusive_range_syntax, "1.7.0", Some(28237)), // X..Y patterns (active, exclusive_range_pattern, "1.11.0", Some(37854)), // impl specialization (RFC 1210) (active, specialization, "1.7.0", Some(31844)), // Allow Drop types in statics/const functions (RFC 1440) (active, drop_types_in_const, "1.9.0", Some(33156)), // Allows cfg(target_has_atomic = "..."). (active, cfg_target_has_atomic, "1.9.0", Some(32976)), // Allows `impl Trait` in function return types. (active, conservative_impl_trait, "1.12.0", Some(34511)), // Permits numeric fields in struct expressions and patterns. (active, relaxed_adts, "1.12.0", Some(35626)), // The `!` type (active, never_type, "1.13.0", Some(35121)), // Allows all literals in attribute lists and values of key-value pairs. (active, attr_literals, "1.13.0", Some(34981)), // Allows the sysV64 ABI to be specified on all platforms // instead of just the platforms on which it is the C ABI (active, abi_sysv64, "1.13.0", Some(36167)), // Allows untagged unions `union U { ... }` (active, untagged_unions, "1.13.0", Some(32836)), // Used to identify the `compiler_builtins` crate // rustc internal (active, compiler_builtins, "1.13.0", None), // Allows attributes on lifetime/type formal parameters in generics (RFC 1327) (active, generic_param_attrs, "1.11.0", Some(34761)), // Allows #[link(..., cfg(..))] (active, link_cfg, "1.14.0", Some(37406)), (active, use_extern_macros, "1.15.0", Some(35896)), // Allows `break {expr}` with a value inside `loop`s. (active, loop_break_value, "1.14.0", Some(37339)), // Allows #[target_feature(...)] (active, target_feature, "1.15.0", None), // `extern "ptx-*" fn()` (active, abi_ptx, "1.15.0", None), // The `i128` type (active, i128_type, "1.16.0", Some(35118)), // The `unadjusted` ABI. Perma unstable. (active, abi_unadjusted, "1.16.0", None), // Macros 1.1 (active, proc_macro, "1.16.0", Some(38356)), // Allows attributes on struct literal fields. (active, struct_field_attributes, "1.16.0", Some(38814)), // Allows #[link(kind="static-nobundle"...] (active, static_nobundle, "1.16.0", Some(37403)), // `extern "msp430-interrupt" fn()` (active, abi_msp430_interrupt, "1.16.0", Some(38487)), // Coerces non capturing closures to function pointers (active, closure_to_fn_coercion, "1.17.0", Some(39817)), // Used to identify crates that contain sanitizer runtimes // rustc internal (active, sanitizer_runtime, "1.17.0", None), // `extern "x86-interrupt" fn()` (active, abi_x86_interrupt, "1.17.0", Some(40180)), // Allows the `catch {...}` expression (active, catch_expr, "1.17.0", Some(31436)), // Allows `repr(align(u16))` struct attribute (RFC 1358) (active, repr_align, "1.17.0", Some(33626)), // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work. (active, rvalue_static_promotion, "1.15.1", Some(38865)), // Used to preserve symbols (see llvm.used) (active, used, "1.18.0", Some(40289)), // Allows module-level inline assembly by way of global_asm!() (active, global_asm, "1.18.0", Some(35119)), // Allows overlapping impls of marker traits (active, overlapping_marker_traits, "1.18.0", Some(29864)), // Allows use of the :vis macro fragment specifier (active, macro_vis_matcher, "1.18.0", Some(41022)), ); declare_features! ( (removed, import_shadowing, "1.0.0", None), (removed, managed_boxes, "1.0.0", None), // Allows use of unary negate on unsigned integers, e.g. -e for e: u8 (removed, negate_unsigned, "1.0.0", Some(29645)), (removed, reflect, "1.0.0", Some(27749)), // A way to temporarily opt out of opt in copy. This will *never* be accepted. (removed, opt_out_copy, "1.0.0", None), (removed, quad_precision_float, "1.0.0", None), (removed, struct_inherit, "1.0.0", None), (removed, test_removed_feature, "1.0.0", None), (removed, visible_private_types, "1.0.0", None), (removed, unsafe_no_drop_flag, "1.0.0", None), // Allows using items which are missing stability attributes // rustc internal (removed, unmarked_api, "1.0.0", None), (removed, pushpop_unsafe, "1.2.0", None), ); declare_features! ( (stable_removed, no_stack_check, "1.0.0", None), ); declare_features! ( (accepted, associated_types, "1.0.0", None), // allow overloading augmented assignment operations like `a += b` (accepted, augmented_assignments, "1.8.0", Some(28235)), // allow empty structs and enum variants with braces (accepted, braced_empty_structs, "1.8.0", Some(29720)), (accepted, default_type_params, "1.0.0", None), (accepted, globs, "1.0.0", None), (accepted, if_let, "1.0.0", None), // A temporary feature gate used to enable parser extensions needed // to bootstrap fix for #5723. (accepted, issue_5723_bootstrap, "1.0.0", None), (accepted, macro_rules, "1.0.0", None), // Allows using #![no_std] (accepted, no_std, "1.6.0", None), (accepted, slicing_syntax, "1.0.0", None), (accepted, struct_variant, "1.0.0", 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), (accepted, tuple_indexing, "1.0.0", None), // Allows macros to appear in the type position. (accepted, type_macros, "1.13.0", Some(27245)), (accepted, while_let, "1.0.0", None), // Allows `#[deprecated]` attribute (accepted, deprecated, "1.9.0", Some(29935)), // `expr?` (accepted, question_mark, "1.13.0", Some(31436)), // Allows `..` in tuple (struct) patterns (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627)), (accepted, item_like_imports, "1.14.0", Some(35120)), // Allows using `Self` and associated types in struct expressions and patterns. (accepted, more_struct_aliases, "1.16.0", Some(37544)), // elide `'static` lifetimes in `static`s and `const`s (accepted, static_in_const, "1.17.0", Some(35897)), // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions. (accepted, field_init_shorthand, "1.17.0", Some(37340)), // Allows the definition recursive static items. (accepted, static_recursion, "1.17.0", Some(29719)), // pub(restricted) visibilities (RFC 1422) (accepted, pub_restricted, "1.18.0", Some(32409)), // The #![windows_subsystem] attribute (accepted, windows_subsystem, "1.18.0", Some(37499)), ); // 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(PartialEq, Copy, Clone, 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, PartialEq, Eq, 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(attr: &ast::Attribute) -> bool { BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.check_name(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_reexport", 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), ("simd", 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, Ungated), ("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))), ("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. There is no \ corresponding `#[task_local]` mapping to the task \ model", 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))), ("allocator", Whitelisted, Gated(Stability::Unstable, "allocator", "the `#[allocator]` attribute is an experimental feature", cfg_fn!(allocator))), ("needs_allocator", Normal, Gated(Stability::Unstable, "needs_allocator", "the `#[needs_allocator]` \ attribute is an experimental \ feature", cfg_fn!(needs_allocator))), ("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_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_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_metadata_dirty", Whitelisted, Gated(Stability::Unstable, "rustc_attrs", "the `#[rustc_metadata_dirty]` attribute \ is just used for rustc unit tests \ and will never be stable", cfg_fn!(rustc_attrs))), ("rustc_metadata_clean", Whitelisted, Gated(Stability::Unstable, "rustc_attrs", "the `#[rustc_metadata_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_translated", 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_move_fragments", Normal, Gated(Stability::Unstable, "rustc_attrs", "the `#[rustc_move_fragments]` attribute \ is just used for rustc unit tests \ and 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))), ("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))), ("allow_internal_unstable", Normal, Gated(Stability::Unstable, "allow_internal_unstable", EXPLAIN_ALLOW_INTERNAL_UNSTABLE, cfg_fn!(allow_internal_unstable))), ("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 trans, 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, Gated( Stability::Unstable, "target_feature", "the `#[target_feature]` attribute is an experimental feature", cfg_fn!(target_feature))), ("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 is an experimental feature", 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, Gated(Stability::Unstable, "proc_macro", "attribute proc macros are currently unstable", cfg_fn!(proc_macro))), ("proc_macro", Normal, Gated(Stability::Unstable, "proc_macro", "function-like proc macros are currently unstable", cfg_fn!(proc_macro))), ("rustc_derive_registrar", Normal, Gated(Stability::Unstable, "rustc_derive_registrar", "used internally by rustc", cfg_fn!(rustc_attrs))), // 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_feature", "cfg_target_feature", cfg_fn!(cfg_target_feature)), ("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, Eq, PartialEq)] pub struct GatedCfg { span: Span, index: usize, } impl GatedCfg { pub fn gate(cfg: &ast::MetaItem) -> Option { 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, $explain: expr) => {{ let (cx, has_feature, span, name, explain) = ($cx, $has_feature, $span, $name, $explain); let has_feature: bool = has_feature(&$cx.features); debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature); if !has_feature && !span.allows_unstable() { emit_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain); } }} } macro_rules! gate_feature { ($cx: expr, $feature: ident, $span: expr, $explain: expr) => { gate_feature_fn!($cx, |x:&Features| x.$feature, $span, stringify!($feature), $explain) } } impl<'a> Context<'a> { fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) { debug!("check_attribute(attr = {:?})", attr); let name = unwrap_or!(attr.name(), return).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); } 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 { gate_feature!(self, custom_attribute, attr.span, &format!("The attribute `{}` is currently \ unknown to the compiler and \ may have meaning \ added to it in the future", attr.path)); } } } } 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); } pub fn find_lang_feature_accepted_version(feature: &str) -> Option<&'static str> { ACCEPTED_FEATURES.iter().find(|t| t.0 == feature).map(|t| t.1) } fn find_lang_feature_issue(feature: &str) -> Option { 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) } 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> { let diag = &sess.span_diagnostic; let issue = match issue { GateIssue::Language => find_lang_feature_issue(feature), GateIssue::Library(lib) => lib, }; let mut err = if let Some(n) = issue { diag.struct_span_err(span, &format!("{} (see issue #{})", explain, n)) } else { diag.struct_span_err(span, explain) }; // #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)); } 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 non-item statements and 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_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_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_PLACEMENT_IN: &'static str = "placement-in expression syntax is experimental and subject to change."; pub const CLOSURE_TO_FN_COERCION: &'static str = "non-capturing closure to fn coercion is experimental"; 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) } }} } 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::RustCall => { gate_feature_post!(&self, unboxed_closures, span, "rust-call ABI is subject to change"); }, Abi::SysV64 => { gate_feature_post!(&self, abi_sysv64, span, "sysv64 ABI is experimental and 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"); }, // Stable Abi::Cdecl | Abi::Stdcall | Abi::Fastcall | Abi::Aapcs | Abi::Win64 | 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, } }), } } fn starts_with_digit(s: &str) -> bool { s.as_bytes().first().cloned().map_or(false, |b| b >= b'0' && b <= b'9') } 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 self.context.features.proc_macro && attr::is_known(attr) { return } let meta = panictry!(attr.parse_meta(self.context.parse_sess)); if 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"); } } fn visit_name(&mut self, sp: Span, name: ast::Name) { if !name.as_str().is_ascii() { gate_feature_post!(&self, non_ascii_idents, sp, "non-ascii idents are not fully supported."); } } fn visit_item(&mut self, i: &'a ast::Item) { match i.node { ast::ItemKind::ExternCrate(_) => { if attr::contains_name(&i.attrs[..], "macro_reexport") { gate_feature_post!(&self, macro_reexport, i.span, "macros reexports are experimental \ and possibly buggy"); } } ast::ItemKind::ForeignMod(ref foreign_module) => { if attr::contains_name(&i.attrs[..], "link_args") { gate_feature_post!(&self, link_args, i.span, "the `link_args` attribute is not portable \ across platforms, it is recommended to \ use `#[link(name = \"foo\")]` instead") } 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 attr::contains_name(&i.attrs[..], "simd") { gate_feature_post!(&self, simd, i.span, "SIMD types are experimental and possibly buggy"); self.context.parse_sess.span_diagnostic.span_warn(i.span, "the `#[simd]` attribute \ is deprecated, use \ `#[repr(simd)]` instead"); } for attr in &i.attrs { if attr.path == "repr" { for item in attr.meta_item_list().unwrap_or_else(Vec::new) { if item.check_name("simd") { gate_feature_post!(&self, repr_simd, i.span, "SIMD types are experimental \ and possibly buggy"); } if item.check_name("align") { gate_feature_post!(&self, repr_align, i.span, "the struct `#[repr(align(u16))]` attribute \ is experimental"); } } } } } ast::ItemKind::Union(..) => { gate_feature_post!(&self, untagged_unions, i.span, "unions are unstable and possibly buggy"); } ast::ItemKind::DefaultImpl(..) => { gate_feature_post!(&self, optin_builtin_traits, i.span, "default trait implementations are experimental \ and possibly buggy"); } ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => { if let ast::ImplPolarity::Negative = polarity { 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"); } } _ => {} } visit::walk_item(self, i); } fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) { let links_to_llvm = match attr::first_attr_value_str_by_name(&i.attrs, "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"); } 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::ImplTrait(..) => { gate_feature_post!(&self, conservative_impl_trait, ty.span, "`impl Trait` is experimental"); } 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 { return } 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::Range(_, _, ast::RangeLimits::Closed) => { gate_feature_post!(&self, inclusive_range_syntax, e.span, "inclusive range syntax is experimental"); } ast::ExprKind::InPlace(..) => { gate_feature_post!(&self, placement_in_syntax, e.span, EXPLAIN_PLACEMENT_IN); } ast::ExprKind::Struct(_, ref fields, _) => { for field in fields { if starts_with_digit(&field.ident.node.name.as_str()) { gate_feature_post!(&self, relaxed_adts, field.span, "numeric fields in struct expressions are unstable"); } } } ast::ExprKind::Break(_, Some(_)) => { gate_feature_post!(&self, loop_break_value, e.span, "`break` with a value is experimental"); } ast::ExprKind::Lit(ref lit) => { if let ast::LitKind::Int(_, ref ty) = lit.node { match *ty { ast::LitIntType::Signed(ast::IntTy::I128) | ast::LitIntType::Unsigned(ast::UintTy::U128) => { gate_feature_post!(&self, i128_type, e.span, "128-bit integers are not stable"); } _ => {} } } } ast::ExprKind::Catch(_) => { gate_feature_post!(&self, catch_expr, e.span, "`catch` expression is experimental"); } _ => {} } visit::walk_expr(self, e); } fn visit_pat(&mut self, pattern: &'a ast::Pat) { match pattern.node { PatKind::Slice(_, Some(_), ref last) if !last.is_empty() => { gate_feature_post!(&self, advanced_slice_patterns, pattern.span, "multiple-element slice matches anywhere \ but at the end of a slice (e.g. \ `[0, ..xs, 0]`) are experimental") } PatKind::Slice(..) => { gate_feature_post!(&self, slice_patterns, pattern.span, "slice pattern syntax is experimental"); } PatKind::Box(..) => { gate_feature_post!(&self, box_patterns, pattern.span, "box pattern syntax is experimental"); } PatKind::Struct(_, ref fields, _) => { for field in fields { if starts_with_digit(&field.node.ident.name.as_str()) { gate_feature_post!(&self, relaxed_adts, field.span, "numeric fields in struct patterns are unstable"); } } } PatKind::Range(_, _, 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) { // check for const fn declarations if let FnKind::ItemFn(_, _, _, Spanned { node: ast::Constness::Const, .. }, _, _, _) = fn_kind { 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. match fn_kind { FnKind::ItemFn(_, _, _, _, abi, _, _) | FnKind::Method(_, &ast::MethodSig { abi, .. }, _, _) => { self.check_abi(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::Const(..) => { gate_feature_post!(&self, associated_consts, ti.span, "associated constants are experimental") } ast::TraitItemKind::Method(ref sig, ref block) => { if block.is_none() { self.check_abi(sig.abi, ti.span); } if sig.constness.node == ast::Constness::Const { gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable"); } } ast::TraitItemKind::Type(_, Some(_)) => { gate_feature_post!(&self, associated_type_defaults, ti.span, "associated type defaults 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::Const(..) => { gate_feature_post!(&self, associated_consts, ii.span, "associated constants are experimental") } ast::ImplItemKind::Method(ref sig, _) => { if sig.constness.node == ast::Constness::Const { gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable"); } } _ => {} } visit::walk_impl_item(self, ii); } fn visit_generics(&mut self, g: &'a ast::Generics) { for t in &g.ty_params { if !t.attrs.is_empty() { gate_feature_post!(&self, generic_param_attrs, t.attrs[0].span, "attributes on type parameter bindings are experimental"); } } visit::walk_generics(self, g) } fn visit_lifetime_def(&mut self, lifetime_def: &'a ast::LifetimeDef) { if !lifetime_def.attrs.is_empty() { gate_feature_post!(&self, generic_param_attrs, lifetime_def.attrs[0].span, "attributes on lifetime bindings are experimental"); } visit::walk_lifetime_def(self, lifetime_def) } } pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute]) -> Features { let mut features = Features::new(); let mut feature_checker = MutexFeatureChecker::default(); for attr in krate_attrs { if !attr.check_name("feature") { continue } match attr.meta_item_list() { None => { span_err!(span_handler, attr.span, E0555, "malformed feature attribute, expected #![feature(...)]"); } Some(list) => { 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(&(_, _, _, setter)) = ACTIVE_FEATURES.iter() .find(|& &(n, _, _, _)| name == n) { *(setter(&mut features)) = true; feature_checker.collect(&features, mi.span); } else if let Some(&(_, _, _)) = REMOVED_FEATURES.iter() .find(|& &(n, _, _)| name == n) .or_else(|| STABLE_REMOVED_FEATURES.iter() .find(|& &(n, _, _)| name == n)) { span_err!(span_handler, mi.span, E0557, "feature has been removed"); } else if let Some(&(_, _, _)) = ACCEPTED_FEATURES.iter() .find(|& &(n, _, _)| name == n) { features.declared_stable_lang_features.push((name, mi.span)); } else { features.declared_lib_features.push((name, mi.span)); } } } } } feature_checker.check(span_handler); features } // A collector for mutually-exclusive features and their flag spans #[derive(Default)] struct MutexFeatureChecker { proc_macro: Option, custom_attribute: Option, } impl MutexFeatureChecker { // If this method turns out to be a hotspot due to branching, // the branching can be eliminated by modifying `setter!()` to set these spans // only for the features that need to be checked for mutual exclusion. fn collect(&mut self, features: &Features, span: Span) { if features.proc_macro { // If self.proc_macro is None, set to Some(span) self.proc_macro = self.proc_macro.or(Some(span)); } if features.custom_attribute { self.custom_attribute = self.custom_attribute.or(Some(span)); } } fn check(self, handler: &Handler) { if let (Some(pm_span), Some(ca_span)) = (self.proc_macro, self.custom_attribute) { handler.struct_span_err(pm_span, "Cannot use `#![feature(proc_macro)]` and \ `#![feature(custom_attribute)] at the same time") .span_note(ca_span, "`#![feature(custom_attribute)]` declared here") .emit(); panic!(FatalError); } } } 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: features, parse_sess: sess, plugin_attributes: plugin_attributes, }; visit::walk_crate(&mut PostExpansionVisitor { context: &ctx }, krate); } #[derive(Clone, Copy, PartialEq, Eq, 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); } } } }