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//! Built-in attributes and `cfg` flag gating.
use AttributeType::*;
use AttributeGate::*;
use super::check::{emit_feature_err, GateIssue};
use super::check::{Stability, EXPLAIN_ALLOW_INTERNAL_UNSAFE, EXPLAIN_ALLOW_INTERNAL_UNSTABLE};
use super::active::Features;
use crate::ast;
use crate::attr::AttributeTemplate;
use crate::symbol::{Symbol, sym};
use crate::parse::ParseSess;
use syntax_pos::Span;
use rustc_data_structures::fx::FxHashMap;
use lazy_static::lazy_static;
type GateFn = fn(&Features) -> bool;
macro_rules! cfg_fn {
($field: ident) => {
(|features| { features.$field }) as GateFn
}
}
/// `cfg(...)`'s that are feature gated.
const GATED_CFGS: &[(Symbol, Symbol, GateFn)] = &[
// (name in cfg, feature, function to check if the feature is enabled)
(sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
(sym::target_has_atomic, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
(sym::rustdoc, sym::doc_cfg, cfg_fn!(doc_cfg)),
(sym::doctest, sym::cfg_doctest, cfg_fn!(cfg_doctest)),
];
#[derive(Debug)]
pub struct GatedCfg {
span: Span,
index: usize,
}
impl GatedCfg {
pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
GATED_CFGS.iter()
.position(|info| cfg.check_name(info.0))
.map(|idx| {
GatedCfg {
span: cfg.span,
index: idx
}
})
}
pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
let (cfg, feature, has_feature) = GATED_CFGS[self.index];
if !has_feature(features) && !self.span.allows_unstable(feature) {
let explain = format!("`cfg({})` is experimental and subject to change", cfg);
emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
}
}
}
// 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,
}
#[derive(Clone, Copy)]
pub enum AttributeGate {
/// Is gated by a given feature gate, reason
/// and function to check if enabled
Gated(Stability, Symbol, &'static str, fn(&Features) -> bool),
/// Ungated attribute, can be used on all release channels
Ungated,
}
// fn() is not Debug
impl std::fmt::Debug for AttributeGate {
fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match *self {
Self::Gated(ref stab, name, expl, _) =>
write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
Self::Ungated => write!(fmt, "Ungated")
}
}
}
impl AttributeGate {
fn is_deprecated(&self) -> bool {
match *self {
Self::Gated(Stability::Deprecated(_, _), ..) => true,
_ => false,
}
}
}
/// A convenience macro for constructing attribute templates.
/// E.g., `template!(Word, List: "description")` means that the attribute
/// supports forms `#[attr]` and `#[attr(description)]`.
macro_rules! template {
(Word) => { template!(@ true, None, None) };
(List: $descr: expr) => { template!(@ false, Some($descr), None) };
(NameValueStr: $descr: expr) => { template!(@ false, None, Some($descr)) };
(Word, List: $descr: expr) => { template!(@ true, Some($descr), None) };
(Word, NameValueStr: $descr: expr) => { template!(@ true, None, Some($descr)) };
(List: $descr1: expr, NameValueStr: $descr2: expr) => {
template!(@ false, Some($descr1), Some($descr2))
};
(Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
template!(@ true, Some($descr1), Some($descr2))
};
(@ $word: expr, $list: expr, $name_value_str: expr) => { AttributeTemplate {
word: $word, list: $list, name_value_str: $name_value_str
} };
}
macro_rules! ungated {
($attr:ident, $typ:expr, $tpl:expr $(,)?) => {
(sym::$attr, $typ, $tpl, Ungated)
};
}
macro_rules! gated {
($attr:ident, $typ:expr, $tpl:expr, $gate:ident, $msg:expr $(,)?) => {
(sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$gate, $msg, cfg_fn!($gate)))
};
($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
(sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$attr, $msg, cfg_fn!($attr)))
};
}
macro_rules! rustc_attr {
(TEST, $attr:ident, $typ:expr, $tpl:expr $(,)?) => {
rustc_attr!(
$attr, $typ, $tpl,
concat!("the `#[", stringify!($attr), "]` attribute is just used for rustc unit tests \
and will never be stable",
),
)
};
($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
(sym::$attr, $typ, $tpl,
Gated(Stability::Unstable, sym::rustc_attrs, $msg, cfg_fn!(rustc_attrs)))
};
}
macro_rules! experimental {
($attr:ident) => {
concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
}
}
const IMPL_DETAIL: &str = "internal implementation detail";
const INTERAL_UNSTABLE: &str = "this is an internal attribute that will never be stable";
pub type BuiltinAttribute = (Symbol, AttributeType, AttributeTemplate, AttributeGate);
/// Attributes that have a special meaning to rustc or rustdoc.
pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
// ==========================================================================
// Stable attributes:
// ==========================================================================
// Condtional compilation:
ungated!(cfg, Normal, template!(List: "predicate")),
ungated!(cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ...")),
// Testing:
ungated!(ignore, Normal, template!(Word, NameValueStr: "reason")),
ungated!(
should_panic, Normal,
template!(Word, List: r#"expected = "reason"#, NameValueStr: "reason"),
),
// FIXME(Centril): This can be used on stable but shouldn't.
ungated!(reexport_test_harness_main, Normal, template!(NameValueStr: "name")),
// Macros:
ungated!(derive, Normal, template!(List: "Trait1, Trait2, ...")),
ungated!(automatically_derived, Normal, template!(Word)),
// FIXME(#14407)
ungated!(macro_use, Normal, template!(Word, List: "name1, name2, ...")),
ungated!(macro_escape, Normal, template!(Word)), // Deprecated synonym for `macro_use`.
ungated!(macro_export, Normal, template!(Word, List: "local_inner_macros")),
ungated!(proc_macro, Normal, template!(Word)),
ungated!(
proc_macro_derive, Normal,
template!(List: "TraitName, /*opt*/ attributes(name1, name2, ...)"),
),
ungated!(proc_macro_attribute, Normal, template!(Word)),
// Lints:
ungated!(warn, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
ungated!(allow, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
ungated!(forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
ungated!(deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
ungated!(must_use, Whitelisted, template!(Word, NameValueStr: "reason")),
// FIXME(#14407)
ungated!(
deprecated, Normal,
template!(
Word,
List: r#"/*opt*/ since = "version", /*opt*/ note = "reason""#,
NameValueStr: "reason"
),
),
// Crate properties:
ungated!(crate_name, CrateLevel, template!(NameValueStr: "name")),
ungated!(crate_type, CrateLevel, template!(NameValueStr: "bin|lib|...")),
ungated!(crate_id, CrateLevel, template!(NameValueStr: "ignored")),
// ABI, linking, symbols, and FFI
ungated!(
link, Whitelisted,
template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...", /*opt*/ cfg = "...""#),
),
ungated!(link_name, Whitelisted, template!(NameValueStr: "name")),
ungated!(no_link, Normal, template!(Word)),
ungated!(repr, Normal, template!(List: "C, packed, ...")),
ungated!(export_name, Whitelisted, template!(NameValueStr: "name")),
ungated!(link_section, Whitelisted, template!(NameValueStr: "name")),
ungated!(no_mangle, Whitelisted, template!(Word)),
ungated!(used, Whitelisted, template!(Word)),
// Limits:
ungated!(recursion_limit, CrateLevel, template!(NameValueStr: "N")),
ungated!(type_length_limit, CrateLevel, template!(NameValueStr: "N")),
// Entry point:
ungated!(main, Normal, template!(Word)),
ungated!(start, Normal, template!(Word)),
ungated!(no_start, CrateLevel, template!(Word)),
ungated!(no_main, CrateLevel, template!(Word)),
// Modules, prelude, and resolution:
ungated!(path, Normal, template!(NameValueStr: "file")),
ungated!(no_std, CrateLevel, template!(Word)),
ungated!(no_implicit_prelude, Normal, template!(Word)),
// Runtime
ungated!(windows_subsystem, Whitelisted, template!(NameValueStr: "windows|console")),
ungated!(panic_handler, Normal, template!(Word)), // RFC 2070
// Code generation:
ungated!(inline, Whitelisted, template!(Word, List: "always|never")),
ungated!(cold, Whitelisted, template!(Word)),
ungated!(no_builtins, Whitelisted, template!(Word)),
ungated!(target_feature, Whitelisted, template!(List: r#"enable = "name""#)),
// FIXME: #14408 whitelist docs since rustdoc looks at them
ungated!(doc, Whitelisted, template!(List: "hidden|inline|...", NameValueStr: "string")),
// ==========================================================================
// Unstable attributes:
// ==========================================================================
// Linking:
gated!(naked, Whitelisted, template!(Word), naked_functions, experimental!(naked)),
gated!(
link_args, Normal, template!(NameValueStr: "args"),
"the `link_args` attribute is experimental and not portable across platforms, \
it is recommended to use `#[link(name = \"foo\")] instead",
),
// Plugins:
ungated!(plugin_registrar, Normal, template!(Word)),
gated!(
plugin, CrateLevel, template!(List: "name|name(args)"),
"compiler plugins are experimental and possibly buggy",
),
// Testing:
gated!(allow_fail, Normal, template!(Word), experimental!(allow_fail)),
gated!(
test_runner, CrateLevel, template!(List: "path"), custom_test_frameworks,
"custom test frameworks are an unstable feature",
),
// RFC #2008
gated!(non_exhaustive, Whitelisted, template!(Word), experimental!(non_exhaustive)),
// RFC #1268
gated!(marker, Normal, template!(Word), marker_trait_attr, experimental!(marker)),
gated!(
thread_local, Whitelisted, template!(Word),
"`#[thread_local]` is an experimental feature, and does not currently handle destructors",
),
gated!(no_core, CrateLevel, template!(Word), experimental!(no_core)),
// RFC 2412
gated!(
optimize, Whitelisted, template!(List: "size|speed"), optimize_attribute,
experimental!(optimize),
),
gated!(ffi_returns_twice, Whitelisted, template!(Word), experimental!(ffi_returns_twice)),
// ==========================================================================
// Internal attributes: Stability, deprecation, and unsafe:
// ==========================================================================
ungated!(feature, CrateLevel, template!(List: "name1, name1, ...")),
// FIXME(#14407) -- only looked at on-demand so we can't
// guarantee they'll have already been checked.
ungated!(
rustc_deprecated, Whitelisted,
template!(List: r#"since = "version", reason = "...""#)
),
// FIXME(#14407)
ungated!(stable, Whitelisted, template!(List: r#"feature = "name", since = "version""#)),
// FIXME(#14407)
ungated!(
unstable, Whitelisted,
template!(List: r#"feature = "name", reason = "...", issue = "N""#),
),
gated!(
rustc_const_unstable, Normal, template!(List: r#"feature = "name""#),
"the `#[rustc_const_unstable]` attribute is an internal feature",
),
gated!(
allow_internal_unstable, Normal, template!(Word, List: "feat1, feat2, ..."),
EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
),
gated!(allow_internal_unsafe, Normal, template!(Word), EXPLAIN_ALLOW_INTERNAL_UNSAFE),
// ==========================================================================
// Internal attributes: Type system related:
// ==========================================================================
gated!(fundamental, Whitelisted, template!(Word), experimental!(fundamental)),
gated!(
// RFC #1445.
structural_match, Whitelisted, template!(Word),
"the semantics of constant patterns is not yet settled",
),
gated!(
may_dangle, Normal, template!(Word), dropck_eyepatch,
"`may_dangle` has unstable semantics and may be removed in the future",
),
// ==========================================================================
// Internal attributes: Runtime related:
// ==========================================================================
rustc_attr!(rustc_allocator, Whitelisted, template!(Word), IMPL_DETAIL),
rustc_attr!(rustc_allocator_nounwind, Whitelisted, template!(Word), IMPL_DETAIL),
gated!(alloc_error_handler, Normal, template!(Word), experimental!(alloc_error_handler)),
gated!(
default_lib_allocator, Whitelisted, template!(Word), allocator_internals,
experimental!(default_lib_allocator),
),
gated!(
needs_allocator, Normal, template!(Word), allocator_internals,
experimental!(needs_allocator),
),
gated!(panic_runtime, Whitelisted, template!(Word), experimental!(panic_runtime)),
gated!(needs_panic_runtime, Whitelisted, template!(Word), experimental!(needs_panic_runtime)),
gated!(
unwind, Whitelisted, template!(List: "allowed|aborts"), unwind_attributes,
experimental!(unwind),
),
gated!(
compiler_builtins, Whitelisted, template!(Word),
"the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
which contains compiler-rt intrinsics and will never be stable",
),
gated!(
sanitizer_runtime, Whitelisted, template!(Word),
"the `#[sanitizer_runtime]` attribute is used to identify crates that contain the runtime \
of a sanitizer and will never be stable",
),
gated!(
profiler_runtime, Whitelisted, template!(Word),
"the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
which contains the profiler runtime and will never be stable",
),
// ==========================================================================
// Internal attributes, Linkage:
// ==========================================================================
gated!(
linkage, Whitelisted, template!(NameValueStr: "external|internal|..."),
"the `linkage` attribute is experimental and not portable across platforms",
),
rustc_attr!(rustc_std_internal_symbol, Whitelisted, template!(Word), INTERAL_UNSTABLE),
// ==========================================================================
// Internal attributes, Macro related:
// ==========================================================================
rustc_attr!(rustc_builtin_macro, Whitelisted, template!(Word), IMPL_DETAIL),
rustc_attr!(rustc_proc_macro_decls, Normal, template!(Word), INTERAL_UNSTABLE),
rustc_attr!(
rustc_macro_transparency, Whitelisted,
template!(NameValueStr: "transparent|semitransparent|opaque"),
"used internally for testing macro hygiene",
),
// ==========================================================================
// Internal attributes, Diagnostics related:
// ==========================================================================
gated!(
rustc_on_unimplemented, Whitelisted,
template!(
List: r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
NameValueStr: "message"
),
on_unimplemented,
experimental!(rustc_on_unimplemented),
),
// Whitelists "identity-like" conversion methods to suggest on type mismatch.
rustc_attr!(rustc_conversion_suggestion, Whitelisted, template!(Word), INTERAL_UNSTABLE),
// ==========================================================================
// Internal attributes, Const related:
// ==========================================================================
rustc_attr!(rustc_promotable, Whitelisted, template!(Word), IMPL_DETAIL),
rustc_attr!(rustc_allow_const_fn_ptr, Whitelisted, template!(Word), IMPL_DETAIL),
rustc_attr!(rustc_args_required_const, Whitelisted, template!(List: "N"), INTERAL_UNSTABLE),
// ==========================================================================
// Internal attributes, Layout related:
// ==========================================================================
rustc_attr!(
rustc_layout_scalar_valid_range_start, Whitelisted, template!(List: "value"),
"the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
niche optimizations in libcore and will never be stable",
),
rustc_attr!(
rustc_layout_scalar_valid_range_end, Whitelisted, template!(List: "value"),
"the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
niche optimizations in libcore and will never be stable",
),
rustc_attr!(
rustc_nonnull_optimization_guaranteed, Whitelisted, template!(Word),
"the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
niche optimizations in libcore and will never be stable",
),
// ==========================================================================
// Internal attributes, Misc:
// ==========================================================================
gated!(
lang, Normal, template!(NameValueStr: "name"), lang_items,
"language items are subject to change",
),
(
sym::rustc_diagnostic_item,
Normal,
template!(NameValueStr: "name"),
Gated(
Stability::Unstable,
sym::rustc_attrs,
"diagnostic items compiler internal support for linting",
cfg_fn!(rustc_attrs),
),
),
(
sym::no_debug, Whitelisted, template!(Word),
Gated(
Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
sym::no_debug,
"the `#[no_debug]` attribute was an experimental feature that has been \
deprecated due to lack of demand",
cfg_fn!(no_debug)
)
),
gated!(
// Used in resolve:
prelude_import, Whitelisted, template!(Word),
"`#[prelude_import]` is for use by rustc only",
),
gated!(
rustc_paren_sugar, Normal, template!(Word), unboxed_closures,
"unboxed_closures are still evolving",
),
rustc_attr!(
rustc_inherit_overflow_checks, Whitelisted, template!(Word),
"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",
),
rustc_attr!(
rustc_test_marker, Normal, template!(Word),
"the `#[rustc_test_marker]` attribute is used internally to track tests",
),
// ==========================================================================
// Internal attributes, Testing:
// ==========================================================================
rustc_attr!(TEST, rustc_outlives, Normal, template!(Word)),
rustc_attr!(TEST, rustc_variance, Normal, template!(Word)),
rustc_attr!(TEST, rustc_layout, Normal, template!(List: "field1, field2, ...")),
rustc_attr!(TEST, rustc_regions, Normal, template!(Word)),
rustc_attr!(TEST, rustc_error, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_dump_user_substs, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_if_this_changed, Whitelisted, template!(Word, List: "DepNode")),
rustc_attr!(TEST, rustc_then_this_would_need, Whitelisted, template!(List: "DepNode")),
rustc_attr!(
TEST, rustc_dirty, Whitelisted,
template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
),
rustc_attr!(
TEST, rustc_clean, Whitelisted,
template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
),
rustc_attr!(
TEST, rustc_partition_reused, Whitelisted,
template!(List: r#"cfg = "...", module = "...""#),
),
rustc_attr!(
TEST, rustc_partition_codegened, Whitelisted,
template!(List: r#"cfg = "...", module = "...""#),
),
rustc_attr!(
TEST, rustc_expected_cgu_reuse, Whitelisted,
template!(List: r#"cfg = "...", module = "...", kind = "...""#),
),
rustc_attr!(TEST, rustc_synthetic, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_symbol_name, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_def_path, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_mir, Whitelisted, template!(List: "arg1, arg2, ...")),
rustc_attr!(TEST, rustc_dump_program_clauses, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_dump_env_program_clauses, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_object_lifetime_default, Whitelisted, template!(Word)),
rustc_attr!(TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/)),
gated!(
omit_gdb_pretty_printer_section, Whitelisted, template!(Word),
"the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
),
];
pub fn deprecated_attributes() -> Vec<&'static BuiltinAttribute> {
BUILTIN_ATTRIBUTES.iter().filter(|(.., gate)| gate.is_deprecated()).collect()
}
pub fn is_builtin_attr_name(name: ast::Name) -> bool {
BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
}
pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).is_some()
}
lazy_static! {
pub static ref BUILTIN_ATTRIBUTE_MAP: FxHashMap<Symbol, &'static BuiltinAttribute> = {
let mut map = FxHashMap::default();
for attr in BUILTIN_ATTRIBUTES.iter() {
if map.insert(attr.0, attr).is_some() {
panic!("duplicate builtin attribute `{}`", attr.0);
}
}
map
};
}
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