diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs index 930fdeb975d87..a3c6132d484d2 100644 --- a/compiler/rustc_attr/src/builtin.rs +++ b/compiler/rustc_attr/src/builtin.rs @@ -18,7 +18,7 @@ use rustc_session::parse::feature_err; use rustc_session::{RustcVersion, Session}; use rustc_span::Span; use rustc_span::hygiene::Transparency; -use rustc_span::symbol::{Symbol, sym}; +use rustc_span::symbol::{Symbol, kw, sym}; use crate::fluent_generated; use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause}; @@ -603,7 +603,23 @@ pub fn eval_condition( let cfg = match cfg { ast::NestedMetaItem::MetaItem(meta_item) => meta_item, - ast::NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => return *b, + ast::NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => { + if let Some(features) = features { + // we can't use `try_gate_cfg` as symbols don't differentiate between `r#true` + // and `true`, and we want to keep the former working without feature gate + gate_cfg( + &(( + if *b { kw::True } else { kw::False }, + sym::cfg_boolean_literals, + |features: &Features| features.cfg_boolean_literals, + )), + cfg.span(), + sess, + features, + ); + } + return *b; + } _ => { dcx.emit_err(session_diagnostics::UnsupportedLiteral { span: cfg.span(), diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs index 1ffd35dbf91d1..643a95e6ea1ef 100644 --- a/compiler/rustc_feature/src/unstable.rs +++ b/compiler/rustc_feature/src/unstable.rs @@ -371,6 +371,8 @@ declare_features! ( (unstable, async_for_loop, "1.77.0", Some(118898)), /// Allows using C-variadics. (unstable, c_variadic, "1.34.0", Some(44930)), + /// Allows the use of `#[cfg()]`. + (unstable, cfg_boolean_literals, "CURRENT_RUSTC_VERSION", Some(131204)), /// Allows the use of `#[cfg(overflow_checks)` to check if integer overflow behaviour. (unstable, cfg_overflow_checks, "1.71.0", Some(111466)), /// Provides the relocation model information as cfg entry diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 8f226b26befda..ea8c5f135abf7 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -543,6 +543,7 @@ symbols! { cfg_accessible, cfg_attr, cfg_attr_multi, + cfg_boolean_literals, cfg_doctest, cfg_eval, cfg_fmt_debug, diff --git a/src/doc/unstable-book/src/language-features/cfg-boolean-literals.md b/src/doc/unstable-book/src/language-features/cfg-boolean-literals.md new file mode 100644 index 0000000000000..ad795ff9d9b26 --- /dev/null +++ b/src/doc/unstable-book/src/language-features/cfg-boolean-literals.md @@ -0,0 +1,22 @@ +# `cfg_boolean_literals` + +The tracking issue for this feature is: [#131204] + +[#131204]: https://github.com/rust-lang/rust/issues/131204 + +------------------------ + +The `cfg_boolean_literals` feature makes it possible to use the `true`/`false` +literal as cfg predicate. They always evaluate to true/false respectively. + +## Examples + +```rust +#![feature(cfg_boolean_literals)] + +#[cfg(true)] +const A: i32 = 5; + +#[cfg(all(false))] +const A: i32 = 58 * 89; +``` diff --git a/tests/ui/cfg/raw-true-false.rs b/tests/ui/cfg/raw-true-false.rs new file mode 100644 index 0000000000000..4cb8bb71c924b --- /dev/null +++ b/tests/ui/cfg/raw-true-false.rs @@ -0,0 +1,19 @@ +//@ check-pass +//@ compile-flags: --cfg false --check-cfg=cfg(r#false) + +#![deny(warnings)] + +#[expect(unexpected_cfgs)] +mod a { + #[cfg(r#true)] + pub fn foo() {} +} + +mod b { + #[cfg(r#false)] + pub fn bar() {} +} + +fn main() { + b::bar() +} diff --git a/tests/ui/cfg/true-false.rs b/tests/ui/cfg/true-false.rs index 0bd1cf427fafd..03d96fbafecbe 100644 --- a/tests/ui/cfg/true-false.rs +++ b/tests/ui/cfg/true-false.rs @@ -1,6 +1,7 @@ //@ run-pass #![feature(link_cfg)] +#![feature(cfg_boolean_literals)] #[cfg(true)] fn foo() -> bool { diff --git a/tests/ui/feature-gates/feature-gate-cfg-boolean-literals.rs b/tests/ui/feature-gates/feature-gate-cfg-boolean-literals.rs new file mode 100644 index 0000000000000..6784b4450490b --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-cfg-boolean-literals.rs @@ -0,0 +1,10 @@ +#[cfg(true)] //~ ERROR `cfg(true)` is experimental +fn foo() {} + +#[cfg_attr(true, cfg(false))] //~ ERROR `cfg(true)` is experimental +//~^ ERROR `cfg(false)` is experimental +fn foo() {} + +fn main() { + cfg!(false); //~ ERROR `cfg(false)` is experimental +} diff --git a/tests/ui/feature-gates/feature-gate-cfg-boolean-literals.stderr b/tests/ui/feature-gates/feature-gate-cfg-boolean-literals.stderr new file mode 100644 index 0000000000000..64491464f1d43 --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-cfg-boolean-literals.stderr @@ -0,0 +1,43 @@ +error[E0658]: `cfg(true)` is experimental and subject to change + --> $DIR/feature-gate-cfg-boolean-literals.rs:1:7 + | +LL | #[cfg(true)] + | ^^^^ + | + = note: see issue #131204 for more information + = help: add `#![feature(cfg_boolean_literals)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: `cfg(true)` is experimental and subject to change + --> $DIR/feature-gate-cfg-boolean-literals.rs:4:12 + | +LL | #[cfg_attr(true, cfg(false))] + | ^^^^ + | + = note: see issue #131204 for more information + = help: add `#![feature(cfg_boolean_literals)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: `cfg(false)` is experimental and subject to change + --> $DIR/feature-gate-cfg-boolean-literals.rs:4:22 + | +LL | #[cfg_attr(true, cfg(false))] + | ^^^^^ + | + = note: see issue #131204 for more information + = help: add `#![feature(cfg_boolean_literals)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: `cfg(false)` is experimental and subject to change + --> $DIR/feature-gate-cfg-boolean-literals.rs:9:10 + | +LL | cfg!(false); + | ^^^^^ + | + = note: see issue #131204 for more information + = help: add `#![feature(cfg_boolean_literals)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error: aborting due to 4 previous errors + +For more information about this error, try `rustc --explain E0658`.