explore a different approach for cfg handling in core/lib.rs

Author: RalfJung

library/core/src/lib.rs

@@ -299,10 +299,7 @@ extern crate core as realcore;
 pub use realcore::*;
 
 // Otherwise, we build the crate as usual. Everything that follows should have
-// `#[cfg(not(all(feature = "miri-test", not(any(test, doctest)))))]`. To avoid having to repeat the
-// same `cfg` so many times, we `include!("lib_.rs")` with the main crate contents, and `cfg` the
-// `include!`. However, some macro-related things can't be behind the `include!` so we have to
-// repeat the `cfg` for them.
+// `#[cfg(not(all(feature = "miri-test", not(any(test, doctest)))))]`.
 
 // allow using `core::` in intra-doc links
 #[cfg(not(all(feature = "miri-test", not(any(test, doctest)))))]
@@ -343,5 +340,168 @@ pub mod prelude;
 #[allow(rustdoc::bare_urls)]
 mod core_arch;
 
+// To avoid repeating the `cfg` over and over, we use an identity macro and `cfg` the macro
+// invocation. We can't use this for *everything* as having macro-related imports inside a macro
+// does not work.
 #[cfg(not(all(feature = "miri-test", not(any(test, doctest)))))]
-include!("lib_.rs");
+macro_rules! identity { ($($x:tt)*) => { $($x)* } }
+#[cfg(not(all(feature = "miri-test", not(any(test, doctest)))))]
+identity! {
+    // We don't export this through #[macro_export] for now, to avoid breakage.
+    // See https://github.com/rust-lang/rust/issues/82913
+    #[cfg(not(test))]
+    #[unstable(feature = "assert_matches", issue = "82775")]
+    /// Unstable module containing the unstable `assert_matches` macro.
+    pub mod assert_matches {
+        #[unstable(feature = "assert_matches", issue = "82775")]
+        pub use crate::macros::{assert_matches, debug_assert_matches};
+    }
+
+    #[unstable(feature = "cfg_match", issue = "115585")]
+    #[cfg(not(all(feature = "miri-test", not(any(test, doctest)))))]
+    pub use crate::macros::cfg_match;
+
+    #[macro_use]
+    mod internal_macros;
+
+    #[path = "num/shells/int_macros.rs"]
+    #[macro_use]
+    mod int_macros;
+
+    #[rustc_diagnostic_item = "i128_legacy_mod"]
+    #[path = "num/shells/i128.rs"]
+    pub mod i128;
+    #[rustc_diagnostic_item = "i16_legacy_mod"]
+    #[path = "num/shells/i16.rs"]
+    pub mod i16;
+    #[rustc_diagnostic_item = "i32_legacy_mod"]
+    #[path = "num/shells/i32.rs"]
+    pub mod i32;
+    #[rustc_diagnostic_item = "i64_legacy_mod"]
+    #[path = "num/shells/i64.rs"]
+    pub mod i64;
+    #[rustc_diagnostic_item = "i8_legacy_mod"]
+    #[path = "num/shells/i8.rs"]
+    pub mod i8;
+    #[rustc_diagnostic_item = "isize_legacy_mod"]
+    #[path = "num/shells/isize.rs"]
+    pub mod isize;
+
+    #[rustc_diagnostic_item = "u128_legacy_mod"]
+    #[path = "num/shells/u128.rs"]
+    pub mod u128;
+    #[rustc_diagnostic_item = "u16_legacy_mod"]
+    #[path = "num/shells/u16.rs"]
+    pub mod u16;
+    #[rustc_diagnostic_item = "u32_legacy_mod"]
+    #[path = "num/shells/u32.rs"]
+    pub mod u32;
+    #[rustc_diagnostic_item = "u64_legacy_mod"]
+    #[path = "num/shells/u64.rs"]
+    pub mod u64;
+    #[rustc_diagnostic_item = "u8_legacy_mod"]
+    #[path = "num/shells/u8.rs"]
+    pub mod u8;
+    #[rustc_diagnostic_item = "usize_legacy_mod"]
+    #[path = "num/shells/usize.rs"]
+    pub mod usize;
+
+    #[path = "num/f32.rs"]
+    pub mod f32;
+    #[path = "num/f64.rs"]
+    pub mod f64;
+
+    #[macro_use]
+    pub mod num;
+
+    /* Core modules for ownership management */
+
+    pub mod hint;
+    pub mod intrinsics;
+    pub mod mem;
+    pub mod ptr;
+    mod ub_checks;
+
+    /* Core language traits */
+
+    pub mod borrow;
+    pub mod clone;
+    pub mod cmp;
+    pub mod convert;
+    pub mod default;
+    pub mod error;
+    pub mod marker;
+    pub mod ops;
+
+    /* Core types and methods on primitives */
+
+    pub mod any;
+    pub mod array;
+    pub mod ascii;
+    pub mod asserting;
+    #[unstable(feature = "async_iterator", issue = "79024")]
+    pub mod async_iter;
+    pub mod cell;
+    pub mod char;
+    pub mod ffi;
+    #[unstable(feature = "core_io_borrowed_buf", issue = "117693")]
+    pub mod io;
+    pub mod iter;
+    pub mod net;
+    pub mod option;
+    pub mod panic;
+    pub mod panicking;
+    pub mod pin;
+    pub mod result;
+    pub mod sync;
+
+    pub mod fmt;
+    pub mod hash;
+    pub mod slice;
+    pub mod str;
+    pub mod time;
+
+    pub mod unicode;
+
+    /* Async */
+    pub mod future;
+    pub mod task;
+
+    /* Heap memory allocator trait */
+    #[allow(missing_docs)]
+    pub mod alloc;
+
+    // note: does not need to be public
+    mod bool;
+    mod escape;
+    mod tuple;
+    mod unit;
+
+    #[stable(feature = "core_primitive", since = "1.43.0")]
+    pub mod primitive;
+
+    #[stable(feature = "simd_arch", since = "1.27.0")]
+    pub mod arch;
+
+    // Pull in the `core_simd` crate directly into core. The contents of
+    // `core_simd` are in a different repository: rust-lang/portable-simd.
+    //
+    // `core_simd` depends on core, but the contents of this module are
+    // set up in such a way that directly pulling it here works such that the
+    // crate uses this crate as its core.
+    #[path = "../../portable-simd/crates/core_simd/src/mod.rs"]
+    #[allow(missing_debug_implementations, dead_code, unsafe_op_in_unsafe_fn)]
+    #[allow(rustdoc::bare_urls)]
+    #[unstable(feature = "portable_simd", issue = "86656")]
+    mod core_simd;
+
+    #[unstable(feature = "portable_simd", issue = "86656")]
+    pub mod simd {
+        #![doc = include_str!("../../portable-simd/crates/core_simd/src/core_simd_docs.md")]
+
+        #[unstable(feature = "portable_simd", issue = "86656")]
+        pub use crate::core_simd::simd::*;
+    }
+
+    include!("primitive_docs.rs");
+}