Move the matches! macro to the prelude

Author: SimonSapin

Cargo.lock

@@ -585,7 +585,6 @@ checksum = "8ff012e225ce166d4422e0e78419d901719760f62ae2b7969ca6b564d1b54a9e"
 name = "core"
 version = "0.0.0"
 dependencies = [
- "matches_macro",
  "rand 0.7.0",
 ]
 
@@ -1901,10 +1900,6 @@ version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7ffc5c5338469d4d3ea17d269fa8ea3512ad247247c30bd2df69e68309ed0a08"
 
-[[package]]
-name = "matches_macro"
-version = "0.0.0"
-
 [[package]]
 name = "mdbook"
 version = "0.3.1"

src/libcore/Cargo.toml

@@ -20,9 +20,6 @@ path = "../libcore/tests/lib.rs"
 name = "corebenches"
 path = "../libcore/benches/lib.rs"
 
-[dependencies]
-matches_macro = { path = "../libmatches_macro" }
-
 [dev-dependencies]
 rand = "0.7"
 

src/libcore/lib.rs

@@ -85,7 +85,6 @@
 #![feature(iter_once_with)]
 #![feature(lang_items)]
 #![feature(link_llvm_intrinsics)]
-#![feature(matches_macro)]
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(exhaustive_patterns)]
@@ -135,16 +134,7 @@
 use prelude::v1::*;
 
 #[macro_use]
-#[path = "macros.rs"]
-mod prelude_macros;
-
-/// Macros that are not in the prelude and need to be imported explicitly
-#[unstable(feature = "matches_macro", issue = "0")]
-pub mod macros {
-    #[unstable(feature = "matches_macro", issue = "0")]
-    #[doc(inline)]
-    pub use matches_macro::matches;
-}
+mod macros;
 
 #[macro_use]
 mod internal_macros;

src/libcore/macros.rs

@@ -238,6 +238,30 @@ macro_rules! debug_assert_ne {
     ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_ne!($($arg)*); })
 }
 
+/// Returns whether the given expression matches (any of) the given pattern(s).
+///
+/// # Examples
+///
+/// ```
+/// #![feature(matches_macro)]
+///
+/// let foo = 'f';
+/// assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
+///
+/// let bar = Some(4);
+/// assert!(matches!(bar, Some(x) if x > 2));
+/// ```
+#[macro_export]
+#[unstable(feature = "matches_macro", issue = "0")]
+macro_rules! matches {
+    ($expression:expr, $( $pattern:pat )|+ $( if $guard: expr )?) => {
+        match $expression {
+            $( $pattern )|+ $( if $guard )? => true,
+            _ => false
+        }
+    }
+}
+
 /// Unwraps a result or propagates its error.
 ///
 /// The `?` operator was added to replace `try!` and should be used instead.

src/libcore/prelude/v1.rs

@@ -82,7 +82,7 @@ pub use crate::{
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow(deprecated)]
 #[doc(no_inline)]
-pub use crate::prelude_macros::builtin::{
+pub use crate::macros::builtin::{
     RustcDecodable,
     RustcEncodable,
     bench,

src/libmatches_macro/Cargo.toml

@@ -354,16 +354,7 @@ extern crate cfg_if;
 
 // The standard macros that are not built-in to the compiler.
 #[macro_use]
-#[path = "macros.rs"]
-mod prelude_macros;
-
-/// Macros that are not in the prelude and need to be imported explicitly
-#[unstable(feature = "matches_macro", issue = "0")]
-pub mod macros {
-    #[unstable(feature = "matches_macro", issue = "0")]
-    #[doc(inline)]
-    pub use core::macros::matches;
-}
+mod macros;
 
 // The Rust prelude
 pub mod prelude;
@@ -537,6 +528,7 @@ pub use core::{
     writeln,
     // Unstable
     todo,
+    matches,
 };
 
 // Re-export built-in macros defined through libcore.

src/libmatches_macro/lib.rs

@@ -5,7 +5,7 @@ LL | macro_rules! unknown { () => () }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: cannot find a built-in macro with name `line`
-  --> <::core::prelude_macros::builtin::line macros>:1:1
+  --> <::core::macros::builtin::line macros>:1:1
    |
 LL | () => { }
    | ^^^^^^^^^