Remove cfg_match from the prelude

library/core/src/lib.rs

@@ -291,6 +291,9 @@ pub mod assert_matches {
     pub use crate::macros::{assert_matches, debug_assert_matches};
 }
 
+#[unstable(feature = "cfg_match", issue = "115585")]
+pub use crate::macros::cfg_match;
+
 #[macro_use]
 mod internal_macros;
 

library/core/src/macros/mod.rs

@@ -168,6 +168,94 @@ pub macro assert_matches {
     },
 }
 
+/// A macro for defining `#[cfg]` match-like statements.
+///
+/// It is similar to the `if/elif` C preprocessor macro by allowing definition of a cascade of
+/// `#[cfg]` cases, emitting the implementation which matches first.
+///
+/// This allows you to conveniently provide a long list `#[cfg]`'d blocks of code
+/// without having to rewrite each clause multiple times.
+///
+/// Trailing `_` wildcard match arms are **optional** and they indicate a fallback branch when
+/// all previous declarations do not evaluate to true.
+///
+/// # Example
+///
+/// ```
+/// #![feature(cfg_match)]
+///
+/// cfg_match! {
+///     cfg(unix) => {
+///         fn foo() { /* unix specific functionality */ }
+///     }
+///     cfg(target_pointer_width = "32") => {
+///         fn foo() { /* non-unix, 32-bit functionality */ }
+///     }
+///     _ => {
+///         fn foo() { /* fallback implementation */ }
+///     }
+/// }
+/// ```
+#[unstable(feature = "cfg_match", issue = "115585")]
+#[rustc_diagnostic_item = "cfg_match"]
+pub macro cfg_match {
+    // with a final wildcard
+    (
+        $(cfg($initial_meta:meta) => { $($initial_tokens:item)* })+
+        _ => { $($extra_tokens:item)* }
+    ) => {
+        cfg_match! {
+            @__items ();
+            $((($initial_meta) ($($initial_tokens)*)),)+
+            (() ($($extra_tokens)*)),
+        }
+    },
+
+    // without a final wildcard
+    (
+        $(cfg($extra_meta:meta) => { $($extra_tokens:item)* })*
+    ) => {
+        cfg_match! {
+            @__items ();
+            $((($extra_meta) ($($extra_tokens)*)),)*
+        }
+    },
+
+    // Internal and recursive macro to emit all the items
+    //
+    // Collects all the previous cfgs in a list at the beginning, so they can be
+    // negated. After the semicolon is all the remaining items.
+    (@__items ($($_:meta,)*);) => {},
+    (
+        @__items ($($no:meta,)*);
+        (($($yes:meta)?) ($($tokens:item)*)),
+        $($rest:tt,)*
+    ) => {
+        // Emit all items within one block, applying an appropriate #[cfg]. The
+        // #[cfg] will require all `$yes` matchers specified and must also negate
+        // all previous matchers.
+        #[cfg(all(
+            $($yes,)?
+            not(any($($no),*))
+        ))]
+        cfg_match! { @__identity $($tokens)* }
+
+        // Recurse to emit all other items in `$rest`, and when we do so add all
+        // our `$yes` matchers to the list of `$no` matchers as future emissions
+        // will have to negate everything we just matched as well.
+        cfg_match! {
+            @__items ($($no,)* $($yes,)?);
+            $($rest,)*
+        }
+    },
+
+    // Internal macro to make __apply work out right for different match types,
+    // because of how macros match/expand stuff.
+    (@__identity $($tokens:item)*) => {
+        $($tokens)*
+    }
+}
+
 /// Asserts that a boolean expression is `true` at runtime.
 ///
 /// This will invoke the [`panic!`] macro if the provided expression cannot be
@@ -321,95 +409,6 @@ pub macro debug_assert_matches($($arg:tt)*) {
     }
 }
 
-/// A macro for defining `#[cfg]` match-like statements.
-///
-/// It is similar to the `if/elif` C preprocessor macro by allowing definition of a cascade of
-/// `#[cfg]` cases, emitting the implementation which matches first.
-///
-/// This allows you to conveniently provide a long list `#[cfg]`'d blocks of code
-/// without having to rewrite each clause multiple times.
-///
-/// Trailing `_` wildcard match arms are **optional** and they indicate a fallback branch when
-/// all previous declarations do not evaluate to true.
-///
-/// # Example
-///
-/// ```
-/// #![feature(cfg_match)]
-///
-/// cfg_match! {
-///     cfg(unix) => {
-///         fn foo() { /* unix specific functionality */ }
-///     }
-///     cfg(target_pointer_width = "32") => {
-///         fn foo() { /* non-unix, 32-bit functionality */ }
-///     }
-///     _ => {
-///         fn foo() { /* fallback implementation */ }
-///     }
-/// }
-/// ```
-#[macro_export]
-#[unstable(feature = "cfg_match", issue = "115585")]
-#[rustc_diagnostic_item = "cfg_match"]
-macro_rules! cfg_match {
-    // with a final wildcard
-    (
-        $(cfg($initial_meta:meta) => { $($initial_tokens:item)* })+
-        _ => { $($extra_tokens:item)* }
-    ) => {
-        cfg_match! {
-            @__items ();
-            $((($initial_meta) ($($initial_tokens)*)),)+
-            (() ($($extra_tokens)*)),
-        }
-    };
-
-    // without a final wildcard
-    (
-        $(cfg($extra_meta:meta) => { $($extra_tokens:item)* })*
-    ) => {
-        cfg_match! {
-            @__items ();
-            $((($extra_meta) ($($extra_tokens)*)),)*
-        }
-    };
-
-    // Internal and recursive macro to emit all the items
-    //
-    // Collects all the previous cfgs in a list at the beginning, so they can be
-    // negated. After the semicolon is all the remaining items.
-    (@__items ($($_:meta,)*);) => {};
-    (
-        @__items ($($no:meta,)*);
-        (($($yes:meta)?) ($($tokens:item)*)),
-        $($rest:tt,)*
-    ) => {
-        // Emit all items within one block, applying an appropriate #[cfg]. The
-        // #[cfg] will require all `$yes` matchers specified and must also negate
-        // all previous matchers.
-        #[cfg(all(
-            $($yes,)?
-            not(any($($no),*))
-        ))]
-        cfg_match! { @__identity $($tokens)* }
-
-        // Recurse to emit all other items in `$rest`, and when we do so add all
-        // our `$yes` matchers to the list of `$no` matchers as future emissions
-        // will have to negate everything we just matched as well.
-        cfg_match! {
-            @__items ($($no,)* $($yes,)?);
-            $($rest,)*
-        }
-    };
-
-    // Internal macro to make __apply work out right for different match types,
-    // because of how macros match/expand stuff.
-    (@__identity $($tokens:item)*) => {
-        $($tokens)*
-    };
-}
-
 /// Returns whether the given expression matches any of the given patterns.
 ///
 /// Like in a `match` expression, the pattern can be optionally followed by `if`