Constify Fn* traits

Author: oli-obk

core/src/ops/function.rs

@@ -72,7 +72,8 @@ use crate::marker::Tuple;
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-// FIXME(const_trait_impl) #[const_trait]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
 pub trait Fn<Args: Tuple>: FnMut<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -159,7 +160,8 @@ pub trait Fn<Args: Tuple>: FnMut<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-// FIXME(const_trait_impl) #[const_trait]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
 pub trait FnMut<Args: Tuple>: FnOnce<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -238,7 +240,8 @@ pub trait FnMut<Args: Tuple>: FnOnce<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-// FIXME(const_trait_impl) #[const_trait]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
 pub trait FnOnce<Args: Tuple> {
     /// The returned type after the call operator is used.
     #[lang = "fn_once_output"]
@@ -254,29 +257,32 @@ mod impls {
     use crate::marker::Tuple;
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> Fn<A> for &F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const Fn<A> for &F
     where
-        F: Fn<A>,
+        F: ~const Fn<A>,
     {
         extern "rust-call" fn call(&self, args: A) -> F::Output {
             (**self).call(args)
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnMut<A> for &F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnMut<A> for &F
     where
-        F: Fn<A>,
+        F: ~const Fn<A>,
     {
         extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
             (**self).call(args)
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnOnce<A> for &F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnOnce<A> for &F
     where
-        F: Fn<A>,
+        F: ~const Fn<A>,
     {
         type Output = F::Output;
 
@@ -286,19 +292,21 @@ mod impls {
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnMut<A> for &mut F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnMut<A> for &mut F
     where
-        F: FnMut<A>,
+        F: ~const FnMut<A>,
     {
         extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
             (*self).call_mut(args)
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnOnce<A> for &mut F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnOnce<A> for &mut F
     where
-        F: FnMut<A>,
+        F: ~const FnMut<A>,
     {
         type Output = F::Output;
         extern "rust-call" fn call_once(self, args: A) -> F::Output {