library/core/src/const_closure.rs

   1 use crate::marker::Destruct;
   2 #[cfg(not(bootstrap))]
   3 use crate::marker::Tuple;
   4
   5 /// Struct representing a closure with mutably borrowed data.
   6 ///
   7 /// Example:
   8 /// ```no_build
   9 /// #![feature(const_mut_refs)]
  10 /// use crate::const_closure::ConstFnMutClosure;
  11 /// const fn imp(state: &mut i32, (arg,): (i32,)) -> i32 {
  12 ///   *state += arg;
  13 ///   *state
  14 /// }
  15 /// let mut i = 5;
  16 /// let mut cl = ConstFnMutClosure::new(&mut i, imp);
  17 ///
  18 /// assert!(7 == cl(2));
  19 /// assert!(8 == cl(1));
  20 /// ```
  21 pub(crate) struct ConstFnMutClosure<CapturedData, Function> {
  22     /// The Data captured by the Closure.
  23     /// Must be either a (mutable) reference or a tuple of (mutable) references.
  24     pub data: CapturedData,
  25     /// The Function of the Closure, must be: Fn(CapturedData, ClosureArgs) -> ClosureReturn
  26     pub func: Function,
  27 }
  28 impl<'a, CapturedData: ?Sized, Function> ConstFnMutClosure<&'a mut CapturedData, Function> {
  29     /// Function for creating a new closure.
  30     ///
  31     /// `data` is the a mutable borrow of data that is captured from the environment.
  32     /// If you want Data to be a tuple of mutable Borrows, the struct must be constructed manually.
  33     ///
  34     /// `func` is the function of the closure, it gets the data and a tuple of the arguments closure
  35     ///   and return the return value of the closure.
  36     pub(crate) const fn new<ClosureArguments, ClosureReturnValue>(
  37         data: &'a mut CapturedData,
  38         func: Function,
  39     ) -> Self
  40     where
  41         Function: ~const Fn(&mut CapturedData, ClosureArguments) -> ClosureReturnValue,
  42     {
  43         Self { data, func }
  44     }
  45 }
  46
  47 macro_rules! impl_fn_mut_tuple {
  48     ($($var:ident)*) => {
  49         #[cfg(bootstrap)]
  50         #[allow(unused_parens)]
  51         impl<'a, $($var,)* ClosureArguments, Function, ClosureReturnValue> const
  52             FnOnce<ClosureArguments> for ConstFnMutClosure<($(&'a mut $var),*), Function>
  53         where
  54             Function: ~const Fn(($(&mut $var),*), ClosureArguments) -> ClosureReturnValue+ ~const Destruct,
  55         {
  56             type Output = ClosureReturnValue;
  57
  58             extern "rust-call" fn call_once(mut self, args: ClosureArguments) -> Self::Output {
  59             self.call_mut(args)
  60             }
  61         }
  62         #[cfg(bootstrap)]
  63         #[allow(unused_parens)]
  64         impl<'a, $($var,)* ClosureArguments, Function, ClosureReturnValue> const
  65             FnMut<ClosureArguments> for ConstFnMutClosure<($(&'a mut $var),*), Function>
  66         where
  67             Function: ~const Fn(($(&mut $var),*), ClosureArguments)-> ClosureReturnValue,
  68         {
  69             extern "rust-call" fn call_mut(&mut self, args: ClosureArguments) -> Self::Output {
  70                 #[allow(non_snake_case)]
  71                 let ($($var),*) = &mut self.data;
  72                 (self.func)(($($var),*), args)
  73             }
  74         }
  75         #[cfg(not(bootstrap))]
  76         #[allow(unused_parens)]
  77         impl<'a, $($var,)* ClosureArguments: Tuple, Function, ClosureReturnValue> const
  78             FnOnce<ClosureArguments> for ConstFnMutClosure<($(&'a mut $var),*), Function>
  79         where
  80             Function: ~const Fn(($(&mut $var),*), ClosureArguments) -> ClosureReturnValue+ ~const Destruct,
  81         {
  82             type Output = ClosureReturnValue;
  83
  84             extern "rust-call" fn call_once(mut self, args: ClosureArguments) -> Self::Output {
  85             self.call_mut(args)
  86             }
  87         }
  88         #[cfg(not(bootstrap))]
  89         #[allow(unused_parens)]
  90         impl<'a, $($var,)* ClosureArguments: Tuple, Function, ClosureReturnValue> const
  91             FnMut<ClosureArguments> for ConstFnMutClosure<($(&'a mut $var),*), Function>
  92         where
  93             Function: ~const Fn(($(&mut $var),*), ClosureArguments)-> ClosureReturnValue,
  94         {
  95             extern "rust-call" fn call_mut(&mut self, args: ClosureArguments) -> Self::Output {
  96                 #[allow(non_snake_case)]
  97                 let ($($var),*) = &mut self.data;
  98                 (self.func)(($($var),*), args)
  99             }
 100         }
 101     };
 102 }
 103 impl_fn_mut_tuple!(A);
 104 impl_fn_mut_tuple!(A B);
 105 impl_fn_mut_tuple!(A B C);
 106 impl_fn_mut_tuple!(A B C D);
 107 impl_fn_mut_tuple!(A B C D E);