library/core/src/const_closure.rs

   1 use crate::marker::Destruct;
   2
   3 /// Struct representing a closure with mutably borrowed data.
   4 ///
   5 /// Example:
   6 /// ```no_build
   7 /// #![feature(const_mut_refs)]
   8 /// use crate::const_closure::ConstFnMutClosure;
   9 /// const fn imp(state: &mut i32, (arg,): (i32,)) -> i32 {
  10 ///   *state += arg;
  11 ///   *state
  12 /// }
  13 /// let mut i = 5;
  14 /// let mut cl = ConstFnMutClosure::new(&mut i, imp);
  15 ///
  16 /// assert!(7 == cl(2));
  17 /// assert!(8 == cl(1));
  18 /// ```
  19 pub(crate) struct ConstFnMutClosure<'a, CapturedData: ?Sized, Function> {
  20     data: &'a mut CapturedData,
  21     func: Function,
  22 }
  23
  24 impl<'a, CapturedData: ?Sized, Function> ConstFnMutClosure<'a, CapturedData, Function> {
  25     /// Function for creating a new closure.
  26     ///
  27     /// `data` is the a mutable borrow of data that is captured from the environment.
  28     ///
  29     /// `func` is the function of the closure, it gets the data and a tuple of the arguments closure
  30     ///   and return the return value of the closure.
  31     pub(crate) const fn new<ClosureArguments, ClosureReturnValue>(
  32         data: &'a mut CapturedData,
  33         func: Function,
  34     ) -> Self
  35     where
  36         Function: ~const Fn(&mut CapturedData, ClosureArguments) -> ClosureReturnValue,
  37     {
  38         Self { data, func }
  39     }
  40 }
  41
  42 impl<'a, CapturedData: ?Sized, ClosureArguments, Function, ClosureReturnValue> const
  43     FnOnce<ClosureArguments> for ConstFnMutClosure<'a, CapturedData, Function>
  44 where
  45     Function:
  46         ~const Fn(&mut CapturedData, ClosureArguments) -> ClosureReturnValue + ~const Destruct,
  47 {
  48     type Output = ClosureReturnValue;
  49
  50     extern "rust-call" fn call_once(mut self, args: ClosureArguments) -> Self::Output {
  51         self.call_mut(args)
  52     }
  53 }
  54
  55 impl<'a, CapturedData: ?Sized, ClosureArguments, Function, ClosureReturnValue> const
  56     FnMut<ClosureArguments> for ConstFnMutClosure<'a, CapturedData, Function>
  57 where
  58     Function: ~const Fn(&mut CapturedData, ClosureArguments) -> ClosureReturnValue,
  59 {
  60     extern "rust-call" fn call_mut(&mut self, args: ClosureArguments) -> Self::Output {
  61         (self.func)(self.data, args)
  62     }
  63 }