Struct scale_info::prelude::ops::RangeToInclusive 1.26.0[−][src]
pub struct RangeToInclusive<Idx> {
pub end: Idx,
}Expand description
A range only bounded inclusively above (..=end).
The RangeToInclusive ..=end contains all values with x <= end.
It cannot serve as an Iterator because it doesn’t have a starting point.
Examples
The ..=end syntax is a RangeToInclusive:
assert_eq!((..=5), std::ops::RangeToInclusive{ end: 5 });It does not have an IntoIterator implementation, so you can’t use it in a
for loop directly. This won’t compile:
// error[E0277]: the trait bound `std::ops::RangeToInclusive<{integer}>:
// std::iter::Iterator` is not satisfied
for i in ..=5 {
// ...
}When used as a slicing index, RangeToInclusive produces a slice of all
array elements up to and including the index indicated by end.
let arr = [0, 1, 2, 3, 4];
assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]);
assert_eq!(arr[ .. 3], [0, 1, 2 ]);
assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); // This is a `RangeToInclusive`
assert_eq!(arr[1.. ], [ 1, 2, 3, 4]);
assert_eq!(arr[1.. 3], [ 1, 2 ]);
assert_eq!(arr[1..=3], [ 1, 2, 3 ]);Fields
end: IdxThe upper bound of the range (inclusive)
Implementations
1.35.0[src]pub fn contains<U>(&self, item: &U) -> bool where
Idx: PartialOrd<U>,
U: PartialOrd<Idx> + ?Sized,
pub fn contains<U>(&self, item: &U) -> bool where
Idx: PartialOrd<U>,
U: PartialOrd<Idx> + ?Sized,
Returns true if item is contained in the range.
Examples
assert!( (..=5).contains(&-1_000_000_000));
assert!( (..=5).contains(&5));
assert!(!(..=5).contains(&6));
assert!( (..=1.0).contains(&1.0));
assert!(!(..=1.0).contains(&f32::NAN));
assert!(!(..=f32::NAN).contains(&0.5));Trait Implementations
impl<'a, O, T> BitSliceIndex<'a, O, T> for RangeToInclusive<usize> where
T: BitStore,
O: BitOrder,
impl<'a, O, T> BitSliceIndex<'a, O, T> for RangeToInclusive<usize> where
T: BitStore,
O: BitOrder,
pub fn get(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
) -> Option<<RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut>
pub fn get(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
) -> Option<<RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut>
Returns a shared reference to the output at this location, if in bounds. Read more
pub fn get_mut(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
) -> Option<<RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut>
pub fn get_mut(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
) -> Option<<RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut>
Returns a mutable reference to the output at this location, if in bounds. Read more
pub unsafe fn get_unchecked(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
pub unsafe fn get_unchecked(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used. Read more
pub unsafe fn get_unchecked_mut(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
pub unsafe fn get_unchecked_mut(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used. Read more
pub fn index(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
pub fn index(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Immut
Returns a shared reference to the output at this location, panicking if out of bounds. Read more
pub fn index_mut(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
pub fn index_mut(
self,
slice: <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
) -> <RangeToInclusive<usize> as BitSliceIndex<'a, O, T>>::Mut
Returns a mutable reference to the output at this location, panicking if out of bounds. Read more
pub fn index_mut(
&mut self,
index: RangeToInclusive<usize>
) -> &mut <BitSlice<O, T> as Index<RangeToInclusive<usize>>>::Output
pub fn index_mut(
&mut self,
index: RangeToInclusive<usize>
) -> &mut <BitSlice<O, T> as Index<RangeToInclusive<usize>>>::Output
Performs the mutable indexing (container[index]) operation. Read more
impl<Idx> PartialEq<RangeToInclusive<Idx>> for RangeToInclusive<Idx> where
Idx: PartialEq<Idx>,
impl<Idx> PartialEq<RangeToInclusive<Idx>> for RangeToInclusive<Idx> where
Idx: PartialEq<Idx>,
This method tests for self and other values to be equal, and is used
by ==. Read more
This method tests for !=.
slice_index_methods)Returns a shared reference to the output at this location, if in bounds. Read more
slice_index_methods)Returns a mutable reference to the output at this location, if in bounds. Read more
slice_index_methods)Returns a shared reference to the output at this location, without
performing any bounds checking.
Calling this method with an out-of-bounds index or a dangling slice pointer
is undefined behavior even if the resulting reference is not used. Read more
slice_index_methods)Returns a mutable reference to the output at this location, without
performing any bounds checking.
Calling this method with an out-of-bounds index or a dangling slice pointer
is undefined behavior even if the resulting reference is not used. Read more
slice_index_methods)Returns a shared reference to the output at this location, panicking if out of bounds. Read more
slice_index_methods)Returns a mutable reference to the output at this location, panicking if out of bounds. Read more
Implements substring slicing with syntax &self[..= end] or &mut self[..= end].
Returns a slice of the given string from the byte range [0, end].
Equivalent to &self [0 .. end + 1], except if end has the maximum
value for usize.
This operation is O(1).
Panics
Panics if end does not point to the ending byte offset of a character
(end + 1 is either a starting byte offset as defined by
is_char_boundary, or equal to len), or if end >= len.
pub fn get(
self,
slice: &str
) -> Option<&<RangeToInclusive<usize> as SliceIndex<str>>::Output>
pub fn get(
self,
slice: &str
) -> Option<&<RangeToInclusive<usize> as SliceIndex<str>>::Output>
slice_index_methods)Returns a shared reference to the output at this location, if in bounds. Read more
pub fn get_mut(
self,
slice: &mut str
) -> Option<&mut <RangeToInclusive<usize> as SliceIndex<str>>::Output>
pub fn get_mut(
self,
slice: &mut str
) -> Option<&mut <RangeToInclusive<usize> as SliceIndex<str>>::Output>
slice_index_methods)Returns a mutable reference to the output at this location, if in bounds. Read more
pub unsafe fn get_unchecked(
self,
slice: *const str
) -> *const <RangeToInclusive<usize> as SliceIndex<str>>::Output
pub unsafe fn get_unchecked(
self,
slice: *const str
) -> *const <RangeToInclusive<usize> as SliceIndex<str>>::Output
slice_index_methods)Returns a shared reference to the output at this location, without
performing any bounds checking.
Calling this method with an out-of-bounds index or a dangling slice pointer
is undefined behavior even if the resulting reference is not used. Read more
pub unsafe fn get_unchecked_mut(
self,
slice: *mut str
) -> *mut <RangeToInclusive<usize> as SliceIndex<str>>::Output
pub unsafe fn get_unchecked_mut(
self,
slice: *mut str
) -> *mut <RangeToInclusive<usize> as SliceIndex<str>>::Output
slice_index_methods)Returns a mutable reference to the output at this location, without
performing any bounds checking.
Calling this method with an out-of-bounds index or a dangling slice pointer
is undefined behavior even if the resulting reference is not used. Read more
slice_index_methods)Returns a shared reference to the output at this location, panicking if out of bounds. Read more
pub fn index_mut(
self,
slice: &mut str
) -> &mut <RangeToInclusive<usize> as SliceIndex<str>>::Output
pub fn index_mut(
self,
slice: &mut str
) -> &mut <RangeToInclusive<usize> as SliceIndex<str>>::Output
slice_index_methods)Returns a mutable reference to the output at this location, panicking if out of bounds. Read more
Auto Trait Implementations
impl<Idx> RefUnwindSafe for RangeToInclusive<Idx> where
Idx: RefUnwindSafe,
impl<Idx> Send for RangeToInclusive<Idx> where
Idx: Send,
impl<Idx> Sync for RangeToInclusive<Idx> where
Idx: Sync,
impl<Idx> Unpin for RangeToInclusive<Idx> where
Idx: Unpin,
impl<Idx> UnwindSafe for RangeToInclusive<Idx> where
Idx: UnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more
fn fmt_binary(self) -> FmtBinary<Self> where
Self: Binary,
fn fmt_binary(self) -> FmtBinary<Self> where
Self: Binary,
Causes self to use its Binary implementation when Debug-formatted.
fn fmt_display(self) -> FmtDisplay<Self> where
Self: Display,
fn fmt_display(self) -> FmtDisplay<Self> where
Self: Display,
Causes self to use its Display implementation when
Debug-formatted. Read more
fn fmt_lower_exp(self) -> FmtLowerExp<Self> where
Self: LowerExp,
fn fmt_lower_exp(self) -> FmtLowerExp<Self> where
Self: LowerExp,
Causes self to use its LowerExp implementation when
Debug-formatted. Read more
fn fmt_lower_hex(self) -> FmtLowerHex<Self> where
Self: LowerHex,
fn fmt_lower_hex(self) -> FmtLowerHex<Self> where
Self: LowerHex,
Causes self to use its LowerHex implementation when
Debug-formatted. Read more
Causes self to use its Octal implementation when Debug-formatted.
fn fmt_pointer(self) -> FmtPointer<Self> where
Self: Pointer,
fn fmt_pointer(self) -> FmtPointer<Self> where
Self: Pointer,
Causes self to use its Pointer implementation when
Debug-formatted. Read more
fn fmt_upper_exp(self) -> FmtUpperExp<Self> where
Self: UpperExp,
fn fmt_upper_exp(self) -> FmtUpperExp<Self> where
Self: UpperExp,
Causes self to use its UpperExp implementation when
Debug-formatted. Read more
fn fmt_upper_hex(self) -> FmtUpperHex<Self> where
Self: UpperHex,
fn fmt_upper_hex(self) -> FmtUpperHex<Self> where
Self: UpperHex,
Causes self to use its UpperHex implementation when
Debug-formatted. Read more
impl<T> Pipe for T where
T: ?Sized,
impl<T> Pipe for T where
T: ?Sized,
Pipes by value. This is generally the method you want to use. Read more
Borrows self and passes that borrow into the pipe function. Read more
fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R where
R: 'a,
fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R where
R: 'a,
Mutably borrows self and passes that borrow into the pipe function. Read more
fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> R where
Self: Borrow<B>,
B: 'a + ?Sized,
R: 'a,
fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> R where
Self: Borrow<B>,
B: 'a + ?Sized,
R: 'a,
Borrows self, then passes self.borrow() into the pipe function. Read more
fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
B: 'a + ?Sized,
R: 'a,
fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
B: 'a + ?Sized,
R: 'a,
Mutably borrows self, then passes self.borrow_mut() into the pipe
function. Read more
fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> R where
Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> R where
Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
Borrows self, then passes self.as_ref() into the pipe function.
fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
Mutably borrows self, then passes self.as_mut() into the pipe
function. Read more
fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
Borrows self, then passes self.deref() into the pipe function.
fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_as_mut<'a, T, R>(&'a mut self, func: impl FnOnce(&'a mut T) -> R) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
fn pipe_as_mut<'a, T, R>(&'a mut self, func: impl FnOnce(&'a mut T) -> R) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
Pipes a trait mutable borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
R: 'a,
fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
R: 'a,
Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_borrow_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
fn pipe_borrow_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
Pipes a trait mutable borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_deref<'a, R>(&'a self, func: impl FnOnce(&'a Self::Target) -> R) -> R where
Self: Deref,
R: 'a,
fn pipe_deref<'a, R>(&'a self, func: impl FnOnce(&'a Self::Target) -> R) -> R where
Self: Deref,
R: 'a,
Pipes a dereference into a function that cannot normally be called in suffix position. Read more
fn pipe_deref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
fn pipe_deref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
Pipes a mutable dereference into a function that cannot normally be called in suffix position. Read more
Pipes a reference into a function that cannot ordinarily be called in suffix position. Read more
fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Immutable access to the Borrow<B> of a value. Read more
fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
Mutable access to the BorrowMut<B> of a value. Read more
Immutable access to the AsRef<R> view of a value. Read more
fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Mutable access to the AsMut<R> view of a value. Read more
Immutable access to the Deref::Target of a value. Read more
Mutable access to the Deref::Target of a value. Read more
Calls .tap() only in debug builds, and is erased in release builds.
fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
Calls .tap_mut() only in debug builds, and is erased in release
builds. Read more
fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Calls .tap_borrow() only in debug builds, and is erased in release
builds. Read more
fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
Calls .tap_borrow_mut() only in debug builds, and is erased in release
builds. Read more
fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
Calls .tap_ref() only in debug builds, and is erased in release
builds. Read more
fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Calls .tap_ref_mut() only in debug builds, and is erased in release
builds. Read more
Provides immutable access for inspection. Read more
Calls tap in debug builds, and does nothing in release builds.
Provides mutable access for modification. Read more
fn tap_mut_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
fn tap_mut_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
Calls tap_mut in debug builds, and does nothing in release builds.
impl<T, U> TapAsRef<U> for T where
U: ?Sized,
impl<T, U> TapAsRef<U> for T where
U: ?Sized,
Provides immutable access to the reference for inspection.
fn tap_ref_dbg<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
fn tap_ref_dbg<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
Calls tap_ref in debug builds, and does nothing in release builds.
fn tap_ref_mut<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_ref_mut<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Provides mutable access to the reference for modification.
fn tap_ref_mut_dbg<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_ref_mut_dbg<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Calls tap_ref_mut in debug builds, and does nothing in release builds.
impl<T, U> TapBorrow<U> for T where
U: ?Sized,
impl<T, U> TapBorrow<U> for T where
U: ?Sized,
fn tap_borrow<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
fn tap_borrow<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Provides immutable access to the borrow for inspection. Read more
fn tap_borrow_dbg<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
fn tap_borrow_dbg<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Calls tap_borrow in debug builds, and does nothing in release builds.
fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Provides mutable access to the borrow for modification.
fn tap_borrow_mut_dbg<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_borrow_mut_dbg<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Calls tap_borrow_mut in debug builds, and does nothing in release
builds. Read more
Immutably dereferences self for inspection.
fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Calls tap_deref in debug builds, and does nothing in release builds.
fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Mutably dereferences self for modification.
fn tap_deref_mut_dbg<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
fn tap_deref_mut_dbg<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Calls tap_deref_mut in debug builds, and does nothing in release
builds. Read more