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Rollup merge of rust-lang#67657 - jumbatm:cleanup-const-hack, r=oli-obk
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Clean up const-hack PRs now that const if / match exist.

Closes rust-lang#67627.

Cleans up these merged PRs tagged with `const-hack`:

- rust-lang#63810
- rust-lang#63786
- rust-lang#61635
- rust-lang#58044

reverting their contents to have the match or if expressions they originally contained.

r? @oli-obk

There's one more PR in those tagged with `const-hack` that originally wasn't merged (rust-lang#65107). Reading the thread, it looks like it was originally closed because the `const-hack` for the checked arithmetic non-negligibly hurt performance, and because there was no way to manipulate the returned Option at compile time anyway (with neither const if nor const match). Would you like me to add these changes to the changes from this PR here too, now that we have the necessary features?
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JohnTitor authored Dec 30, 2019
2 parents 0eb19dc + 91c2f78 commit 047a4bb
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Showing 3 changed files with 20 additions and 16 deletions.
2 changes: 2 additions & 0 deletions src/libcore/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,8 @@
#![feature(cfg_target_has_atomic)]
#![feature(concat_idents)]
#![feature(const_fn)]
#![feature(const_if_match)]
#![feature(const_panic)]
#![feature(const_fn_union)]
#![feature(const_generics)]
#![feature(const_ptr_offset_from)]
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29 changes: 17 additions & 12 deletions src/libcore/num/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1416,18 +1416,14 @@ $EndFeature, "
```"),
#[stable(feature = "no_panic_abs", since = "1.13.0")]
#[rustc_const_stable(feature = "const_int_methods", since = "1.32.0")]
#[allow_internal_unstable(const_if_match)]
#[inline]
pub const fn wrapping_abs(self) -> Self {
// sign is -1 (all ones) for negative numbers, 0 otherwise.
let sign = self >> ($BITS - 1);
// For positive self, sign == 0 so the expression is simply
// (self ^ 0).wrapping_sub(0) == self == abs(self).
//
// For negative self, self ^ sign == self ^ all_ones.
// But all_ones ^ self == all_ones - self == -1 - self.
// So for negative numbers, (self ^ sign).wrapping_sub(sign) is
// (-1 - self).wrapping_sub(-1) == -self == abs(self).
(self ^ sign).wrapping_sub(sign)
if self.is_negative() {
self.wrapping_neg()
} else {
self
}
}
}

Expand Down Expand Up @@ -1713,8 +1709,13 @@ assert_eq!(", stringify!($SelfT), "::MIN.overflowing_neg(), (", stringify!($Self
#[inline]
#[stable(feature = "wrapping", since = "1.7.0")]
#[rustc_const_stable(feature = "const_int_methods", since = "1.32.0")]
#[allow_internal_unstable(const_if_match)]
pub const fn overflowing_neg(self) -> (Self, bool) {
((!self).wrapping_add(1), self == Self::min_value())
if self == Self::min_value() {
(Self::min_value(), true)
} else {
(-self, false)
}
}
}

Expand Down Expand Up @@ -2041,7 +2042,11 @@ $EndFeature, "
#[rustc_const_unstable(feature = "const_int_sign", issue = "53718")]
#[inline]
pub const fn signum(self) -> Self {
(self > 0) as Self - (self < 0) as Self
match self {
n if n > 0 => 1,
0 => 0,
_ => -1,
}
}
}

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5 changes: 1 addition & 4 deletions src/libcore/ptr/const_ptr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -288,10 +288,7 @@ impl<T: ?Sized> *const T {
T: Sized,
{
let pointee_size = mem::size_of::<T>();
let ok = 0 < pointee_size && pointee_size <= isize::max_value() as usize;
// assert that the pointee size is valid in a const eval compatible way
// FIXME: do this with a real assert at some point
[()][(!ok) as usize];
assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
intrinsics::ptr_offset_from(self, origin)
}

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