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remove use of from_u32_unchecked

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This commit is contained in:
Niko Matsakis 2018-08-30 16:52:53 -04:00
parent 3b6361d29d
commit 3805ebeeb9
2 changed files with 22 additions and 8 deletions
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8
src/librustc/ty/sty.rs
View File

@ -1274,9 +1274,7 @@ impl DebruijnIndex {
/// you would need to shift the index for `'a` into 1 new binder.
#[must_use]
pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
unsafe {
DebruijnIndex::from_u32_unchecked(self.as_u32() + amount)
}
DebruijnIndex::from_u32(self.as_u32() + amount)
}
/// Update this index in place by shifting it "in" through
@ -1289,9 +1287,7 @@ impl DebruijnIndex {
/// `amount` number of new binders.
#[must_use]
pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
unsafe {
DebruijnIndex::from_u32_unchecked(self.as_u32() - amount)
}
DebruijnIndex::from_u32(self.as_u32() - amount)
}
/// Update in place by shifting out from `amount` binders.

22
src/librustc_data_structures/indexed_vec.rs
View File

@ -104,7 +104,7 @@ macro_rules! newtype_index {
impl $type {
$v const MAX_AS_U32: u32 = $max;
$v const MAX: $type = unsafe { $type::from_u32_unchecked($max) };
$v const MAX: $type = $type::from_u32_const($max);
#[inline]
$v fn from_usize(value: usize) -> Self {
@ -122,6 +122,24 @@ macro_rules! newtype_index {
}
}
/// Hacky variant of `from_u32` for use in constants.
/// This version checks the "max" constraint by using an
/// invalid array dereference.
#[inline]
$v const fn from_u32_const(value: u32) -> Self {
// This will fail at const eval time unless `value <=
// max` is true (in which case we get the index 0).
// It will also fail at runtime, of course, but in a
// kind of wacky way.
let _ = ["out of range value used"][
!(value <= $max) as usize
];
unsafe {
$type::from_u32_unchecked(value)
}
}
#[inline]
$v const unsafe fn from_u32_unchecked(value: u32) -> Self {
$type { private: ::std::num::NonZeroU32::new_unchecked(value + 1) }
@ -424,7 +442,7 @@ macro_rules! newtype_index {
const $name:ident = $constant:expr,
$($tokens:tt)*) => (
$(#[doc = $doc])*
pub const $name: $type = unsafe { $type::from_u32_unchecked($constant) };
pub const $name: $type = $type::from_u32_const($constant);
newtype_index!(
@derives [$($derives,)*]
@type [$type]