Struct rustc_pattern_analysis::constructor::IntRange

pub struct IntRange {
    pub lo: MaybeInfiniteInt,
    pub hi: MaybeInfiniteInt,
}

An exclusive interval, used for precise integer exhaustiveness checking. IntRanges always store a contiguous range.

IntRange is never used to encode an empty range or a “range” that wraps around the (offset) space: i.e., range.lo < range.hi.

Fields

lo: MaybeInfiniteInt

hi: MaybeInfiniteInt

Implementations

impl IntRange

pub fn is_singleton(&self) -> bool

Best effort; will not know that e.g. 255u8.. is a singleton.

pub fn from_singleton(x: MaybeInfiniteInt) -> IntRange

Construct a singleton range. x must be a Finite(_) value.

pub fn from_range( lo: MaybeInfiniteInt, hi: MaybeInfiniteInt, end: RangeEnd ) -> IntRange

Construct a range with these boundaries. lo must not be PosInfinity. hi must not be NegInfinity.

fn is_subrange(&self, other: &Self) -> bool

fn intersection(&self, other: &Self) -> Option<Self>

fn split( &self, column_ranges: impl Iterator<Item = IntRange> ) -> impl Iterator<Item = (Presence, IntRange)>

Partition a range of integers into disjoint subranges. This does constructor splitting for integer ranges as explained at the top of the file.

This returns an output that covers self. The output is split so that the only intersections between an output range and a column range are inclusions. No output range straddles the boundary of one of the inputs.

Additionally, we track for each output range whether it is covered by one of the column ranges or not.

The following input:

  (--------------------------) // `self`
(------) (----------)    (-)
    (------) (--------)

is first intersected with self:

  (--------------------------) // `self`
  (----) (----------)    (-)
    (------) (--------)

and then iterated over as follows:

  (-(--)-(-)-(------)-)--(-)-

where each sequence of dashes is an output range, and dashes outside parentheses are marked as Presence::Missing.

isize/usize

Whereas a wildcard of type i32 stands for the range i32::MIN..=i32::MAX, a usize wildcard stands for 0..PosInfinity and a isize wildcard stands for NegInfinity..PosInfinity. In other words, as far as IntRange is concerned, there are values before isize::MIN and after usize::MAX/isize::MAX. This is to avoid e.g. 0..(u32::MAX as usize) from being exhaustive on one architecture and not others. This was decided in https://github.com/rust-lang/rfcs/pull/2591.

These infinities affect splitting subtly: it is possible to get NegInfinity..0 and usize::MAX+1..PosInfinity in the output. Diagnostics must be careful to handle these fictitious ranges sensibly.

Trait Implementations

impl Clone for IntRange

fn clone(&self) -> IntRange

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for IntRange

Note: this will render signed ranges incorrectly. To render properly, convert to a pattern first.

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for IntRange

fn eq(&self, other: &IntRange) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for IntRange

impl Eq for IntRange

impl StructuralPartialEq for IntRange

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 64 bytes