employer
/
tame
1
0
Fork 0
Code Packages Releases Activity
tame/tamer/src/span.rs

974 lines
31 KiB
Rust
Raw Blame History

This file contains invisible Unicode characters!

This file contains invisible Unicode characters that may be processed differently from what appears below. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to reveal hidden characters.

// Source spans
//
// Copyright (C) 2014-2023 Ryan Specialty, LLC.
//
// This file is part of TAME.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//! Mapping to source input byte intervals.
//!
//! A [`Span`] is a mapping to a byte interval within a source file,
//! representing primarily where some IR entity originated.
//! This underpins the diagnostic system,
//! intended to:
//!
//! 1. Give the user specific information for debugging errors in their
//! programs; and
//! 2. Provide high-resolution information for source code inquiries,
//! such as "where is this identifier?" and "what exists at my cursor
//! position within this file"?
//!
//! A span contains a [`Context`] representing the source location.
//! A context's path is a [`PathSymbolId`],
//! which represents an interned string slice,
//! _not_ a [`PathBuf`](std::path::PathBuf) or
//! [`OsStr`](std::ffi::OsStr).
//!
//! ```
//! use tamer::span::{Span, Context};
//! use tamer::sym::GlobalSymbolIntern;
//!
//! // From raw parts
//! let ctx: Context = "some/path/foo".intern().into();
//! let span = Span::new(2, 6, ctx);
//!
//! assert_eq!(2, span.offset());
//! assert_eq!(6, span.len());
//! assert_eq!(ctx, span.context());
//!
//! // From a closed byte interval
//! let spani = Span::from_byte_interval((10, 25), "some/path/bar".intern());
//! assert_eq!(10, spani.offset());
//! assert_eq!(15, spani.len());
//!
//! // Freely copyable
//! let cp = span;
//! assert_eq!(cp, span);
//! ```
//!
//! Span is expected to be able to fit within a general-purpose CPU register
//! on a 64-bit system, and so does not exceed 8 bytes in length.
//!
//! Spans are one of the most common objects in TAMER,
//! competing only with [symbols](crate::sym).
//! But unlike symbols,
//! [`Span`]s are designed to be meaningfully identifiable and copyable
//! without interning.
//!
//! A span is ordered as such:
//!
//! 1. Spans group by [`Context`],
//! though the relative ordering of each [`Context`] isn't
//! necessarily meaningful;
//! 2. Spans are then ordered relative to their offset; and
//! 3. Spans are finally ordered by their length.
//!
//! Note that this means that a span beginning after but ending before
//! another span will still order higher,
//! as shown in the example below.
//!
//! ```
//! # use tamer::span::{Span, Context};
//! # use tamer::sym::GlobalSymbolIntern;
//! #
//! # let ctx: Context = "some/path/foo".intern().into();
//! #
//! // Visualization of spans:
//! // [....,....,....,....,]
//! // [A-+-] [B-+]|
//! // | [C-] |
//! // | [D-+-]
//! // | [E]
//! // [F----] |
//! // [G------]
//!
//! let A = Span::new(2, 6, ctx);
//! let B = Span::new(10, 5, ctx);
//! let C = Span::new(10, 4, ctx);
//! let D = Span::new(10, 6, ctx);
//! let E = Span::new(11, 3, ctx);
//! let F = Span::new(5, 7, ctx);
//! let G = Span::new(5, 8, ctx);
//!
//! let mut spans = vec![A, B, C, D, E, F, G];
//! spans.sort();
//!
//! assert_eq!(spans, vec![A, F, G, C, B, D, E]);
//! ```
//!
//! Design Rationale
//! ================
//! It is expected that spans will be created and copied frequently,
//! as they are propagated to every IR in the system.
//! It is further expected that the data within a span will only be
//! referenced for diagnostic purposes,
//! or for utilities operating on original source code
//! (such as code formatters).
//!
//! When a span is referenced,
//! it will either be to determine the exact location of a particular
//! entity,
//! or it will be to attempt to locate a similar entity in a higher-level
//! IR associated with the same region of code.
//! The latter requires that spans be comparable in a meaningful way,
//! exhibiting at least partial ordering.
//!
//! Spans are therefore optimized for three primary use cases:
//! - copying;
//! - comparison; and
//! - ordering.
//!
//! Span Structure
//! --------------
//! Spans are packed into 64-bit values that can be readily converted into a
//! [`u64`] value that is totally ordered relative to a given [`Context`],
//! byte offset, and byte length.
//! This means that sorting a collection of [`Span`]s will group spans by
//! their [`Context`];
//! will sort those spans relative to their starting offset within that
//! context; and
//! will sort again by the ending offset.
//!
//! This means that spans are [`Eq`] and [`Ord`],
//! and efficiently so by simply comparing the byte values of the entire
//! struct as a single [`u64`].
//! This allows spans to be sorted relative to their positions within a
//! context;
//! be placed into a binary tree for mapping back to higher-level IRs;
//! gives spans a meaningful unique identifier;
//! be freely copied without cost;
//! and more,
//! all very efficiently and without having to access individual
//! struct members.
//!
//! To accomplish this,
//! [`Span`] uses `repr(packed)` and orders the fields for little endian
//! systems like `x86_64`,
//! which is what our team uses.
//! The `packed` representation had to be used because the byte orderings
//! are [`u16`], [`u32`], [`u16`],
//! which makes the [`u32`] byte offset unaligned.
//! Note that,
//! while this _is_ unaligned,
//! this is _not_ unaligned _memory_ access,
//! since the entire [`Span`] will be retrieved from (aligned) memory at
//! once;
//! the unaligned fields within the [`u64`] do not incur a measurable
//! performance cost.
//!
//! Related Work
//! ============
//! This span is motivated by [rustc's compressed `Span`](rustc-span).
//! TAMER's span size relies on 16 bits being sufficient for holding
//! interned paths,
//! which _should_ be a very reasonable assumption unless the interner
//! ends up being shared with too many different things.
//! If ever that assumption becomes violated,
//! and it is deemed that packages containing so many symbols should be permitted,
//! TAMER's [`Span`] can accommodate in a similar with to rustc's by
//! interning the larger span data and tagging this span as such.
//!
//!
//! [rustc-span]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_span/struct.Span.html
use crate::{
debug_diagnostic_panic, global,
sym::{st16, ContextStaticSymbolId, GlobalSymbolResolve, SymbolId},
};
use std::{convert::TryInto, fmt::Display, path::Path};
/// A symbol size sufficient for holding interned paths.
pub type PathSymbolId = SymbolId<u16>;
/// Size of a [`Span`]'s `offset` field.
pub type SpanOffsetSize = global::SourceFileSize;
/// Size of a [`Span`]'s `len` field.
pub type SpanLenSize = global::FrontendTokenLength;
/// Description of a source location and byte interval for some object.
///
/// Spans represent byte intervals within a given source context.
/// A span should map to useful positions for helping users debug error
/// messages.
/// If code is generated, desugared, or otherwise manipulated,
/// the span ought to reference the original location of the code that can
/// be referenced and modified to correct any problems.
///
/// See the [module-level documentation](self) for more information.
#[cfg(target_endian = "little")]
#[repr(packed)]
#[derive(Debug, Clone, Copy)]
pub struct Span {
/// Token length (ending byte offset - `offset`).
len: SpanLenSize,
/// Starting 0-indexed byte position, inclusive.
offset: SpanOffsetSize,
/// Context onto which byte offsets are mapped,
/// such as a source file.
///
/// N.B.: This is an unaligned field,
/// and accessing it frequently may have a negative impact on
/// performance.
ctx: Context,
}
assert_eq_size!(Span, Option<Span>);
impl Span {
/// Create a new span from its constituent parts.
pub fn new<C: Into<Context>>(
offset: SpanOffsetSize,
len: SpanLenSize,
ctx: C,
) -> Self {
Self {
ctx: ctx.into(),
offset,
len,
}
}
/// Create a constant span from a static context.
pub const fn st_ctx(sym: ContextStaticSymbolId) -> Self {
Self {
ctx: Context(sym.as_sym()),
offset: 0,
len: 0,
}
}
/// Create a span from a byte interval and context.
///
/// Panics
/// ======
/// This will panic in the unlikely case that the difference between the
/// start and end of the interval exceeds the maximum of
/// [`global::FrontendTokenLength`].
///
/// If this error occurs,
/// the parser should consider splitting large tokens up into multiple
/// tokens;
/// increasing [`global::FrontendTokenLength`] should be a last
/// resort,
/// since it has wide-reaching implications on the size of
/// [`Span`].
///
/// The user is not expected to know how to recover from this error
/// without debugging the compiler.
/// It is not expected that this would occur on any valid inputs.
pub fn from_byte_interval<B, C>(interval: B, ctx: C) -> Self
where
B: Into<ClosedByteInterval>,
C: Into<Context>,
{
let binterval = interval.into();
Self {
offset: binterval.0,
len: (binterval.1 - binterval.0)
.try_into()
.expect("span length exceeds global::FrontendTokenLength"),
ctx: ctx.into(),
}
}
// A span represented uniquely as a totally ordered [`u64`].
//
// For more information on this important properly,
// see the documentation for [`Span`] itself.
pub fn as_u64(self) -> u64 {
// We take a number of precautions to make this safe (in the sense
// of correctness),
// through struct packing and a `cfg` directive for endianness.
// In any case,
// a `u64` isn't going to harm anyone.
unsafe { std::mem::transmute(self) }
}
/// Byte offset of the beginning of the span relative to its context.
pub fn offset(&self) -> SpanOffsetSize {
self.offset
}
/// Length of the span in bytes.
///
/// The interval of the span is `[offset, offset+len]`.
pub fn len(&self) -> SpanLenSize {
self.len
}
/// The context to which the span applies.
///
/// The context is, for example, a file.
pub fn context(&self) -> Context {
self.ctx
}
/// Further offset a span.
///
/// This attempts to offset a span relative to its current offset by the
/// provided value.
/// If the resulting offset exceeds [`SpanOffsetSize`],
/// the result will be [`None`].
pub const fn offset_add(self, value: SpanOffsetSize) -> Option<Self> {
match self.offset.checked_add(value) {
Some(offset) => Some(Self { offset, ..self }),
None => None,
}
}
/// Create two zero-length spans representing respectively the first and
/// last offsets in the span.
///
/// The second endpoint will be [`None`] if the offset cannot be
/// represented by [`SpanOffsetSize`].
///
/// ```
/// # use tamer::span::{Span, Context};
/// # use tamer::sym::GlobalSymbolIntern;
/// #
/// # let ctx: Context = "some/path/foo".intern().into();
/// #
/// // [0123456789]
/// // [---]
/// // 2 6
/// // A
/// let A = Span::new(2, 6, ctx);
///
/// assert_eq!(
/// A.endpoints(),
/// (
/// Span::new(2, 0, ctx),
/// Some(Span::new(8, 0, ctx)),
/// ),
/// );
/// ```
pub const fn endpoints(self) -> (Self, Option<Self>) {
(
// First endpoint.
Self {
offset: self.offset,
len: 0,
..self
},
// Second endpoint.
match self.offset.checked_add(self.len as u32) {
Some(offset) => Some(Self {
offset,
len: 0,
..self
}),
None => None,
},
)
}
/// Create two zero-length spans representing respectively the first and
/// last offsets in the span,
/// saturating the ending offset if it cannot be represented by
/// [`SpanOffsetSize`].
///
/// Aside from the saturation,
/// this is identical to [`Span::endpoints`].
pub fn endpoints_saturated(self) -> (Self, Self) {
let endpoints = self.endpoints();
(
endpoints.0,
endpoints.1.unwrap_or(Self {
offset: SpanOffsetSize::MAX,
..endpoints.0
}),
)
}
/// Create a new span that is a slice of this one.
///
/// If either `rel_offset` or `len` are too large,
/// then a copy of the span will be returned unsliced.
///
/// Panics (Debug Mode)
/// -------------------
/// If the offset and length exceeds the bounds of the span,
/// then the system has an arithmetic bug that ought to be corrected,
/// and so this will panic with a diagnostic message.
/// This check does not occur on release builds since this is not a
/// safety issue and should be caught by tests.
pub fn slice(self, rel_offset: usize, len: usize) -> Self {
let (irel_offset, ilen) = match (rel_offset.try_into(), len.try_into())
{
(Ok(x), Ok(y)) => (x, y),
_ => (0, self.len()),
};
// We shouldn't ignore slices that exceed the length of the span,
// since this represents a bug that'll cause nonsense diagnostic
// data and it represents an arithmetic bug in the system
// (but there are no safety concerns).
if ((irel_offset as usize).saturating_add(ilen as usize))
> self.len() as usize
{
use crate::diagnose::Annotate;
debug_diagnostic_panic!(
self.error("attempting to slice this span").into(),
"length {len} at offset {rel_offset} \
exceeds bounds of span {self}",
);
}
Self {
ctx: self.ctx,
offset: self.offset.saturating_add(irel_offset),
len: ilen,
}
}
/// Adjust span such that its offset is relative to the provided span.
///
/// If the provide `rel_span` does not precede this span,
/// [`None`] will be returned.
///
/// If the two spans do not share the same [`Context`],
/// no comparison can be made and [`None`] will be returned.
pub fn relative_to(self, rel_span: Span) -> Option<Self> {
// Note that this is unaligned.
if self.context() != rel_span.context() {
return None;
}
if self.offset() < rel_span.offset() {
return None;
}
Some(Self {
ctx: self.ctx,
offset: self.offset.saturating_sub(rel_span.offset),
len: self.len,
})
}
/// Merge with another span `b` such that the combined span begins at
/// the offset of the earlier of the two spans and extends to the end
/// of the later of the two.
///
/// Both spans must have the same [`Context`],
/// otherwise the result will be [`None`].
/// Merged values beyond [`SpanOffsetSize`] and [`SpanLenSize`] will
/// also result in [`None`].
///
/// This properly handles overlapping spans,
/// including the case where one of the spans is entirely contained
/// within another.
/// See test cases for more information.
/// (TODO: Maybe we should move the test cases into these docs?)
pub fn merge<S: Into<Span>>(self, other: S) -> Option<Span> {
let b = other.into();
if self.context() != b.context() {
return None;
}
// Order arguments such that `self` is placed at or before `b`
// rather than having to worry about confounding accommodations
// below.
if self.offset() > b.offset() {
return b.merge(self);
}
let (_, end) = b.endpoints();
end.and_then(|Span { offset, .. }| {
SpanLenSize::try_from(offset - self.offset).ok()
})
.map(|new_len| Self {
ctx: self.ctx,
offset: self.offset,
len: self.len.max(new_len),
})
}
}
impl From<Span> for u64 {
fn from(val: Span) -> Self {
val.as_u64()
}
}
impl PartialEq for Span {
fn eq(&self, other: &Self) -> bool {
self.as_u64() == other.as_u64()
}
}
impl Eq for Span {}
impl PartialOrd for Span {
fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
Some(self.cmp(other))
}
}
impl Ord for Span {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
self.as_u64().cmp(&other.as_u64())
}
}
// This assertion verifies our above expectations.
// If this fails,
// then you have either modified [`global`] constants or you have modified
// the fields of [`Span`] itself,
// in which case you should read "Related Work" above to determine
// whether this was a good idea or if interned spans should be
// introduced.
// In any case,
// hopefully this was planned for,
// because otherwise your week has just been ruined.
assert_eq_size!(Span, u64);
impl From<Span> for (Span, Span) {
/// Expand a [`Span`] into a two-span.
///
/// A two-span `(A, B)` is equivalent to a span beginning at the start
/// of `A` and ending at the end of `B`.
///
/// We gain no resolution from performing this operation,
/// but it does allow for using a single span in contexts where a
/// higher resolution is supported.
fn from(span: Span) -> Self {
(span, span)
}
}
impl Display for Span {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// Needed to avoid unaligned references since Span is packed.
let ctx = self.ctx;
let offset = self.offset as usize;
let end = offset + self.len as usize;
// Very primitive information to begin with; we'll have something
// more useful in the future.
write!(f, "[{} offset {}-{}]", ctx, offset, end)
}
}
/// A placeholder span indicating that a span is expected but is not yet
/// known.
pub const UNKNOWN_SPAN: Span = Span::st_ctx(st16::CTX_UNKNOWN);
/// Context for byte offsets (e.g. a source file).
///
/// A context is lifetime-free and [`Copy`]-able,
/// with the assumption that an interned [`PathSymbolId`] will only need
/// to be resolved to its underlying value in a diagnostic context where
/// the internment system is readily available.
///
/// Since this is used within [`Span`],
/// it must be kept as small as possible.
#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
pub struct Context(PathSymbolId);
impl Context {
/// Produce a [`Span`] within the given context.
#[inline]
pub const fn span(self, offset: SpanOffsetSize, len: SpanLenSize) -> Span {
Span {
ctx: self,
offset,
len,
}
}
/// Attempt to produce a [`Span`] of the given length at the given
/// offset,
/// otherwise fall back to a `(0,0)` (ZZ) span.
///
/// If the offset cannot be stored,
/// then the length will always be `0` even if it could otherwise be
/// represented;
/// `(0,0)` indicates no span,
/// whereas `(0,N)` would indicate a span of length `N` at
/// offset `0`,
/// which would not be true.
///
/// If the offset can be represented but not the length,
/// then a zero-length span at that offset will be produced,
/// which still provides useful information.
/// This may be the case for very large objects,
/// like compiled text fragments.
///
/// The rationale here is that spans are intended to be informative.
/// If we are unable to provide that information due to exceptional
/// circumstances
/// (very large file or very large token),
/// then it's better to provide _some_ information than to bail out
/// with an error and interrupt the entire process,
/// potentially masking errors in the process.
#[inline]
pub fn span_or_zz(self, offset: usize, len: usize) -> Span {
self.span(offset.try_into().unwrap_or(0), len.try_into().unwrap_or(0))
}
}
/// A placeholder context indicating that a context is expected but is not
/// yet known.
pub const UNKNOWN_CONTEXT: Context = Context(st16::raw::CTX_UNKNOWN);
impl<P: Into<PathSymbolId>> From<P> for Context {
fn from(sym: P) -> Self {
Self(sym.into())
}
}
impl Display for Context {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.0.fmt(f)
}
}
impl AsRef<Path> for Context {
fn as_ref(&self) -> &Path {
Path::new(self.0.lookup_str())
}
}
/// A closed interval (range of values including its endpoints) representing
/// source bytes associated with a token.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct ClosedByteInterval<T = SpanOffsetSize>(pub T, pub T)
where
T: Copy + PartialOrd;
impl<T: Copy + PartialOrd> From<(T, T)> for ClosedByteInterval<T> {
/// Convert a tuple into a closed byte interval where the first index
/// represents the start of the interval and the second index the
/// end.
///
/// Panics
/// ======
/// The second value must be ≥ the first.
fn from(src: (T, T)) -> Self {
assert!(src.1 >= src.0);
Self(src.0, src.1)
}
}
assert_eq_size!(ClosedByteInterval, u64);
/// Dummy spans for testing.
#[cfg(test)]
pub mod dummy {
use super::{st16, Context, Span};
/// A dummy span that can be used in contexts where a span is expected
/// but is not important.
///
/// This is intended primarily for tests;
/// you should always use an appropriate span to permit sensible error
/// messages and source analysis.
/// For spans that are actually unknown,
/// use [`super::UNKNOWN_SPAN`].
///
/// Additional dummy spans can be derived from this one.
pub const DUMMY_SPAN: Span = Span::st_ctx(st16::CTX_DUMMY);
/// A dummy context that can be used where a span is expected but is not
/// important.
///
/// This is intended primarily for tests;
/// you should always use an appropriate span to permit sensible error
/// messages and source analysis.
/// For contexts that are actually unknown,
/// use [`super::UNKNOWN_CONTEXT`].
///
/// See also [`UNKNOWN_CONTEXT`].
pub const DUMMY_CONTEXT: Context = Context(st16::raw::CTX_DUMMY);
// This name is for brevity;
// we don't want to expose it because we don't want anyone to assume
// that a different name means that it's somehow different from
// `DUMMY_SPAN`.
const S0: Span = DUMMY_SPAN;
pub const S1: Span = S0.offset_add(1).unwrap();
pub const S2: Span = S0.offset_add(2).unwrap();
pub const S3: Span = S0.offset_add(3).unwrap();
pub const S4: Span = S0.offset_add(4).unwrap();
pub const S5: Span = S0.offset_add(5).unwrap();
pub const S6: Span = S0.offset_add(6).unwrap();
pub const S7: Span = S0.offset_add(7).unwrap();
pub const S8: Span = S0.offset_add(8).unwrap();
pub const S9: Span = S0.offset_add(9).unwrap();
pub const S10: Span = S0.offset_add(10).unwrap();
pub const S11: Span = S0.offset_add(11).unwrap();
pub const S12: Span = S0.offset_add(12).unwrap();
pub const S13: Span = S0.offset_add(13).unwrap();
pub const S14: Span = S0.offset_add(14).unwrap();
pub const S15: Span = S0.offset_add(15).unwrap();
pub const S16: Span = S0.offset_add(16).unwrap();
pub const S17: Span = S0.offset_add(17).unwrap();
pub const S18: Span = S0.offset_add(18).unwrap();
pub const S19: Span = S0.offset_add(19).unwrap();
pub const S20: Span = S0.offset_add(20).unwrap();
}
#[cfg(test)]
mod test {
use super::*;
// Little endian check.
//
// This ensures that the byte ordering is as expected,
// otherwise the resulting integer will not have the properties we
// require for sorting and comparison.
#[cfg(target_endian = "little")]
#[test]
fn span_pack_le() {
let span =
Span::new(0xA3A2A1A0, 0xB1B0, SymbolId::test_from_int(0xC1C0));
assert_eq!(
0xC1C0_A3A2A1A0_B1B0,
// ^ ^ ^
// ctx offset len
span.as_u64(),
"endianness check failed: {:X?}",
span.as_u64()
);
}
#[cfg(target_endian = "big")]
#[test]
fn span_pack_be_not_supported() {
panic!("Big-endian systems are not currently supported");
}
// The tests that follow are corollaries of the above, but the below
// tests do test that the implementations function as intended.
#[test]
fn span_at_later_offset_in_same_context_compares_greater() {
let ctx = Context::from("imaginary");
let first = ctx.span(10, 5);
let second = ctx.span(20, 5);
// These two assertions must be identical.
assert!(second > first);
assert!(second.as_u64() > first.as_u64());
}
#[test]
fn spans_order_by_context_start_and_len() {
let ctxa = Context::from("context a");
let ctxb = Context::from("context b");
// Sanity check, otherwise this test won't work as expected.
assert!(ctxa.0 < ctxb.0);
let sa1 = ctxa.span(10, 1);
let sa2 = ctxa.span(22, 1);
let sa3 = ctxa.span(35, 1);
let sb1 = ctxb.span(11, 1);
let sb2 = ctxb.span(20, 1);
let sb3 = ctxb.span(33, 1);
let mut spans = vec![sa3, sb2, sb1, sa2, sa1, sb3];
spans.sort();
assert_eq!(spans, vec![sa1, sa2, sa3, sb1, sb2, sb3]);
}
#[test]
fn retrieve_span_components() {
let ctx = Context::from("foo");
let offset = 100;
let len = 50;
let span = ctx.span(offset, len);
assert_eq!(
(offset, len, ctx),
(span.offset(), span.len(), span.context())
);
}
#[test]
fn span_offset_add() {
let ctx = Context::from("addtest");
let offset = 10;
let len = 5;
let span = ctx.span(offset, len);
// Successful add.
assert_eq!(
span.offset_add(10),
Some(Span {
offset: offset + 10,
len,
ctx
})
);
// Fail, do not wrap.
assert_eq!(span.offset_add(SpanOffsetSize::MAX), None);
}
#[test]
fn span_into_twospan() {
let ctx = Context::from("foo");
let span = ctx.span(10, 50);
assert_eq!((span, span), span.into());
}
#[test]
fn span_endpoints() {
let ctx = Context::from("end");
let span = ctx.span(10, 20);
let (start, end) = span.endpoints();
assert_eq!(start, Span::new(10, 0, ctx));
assert_eq!(end, Some(Span::new(30, 0, ctx)));
}
#[test]
fn span_endpoints_exceeding_max_offset() {
let ctx = Context::from("end");
let offset = SpanOffsetSize::MAX - 5;
let span = ctx.span(offset, 10);
let (start, end) = span.endpoints();
assert_eq!(start, Span::new(offset, 0, ctx));
assert_eq!(end, None);
}
#[test]
fn span_endpoints_saturated() {
let ctx = Context::from("end");
let offset = SpanOffsetSize::MAX - 5;
let span = ctx.span(offset, 10);
let (start, end) = span.endpoints_saturated();
assert_eq!(start, Span::new(offset, 0, ctx));
assert_eq!(end, Span::new(SpanOffsetSize::MAX, 0, ctx));
}
#[test]
fn span_slice_yields_slice_within_original() {
let ctx = Context::from("slice");
let span = ctx.span(10, 10);
assert_eq!(ctx.span(15, 5), span.slice(5, 5));
}
#[test]
fn span_slice_large_values_yield_original() {
let span = Context::from("slice").span(0, 50);
// Too large of an offset should return original even though legnth
// is okay.
assert_eq!(span, span.slice(usize::MAX, 5));
// Too large of length should return original even though offset is
// okay.
assert_eq!(span, span.slice(0, usize::MAX));
}
#[test]
fn span_merge_one_after_other() {
let ctx = Context::from("merge");
// "an example string"
// [-----] [----]
// 3 9 11 16
// | A B |
// [------------]
// 3 16
// C
let a = ctx.span(3, 7);
let b = ctx.span(11, 6);
let c = ctx.span(3, 14);
assert_eq!(a.merge(b), Some(c));
assert_eq!(b.merge(a), Some(c));
}
#[test]
fn span_merge_overlap() {
let ctx = Context::from("merge");
// "an example string"
// [---+-] |
// 3 | 9 |
// | A| |
// | [--------]
// | 7 16
// | B |
// [------------]
// 3 16
// C
let a = ctx.span(3, 7);
let b = ctx.span(7, 10);
let c = ctx.span(3, 14);
// We compare in both orders,
// so this will test when a span overlaps on either side.
assert_eq!(a.merge(b), Some(c));
assert_eq!(b.merge(a), Some(c));
}
#[test]
fn span_merge_overlap_within() {
let ctx = Context::from("merge");
// "an example string"
// |[----] |
// |1 6 |
// | B |
// [--------]
// 0 9
// C
let b = ctx.span(1, 6);
let c = ctx.span(0, 10);
assert_eq!(b.merge(c), Some(c));
assert_eq!(c.merge(b), Some(c));
}
// It doesn't make sense to merge two spans that are located in
// different contexts.
#[test]
fn span_merge_different_contexts() {
let ctx_a = Context::from("merge_a");
let ctx_b = Context::from("merge_b");
assert_eq!(ctx_a.span(0, 1).merge(ctx_b.span(1, 2)), None);
}
}
View Git Blame Copy Permalink