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//! Spans map elements to the part of source code they originate from.
use std::fmt::{self, Debug, Formatter};
use std::ops::{Add, Sub};
use serde::Serialize;
/// Zero-indexed line-column position in source code.
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize)]
pub struct Position {
/// The zero-indexed line.
pub line: usize,
/// The zero-indexed column.
pub column: usize,
}
impl Position {
/// The line 0, column 0 position.
pub const ZERO: Position = Position { line: 0, column: 0 };
/// Crete a new instance from line and column.
pub fn new(line: usize, column: usize) -> Position {
Position { line, column }
}
}
impl Add for Position {
type Output = Position;
fn add(self, rhs: Position) -> Position {
if rhs.line == 0 {
Position {
line: self.line,
column: self.column + rhs.column
}
} else {
Position {
line: self.line + rhs.line,
column: rhs.column,
}
}
}
}
impl Sub for Position {
type Output = Position;
fn sub(self, rhs: Position) -> Position {
if self.line == rhs.line {
Position {
line: 0,
column: self.column - rhs.column
}
} else {
Position {
line: self.line - rhs.line,
column: self.column,
}
}
}
}
impl Debug for Position {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
write!(f, "{}:{}", self.line, self.column)
}
}
/// Locates a slice of source code.
#[derive(Copy, Clone, Eq, PartialEq, Hash, Serialize)]
pub struct Span {
/// The inclusive start position.
pub start: Position,
/// The inclusive end position.
pub end: Position,
}
impl Span {
/// A dummy span.
pub const ZERO: Span = Span { start: Position::ZERO, end: Position::ZERO };
/// Create a new span from start and end positions.
pub fn new(start: Position, end: Position) -> Span {
Span { start, end }
}
/// Create a new span with the earlier start and later end position.
pub fn merge(a: Span, b: Span) -> Span {
Span {
start: a.start.min(b.start),
end: a.end.max(b.end),
}
}
/// Create a span including just a single position.
pub fn at(pos: Position) -> Span {
Span { start: pos, end: pos }
}
/// Offset a span by a start position.
///
/// This is, for example, used to translate error spans from function local
/// to global.
pub fn offset(self, start: Position) -> Span {
Span {
start: start + self.start,
end: start + self.end,
}
}
}
impl Debug for Span {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
write!(f, "({:?} -> {:?})", self.start, self.end)
}
}
/// A value with the span it corresponds to in the source code.
#[derive(Copy, Clone, Eq, PartialEq, Hash, Serialize)]
pub struct Spanned<T> {
/// The value.
pub v: T,
/// The corresponding span.
pub span: Span,
}
impl<T> Spanned<T> {
/// Create a new instance from a value and its span.
pub fn new(v: T, span: Span) -> Spanned<T> {
Spanned { v, span }
}
/// Access the value.
pub fn value(self) -> T {
self.v
}
/// Map the value using a function while keeping the span.
pub fn map<V, F>(self, f: F) -> Spanned<V> where F: FnOnce(T) -> V {
Spanned { v: f(self.v), span: self.span }
}
/// Maps the span while keeping the value.
pub fn map_span<F>(mut self, f: F) -> Spanned<T> where F: FnOnce(Span) -> Span {
self.span = f(self.span);
self
}
}
impl<T: Debug> Debug for Spanned<T> {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
self.span.fmt(f)?;
f.write_str(": ")?;
self.v.fmt(f)
}
}
/// A vector of spanned things.
pub type SpanVec<T> = Vec<Spanned<T>>;
/// [Offset](Span::offset) all spans in a vector of spanned things by a start
/// position.
pub fn offset_spans<T>(start: Position, vec: SpanVec<T>) -> impl Iterator<Item=Spanned<T>> {
vec.into_iter()
.map(move |s| s.map_span(|span| span.offset(start)))
}
|
