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use std::fmt::{self, Debug, Formatter};
use std::num::NonZeroU64;
use crate::syntax::SourceId;
/// A value with the span it corresponds to in the source code.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct Spanned<T> {
/// The spanned value.
pub v: T,
/// The location in source code of the value.
pub span: Span,
}
impl<T> Spanned<T> {
/// Create a new instance from a value and its span.
pub fn new(v: T, span: impl Into<Span>) -> Self {
Self { v, span: span.into() }
}
/// Convert from `&Spanned<T>` to `Spanned<&T>`
pub fn as_ref(&self) -> Spanned<&T> {
Spanned { v: &self.v, span: self.span }
}
/// Map the value using a function keeping the span.
pub fn map<F, U>(self, f: F) -> Spanned<U>
where
F: FnOnce(T) -> U,
{
Spanned { v: f(self.v), span: self.span }
}
}
impl<T: Debug> Debug for Spanned<T> {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
self.v.fmt(f)
}
}
/// A unique identifier for a syntax node.
///
/// This is used throughout the compiler to track which source section an error
/// or element stems from. Can be mapped back to a source id + byte range for
/// user facing display.
///
/// Node ids are ordered in the tree to enable quickly finding the node with
/// some id:
/// - The id of a parent is always smaller than the ids of any of its children.
/// - The id of a node is always greater than any id in the subtrees of any left
/// sibling and smaller than any id the subtrees of any right sibling.
///
/// Node ids stay mostly stable, even for nodes behind an insertion. This is not
/// true for simple spans/ranges as they shift. Node ids can be used as inputs
/// to memoized functions without hurting cache performance when text is
/// inserted somewhere in the document other than the end.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct Span(NonZeroU64);
impl Span {
/// Create a new span from a source id and a unique number.
pub const fn new(id: SourceId, number: u64) -> Self {
assert!(number > 0 && number < (1 << 48));
let bits = ((id.into_raw() as u64) << 48) | number;
Self(nonzero(bits))
}
/// A node that does not belong to any source file.
pub const fn detached() -> Self {
Self(nonzero(1))
}
/// The id of the source file the span points into.
pub const fn source(self) -> SourceId {
SourceId::from_raw((self.0.get() >> 48) as u16)
}
}
/// Convert to a non zero u64.
const fn nonzero(v: u64) -> NonZeroU64 {
match NonZeroU64::new(v) {
Some(v) => v,
None => unreachable!(),
}
}
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