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use std::borrow::Borrow;
use std::ops::Deref;
use unicode_xid::UnicodeXID;
use super::Span;
use crate::util::EcoString;
/// An unicode identifier with a few extra permissible characters.
///
/// In addition to what is specified in the [Unicode Standard][uax31], we allow:
/// - `_` as a starting character,
/// - `_` and `-` as continuing characters.
///
/// [uax31]: http://www.unicode.org/reports/tr31/
#[derive(Debug, Clone, PartialEq)]
pub struct Ident {
/// The source code location.
pub span: Span,
/// The identifier string.
pub string: EcoString,
}
impl Ident {
/// Create a new identifier from a string checking that it is a valid.
pub fn new(
string: impl AsRef<str> + Into<EcoString>,
span: impl Into<Span>,
) -> Option<Self> {
if is_ident(string.as_ref()) {
Some(Self { span: span.into(), string: string.into() })
} else {
None
}
}
/// Return a reference to the underlying string.
pub fn as_str(&self) -> &str {
self
}
}
impl Deref for Ident {
type Target = str;
fn deref(&self) -> &Self::Target {
self.string.as_str()
}
}
impl AsRef<str> for Ident {
fn as_ref(&self) -> &str {
self
}
}
impl Borrow<str> for Ident {
fn borrow(&self) -> &str {
self
}
}
impl From<&Ident> for EcoString {
fn from(ident: &Ident) -> Self {
ident.string.clone()
}
}
/// Whether a string is a valid identifier.
pub fn is_ident(string: &str) -> bool {
let mut chars = string.chars();
chars
.next()
.map_or(false, |c| is_id_start(c) && chars.all(is_id_continue))
}
/// Whether a character can start an identifier.
pub fn is_id_start(c: char) -> bool {
c.is_xid_start() || c == '_'
}
/// Whether a character can continue an identifier.
pub fn is_id_continue(c: char) -> bool {
c.is_xid_continue() || c == '_' || c == '-'
}
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