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use core::convert::Infallible;
use core::fmt;
/// Errors raised while building a tree.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[non_exhaustive]
pub enum Error<E = Infallible> {
/// Error raised by [Builder::close][crate::Builder::close] if there
/// currently is no node being built.
///
/// # Examples
///
/// ```
/// use syntree::{Builder, Error};
///
/// let mut tree = Builder::new();
///
/// tree.open("root")?;
/// tree.close()?;
///
/// // Syntax::Root and Syntax::Child is left open.
/// assert_eq!(tree.close(), Err(Error::CloseError));
/// # Ok::<_, Box<dyn core::error::Error>>(())
/// ```
CloseError,
/// Error raised by [Builder::build][crate::Builder::build] if the
/// tree isn't correctly balanced.
///
/// # Examples
///
/// ```
/// use syntree::{Builder, Error};
///
/// let mut tree = Builder::new();
///
/// tree.open("number")?;
/// tree.token("lit", 3)?;
/// tree.close()?;
///
/// tree.open("number")?;
///
/// // Syntax::Number is left open.
/// assert_eq!(tree.build(), Err(Error::BuildError));
/// # Ok::<_, Box<dyn core::error::Error>>(())
/// ```
BuildError,
/// Error raised by [Builder::close_at][crate::Builder::close_at] if
/// we're not trying to close at a sibling node.
///
/// # Examples
///
/// ```
/// use syntree::{Builder, Error};
///
/// let mut tree = Builder::new();
///
/// let c = tree.checkpoint()?;
///
/// tree.open("child")?;
/// tree.token("token", 3)?;
///
/// assert_eq!(tree.close_at(&c, "operation"), Err(Error::CloseAtError));
/// # Ok::<_, Box<dyn core::error::Error>>(())
/// ```
CloseAtError,
/// Numerical overflow.
///
/// This only happens under extreme circumstances or if a feature is enabled
/// which narrows the width of an identifier to the degree that this error
/// is easier to accomplish.
///
/// # Examples
///
/// This is an example where we're trying to build a really small tree using
/// u8 pointers:
///
/// ```
/// use syntree::{Builder, Error};
///
/// syntree::flavor! {
/// struct CustomFlavor {
/// type Index = u32;
/// type Width = u8;
/// }
/// }
///
/// let mut tree: Builder<_, CustomFlavor> = Builder::new_with();
///
/// for d in 0..u8::MAX {
/// tree.token(d, 1)?;
/// }
///
/// assert_eq!(tree.token(255, 1), Err(Error::Overflow));
/// # Ok::<_, Box<dyn core::error::Error>>(())
/// ```
Overflow,
/// The node of the given id is missing.
///
/// # Examples
///
/// The following showcases what could happen if you mix checkpoints from
/// two compatible trees:
///
/// ```
/// use syntree::{Builder, Error};
///
/// let mut a = Builder::new();
/// let mut b = Builder::new();
///
/// b.open("child")?;
/// b.close()?;
///
/// let c = b.checkpoint()?;
///
/// assert_eq!(a.close_at(&c, "operation"), Err(Error::MissingNode(0)));
/// # Ok::<_, Box<dyn core::error::Error>>(())
/// ```
MissingNode(usize),
/// An error raised by the particular [Flavor] in use.
///
/// [Flavor]: crate::Flavor
Flavor(E),
}
impl<E> From<E> for Error<E> {
#[inline]
fn from(error: E) -> Self {
Error::Flavor(error)
}
}
impl<E> core::error::Error for Error<E>
where
E: 'static + core::error::Error,
{
#[inline]
fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
match self {
Error::Flavor(error) => Some(error),
_ => None,
}
}
}
impl<E> fmt::Display for Error<E>
where
E: fmt::Display,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Error::CloseError => {
write!(f, "no node being built")
}
Error::BuildError => {
write!(f, "tree is currently being built")
}
Error::CloseAtError => {
write!(
f,
"trying to close a node which is not a sibling of the checkpoint being closed"
)
}
Error::Overflow => {
write!(f, "numerical overflow")
}
Error::MissingNode(p) => {
write!(f, "missing node with id `{p}`")
}
Error::Flavor(error) => error.fmt(f),
}
}
}