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use alloc::string::String;
use core::fmt::{Display, Error, Formatter};

/// Type of the parser result.
pub type PResult<T> = Result<T, PError>;

/// The error of parser handling, returned by [`Parser`](super::Parser).
///
/// Please see [module level document](super) for more error information.
#[derive(Debug)]
pub enum PError {
    /// If parser mismatched, just choose another one.
    Mismatch,
    /// The parser is the only one can be matched.
    Terminate {
        /// Name of sub-parser group.
        name: &'static str,
        /// Document position.
        msg: String,
    },
}

impl Display for PError {
    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
        match self {
            Self::Mismatch => write!(f, "not matched"),
            Self::Terminate { name, msg } => {
                write!(f, "invalid {}: \n\n{}", name, msg)
            }
        }
    }
}