53 lines
1.4 KiB
Rust
53 lines
1.4 KiB
Rust
//! Define the `Location`, `ParseError`, and `ParseResult` types.
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#![macro_use]
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use std::fmt;
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/// The location of a `Token` or `Error`.
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
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pub struct Location {
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/// Line number. Command-line arguments are line 0 and source file
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/// lines start from 1.
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pub line_number: usize,
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}
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/// A parse error is returned when the parse failed.
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#[derive(Debug)]
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pub struct ParseError {
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/// Location of the error.
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pub location: Location,
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/// Error message.
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pub message: String,
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}
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impl fmt::Display for ParseError {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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if self.location.line_number == 0 {
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write!(f, "command-line arguments: {}", self.message)
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} else {
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write!(f, "{}: {}", self.location.line_number, self.message)
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}
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}
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}
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/// Result of a parser operation. The `ParseError` variant includes a location.
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pub type ParseResult<T> = Result<T, ParseError>;
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// Create an `Err` variant of `ParseResult<X>` from a location and `format!` args.
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macro_rules! err {
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( $loc:expr, $msg:expr ) => {
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Err($crate::ParseError {
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location: $loc.clone(),
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message: $msg.to_string(),
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})
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};
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( $loc:expr, $fmt:expr, $( $arg:expr ),+ ) => {
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Err($crate::ParseError {
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location: $loc.clone(),
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message: format!( $fmt, $( $arg ),+ ),
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})
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};
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}
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