litrs/
err.rs

1use std::{fmt, ops::Range};
2
3
4/// An error signaling that a different kind of token was expected. Returned by
5/// the various `TryFrom` impls.
6#[derive(Debug, Clone, Copy)]
7pub struct InvalidToken {
8    pub(crate) expected: TokenKind,
9    pub(crate) actual: TokenKind,
10    pub(crate) span: Span,
11}
12
13impl InvalidToken {
14    /// Returns a token stream representing `compile_error!("msg");` where
15    /// `"msg"` is the output of `self.to_string()`. **Panics if called outside
16    /// of a proc-macro context!**
17    pub fn to_compile_error(&self) -> proc_macro::TokenStream {
18        use proc_macro::{Delimiter, Ident, Group, Punct, Spacing, TokenTree};
19
20        let span = match self.span {
21            Span::One(s) => s,
22            #[cfg(feature = "proc-macro2")]
23            Span::Two(s) => s.unwrap(),
24        };
25        let msg = self.to_string();
26        let tokens = vec![
27            TokenTree::from(Ident::new("compile_error", span)),
28            TokenTree::from(Punct::new('!', Spacing::Alone)),
29            TokenTree::from(Group::new(
30                Delimiter::Parenthesis,
31                TokenTree::from(proc_macro::Literal::string(&msg)).into(),
32            )),
33        ];
34
35
36        tokens.into_iter().map(|mut t| { t.set_span(span); t }).collect()
37    }
38
39    /// Like [`to_compile_error`][Self::to_compile_error], but returns a token
40    /// stream from `proc_macro2` and does not panic outside of a proc-macro
41    /// context.
42    #[cfg(feature = "proc-macro2")]
43    pub fn to_compile_error2(&self) -> proc_macro2::TokenStream {
44        use proc_macro2::{Delimiter, Ident, Group, Punct, Spacing, TokenTree};
45
46        let span = match self.span {
47            Span::One(s) => proc_macro2::Span::from(s),
48            Span::Two(s) => s,
49        };
50        let msg = self.to_string();
51        let tokens = vec![
52            TokenTree::from(Ident::new("compile_error", span)),
53            TokenTree::from(Punct::new('!', Spacing::Alone)),
54            TokenTree::from(Group::new(
55                Delimiter::Parenthesis,
56                TokenTree::from(proc_macro2::Literal::string(&msg)).into(),
57            )),
58        ];
59
60
61        tokens.into_iter().map(|mut t| { t.set_span(span); t }).collect()
62    }
63}
64
65impl std::error::Error for InvalidToken {}
66
67impl fmt::Display for InvalidToken {
68    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
69        fn kind_desc(kind: TokenKind) -> &'static str {
70            match kind {
71                TokenKind::Punct => "a punctuation character",
72                TokenKind::Ident => "an identifier",
73                TokenKind::Group => "a group",
74                TokenKind::Literal => "a literal",
75                TokenKind::BoolLit => "a bool literal (`true` or `false`)",
76                TokenKind::ByteLit => "a byte literal (e.g. `b'r')",
77                TokenKind::ByteStringLit => r#"a byte string literal (e.g. `b"fox"`)"#,
78                TokenKind::CharLit => "a character literal (e.g. `'P'`)",
79                TokenKind::FloatLit => "a float literal (e.g. `3.14`)",
80                TokenKind::IntegerLit => "an integer literal (e.g. `27`)",
81                TokenKind::StringLit => r#"a string literal (e.g. "Ferris")"#,
82            }
83        }
84
85        write!(f, "expected {}, but found {}", kind_desc(self.expected), kind_desc(self.actual))
86    }
87}
88
89#[derive(Debug, Clone, Copy, PartialEq, Eq)]
90pub(crate) enum TokenKind {
91    Punct,
92    Ident,
93    Group,
94    Literal,
95    BoolLit,
96    ByteLit,
97    ByteStringLit,
98    CharLit,
99    FloatLit,
100    IntegerLit,
101    StringLit,
102}
103
104/// Unfortunately, we have to deal with both cases.
105#[derive(Debug, Clone, Copy)]
106pub(crate) enum Span {
107    One(proc_macro::Span),
108    #[cfg(feature = "proc-macro2")]
109    Two(proc_macro2::Span),
110}
111
112impl From<proc_macro::Span> for Span {
113    fn from(src: proc_macro::Span) -> Self {
114        Self::One(src)
115    }
116}
117
118#[cfg(feature = "proc-macro2")]
119impl From<proc_macro2::Span> for Span {
120    fn from(src: proc_macro2::Span) -> Self {
121        Self::Two(src)
122    }
123}
124
125/// Errors during parsing.
126///
127/// This type should be seen primarily for error reporting and not for catching
128/// specific cases. The span and error kind are not guaranteed to be stable
129/// over different versions of this library, meaning that a returned error can
130/// change from one version to the next. There are simply too many fringe cases
131/// that are not easy to classify as a specific error kind. It depends entirely
132/// on the specific parser code how an invalid input is categorized.
133///
134/// Consider these examples:
135/// - `'\` can be seen as
136///     - invalid escape in character literal, or
137///     - unterminated character literal.
138/// - `'''` can be seen as
139///     - empty character literal, or
140///     - unescaped quote character in character literal.
141/// - `0b64` can be seen as
142///     - binary integer literal with invalid digit 6, or
143///     - binary integer literal with invalid digit 4, or
144///     - decimal integer literal with invalid digit b, or
145///     - decimal integer literal 0 with unknown type suffix `b64`.
146///
147/// If you want to see more if these examples, feel free to check out the unit
148/// tests of this library.
149///
150/// While this library does its best to emit sensible and precise errors, and to
151/// keep the returned errors as stable as possible, full stability cannot be
152/// guaranteed.
153#[derive(Debug, Clone)]
154pub struct ParseError {
155    pub(crate) span: Option<Range<usize>>,
156    pub(crate) kind: ParseErrorKind,
157}
158
159impl ParseError {
160    /// Returns a span of this error, if available. **Note**: the returned span
161    /// might change in future versions of this library. See [the documentation
162    /// of this type][ParseError] for more information.
163    pub fn span(&self) -> Option<Range<usize>> {
164        self.span.clone()
165    }
166}
167
168/// This is a free standing function instead of an associated one to reduce
169/// noise around parsing code. There are lots of places that create errors, we
170/// I wanna keep them as short as possible.
171pub(crate) fn perr(span: impl SpanLike, kind: ParseErrorKind) -> ParseError {
172    ParseError {
173        span: span.into_span(),
174        kind,
175    }
176}
177
178pub(crate) trait SpanLike {
179    fn into_span(self) -> Option<Range<usize>>;
180}
181
182impl SpanLike for Option<Range<usize>> {
183    #[inline(always)]
184    fn into_span(self) -> Option<Range<usize>> {
185        self
186    }
187}
188impl SpanLike for Range<usize> {
189    #[inline(always)]
190    fn into_span(self) -> Option<Range<usize>> {
191        Some(self)
192    }
193}
194impl SpanLike for usize {
195    #[inline(always)]
196    fn into_span(self) -> Option<Range<usize>> {
197        Some(self..self + 1)
198    }
199}
200
201
202/// Kinds of errors.
203#[derive(Debug, Clone, Copy, PartialEq, Eq)]
204#[non_exhaustive]
205pub(crate) enum ParseErrorKind {
206    /// The input was an empty string
207    Empty,
208
209    /// An unexpected char was encountered.
210    UnexpectedChar,
211
212    /// Literal was not recognized.
213    InvalidLiteral,
214
215    /// Input does not start with decimal digit when trying to parse an integer.
216    DoesNotStartWithDigit,
217
218    /// A digit invalid for the specified integer base was found.
219    InvalidDigit,
220
221    /// Integer literal does not contain any valid digits.
222    NoDigits,
223
224    /// Exponent of a float literal does not contain any digits.
225    NoExponentDigits,
226
227    /// An unknown escape code, e.g. `\b`.
228    UnknownEscape,
229
230    /// A started escape sequence where the input ended before the escape was
231    /// finished.
232    UnterminatedEscape,
233
234    /// An `\x` escape where the two digits are not valid hex digits.
235    InvalidXEscape,
236
237    /// A string or character literal using the `\xNN` escape where `NN > 0x7F`.
238    NonAsciiXEscape,
239
240    /// A `\u{...}` escape in a byte or byte string literal.
241    UnicodeEscapeInByteLiteral,
242
243    /// A Unicode escape that does not start with a hex digit.
244    InvalidStartOfUnicodeEscape,
245
246    /// A `\u{...}` escape that lacks the opening brace.
247    UnicodeEscapeWithoutBrace,
248
249    /// In a `\u{...}` escape, a non-hex digit and non-underscore character was
250    /// found.
251    NonHexDigitInUnicodeEscape,
252
253    /// More than 6 digits found in unicode escape.
254    TooManyDigitInUnicodeEscape,
255
256    /// The value from a unicode escape does not represent a valid character.
257    InvalidUnicodeEscapeChar,
258
259    /// A `\u{..` escape that is not terminated (lacks the closing brace).
260    UnterminatedUnicodeEscape,
261
262    /// A character literal that's not terminated.
263    UnterminatedCharLiteral,
264
265    /// A character literal that contains more than one character.
266    OverlongCharLiteral,
267
268    /// An empty character literal, i.e. `''`.
269    EmptyCharLiteral,
270
271    UnterminatedByteLiteral,
272    OverlongByteLiteral,
273    EmptyByteLiteral,
274    NonAsciiInByteLiteral,
275
276    /// A `'` character was not escaped in a character or byte literal, or a `"`
277    /// character was not escaped in a string or byte string literal.
278    UnescapedSingleQuote,
279
280    /// A \n, \t or \r raw character in a char or byte literal.
281    UnescapedSpecialWhitespace,
282
283    /// When parsing a character, byte, string or byte string literal directly
284    /// and the input does not start with the corresponding quote character
285    /// (plus optional raw string prefix).
286    DoesNotStartWithQuote,
287
288    /// Unterminated raw string literal.
289    UnterminatedRawString,
290
291    /// String literal without a `"` at the end.
292    UnterminatedString,
293
294    /// Invalid start for a string literal.
295    InvalidStringLiteralStart,
296
297    /// Invalid start for a byte literal.
298    InvalidByteLiteralStart,
299
300    InvalidByteStringLiteralStart,
301
302    /// An literal `\r` character not followed by a `\n` character in a
303    /// (raw) string or byte string literal.
304    IsolatedCr,
305
306    /// Literal suffix is not a valid identifier.
307    InvalidSuffix,
308
309    /// Returned by `Float::parse` if an integer literal (no fractional nor
310    /// exponent part) is passed.
311    UnexpectedIntegerLit,
312
313    /// Integer suffixes cannot start with `e` or `E` as this conflicts with the
314    /// grammar for float literals.
315    IntegerSuffixStartingWithE,
316}
317
318impl std::error::Error for ParseError {}
319
320impl fmt::Display for ParseError {
321    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
322        use ParseErrorKind::*;
323
324        let description = match self.kind {
325            Empty => "input is empty",
326            UnexpectedChar => "unexpected character",
327            InvalidLiteral => "invalid literal",
328            DoesNotStartWithDigit => "number literal does not start with decimal digit",
329            InvalidDigit => "integer literal contains a digit invalid for its base",
330            NoDigits => "integer literal does not contain any digits",
331            NoExponentDigits => "exponent of floating point literal does not contain any digits",
332            UnknownEscape => "unknown escape",
333            UnterminatedEscape => "unterminated escape: input ended too soon",
334            InvalidXEscape => r"invalid `\x` escape: not followed by two hex digits",
335            NonAsciiXEscape => r"`\x` escape in char/string literal exceed ASCII range",
336            UnicodeEscapeInByteLiteral => r"`\u{...}` escape in byte (string) literal not allowed",
337            InvalidStartOfUnicodeEscape => r"invalid start of `\u{...}` escape",
338            UnicodeEscapeWithoutBrace => r"`Unicode \u{...}` escape without opening brace",
339            NonHexDigitInUnicodeEscape => r"non-hex digit found in `\u{...}` escape",
340            TooManyDigitInUnicodeEscape => r"more than six digits in `\u{...}` escape",
341            InvalidUnicodeEscapeChar => r"value specified in `\u{...}` escape is not a valid char",
342            UnterminatedUnicodeEscape => r"unterminated `\u{...}` escape",
343            UnterminatedCharLiteral => "character literal is not terminated",
344            OverlongCharLiteral => "character literal contains more than one character",
345            EmptyCharLiteral => "empty character literal",
346            UnterminatedByteLiteral => "byte literal is not terminated",
347            OverlongByteLiteral => "byte literal contains more than one byte",
348            EmptyByteLiteral => "empty byte literal",
349            NonAsciiInByteLiteral => "non ASCII character in byte (string) literal",
350            UnescapedSingleQuote => "character literal contains unescaped ' character",
351            UnescapedSpecialWhitespace => r"unescaped newline (\n), tab (\t) or cr (\r) character",
352            DoesNotStartWithQuote => "invalid start for char/byte/string literal",
353            UnterminatedRawString => "unterminated raw (byte) string literal",
354            UnterminatedString => "unterminated (byte) string literal",
355            InvalidStringLiteralStart => "invalid start for string literal",
356            InvalidByteLiteralStart => "invalid start for byte literal",
357            InvalidByteStringLiteralStart => "invalid start for byte string literal",
358            IsolatedCr => r"`\r` not immediately followed by `\n` in string",
359            InvalidSuffix => "literal suffix is not a valid identifier",
360            UnexpectedIntegerLit => "expected float literal, but found integer",
361            IntegerSuffixStartingWithE => "integer literal suffix must not start with 'e' or 'E'",
362        };
363
364        description.fmt(f)?;
365        if let Some(span) = &self.span {
366            write!(f, " (at {}..{})", span.start, span.end)?;
367        }
368
369        Ok(())
370    }
371}
litrs/err.rs

litrs/
err.rs
