litrs/
err.rs

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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    fn into_span(self) -> Option<Range<usize>> {
184        self
185    }
186}
187impl SpanLike for Range<usize> {
188    fn into_span(self) -> Option<Range<usize>> {
189        Some(self)
190    }
191}
192impl SpanLike for usize {
193    fn into_span(self) -> Option<Range<usize>> {
194        Some(self..self + 1)
195    }
196}
197
198
199/// Kinds of errors.
200#[derive(Debug, Clone, Copy, PartialEq, Eq)]
201#[non_exhaustive]
202pub(crate) enum ParseErrorKind {
203    /// The input was an empty string
204    Empty,
205
206    /// An unexpected char was encountered.
207    UnexpectedChar,
208
209    /// Literal was not recognized.
210    InvalidLiteral,
211
212    /// Input does not start with decimal digit when trying to parse an integer.
213    DoesNotStartWithDigit,
214
215    /// A digit invalid for the specified integer base was found.
216    InvalidDigit,
217
218    /// Integer literal does not contain any valid digits.
219    NoDigits,
220
221    /// Found a integer type suffix that is invalid.
222    InvalidIntegerTypeSuffix,
223
224    /// Found a float type suffix that is invalid. Only `f32` and `f64` are
225    /// valid.
226    InvalidFloatTypeSuffix,
227
228    /// Exponent of a float literal does not contain any digits.
229    NoExponentDigits,
230
231    /// An unknown escape code, e.g. `\b`.
232    UnknownEscape,
233
234    /// A started escape sequence where the input ended before the escape was
235    /// finished.
236    UnterminatedEscape,
237
238    /// An `\x` escape where the two digits are not valid hex digits.
239    InvalidXEscape,
240
241    /// A string or character literal using the `\xNN` escape where `NN > 0x7F`.
242    NonAsciiXEscape,
243
244    /// A `\u{...}` escape in a byte or byte string literal.
245    UnicodeEscapeInByteLiteral,
246
247    /// A Unicode escape that does not start with a hex digit.
248    InvalidStartOfUnicodeEscape,
249
250    /// A `\u{...}` escape that lacks the opening brace.
251    UnicodeEscapeWithoutBrace,
252
253    /// In a `\u{...}` escape, a non-hex digit and non-underscore character was
254    /// found.
255    NonHexDigitInUnicodeEscape,
256
257    /// More than 6 digits found in unicode escape.
258    TooManyDigitInUnicodeEscape,
259
260    /// The value from a unicode escape does not represent a valid character.
261    InvalidUnicodeEscapeChar,
262
263    /// A `\u{..` escape that is not terminated (lacks the closing brace).
264    UnterminatedUnicodeEscape,
265
266    /// A character literal that's not terminated.
267    UnterminatedCharLiteral,
268
269    /// A character literal that contains more than one character.
270    OverlongCharLiteral,
271
272    /// An empty character literal, i.e. `''`.
273    EmptyCharLiteral,
274
275    UnterminatedByteLiteral,
276    OverlongByteLiteral,
277    EmptyByteLiteral,
278    NonAsciiInByteLiteral,
279
280    /// A `'` character was not escaped in a character or byte literal, or a `"`
281    /// character was not escaped in a string or byte string literal.
282    UnescapedSingleQuote,
283
284    /// A \n, \t or \r raw character in a char or byte literal.
285    UnescapedSpecialWhitespace,
286
287    /// When parsing a character, byte, string or byte string literal directly
288    /// and the input does not start with the corresponding quote character
289    /// (plus optional raw string prefix).
290    DoesNotStartWithQuote,
291
292    /// Unterminated raw string literal.
293    UnterminatedRawString,
294
295    /// String literal without a `"` at the end.
296    UnterminatedString,
297
298    /// Invalid start for a string literal.
299    InvalidStringLiteralStart,
300
301    /// Invalid start for a byte literal.
302    InvalidByteLiteralStart,
303
304    InvalidByteStringLiteralStart,
305
306    /// An literal `\r` character not followed by a `\n` character in a
307    /// (raw) string or byte string literal.
308    IsolatedCr,
309}
310
311impl std::error::Error for ParseError {}
312
313impl fmt::Display for ParseError {
314    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
315        use ParseErrorKind::*;
316
317        let description = match self.kind {
318            Empty => "input is empty",
319            UnexpectedChar => "unexpected character",
320            InvalidLiteral => "invalid literal",
321            DoesNotStartWithDigit => "number literal does not start with decimal digit",
322            InvalidDigit => "integer literal contains a digit invalid for its base",
323            NoDigits => "integer literal does not contain any digits",
324            InvalidIntegerTypeSuffix => "invalid integer type suffix",
325            InvalidFloatTypeSuffix => "invalid floating point type suffix",
326            NoExponentDigits => "exponent of floating point literal does not contain any digits",
327            UnknownEscape => "unknown escape",
328            UnterminatedEscape => "unterminated escape: input ended too soon",
329            InvalidXEscape => r"invalid `\x` escape: not followed by two hex digits",
330            NonAsciiXEscape => r"`\x` escape in char/string literal exceed ASCII range",
331            UnicodeEscapeInByteLiteral => r"`\u{...}` escape in byte (string) literal not allowed",
332            InvalidStartOfUnicodeEscape => r"invalid start of `\u{...}` escape",
333            UnicodeEscapeWithoutBrace => r"`Unicode \u{...}` escape without opening brace",
334            NonHexDigitInUnicodeEscape => r"non-hex digit found in `\u{...}` escape",
335            TooManyDigitInUnicodeEscape => r"more than six digits in `\u{...}` escape",
336            InvalidUnicodeEscapeChar => r"value specified in `\u{...}` escape is not a valid char",
337            UnterminatedUnicodeEscape => r"unterminated `\u{...}` escape",
338            UnterminatedCharLiteral => "character literal is not terminated",
339            OverlongCharLiteral => "character literal contains more than one character",
340            EmptyCharLiteral => "empty character literal",
341            UnterminatedByteLiteral => "byte literal is not terminated",
342            OverlongByteLiteral => "byte literal contains more than one byte",
343            EmptyByteLiteral => "empty byte literal",
344            NonAsciiInByteLiteral => "non ASCII character in byte (string) literal",
345            UnescapedSingleQuote => "character literal contains unescaped ' character",
346            UnescapedSpecialWhitespace => r"unescaped newline (\n), tab (\t) or cr (\r) character",
347            DoesNotStartWithQuote => "invalid start for char/byte/string literal",
348            UnterminatedRawString => "unterminated raw (byte) string literal",
349            UnterminatedString => "unterminated (byte) string literal",
350            InvalidStringLiteralStart => "invalid start for string literal",
351            InvalidByteLiteralStart => "invalid start for byte literal",
352            InvalidByteStringLiteralStart => "invalid start for byte string literal",
353            IsolatedCr => r"`\r` not immediately followed by `\n` in string",
354        };
355
356        description.fmt(f)?;
357        if let Some(span) = &self.span {
358            write!(f, " (at {}..{})", span.start, span.end)?;
359        }
360
361        Ok(())
362    }
363}
litrs/err.rs

litrs/
err.rs
