clippy_utils/
numeric_literal.rs

1use rustc_ast::ast::{LitFloatType, LitIntType, LitKind};
2use std::iter;
3
4/// Represents the base of a numeric literal, used for parsing and formatting.
5#[derive(Debug, PartialEq, Eq, Copy, Clone)]
6pub enum Radix {
7    /// A binary literal (e.g., `0b1010`)
8    Binary,
9    /// An octal literal (e.g., `0o670`)
10    Octal,
11    /// A decimal literal (e.g., `123`)
12    Decimal,
13    /// A hexadecimal literal (e.g., `0xFF`)
14    Hexadecimal,
15}
16
17impl Radix {
18    /// Returns a reasonable digit group size for this radix.
19    #[must_use]
20    fn suggest_grouping(self) -> usize {
21        match self {
22            Self::Binary | Self::Hexadecimal => 4,
23            Self::Octal | Self::Decimal => 3,
24        }
25    }
26}
27
28/// A helper method to format numeric literals with digit grouping.
29/// `lit` must be a valid numeric literal without suffix.
30pub fn format(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
31    NumericLiteral::new(lit, type_suffix, float).format()
32}
33
34#[derive(Debug)]
35pub struct NumericLiteral<'a> {
36    /// Which radix the literal was represented in.
37    pub radix: Radix,
38    /// The radix prefix, if present.
39    pub prefix: Option<&'a str>,
40
41    /// The integer part of the number.
42    pub integer: &'a str,
43    /// The fraction part of the number.
44    pub fraction: Option<&'a str>,
45    /// The exponent separator (b'e' or b'E') including preceding underscore if present
46    /// and the exponent part.
47    pub exponent: Option<(&'a str, &'a str)>,
48
49    /// The type suffix, including preceding underscore if present.
50    pub suffix: Option<&'a str>,
51}
52
53impl<'a> NumericLiteral<'a> {
54    /// Attempts to parse a `NumericLiteral` from the source string of an `ast::LitKind`.
55    pub fn from_lit_kind(src: &'a str, lit_kind: &LitKind) -> Option<NumericLiteral<'a>> {
56        let unsigned_src = src.strip_prefix('-').map_or(src, |s| s);
57        if lit_kind.is_numeric()
58            && unsigned_src
59                .trim_start()
60                .chars()
61                .next()
62                .is_some_and(|c| c.is_ascii_digit())
63        {
64            let (unsuffixed, suffix) = split_suffix(src, lit_kind);
65            let float = matches!(lit_kind, LitKind::Float(..));
66            Some(NumericLiteral::new(unsuffixed, suffix, float))
67        } else {
68            None
69        }
70    }
71
72    /// Parses a raw numeric literal string into its structured `NumericLiteral` parts.
73    #[must_use]
74    pub fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
75        let unsigned_lit = lit.trim_start_matches('-');
76        // Determine delimiter for radix prefix, if present, and radix.
77        let radix = if unsigned_lit.starts_with("0x") {
78            Radix::Hexadecimal
79        } else if unsigned_lit.starts_with("0b") {
80            Radix::Binary
81        } else if unsigned_lit.starts_with("0o") {
82            Radix::Octal
83        } else {
84            Radix::Decimal
85        };
86
87        // Grab part of the literal after prefix, if present.
88        let (prefix, mut sans_prefix) = if radix == Radix::Decimal {
89            (None, lit)
90        } else {
91            let (p, s) = lit.split_at(2);
92            (Some(p), s)
93        };
94
95        if suffix.is_some() && sans_prefix.ends_with('_') {
96            // The '_' before the suffix isn't part of the digits
97            sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
98        }
99
100        let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
101
102        Self {
103            radix,
104            prefix,
105            integer,
106            fraction,
107            exponent,
108            suffix,
109        }
110    }
111
112    /// Checks if the literal's radix is `Radix::Decimal`
113    pub fn is_decimal(&self) -> bool {
114        self.radix == Radix::Decimal
115    }
116
117    fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(&str, &str)>) {
118        let mut integer = digits;
119        let mut fraction = None;
120        let mut exponent = None;
121
122        if float {
123            for (i, c) in digits.char_indices() {
124                match c {
125                    '.' => {
126                        integer = &digits[..i];
127                        fraction = Some(&digits[i + 1..]);
128                    },
129                    'e' | 'E' => {
130                        let exp_start = if digits[..i].ends_with('_') { i - 1 } else { i };
131
132                        if integer.len() > exp_start {
133                            integer = &digits[..exp_start];
134                        } else {
135                            fraction = Some(&digits[integer.len() + 1..exp_start]);
136                        }
137                        exponent = Some((&digits[exp_start..=i], &digits[i + 1..]));
138                        break;
139                    },
140                    _ => {},
141                }
142            }
143        }
144
145        (integer, fraction, exponent)
146    }
147
148    /// Returns literal formatted in a sensible way.
149    pub fn format(&self) -> String {
150        let mut output = String::new();
151
152        if let Some(prefix) = self.prefix {
153            output.push_str(prefix);
154        }
155
156        let group_size = self.radix.suggest_grouping();
157
158        Self::group_digits(
159            &mut output,
160            self.integer,
161            group_size,
162            true,
163            self.radix == Radix::Hexadecimal,
164        );
165
166        if let Some(fraction) = self.fraction {
167            output.push('.');
168            Self::group_digits(&mut output, fraction, group_size, false, false);
169        }
170
171        if let Some((separator, exponent)) = self.exponent {
172            if !exponent.is_empty() && exponent != "0" {
173                output.push_str(separator);
174                Self::group_digits(&mut output, exponent, group_size, true, false);
175            } else if exponent == "0" && self.fraction.is_none() && self.suffix.is_none() {
176                output.push_str(".0");
177            }
178        }
179
180        if let Some(suffix) = self.suffix {
181            if output.ends_with('.') {
182                output.push('0');
183            }
184            output.push('_');
185            output.push_str(suffix);
186        }
187
188        output
189    }
190
191    fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, zero_pad: bool) {
192        debug_assert!(group_size > 0);
193
194        let mut digits = input.chars().filter(|&c| c != '_');
195
196        // The exponent may have a sign, output it early, otherwise it will be
197        // treated as a digit
198        if digits.clone().next() == Some('-') {
199            let _: Option<char> = digits.next();
200            output.push('-');
201        }
202
203        let first_group_size;
204
205        if partial_group_first {
206            first_group_size = (digits.clone().count() - 1) % group_size + 1;
207            if zero_pad {
208                for _ in 0..group_size - first_group_size {
209                    output.push('0');
210                }
211            }
212        } else {
213            first_group_size = group_size;
214        }
215
216        for _ in 0..first_group_size {
217            if let Some(digit) = digits.next() {
218                output.push(digit);
219            }
220        }
221
222        for (c, i) in iter::zip(digits, (0..group_size).cycle()) {
223            if i == 0 {
224                output.push('_');
225            }
226            output.push(c);
227        }
228    }
229}
230
231fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
232    debug_assert!(lit_kind.is_numeric());
233    lit_suffix_length(lit_kind)
234        .and_then(|suffix_length| src.len().checked_sub(suffix_length))
235        .map_or((src, None), |split_pos| {
236            let (unsuffixed, suffix) = src.split_at(split_pos);
237            (unsuffixed, Some(suffix))
238        })
239}
240
241fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
242    debug_assert!(lit_kind.is_numeric());
243    let suffix = match lit_kind {
244        LitKind::Int(_, int_lit_kind) => match int_lit_kind {
245            LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
246            LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
247            LitIntType::Unsuffixed => None,
248        },
249        LitKind::Float(_, float_lit_kind) => match float_lit_kind {
250            LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
251            LitFloatType::Unsuffixed => None,
252        },
253        _ => None,
254    };
255
256    suffix.map(str::len)
257}
clippy_utils/numeric_literal.rs

clippy_utils/
numeric_literal.rs
