clippy_utils/
numeric_literal.rs

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

clippy_utils/
numeric_literal.rs
