1 //! Lints concerned with the grouping of digits with underscores in integral or
2 //! floating-point literal expressions.
4 use crate::utils::{in_macro, snippet_opt, span_lint_and_sugg};
5 use if_chain::if_chain;
6 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
7 use rustc::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
8 use rustc_errors::Applicability;
12 declare_clippy_lint! {
13 /// **What it does:** Warns if a long integral or floating-point constant does
14 /// not contain underscores.
16 /// **Why is this bad?** Reading long numbers is difficult without separators.
18 /// **Known problems:** None.
23 /// let x: u64 = 61864918973511;
25 pub UNREADABLE_LITERAL,
27 "long integer literal without underscores"
30 declare_clippy_lint! {
31 /// **What it does:** Warns for mistyped suffix in literals
33 /// **Why is this bad?** This is most probably a typo
35 /// **Known problems:**
36 /// - Recommends a signed suffix, even though the number might be too big and an unsigned
37 /// suffix is required
38 /// - Does not match on `_128` since that is a valid grouping for decimal and octal numbers
45 pub MISTYPED_LITERAL_SUFFIXES,
47 "mistyped literal suffix"
50 declare_clippy_lint! {
51 /// **What it does:** Warns if an integral or floating-point constant is
52 /// grouped inconsistently with underscores.
54 /// **Why is this bad?** Readers may incorrectly interpret inconsistently
57 /// **Known problems:** None.
62 /// let x: u64 = 618_64_9189_73_511;
64 pub INCONSISTENT_DIGIT_GROUPING,
66 "integer literals with digits grouped inconsistently"
69 declare_clippy_lint! {
70 /// **What it does:** Warns if the digits of an integral or floating-point
71 /// constant are grouped into groups that
74 /// **Why is this bad?** Negatively impacts readability.
76 /// **Known problems:** None.
81 /// let x: u64 = 6186491_8973511;
83 pub LARGE_DIGIT_GROUPS,
85 "grouping digits into groups that are too large"
88 declare_clippy_lint! {
89 /// **What it does:** Warns if there is a better representation for a numeric literal.
91 /// **Why is this bad?** Especially for big powers of 2 a hexadecimal representation is more
92 /// readable than a decimal representation.
94 /// **Known problems:** None.
99 /// `65_535` => `0xFFFF`
100 /// `4_042_322_160` => `0xF0F0_F0F0`
101 pub DECIMAL_LITERAL_REPRESENTATION,
103 "using decimal representation when hexadecimal would be better"
106 #[derive(Debug, PartialEq)]
107 pub(super) enum Radix {
115 /// Returns a reasonable digit group size for this radix.
117 crate fn suggest_grouping(&self) -> usize {
119 Self::Binary | Self::Hexadecimal => 4,
120 Self::Octal | Self::Decimal => 3,
126 pub(super) struct DigitInfo<'a> {
127 /// Characters of a literal between the radix prefix and type suffix.
128 crate digits: &'a str,
129 /// Which radix the literal was represented in.
131 /// The radix prefix, if present.
132 crate prefix: Option<&'a str>,
133 /// The type suffix, including preceding underscore if present.
134 crate suffix: Option<&'a str>,
135 /// True for floating-point literals.
139 impl<'a> DigitInfo<'a> {
141 crate fn new(lit: &'a str, float: bool) -> Self {
142 // Determine delimiter for radix prefix, if present, and radix.
143 let radix = if lit.starts_with("0x") {
145 } else if lit.starts_with("0b") {
147 } else if lit.starts_with("0o") {
153 // Grab part of the literal after prefix, if present.
154 let (prefix, sans_prefix) = if let Radix::Decimal = radix {
157 let (p, s) = lit.split_at(2);
161 let len = sans_prefix.len();
162 let mut last_d = '\0';
163 for (d_idx, d) in sans_prefix.char_indices() {
164 let suffix_start = if last_d == '_' { d_idx - 1 } else { d_idx };
167 || is_possible_float_suffix_index(&sans_prefix, suffix_start, len)
168 || ((d == 'E' || d == 'e') && !has_possible_float_suffix(&sans_prefix)))
169 || !float && (d == 'i' || d == 'u' || is_possible_suffix_index(&sans_prefix, suffix_start, len))
171 let (digits, suffix) = sans_prefix.split_at(suffix_start);
176 suffix: Some(suffix),
193 fn split_digit_parts(&self) -> (&str, Option<&str>, Option<(char, &str)>) {
194 let digits = self.digits;
196 let mut integer = digits;
197 let mut fraction = None;
198 let mut exponent = None;
201 for (i, c) in digits.char_indices() {
204 integer = &digits[..i];
205 fraction = Some(&digits[i + 1..]);
208 if integer.len() > i {
209 integer = &digits[..i];
211 fraction = Some(&digits[integer.len() + 1..i]);
213 exponent = Some((c, &digits[i + 1..]));
221 (integer, fraction, exponent)
224 /// Returns literal formatted in a sensible way.
225 crate fn grouping_hint(&self) -> String {
226 let mut output = String::new();
228 if let Some(prefix) = self.prefix {
229 output.push_str(prefix);
232 let group_size = self.radix.suggest_grouping();
234 let (integer, fraction, exponent) = &self.split_digit_parts();
236 let int_digits: Vec<_> = integer.chars().rev().filter(|&c| c != '_').collect();
237 let int_part_hint = int_digits
239 .map(|chunk| chunk.iter().rev().collect())
241 .collect::<Vec<String>>()
244 // Pad leading hexidecimal group with zeros
245 if self.radix == Radix::Hexadecimal {
246 debug_assert!(group_size > 0);
247 let first_group_size = (int_digits.len() + group_size - 1) % group_size + 1;
248 for _ in 0..group_size - first_group_size {
253 output.push_str(&int_part_hint);
255 if let Some(fraction) = fraction {
256 let frac_part_hint = fraction
258 .filter(|&c| c != '_')
261 .map(|chunk| chunk.iter().collect())
262 .collect::<Vec<String>>()
266 output.push_str(&frac_part_hint);
269 if let Some((separator, exponent)) = exponent {
270 let after_e_hint = exponent
273 .filter(|&c| c != '_')
276 .map(|chunk| chunk.iter().rev().collect())
278 .collect::<Vec<String>>()
281 output.push(*separator);
282 output.push_str(&after_e_hint);
285 if let Some(suffix) = self.suffix {
286 if self.float && is_mistyped_float_suffix(suffix) {
287 output.push_str("_f");
288 output.push_str(&suffix[1..]);
289 } else if is_mistyped_suffix(suffix) {
290 output.push_str("_i");
291 output.push_str(&suffix[1..]);
293 output.push_str(suffix);
303 InconsistentDigitGrouping,
305 DecimalRepresentation,
306 MistypedLiteralSuffix,
310 crate fn display(&self, grouping_hint: &str, cx: &EarlyContext<'_>, span: syntax_pos::Span) {
312 Self::MistypedLiteralSuffix => span_lint_and_sugg(
314 MISTYPED_LITERAL_SUFFIXES,
316 "mistyped literal suffix",
317 "did you mean to write",
318 grouping_hint.to_string(),
319 Applicability::MaybeIncorrect,
321 Self::UnreadableLiteral => span_lint_and_sugg(
325 "long literal lacking separators",
327 grouping_hint.to_owned(),
328 Applicability::MachineApplicable,
330 Self::LargeDigitGroups => span_lint_and_sugg(
334 "digit groups should be smaller",
336 grouping_hint.to_owned(),
337 Applicability::MachineApplicable,
339 Self::InconsistentDigitGrouping => span_lint_and_sugg(
341 INCONSISTENT_DIGIT_GROUPING,
343 "digits grouped inconsistently by underscores",
345 grouping_hint.to_owned(),
346 Applicability::MachineApplicable,
348 Self::DecimalRepresentation => span_lint_and_sugg(
350 DECIMAL_LITERAL_REPRESENTATION,
352 "integer literal has a better hexadecimal representation",
354 grouping_hint.to_owned(),
355 Applicability::MachineApplicable,
361 declare_lint_pass!(LiteralDigitGrouping => [
363 INCONSISTENT_DIGIT_GROUPING,
365 MISTYPED_LITERAL_SUFFIXES,
368 impl EarlyLintPass for LiteralDigitGrouping {
369 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
370 if in_external_macro(cx.sess(), expr.span) {
374 if let ExprKind::Lit(ref lit) = expr.kind {
375 Self::check_lit(cx, lit)
380 impl LiteralDigitGrouping {
381 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
382 let in_macro = in_macro(lit.span);
385 if let Some(src) = snippet_opt(cx, lit.span);
386 if let Some(firstch) = src.chars().next();
387 if char::is_digit(firstch, 10);
390 let digit_info = match lit.kind {
391 LitKind::Int(..) => DigitInfo::new(&src, false),
392 LitKind::Float(..) => DigitInfo::new(&src, true),
397 if let Some(suffix) = digit_info.suffix {
398 if is_mistyped_suffix(suffix) {
399 return Err(WarningType::MistypedLiteralSuffix);
403 let (integer, fraction, _) = digit_info.split_digit_parts();
405 let integral_group_size = Self::do_lint(integer, in_macro)?;
406 if let Some(fraction) = fraction {
407 let fractional_part = fraction.chars().rev().collect::<String>();
408 let fractional_group_size = Self::do_lint(&fractional_part, in_macro)?;
410 let consistent = Self::parts_consistent(integral_group_size,
411 fractional_group_size,
415 return Err(WarningType::InconsistentDigitGrouping);
422 if let Err(warning_type) = result {
423 warning_type.display(&digit_info.grouping_hint(), cx, lit.span)
429 /// Given the sizes of the digit groups of both integral and fractional
430 /// parts, and the length
431 /// of both parts, determine if the digits have been grouped consistently.
433 fn parts_consistent(int_group_size: usize, frac_group_size: usize, int_size: usize, frac_size: usize) -> bool {
434 match (int_group_size, frac_group_size) {
435 // No groups on either side of decimal point - trivially consistent.
437 // Integral part has grouped digits, fractional part does not.
438 (_, 0) => frac_size <= int_group_size,
439 // Fractional part has grouped digits, integral part does not.
440 (0, _) => int_size <= frac_group_size,
441 // Both parts have grouped digits. Groups should be the same size.
442 (_, _) => int_group_size == frac_group_size,
446 /// Performs lint on `digits` (no decimal point) and returns the group
447 /// size on success or `WarningType` when emitting a warning.
448 fn do_lint(digits: &str, in_macro: bool) -> Result<usize, WarningType> {
449 // Grab underscore indices with respect to the units digit.
450 let underscore_positions: Vec<usize> = digits
454 .filter_map(|(idx, digit)| if digit == '_' { Some(idx) } else { None })
457 if underscore_positions.is_empty() {
458 // Check if literal needs underscores.
459 if !in_macro && digits.len() > 5 {
460 Err(WarningType::UnreadableLiteral)
465 // Check consistency and the sizes of the groups.
466 let group_size = underscore_positions[0];
467 let consistent = underscore_positions
469 .all(|ps| ps[1] - ps[0] == group_size + 1)
470 // number of digits to the left of the last group cannot be bigger than group size.
471 && (digits.len() - underscore_positions.last()
472 .expect("there's at least one element") <= group_size + 1);
475 return Err(WarningType::InconsistentDigitGrouping);
476 } else if group_size > 4 {
477 return Err(WarningType::LargeDigitGroups);
484 #[allow(clippy::module_name_repetitions)]
485 #[derive(Copy, Clone)]
486 pub struct DecimalLiteralRepresentation {
490 impl_lint_pass!(DecimalLiteralRepresentation => [DECIMAL_LITERAL_REPRESENTATION]);
492 impl EarlyLintPass for DecimalLiteralRepresentation {
493 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
494 if in_external_macro(cx.sess(), expr.span) {
498 if let ExprKind::Lit(ref lit) = expr.kind {
499 self.check_lit(cx, lit)
504 impl DecimalLiteralRepresentation {
506 pub fn new(threshold: u64) -> Self {
509 fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
510 // Lint integral literals.
512 if let LitKind::Int(val, _) = lit.kind;
513 if let Some(src) = snippet_opt(cx, lit.span);
514 if let Some(firstch) = src.chars().next();
515 if char::is_digit(firstch, 10);
516 let digit_info = DigitInfo::new(&src, false);
517 if digit_info.radix == Radix::Decimal;
518 if val >= u128::from(self.threshold);
520 let hex = format!("{:#X}", val);
521 let digit_info = DigitInfo::new(&hex, false);
522 let _ = Self::do_lint(digit_info.digits).map_err(|warning_type| {
523 warning_type.display(&digit_info.grouping_hint(), cx, lit.span)
529 fn do_lint(digits: &str) -> Result<(), WarningType> {
530 if digits.len() == 1 {
531 // Lint for 1 digit literals, if someone really sets the threshold that low
540 return Err(WarningType::DecimalRepresentation);
542 } else if digits.len() < 4 {
543 // Lint for Literals with a hex-representation of 2 or 3 digits
544 let f = &digits[0..1]; // first digit
545 let s = &digits[1..]; // suffix
548 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && s.chars().all(|c| c == '0'))
549 // Powers of 2 minus 1
550 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && s.chars().all(|c| c == 'F'))
552 return Err(WarningType::DecimalRepresentation);
555 // Lint for Literals with a hex-representation of 4 digits or more
556 let f = &digits[0..1]; // first digit
557 let m = &digits[1..digits.len() - 1]; // middle digits, except last
558 let s = &digits[1..]; // suffix
560 // Powers of 2 with a margin of +15/-16
561 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && m.chars().all(|c| c == '0'))
562 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && m.chars().all(|c| c == 'F'))
563 // Lint for representations with only 0s and Fs, while allowing 7 as the first
565 || ((f.eq("7") || f.eq("F")) && s.chars().all(|c| c == '0' || c == 'F'))
567 return Err(WarningType::DecimalRepresentation);
576 fn is_mistyped_suffix(suffix: &str) -> bool {
577 ["_8", "_16", "_32", "_64"].contains(&suffix)
581 fn is_possible_suffix_index(lit: &str, idx: usize, len: usize) -> bool {
582 ((len > 3 && idx == len - 3) || (len > 2 && idx == len - 2)) && is_mistyped_suffix(lit.split_at(idx).1)
586 fn is_mistyped_float_suffix(suffix: &str) -> bool {
587 ["_32", "_64"].contains(&suffix)
591 fn is_possible_float_suffix_index(lit: &str, idx: usize, len: usize) -> bool {
592 (len > 3 && idx == len - 3) && is_mistyped_float_suffix(lit.split_at(idx).1)
596 fn has_possible_float_suffix(lit: &str) -> bool {
597 lit.ends_with("_32") || lit.ends_with("_64")