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 hexadecimal 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 /// Returns literal formatted in a sensible way.
194 crate fn grouping_hint(&self) -> String {
195 let group_size = self.radix.suggest_grouping();
196 if self.digits.contains('.') {
197 let mut parts = self.digits.split('.');
198 let int_part_hint = parts
200 .expect("split always returns at least one element")
203 .filter(|&c| c != '_')
206 .map(|chunk| chunk.iter().rev().collect())
208 .collect::<Vec<String>>()
210 let frac_part_hint = parts
212 .expect("already checked that there is a `.`")
214 .filter(|&c| c != '_')
217 .map(|chunk| chunk.iter().collect())
218 .collect::<Vec<String>>()
220 let suffix_hint = match self.suffix {
221 Some(suffix) if is_mistyped_float_suffix(suffix) => format!("_f{}", &suffix[1..]),
222 Some(suffix) => suffix.to_string(),
223 None => String::new(),
225 format!("{}.{}{}", int_part_hint, frac_part_hint, suffix_hint)
226 } else if self.float && (self.digits.contains('E') || self.digits.contains('e')) {
227 let which_e = if self.digits.contains('E') { 'E' } else { 'e' };
228 let parts: Vec<&str> = self.digits.split(which_e).collect();
229 let filtered_digits_vec_0 = parts[0].chars().filter(|&c| c != '_').rev().collect::<Vec<_>>();
230 let filtered_digits_vec_1 = parts[1].chars().filter(|&c| c != '_').rev().collect::<Vec<_>>();
231 let before_e_hint = filtered_digits_vec_0
233 .map(|chunk| chunk.iter().rev().collect())
235 .collect::<Vec<String>>()
237 let after_e_hint = filtered_digits_vec_1
239 .map(|chunk| chunk.iter().rev().collect())
241 .collect::<Vec<String>>()
243 let suffix_hint = match self.suffix {
244 Some(suffix) if is_mistyped_float_suffix(suffix) => format!("_f{}", &suffix[1..]),
245 Some(suffix) => suffix.to_string(),
246 None => String::new(),
250 self.prefix.unwrap_or(""),
257 let filtered_digits_vec = self.digits.chars().filter(|&c| c != '_').rev().collect::<Vec<_>>();
258 let mut hint = filtered_digits_vec
260 .map(|chunk| chunk.iter().rev().collect())
262 .collect::<Vec<String>>()
264 // Forces hexadecimal values to be grouped by 4 being filled with zeroes (e.g 0x00ab_cdef)
265 let nb_digits_to_fill = filtered_digits_vec.len() % 4;
266 if self.radix == Radix::Hexadecimal && nb_digits_to_fill != 0 {
267 hint = format!("{:0>4}{}", &hint[..nb_digits_to_fill], &hint[nb_digits_to_fill..]);
269 let suffix_hint = match self.suffix {
270 Some(suffix) if is_mistyped_suffix(suffix) => format!("_i{}", &suffix[1..]),
271 Some(suffix) => suffix.to_string(),
272 None => String::new(),
274 format!("{}{}{}", self.prefix.unwrap_or(""), hint, suffix_hint)
281 InconsistentDigitGrouping,
283 DecimalRepresentation,
284 MistypedLiteralSuffix,
288 crate fn display(&self, grouping_hint: &str, cx: &EarlyContext<'_>, span: syntax_pos::Span) {
290 Self::MistypedLiteralSuffix => span_lint_and_sugg(
292 MISTYPED_LITERAL_SUFFIXES,
294 "mistyped literal suffix",
295 "did you mean to write",
296 grouping_hint.to_string(),
297 Applicability::MaybeIncorrect,
299 Self::UnreadableLiteral => span_lint_and_sugg(
303 "long literal lacking separators",
305 grouping_hint.to_owned(),
306 Applicability::MachineApplicable,
308 Self::LargeDigitGroups => span_lint_and_sugg(
312 "digit groups should be smaller",
314 grouping_hint.to_owned(),
315 Applicability::MachineApplicable,
317 Self::InconsistentDigitGrouping => span_lint_and_sugg(
319 INCONSISTENT_DIGIT_GROUPING,
321 "digits grouped inconsistently by underscores",
323 grouping_hint.to_owned(),
324 Applicability::MachineApplicable,
326 Self::DecimalRepresentation => span_lint_and_sugg(
328 DECIMAL_LITERAL_REPRESENTATION,
330 "integer literal has a better hexadecimal representation",
332 grouping_hint.to_owned(),
333 Applicability::MachineApplicable,
339 declare_lint_pass!(LiteralDigitGrouping => [
341 INCONSISTENT_DIGIT_GROUPING,
343 MISTYPED_LITERAL_SUFFIXES,
346 impl EarlyLintPass for LiteralDigitGrouping {
347 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
348 if in_external_macro(cx.sess(), expr.span) {
352 if let ExprKind::Lit(ref lit) = expr.kind {
353 Self::check_lit(cx, lit)
358 impl LiteralDigitGrouping {
359 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
360 let in_macro = in_macro(lit.span);
362 LitKind::Int(..) => {
363 // Lint integral literals.
365 if let Some(src) = snippet_opt(cx, lit.span);
366 if let Some(firstch) = src.chars().next();
367 if char::is_digit(firstch, 10);
369 let digit_info = DigitInfo::new(&src, false);
370 let _ = Self::do_lint(digit_info.digits, digit_info.suffix, in_macro).map_err(|warning_type| {
371 warning_type.display(&digit_info.grouping_hint(), cx, lit.span)
376 LitKind::Float(..) => {
377 // Lint floating-point literals.
379 if let Some(src) = snippet_opt(cx, lit.span);
380 if let Some(firstch) = src.chars().next();
381 if char::is_digit(firstch, 10);
383 let digit_info = DigitInfo::new(&src, true);
384 // Separate digits into integral and fractional parts.
385 let parts: Vec<&str> = digit_info
387 .split_terminator('.')
390 // Lint integral and fractional parts separately, and then check consistency of digit
391 // groups if both pass.
392 let _ = Self::do_lint(parts[0], digit_info.suffix, in_macro)
393 .map(|integral_group_size| {
395 // Lint the fractional part of literal just like integral part, but reversed.
396 let fractional_part = &parts[1].chars().rev().collect::<String>();
397 let _ = Self::do_lint(fractional_part, None, in_macro)
398 .map(|fractional_group_size| {
399 let consistent = Self::parts_consistent(integral_group_size,
400 fractional_group_size,
404 WarningType::InconsistentDigitGrouping.display(
405 &digit_info.grouping_hint(),
411 .map_err(|warning_type| warning_type.display(&digit_info.grouping_hint(),
416 .map_err(|warning_type| warning_type.display(&digit_info.grouping_hint(), cx, lit.span));
424 /// Given the sizes of the digit groups of both integral and fractional
425 /// parts, and the length
426 /// of both parts, determine if the digits have been grouped consistently.
428 fn parts_consistent(int_group_size: usize, frac_group_size: usize, int_size: usize, frac_size: usize) -> bool {
429 match (int_group_size, frac_group_size) {
430 // No groups on either side of decimal point - trivially consistent.
432 // Integral part has grouped digits, fractional part does not.
433 (_, 0) => frac_size <= int_group_size,
434 // Fractional part has grouped digits, integral part does not.
435 (0, _) => int_size <= frac_group_size,
436 // Both parts have grouped digits. Groups should be the same size.
437 (_, _) => int_group_size == frac_group_size,
441 /// Performs lint on `digits` (no decimal point) and returns the group
442 /// size on success or `WarningType` when emitting a warning.
443 fn do_lint(digits: &str, suffix: Option<&str>, in_macro: bool) -> Result<usize, WarningType> {
444 if let Some(suffix) = suffix {
445 if is_mistyped_suffix(suffix) {
446 return Err(WarningType::MistypedLiteralSuffix);
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")