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 NumericLiteral<'a> {
127 /// Which radix the literal was represented in.
129 /// The radix prefix, if present.
130 crate prefix: Option<&'a str>,
132 /// The integer part of the number.
134 /// The fraction part of the number.
135 fraction: Option<&'a str>,
136 /// The character used as exponent seperator (b'e' or b'E') and the exponent part.
137 exponent: Option<(char, &'a str)>,
139 /// The type suffix, including preceding underscore if present.
140 crate suffix: Option<&'a str>,
143 impl<'a> NumericLiteral<'a> {
144 fn from_lit(src: &'a str, lit: &Lit) -> Option<NumericLiteral<'a>> {
145 if lit.kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
146 let (unsuffixed, suffix) = split_suffix(&src, &lit.kind);
147 let float = if let LitKind::Float(..) = lit.kind { true } else { false };
148 Some(NumericLiteral::new(unsuffixed, suffix, float))
155 crate fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
156 // Determine delimiter for radix prefix, if present, and radix.
157 let radix = if lit.starts_with("0x") {
159 } else if lit.starts_with("0b") {
161 } else if lit.starts_with("0o") {
167 // Grab part of the literal after prefix, if present.
168 let (prefix, mut sans_prefix) = if let Radix::Decimal = radix {
171 let (p, s) = lit.split_at(2);
175 if suffix.is_some() && sans_prefix.ends_with('_') {
176 // The '_' before the suffix isn't part of the digits
177 sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
180 let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
192 fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(char, &str)>) {
193 let mut integer = digits;
194 let mut fraction = None;
195 let mut exponent = None;
198 for (i, c) in digits.char_indices() {
201 integer = &digits[..i];
202 fraction = Some(&digits[i + 1..]);
205 if integer.len() > i {
206 integer = &digits[..i];
208 fraction = Some(&digits[integer.len() + 1..i]);
210 exponent = Some((c, &digits[i + 1..]));
218 (integer, fraction, exponent)
221 /// Returns literal formatted in a sensible way.
222 crate fn format(&self) -> String {
223 let mut output = String::new();
225 if let Some(prefix) = self.prefix {
226 output.push_str(prefix);
229 let group_size = self.radix.suggest_grouping();
236 self.radix == Radix::Hexadecimal,
239 if let Some(fraction) = self.fraction {
241 Self::group_digits(&mut output, fraction, group_size, false, false);
244 if let Some((separator, exponent)) = self.exponent {
245 output.push(separator);
246 Self::group_digits(&mut output, exponent, group_size, true, false);
249 if let Some(suffix) = self.suffix {
251 output.push_str(suffix);
257 fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
258 debug_assert!(group_size > 0);
260 let mut digits = input.chars().filter(|&c| c != '_');
262 let first_group_size;
264 if partial_group_first {
265 first_group_size = (digits.clone().count() + group_size - 1) % group_size + 1;
267 for _ in 0..group_size - first_group_size {
272 first_group_size = group_size;
275 for _ in 0..first_group_size {
276 if let Some(digit) = digits.next() {
281 for (c, i) in digits.zip((0..group_size).cycle()) {
290 fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
291 debug_assert!(lit_kind.is_numeric());
292 if let Some(suffix_length) = lit_suffix_length(lit_kind) {
293 let (unsuffixed, suffix) = src.split_at(src.len() - suffix_length);
294 (unsuffixed, Some(suffix))
300 fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
301 debug_assert!(lit_kind.is_numeric());
302 let suffix = match lit_kind {
303 LitKind::Int(_, int_lit_kind) => match int_lit_kind {
304 LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
305 LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
306 LitIntType::Unsuffixed => None,
308 LitKind::Float(_, float_lit_kind) => match float_lit_kind {
309 LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
310 LitFloatType::Unsuffixed => None,
320 InconsistentDigitGrouping,
322 DecimalRepresentation,
323 MistypedLiteralSuffix,
327 crate fn display(&self, suggested_format: String, cx: &EarlyContext<'_>, span: syntax_pos::Span) {
329 Self::MistypedLiteralSuffix => span_lint_and_sugg(
331 MISTYPED_LITERAL_SUFFIXES,
333 "mistyped literal suffix",
334 "did you mean to write",
336 Applicability::MaybeIncorrect,
338 Self::UnreadableLiteral => span_lint_and_sugg(
342 "long literal lacking separators",
345 Applicability::MachineApplicable,
347 Self::LargeDigitGroups => span_lint_and_sugg(
351 "digit groups should be smaller",
354 Applicability::MachineApplicable,
356 Self::InconsistentDigitGrouping => span_lint_and_sugg(
358 INCONSISTENT_DIGIT_GROUPING,
360 "digits grouped inconsistently by underscores",
363 Applicability::MachineApplicable,
365 Self::DecimalRepresentation => span_lint_and_sugg(
367 DECIMAL_LITERAL_REPRESENTATION,
369 "integer literal has a better hexadecimal representation",
372 Applicability::MachineApplicable,
378 declare_lint_pass!(LiteralDigitGrouping => [
380 INCONSISTENT_DIGIT_GROUPING,
382 MISTYPED_LITERAL_SUFFIXES,
385 impl EarlyLintPass for LiteralDigitGrouping {
386 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
387 if in_external_macro(cx.sess(), expr.span) {
391 if let ExprKind::Lit(ref lit) = expr.kind {
392 Self::check_lit(cx, lit)
397 impl LiteralDigitGrouping {
398 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
399 let in_macro = in_macro(lit.span);
402 if let Some(src) = snippet_opt(cx, lit.span);
403 if let Some(mut num_lit) = NumericLiteral::from_lit(&src, &lit);
405 if !Self::check_for_mistyped_suffix(cx, lit.span, &mut num_lit) {
411 let integral_group_size = Self::get_group_size(num_lit.integer.split('_'), in_macro)?;
412 if let Some(fraction) = num_lit.fraction {
413 let fractional_group_size = Self::get_group_size(fraction.rsplit('_'), in_macro)?;
415 let consistent = Self::parts_consistent(integral_group_size,
416 fractional_group_size,
417 num_lit.integer.len(),
420 return Err(WarningType::InconsistentDigitGrouping);
427 if let Err(warning_type) = result {
428 warning_type.display(num_lit.format(), cx, lit.span)
434 // Returns `false` if the check fails
435 fn check_for_mistyped_suffix(
436 cx: &EarlyContext<'_>,
437 span: syntax_pos::Span,
438 num_lit: &mut NumericLiteral<'_>,
440 if num_lit.suffix.is_some() {
444 let (part, mistyped_suffixes, missing_char) = if let Some((_, exponent)) = &mut num_lit.exponent {
445 (exponent, &["32", "64"][..], 'f')
446 } else if let Some(fraction) = &mut num_lit.fraction {
447 (fraction, &["32", "64"][..], 'f')
449 (&mut num_lit.integer, &["8", "16", "32", "64"][..], 'i')
452 let mut split = part.rsplit('_');
453 let last_group = split.next().expect("At least one group");
454 if split.next().is_some() && mistyped_suffixes.contains(&last_group) {
455 *part = &part[..part.len() - last_group.len()];
456 let mut sugg = num_lit.format();
458 sugg.push(missing_char);
459 sugg.push_str(last_group);
460 WarningType::MistypedLiteralSuffix.display(sugg, cx, span);
467 /// Given the sizes of the digit groups of both integral and fractional
468 /// parts, and the length
469 /// of both parts, determine if the digits have been grouped consistently.
472 int_group_size: Option<usize>,
473 frac_group_size: Option<usize>,
477 match (int_group_size, frac_group_size) {
478 // No groups on either side of decimal point - trivially consistent.
479 (None, None) => true,
480 // Integral part has grouped digits, fractional part does not.
481 (Some(int_group_size), None) => frac_size <= int_group_size,
482 // Fractional part has grouped digits, integral part does not.
483 (None, Some(frac_group_size)) => int_size <= frac_group_size,
484 // Both parts have grouped digits. Groups should be the same size.
485 (Some(int_group_size), Some(frac_group_size)) => int_group_size == frac_group_size,
489 /// Returns the size of the digit groups (or None if ungrouped) if successful,
490 /// otherwise returns a `WarningType` for linting.
491 fn get_group_size<'a>(groups: impl Iterator<Item = &'a str>, in_macro: bool) -> Result<Option<usize>, WarningType> {
492 let mut groups = groups.map(str::len);
494 let first = groups.next().expect("At least one group");
496 if let Some(second) = groups.next() {
497 if !groups.all(|x| x == second) || first > second {
498 Err(WarningType::InconsistentDigitGrouping)
499 } else if second > 4 {
500 Err(WarningType::LargeDigitGroups)
504 } else if first > 5 && !in_macro {
505 Err(WarningType::UnreadableLiteral)
512 #[allow(clippy::module_name_repetitions)]
513 #[derive(Copy, Clone)]
514 pub struct DecimalLiteralRepresentation {
518 impl_lint_pass!(DecimalLiteralRepresentation => [DECIMAL_LITERAL_REPRESENTATION]);
520 impl EarlyLintPass for DecimalLiteralRepresentation {
521 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
522 if in_external_macro(cx.sess(), expr.span) {
526 if let ExprKind::Lit(ref lit) = expr.kind {
527 self.check_lit(cx, lit)
532 impl DecimalLiteralRepresentation {
534 pub fn new(threshold: u64) -> Self {
537 fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
538 // Lint integral literals.
540 if let LitKind::Int(val, _) = lit.kind;
541 if let Some(src) = snippet_opt(cx, lit.span);
542 if let Some(num_lit) = NumericLiteral::from_lit(&src, &lit);
543 if num_lit.radix == Radix::Decimal;
544 if val >= u128::from(self.threshold);
546 let hex = format!("{:#X}", val);
547 let num_lit = NumericLiteral::new(&hex, None, false);
548 let _ = Self::do_lint(num_lit.integer).map_err(|warning_type| {
549 warning_type.display(num_lit.format(), cx, lit.span)
555 fn do_lint(digits: &str) -> Result<(), WarningType> {
556 if digits.len() == 1 {
557 // Lint for 1 digit literals, if someone really sets the threshold that low
566 return Err(WarningType::DecimalRepresentation);
568 } else if digits.len() < 4 {
569 // Lint for Literals with a hex-representation of 2 or 3 digits
570 let f = &digits[0..1]; // first digit
571 let s = &digits[1..]; // suffix
574 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && s.chars().all(|c| c == '0'))
575 // Powers of 2 minus 1
576 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && s.chars().all(|c| c == 'F'))
578 return Err(WarningType::DecimalRepresentation);
581 // Lint for Literals with a hex-representation of 4 digits or more
582 let f = &digits[0..1]; // first digit
583 let m = &digits[1..digits.len() - 1]; // middle digits, except last
584 let s = &digits[1..]; // suffix
586 // Powers of 2 with a margin of +15/-16
587 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && m.chars().all(|c| c == '0'))
588 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && m.chars().all(|c| c == 'F'))
589 // Lint for representations with only 0s and Fs, while allowing 7 as the first
591 || ((f.eq("7") || f.eq("F")) && s.chars().all(|c| c == '0' || c == 'F'))
593 return Err(WarningType::DecimalRepresentation);