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;
7 use rustc_ast::ast::{Expr, ExprKind, Lit, LitFloatType, LitIntType, LitKind};
8 use rustc_errors::Applicability;
9 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
10 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
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 `_127` 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 fn suggest_grouping(&self) -> usize {
119 Self::Binary | Self::Hexadecimal => 4,
120 Self::Octal | Self::Decimal => 3,
125 /// A helper method to format numeric literals with digit grouping.
126 /// `lit` must be a valid numeric literal without suffix.
127 pub fn format_numeric_literal(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
128 NumericLiteral::new(lit, type_suffix, float).format()
132 pub(super) struct NumericLiteral<'a> {
133 /// Which radix the literal was represented in.
135 /// The radix prefix, if present.
136 prefix: Option<&'a str>,
138 /// The integer part of the number.
140 /// The fraction part of the number.
141 fraction: Option<&'a str>,
142 /// The character used as exponent seperator (b'e' or b'E') and the exponent part.
143 exponent: Option<(char, &'a str)>,
145 /// The type suffix, including preceding underscore if present.
146 suffix: Option<&'a str>,
149 impl<'a> NumericLiteral<'a> {
150 pub fn from_lit_kind(src: &'a str, lit_kind: &LitKind) -> Option<NumericLiteral<'a>> {
151 if lit_kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
152 let (unsuffixed, suffix) = split_suffix(&src, lit_kind);
153 let float = if let LitKind::Float(..) = lit_kind { true } else { false };
154 Some(NumericLiteral::new(unsuffixed, suffix, float))
160 fn from_lit(src: &'a str, lit: &Lit) -> Option<NumericLiteral<'a>> {
161 NumericLiteral::from_lit_kind(src, &lit.kind)
165 fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
166 // Determine delimiter for radix prefix, if present, and radix.
167 let radix = if lit.starts_with("0x") {
169 } else if lit.starts_with("0b") {
171 } else if lit.starts_with("0o") {
177 // Grab part of the literal after prefix, if present.
178 let (prefix, mut sans_prefix) = if let Radix::Decimal = radix {
181 let (p, s) = lit.split_at(2);
185 if suffix.is_some() && sans_prefix.ends_with('_') {
186 // The '_' before the suffix isn't part of the digits
187 sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
190 let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
202 fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(char, &str)>) {
203 let mut integer = digits;
204 let mut fraction = None;
205 let mut exponent = None;
208 for (i, c) in digits.char_indices() {
211 integer = &digits[..i];
212 fraction = Some(&digits[i + 1..]);
215 if integer.len() > i {
216 integer = &digits[..i];
218 fraction = Some(&digits[integer.len() + 1..i]);
220 exponent = Some((c, &digits[i + 1..]));
228 (integer, fraction, exponent)
231 /// Returns literal formatted in a sensible way.
232 fn format(&self) -> String {
233 let mut output = String::new();
235 if let Some(prefix) = self.prefix {
236 output.push_str(prefix);
239 let group_size = self.radix.suggest_grouping();
246 self.radix == Radix::Hexadecimal,
249 if let Some(fraction) = self.fraction {
251 Self::group_digits(&mut output, fraction, group_size, false, false);
254 if let Some((separator, exponent)) = self.exponent {
255 output.push(separator);
256 Self::group_digits(&mut output, exponent, group_size, true, false);
259 if let Some(suffix) = self.suffix {
261 output.push_str(suffix);
267 fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
268 debug_assert!(group_size > 0);
270 let mut digits = input.chars().filter(|&c| c != '_');
272 let first_group_size;
274 if partial_group_first {
275 first_group_size = (digits.clone().count() - 1) % group_size + 1;
277 for _ in 0..group_size - first_group_size {
282 first_group_size = group_size;
285 for _ in 0..first_group_size {
286 if let Some(digit) = digits.next() {
291 for (c, i) in digits.zip((0..group_size).cycle()) {
300 fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
301 debug_assert!(lit_kind.is_numeric());
302 if let Some(suffix_length) = lit_suffix_length(lit_kind) {
303 let (unsuffixed, suffix) = src.split_at(src.len() - suffix_length);
304 (unsuffixed, Some(suffix))
310 fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
311 debug_assert!(lit_kind.is_numeric());
312 let suffix = match lit_kind {
313 LitKind::Int(_, int_lit_kind) => match int_lit_kind {
314 LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
315 LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
316 LitIntType::Unsuffixed => None,
318 LitKind::Float(_, float_lit_kind) => match float_lit_kind {
319 LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
320 LitFloatType::Unsuffixed => None,
330 InconsistentDigitGrouping,
332 DecimalRepresentation,
333 MistypedLiteralSuffix,
337 fn display(&self, suggested_format: String, cx: &EarlyContext<'_>, span: rustc_span::Span) {
339 Self::MistypedLiteralSuffix => span_lint_and_sugg(
341 MISTYPED_LITERAL_SUFFIXES,
343 "mistyped literal suffix",
344 "did you mean to write",
346 Applicability::MaybeIncorrect,
348 Self::UnreadableLiteral => span_lint_and_sugg(
352 "long literal lacking separators",
355 Applicability::MachineApplicable,
357 Self::LargeDigitGroups => span_lint_and_sugg(
361 "digit groups should be smaller",
364 Applicability::MachineApplicable,
366 Self::InconsistentDigitGrouping => span_lint_and_sugg(
368 INCONSISTENT_DIGIT_GROUPING,
370 "digits grouped inconsistently by underscores",
373 Applicability::MachineApplicable,
375 Self::DecimalRepresentation => span_lint_and_sugg(
377 DECIMAL_LITERAL_REPRESENTATION,
379 "integer literal has a better hexadecimal representation",
382 Applicability::MachineApplicable,
388 declare_lint_pass!(LiteralDigitGrouping => [
390 INCONSISTENT_DIGIT_GROUPING,
392 MISTYPED_LITERAL_SUFFIXES,
395 impl EarlyLintPass for LiteralDigitGrouping {
396 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
397 if in_external_macro(cx.sess(), expr.span) {
401 if let ExprKind::Lit(ref lit) = expr.kind {
402 Self::check_lit(cx, lit)
407 impl LiteralDigitGrouping {
408 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
410 if let Some(src) = snippet_opt(cx, lit.span);
411 if let Some(mut num_lit) = NumericLiteral::from_lit(&src, &lit);
413 if !Self::check_for_mistyped_suffix(cx, lit.span, &mut num_lit) {
419 let integral_group_size = Self::get_group_size(num_lit.integer.split('_'))?;
420 if let Some(fraction) = num_lit.fraction {
421 let fractional_group_size = Self::get_group_size(fraction.rsplit('_'))?;
423 let consistent = Self::parts_consistent(integral_group_size,
424 fractional_group_size,
425 num_lit.integer.len(),
428 return Err(WarningType::InconsistentDigitGrouping);
435 if let Err(warning_type) = result {
436 let should_warn = match warning_type {
437 | WarningType::UnreadableLiteral
438 | WarningType::InconsistentDigitGrouping
439 | WarningType::LargeDigitGroups => {
442 WarningType::DecimalRepresentation | WarningType::MistypedLiteralSuffix => {
447 warning_type.display(num_lit.format(), cx, lit.span)
454 // Returns `false` if the check fails
455 fn check_for_mistyped_suffix(
456 cx: &EarlyContext<'_>,
457 span: rustc_span::Span,
458 num_lit: &mut NumericLiteral<'_>,
460 if num_lit.suffix.is_some() {
464 let (part, mistyped_suffixes, missing_char) = if let Some((_, exponent)) = &mut num_lit.exponent {
465 (exponent, &["32", "64"][..], 'f')
466 } else if let Some(fraction) = &mut num_lit.fraction {
467 (fraction, &["32", "64"][..], 'f')
469 (&mut num_lit.integer, &["8", "16", "32", "64"][..], 'i')
472 let mut split = part.rsplit('_');
473 let last_group = split.next().expect("At least one group");
474 if split.next().is_some() && mistyped_suffixes.contains(&last_group) {
475 *part = &part[..part.len() - last_group.len()];
476 let mut sugg = num_lit.format();
478 sugg.push(missing_char);
479 sugg.push_str(last_group);
480 WarningType::MistypedLiteralSuffix.display(sugg, cx, span);
487 /// Given the sizes of the digit groups of both integral and fractional
488 /// parts, and the length
489 /// of both parts, determine if the digits have been grouped consistently.
492 int_group_size: Option<usize>,
493 frac_group_size: Option<usize>,
497 match (int_group_size, frac_group_size) {
498 // No groups on either side of decimal point - trivially consistent.
499 (None, None) => true,
500 // Integral part has grouped digits, fractional part does not.
501 (Some(int_group_size), None) => frac_size <= int_group_size,
502 // Fractional part has grouped digits, integral part does not.
503 (None, Some(frac_group_size)) => int_size <= frac_group_size,
504 // Both parts have grouped digits. Groups should be the same size.
505 (Some(int_group_size), Some(frac_group_size)) => int_group_size == frac_group_size,
509 /// Returns the size of the digit groups (or None if ungrouped) if successful,
510 /// otherwise returns a `WarningType` for linting.
511 fn get_group_size<'a>(groups: impl Iterator<Item = &'a str>) -> Result<Option<usize>, WarningType> {
512 let mut groups = groups.map(str::len);
514 let first = groups.next().expect("At least one group");
516 if let Some(second) = groups.next() {
517 if !groups.all(|x| x == second) || first > second {
518 Err(WarningType::InconsistentDigitGrouping)
519 } else if second > 4 {
520 Err(WarningType::LargeDigitGroups)
524 } else if first > 5 {
525 Err(WarningType::UnreadableLiteral)
532 #[allow(clippy::module_name_repetitions)]
533 #[derive(Copy, Clone)]
534 pub struct DecimalLiteralRepresentation {
538 impl_lint_pass!(DecimalLiteralRepresentation => [DECIMAL_LITERAL_REPRESENTATION]);
540 impl EarlyLintPass for DecimalLiteralRepresentation {
541 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
542 if in_external_macro(cx.sess(), expr.span) {
546 if let ExprKind::Lit(ref lit) = expr.kind {
547 self.check_lit(cx, lit)
552 impl DecimalLiteralRepresentation {
554 pub fn new(threshold: u64) -> Self {
557 fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
558 // Lint integral literals.
560 if let LitKind::Int(val, _) = lit.kind;
561 if let Some(src) = snippet_opt(cx, lit.span);
562 if let Some(num_lit) = NumericLiteral::from_lit(&src, &lit);
563 if num_lit.radix == Radix::Decimal;
564 if val >= u128::from(self.threshold);
566 let hex = format!("{:#X}", val);
567 let num_lit = NumericLiteral::new(&hex, num_lit.suffix, false);
568 let _ = Self::do_lint(num_lit.integer).map_err(|warning_type| {
569 warning_type.display(num_lit.format(), cx, lit.span)
575 fn do_lint(digits: &str) -> Result<(), WarningType> {
576 if digits.len() == 1 {
577 // Lint for 1 digit literals, if someone really sets the threshold that low
586 return Err(WarningType::DecimalRepresentation);
588 } else if digits.len() < 4 {
589 // Lint for Literals with a hex-representation of 2 or 3 digits
590 let f = &digits[0..1]; // first digit
591 let s = &digits[1..]; // suffix
594 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && s.chars().all(|c| c == '0'))
595 // Powers of 2 minus 1
596 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && s.chars().all(|c| c == 'F'))
598 return Err(WarningType::DecimalRepresentation);
601 // Lint for Literals with a hex-representation of 4 digits or more
602 let f = &digits[0..1]; // first digit
603 let m = &digits[1..digits.len() - 1]; // middle digits, except last
604 let s = &digits[1..]; // suffix
606 // Powers of 2 with a margin of +15/-16
607 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && m.chars().all(|c| c == '0'))
608 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && m.chars().all(|c| c == 'F'))
609 // Lint for representations with only 0s and Fs, while allowing 7 as the first
611 || ((f.eq("7") || f.eq("F")) && s.chars().all(|c| c == '0' || c == 'F'))
613 return Err(WarningType::DecimalRepresentation);