1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 //! Lints concerned with the grouping of digits with underscores in integral or
12 //! floating-point literal expressions.
14 use crate::rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass, in_external_macro, LintContext};
15 use crate::rustc::{declare_tool_lint, lint_array};
16 use if_chain::if_chain;
17 use crate::syntax::ast::*;
18 use crate::syntax_pos;
19 use crate::utils::{snippet_opt, span_lint_and_sugg};
21 /// **What it does:** Warns if a long integral or floating-point constant does
22 /// not contain underscores.
24 /// **Why is this bad?** Reading long numbers is difficult without separators.
26 /// **Known problems:** None.
33 declare_clippy_lint! {
34 pub UNREADABLE_LITERAL,
36 "long integer literal without underscores"
39 /// **What it does:** Warns for mistyped suffix in literals
41 /// **Why is this bad?** This is most probably a typo
43 /// **Known problems:**
44 /// - Recommends a signed suffix, even though the number might be too big and an unsigned
45 /// suffix is required
46 /// - Does not match on `_128` since that is a valid grouping for decimal and octal numbers
53 declare_clippy_lint! {
54 pub MISTYPED_LITERAL_SUFFIXES,
56 "mistyped literal suffix"
59 /// **What it does:** Warns if an integral or floating-point constant is
60 /// grouped inconsistently with underscores.
62 /// **Why is this bad?** Readers may incorrectly interpret inconsistently
65 /// **Known problems:** None.
70 /// 618_64_9189_73_511
72 declare_clippy_lint! {
73 pub INCONSISTENT_DIGIT_GROUPING,
75 "integer literals with digits grouped inconsistently"
78 /// **What it does:** Warns if the digits of an integral or floating-point
79 /// constant are grouped into groups that
82 /// **Why is this bad?** Negatively impacts readability.
84 /// **Known problems:** None.
91 declare_clippy_lint! {
92 pub LARGE_DIGIT_GROUPS,
94 "grouping digits into groups that are too large"
97 /// **What it does:** Warns if there is a better representation for a numeric literal.
99 /// **Why is this bad?** Especially for big powers of 2 a hexadecimal representation is more
100 /// readable than a decimal representation.
102 /// **Known problems:** None.
107 /// `65_535` => `0xFFFF`
108 /// `4_042_322_160` => `0xF0F0_F0F0`
109 declare_clippy_lint! {
110 pub DECIMAL_LITERAL_REPRESENTATION,
112 "using decimal representation when hexadecimal would be better"
115 #[derive(Debug, PartialEq)]
116 pub(super) enum Radix {
124 /// Return a reasonable digit group size for this radix.
125 crate fn suggest_grouping(&self) -> usize {
127 Radix::Binary | Radix::Hexadecimal => 4,
128 Radix::Octal | Radix::Decimal => 3,
134 pub(super) struct DigitInfo<'a> {
135 /// Characters of a literal between the radix prefix and type suffix.
136 crate digits: &'a str,
137 /// Which radix the literal was represented in.
139 /// The radix prefix, if present.
140 crate prefix: Option<&'a str>,
141 /// The type suffix, including preceding underscore if present.
142 crate suffix: Option<&'a str>,
143 /// True for floating-point literals.
147 impl<'a> DigitInfo<'a> {
148 crate fn new(lit: &'a str, float: bool) -> Self {
149 // Determine delimiter for radix prefix, if present, and radix.
150 let radix = if lit.starts_with("0x") {
152 } else if lit.starts_with("0b") {
154 } else if lit.starts_with("0o") {
160 // Grab part of the literal after prefix, if present.
161 let (prefix, sans_prefix) = if let Radix::Decimal = radix {
164 let (p, s) = lit.split_at(2);
168 let len = sans_prefix.len();
169 let mut last_d = '\0';
170 for (d_idx, d) in sans_prefix.char_indices() {
171 let suffix_start = if last_d == '_' {
176 if float && (d == 'f' || d == 'e' || d == 'E') ||
177 !float && (d == 'i' || d == 'u' || is_possible_suffix_index(&sans_prefix, suffix_start, len)) {
178 let (digits, suffix) = sans_prefix.split_at(suffix_start);
183 suffix: Some(suffix),
200 /// Returns literal formatted in a sensible way.
201 crate fn grouping_hint(&self) -> String {
202 let group_size = self.radix.suggest_grouping();
203 if self.digits.contains('.') {
204 let mut parts = self.digits.split('.');
205 let int_part_hint = parts
207 .expect("split always returns at least one element")
210 .filter(|&c| c != '_')
213 .map(|chunk| chunk.into_iter().rev().collect())
215 .collect::<Vec<String>>()
217 let frac_part_hint = parts
219 .expect("already checked that there is a `.`")
221 .filter(|&c| c != '_')
224 .map(|chunk| chunk.into_iter().collect())
225 .collect::<Vec<String>>()
231 self.suffix.unwrap_or("")
234 let filtered_digits_vec = self.digits
236 .filter(|&c| c != '_')
238 .collect::<Vec<_>>();
239 let mut hint = filtered_digits_vec
241 .map(|chunk| chunk.into_iter().rev().collect())
243 .collect::<Vec<String>>()
245 // Forces hexadecimal values to be grouped by 4 being filled with zeroes (e.g 0x00ab_cdef)
246 let nb_digits_to_fill = filtered_digits_vec.len() % 4;
247 if self.radix == Radix::Hexadecimal && nb_digits_to_fill != 0 {
248 hint = format!("{:0>4}{}", &hint[..nb_digits_to_fill], &hint[nb_digits_to_fill..]);
250 let suffix_hint = match self.suffix {
251 Some(suffix) if is_mistyped_suffix(suffix) => {
252 format!("_i{}", &suffix[1..])
254 Some(suffix) => suffix.to_string(),
255 None => String::new()
259 self.prefix.unwrap_or(""),
269 InconsistentDigitGrouping,
271 DecimalRepresentation,
272 MistypedLiteralSuffix
276 crate fn display(&self, grouping_hint: &str, cx: &EarlyContext<'_>, span: syntax_pos::Span) {
278 WarningType::MistypedLiteralSuffix => {
281 MISTYPED_LITERAL_SUFFIXES,
283 "mistyped literal suffix",
284 "did you mean to write",
285 grouping_hint.to_string()
288 WarningType::UnreadableLiteral => span_lint_and_sugg(
292 "long literal lacking separators",
294 grouping_hint.to_owned(),
296 WarningType::LargeDigitGroups => span_lint_and_sugg(
300 "digit groups should be smaller",
302 grouping_hint.to_owned(),
304 WarningType::InconsistentDigitGrouping => span_lint_and_sugg(
306 INCONSISTENT_DIGIT_GROUPING,
308 "digits grouped inconsistently by underscores",
310 grouping_hint.to_owned(),
312 WarningType::DecimalRepresentation => span_lint_and_sugg(
314 DECIMAL_LITERAL_REPRESENTATION,
316 "integer literal has a better hexadecimal representation",
318 grouping_hint.to_owned(),
324 #[derive(Copy, Clone)]
325 pub struct LiteralDigitGrouping;
327 impl LintPass for LiteralDigitGrouping {
328 fn get_lints(&self) -> LintArray {
331 INCONSISTENT_DIGIT_GROUPING,
337 impl EarlyLintPass for LiteralDigitGrouping {
338 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
339 if in_external_macro(cx.sess(), expr.span) {
343 if let ExprKind::Lit(ref lit) = expr.node {
344 self.check_lit(cx, lit)
349 impl LiteralDigitGrouping {
350 fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
352 LitKind::Int(..) => {
353 // Lint integral literals.
355 if let Some(src) = snippet_opt(cx, lit.span);
356 if let Some(firstch) = src.chars().next();
357 if char::to_digit(firstch, 10).is_some();
359 let digit_info = DigitInfo::new(&src, false);
360 let _ = Self::do_lint(digit_info.digits, digit_info.suffix).map_err(|warning_type| {
361 warning_type.display(&digit_info.grouping_hint(), cx, lit.span)
366 LitKind::Float(..) | LitKind::FloatUnsuffixed(..) => {
367 // Lint floating-point literals.
369 if let Some(src) = snippet_opt(cx, lit.span);
370 if let Some(firstch) = src.chars().next();
371 if char::to_digit(firstch, 10).is_some();
373 let digit_info = DigitInfo::new(&src, true);
374 // Separate digits into integral and fractional parts.
375 let parts: Vec<&str> = digit_info
377 .split_terminator('.')
380 // Lint integral and fractional parts separately, and then check consistency of digit
381 // groups if both pass.
382 let _ = Self::do_lint(parts[0], None)
383 .map(|integral_group_size| {
385 // Lint the fractional part of literal just like integral part, but reversed.
386 let fractional_part = &parts[1].chars().rev().collect::<String>();
387 let _ = Self::do_lint(fractional_part, None)
388 .map(|fractional_group_size| {
389 let consistent = Self::parts_consistent(integral_group_size,
390 fractional_group_size,
394 WarningType::InconsistentDigitGrouping.display(&digit_info.grouping_hint(),
399 .map_err(|warning_type| warning_type.display(&digit_info.grouping_hint(),
404 .map_err(|warning_type| warning_type.display(&digit_info.grouping_hint(), cx, lit.span));
412 /// Given the sizes of the digit groups of both integral and fractional
413 /// parts, and the length
414 /// of both parts, determine if the digits have been grouped consistently.
415 fn parts_consistent(int_group_size: usize, frac_group_size: usize, int_size: usize, frac_size: usize) -> bool {
416 match (int_group_size, frac_group_size) {
417 // No groups on either side of decimal point - trivially consistent.
419 // Integral part has grouped digits, fractional part does not.
420 (_, 0) => frac_size <= int_group_size,
421 // Fractional part has grouped digits, integral part does not.
422 (0, _) => int_size <= frac_group_size,
423 // Both parts have grouped digits. Groups should be the same size.
424 (_, _) => int_group_size == frac_group_size,
428 /// Performs lint on `digits` (no decimal point) and returns the group
429 /// size on success or `WarningType` when emitting a warning.
430 fn do_lint(digits: &str, suffix: Option<&str>) -> Result<usize, WarningType> {
431 if let Some(suffix) = suffix {
432 if is_mistyped_suffix(suffix) {
433 return Err(WarningType::MistypedLiteralSuffix);
436 // Grab underscore indices with respect to the units digit.
437 let underscore_positions: Vec<usize> = digits
441 .filter_map(|(idx, digit)| if digit == '_' { Some(idx) } else { None })
444 if underscore_positions.is_empty() {
445 // Check if literal needs underscores.
446 if digits.len() > 5 {
447 Err(WarningType::UnreadableLiteral)
452 // Check consistency and the sizes of the groups.
453 let group_size = underscore_positions[0];
454 let consistent = underscore_positions
456 .all(|ps| ps[1] - ps[0] == group_size + 1)
457 // number of digits to the left of the last group cannot be bigger than group size.
458 && (digits.len() - underscore_positions.last()
459 .expect("there's at least one element") <= group_size + 1);
462 return Err(WarningType::InconsistentDigitGrouping);
463 } else if group_size > 4 {
464 return Err(WarningType::LargeDigitGroups);
471 #[derive(Copy, Clone)]
472 pub struct LiteralRepresentation {
476 impl LintPass for LiteralRepresentation {
477 fn get_lints(&self) -> LintArray {
478 lint_array!(DECIMAL_LITERAL_REPRESENTATION)
482 impl EarlyLintPass for LiteralRepresentation {
483 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
484 if in_external_macro(cx.sess(), expr.span) {
488 if let ExprKind::Lit(ref lit) = expr.node {
489 self.check_lit(cx, lit)
494 impl LiteralRepresentation {
495 pub fn new(threshold: u64) -> Self {
500 fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
501 // Lint integral literals.
503 if let LitKind::Int(..) = lit.node;
504 if let Some(src) = snippet_opt(cx, lit.span);
505 if let Some(firstch) = src.chars().next();
506 if char::to_digit(firstch, 10).is_some();
508 let digit_info = DigitInfo::new(&src, false);
509 if digit_info.radix == Radix::Decimal {
510 let val = digit_info.digits
512 .filter(|&c| c != '_')
514 .parse::<u128>().unwrap();
515 if val < u128::from(self.threshold) {
518 let hex = format!("{:#X}", val);
519 let digit_info = DigitInfo::new(&hex[..], false);
520 let _ = Self::do_lint(digit_info.digits).map_err(|warning_type| {
521 warning_type.display(&digit_info.grouping_hint(), cx, lit.span)
528 fn do_lint(digits: &str) -> Result<(), WarningType> {
529 if digits.len() == 1 {
530 // Lint for 1 digit literals, if someone really sets the threshold that low
531 if digits == "1" || digits == "2" || digits == "4" || digits == "8" || digits == "3" || digits == "7"
534 return Err(WarningType::DecimalRepresentation);
536 } else if digits.len() < 4 {
537 // Lint for Literals with a hex-representation of 2 or 3 digits
538 let f = &digits[0..1]; // first digit
539 let s = &digits[1..]; // suffix
541 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && s.chars().all(|c| c == '0'))
542 // Powers of 2 minus 1
543 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && s.chars().all(|c| c == 'F'))
545 return Err(WarningType::DecimalRepresentation);
548 // Lint for Literals with a hex-representation of 4 digits or more
549 let f = &digits[0..1]; // first digit
550 let m = &digits[1..digits.len() - 1]; // middle digits, except last
551 let s = &digits[1..]; // suffix
552 // Powers of 2 with a margin of +15/-16
553 if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && m.chars().all(|c| c == '0'))
554 || ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && m.chars().all(|c| c == 'F'))
555 // Lint for representations with only 0s and Fs, while allowing 7 as the first
557 || ((f.eq("7") || f.eq("F")) && s.chars().all(|c| c == '0' || c == 'F'))
559 return Err(WarningType::DecimalRepresentation);
567 fn is_mistyped_suffix(suffix: &str) -> bool {
568 ["_8", "_16", "_32", "_64"].contains(&suffix)
571 fn is_possible_suffix_index(lit: &str, idx: usize, len: usize) -> bool {
572 ((len > 3 && idx == len - 3) || (len > 2 && idx == len - 2)) &&
573 is_mistyped_suffix(lit.split_at(idx).1)