1 //! Lints concerned with the grouping of digits with underscores in integral or
2 //! floating-point literal expressions.
7 use utils
::{in_external_macro, snippet_opt, span_lint_and_sugg}
;
9 /// **What it does:** Warns if a long integral or floating-point constant does
10 /// not contain underscores.
12 /// **Why is this bad?** Reading long numbers is difficult without separators.
14 /// **Known problems:** None.
21 declare_clippy_lint
! {
22 pub UNREADABLE_LITERAL
,
24 "long integer literal without underscores"
27 /// **What it does:** Warns if an integral or floating-point constant is
28 /// grouped inconsistently with underscores.
30 /// **Why is this bad?** Readers may incorrectly interpret inconsistently
33 /// **Known problems:** None.
38 /// 618_64_9189_73_511
40 declare_clippy_lint
! {
41 pub INCONSISTENT_DIGIT_GROUPING
,
43 "integer literals with digits grouped inconsistently"
46 /// **What it does:** Warns if the digits of an integral or floating-point
47 /// constant are grouped into groups that
50 /// **Why is this bad?** Negatively impacts readability.
52 /// **Known problems:** None.
59 declare_clippy_lint
! {
60 pub LARGE_DIGIT_GROUPS
,
62 "grouping digits into groups that are too large"
65 /// **What it does:** Warns if there is a better representation for a numeric literal.
67 /// **Why is this bad?** Especially for big powers of 2 a hexadecimal representation is more
68 /// readable than a decimal representation.
70 /// **Known problems:** None.
75 /// `65_535` => `0xFFFF`
76 /// `4_042_322_160` => `0xF0F0_F0F0`
77 declare_clippy_lint
! {
78 pub DECIMAL_LITERAL_REPRESENTATION
,
80 "using decimal representation when hexadecimal would be better"
83 #[derive(Debug, PartialEq)]
84 pub(super) enum Radix
{
92 /// Return a reasonable digit group size for this radix.
93 pub fn suggest_grouping(&self) -> usize {
95 Radix
::Binary
| Radix
::Hexadecimal
=> 4,
96 Radix
::Octal
| Radix
::Decimal
=> 3,
102 pub(super) struct DigitInfo
<'a
> {
103 /// Characters of a literal between the radix prefix and type suffix.
105 /// Which radix the literal was represented in.
107 /// The radix prefix, if present.
108 pub prefix
: Option
<&'a
str>,
109 /// The type suffix, including preceding underscore if present.
110 pub suffix
: Option
<&'a
str>,
111 /// True for floating-point literals.
115 impl<'a
> DigitInfo
<'a
> {
116 pub fn new(lit
: &'a
str, float
: bool
) -> Self {
117 // Determine delimiter for radix prefix, if present, and radix.
118 let radix
= if lit
.starts_with("0x") {
120 } else if lit
.starts_with("0b") {
122 } else if lit
.starts_with("0o") {
128 // Grab part of the literal after prefix, if present.
129 let (prefix
, sans_prefix
) = if let Radix
::Decimal
= radix
{
132 let (p
, s
) = lit
.split_at(2);
136 let mut last_d
= '
\0'
;
137 for (d_idx
, d
) in sans_prefix
.char_indices() {
138 if !float
&& (d
== 'i'
|| d
== 'u'
) || float
&& (d
== 'f'
|| d
== 'e'
|| d
== 'E'
) {
139 let suffix_start
= if last_d
== '_' { d_idx - 1 }
else { d_idx }
;
140 let (digits
, suffix
) = sans_prefix
.split_at(suffix_start
);
145 suffix
: Some(suffix
),
162 /// Returns digits grouped in a sensible way.
163 pub fn grouping_hint(&self) -> String
{
164 let group_size
= self.radix
.suggest_grouping();
165 if self.digits
.contains('
.'
) {
166 let mut parts
= self.digits
.split('
.'
);
167 let int_part_hint
= parts
169 .expect("split always returns at least one element")
172 .filter(|&c
| c
!= '_'
)
175 .map(|chunk
| chunk
.into_iter().rev().collect())
177 .collect
::<Vec
<String
>>()
179 let frac_part_hint
= parts
181 .expect("already checked that there is a `.`")
183 .filter(|&c
| c
!= '_'
)
186 .map(|chunk
| chunk
.into_iter().collect())
187 .collect
::<Vec
<String
>>()
193 self.suffix
.unwrap_or("")
196 let hint
= self.digits
199 .filter(|&c
| c
!= '_'
)
202 .map(|chunk
| chunk
.into_iter().rev().collect())
204 .collect
::<Vec
<String
>>()
208 self.prefix
.unwrap_or(""),
210 self.suffix
.unwrap_or("")
218 InconsistentDigitGrouping
,
220 DecimalRepresentation
,
224 pub fn display(&self, grouping_hint
: &str, cx
: &EarlyContext
, span
: &syntax_pos
::Span
) {
226 WarningType
::UnreadableLiteral
=> span_lint_and_sugg(
230 "long literal lacking separators",
232 grouping_hint
.to_owned(),
234 WarningType
::LargeDigitGroups
=> span_lint_and_sugg(
238 "digit groups should be smaller",
240 grouping_hint
.to_owned(),
242 WarningType
::InconsistentDigitGrouping
=> span_lint_and_sugg(
244 INCONSISTENT_DIGIT_GROUPING
,
246 "digits grouped inconsistently by underscores",
248 grouping_hint
.to_owned(),
250 WarningType
::DecimalRepresentation
=> span_lint_and_sugg(
252 DECIMAL_LITERAL_REPRESENTATION
,
254 "integer literal has a better hexadecimal representation",
256 grouping_hint
.to_owned(),
262 #[derive(Copy, Clone)]
263 pub struct LiteralDigitGrouping
;
265 impl LintPass
for LiteralDigitGrouping
{
266 fn get_lints(&self) -> LintArray
{
269 INCONSISTENT_DIGIT_GROUPING
,
275 impl EarlyLintPass
for LiteralDigitGrouping
{
276 fn check_expr(&mut self, cx
: &EarlyContext
, expr
: &Expr
) {
277 if in_external_macro(cx
, expr
.span
) {
281 if let ExprKind
::Lit(ref lit
) = expr
.node
{
282 self.check_lit(cx
, lit
)
287 impl LiteralDigitGrouping
{
288 fn check_lit(&self, cx
: &EarlyContext
, lit
: &Lit
) {
290 LitKind
::Int(..) => {
291 // Lint integral literals.
293 if let Some(src
) = snippet_opt(cx
, lit
.span
);
294 if let Some(firstch
) = src
.chars().next();
295 if char::to_digit(firstch
, 10).is_some();
297 let digit_info
= DigitInfo
::new(&src
, false);
298 let _
= Self::do_lint(digit_info
.digits
).map_err(|warning_type
| {
299 warning_type
.display(&digit_info
.grouping_hint(), cx
, &lit
.span
)
304 LitKind
::Float(..) | LitKind
::FloatUnsuffixed(..) => {
305 // Lint floating-point literals.
307 if let Some(src
) = snippet_opt(cx
, lit
.span
);
308 if let Some(firstch
) = src
.chars().next();
309 if char::to_digit(firstch
, 10).is_some();
311 let digit_info
= DigitInfo
::new(&src
, true);
312 // Separate digits into integral and fractional parts.
313 let parts
: Vec
<&str> = digit_info
315 .split_terminator('
.'
)
318 // Lint integral and fractional parts separately, and then check consistency of digit
319 // groups if both pass.
320 let _
= Self::do_lint(parts
[0])
321 .map(|integral_group_size
| {
323 // Lint the fractional part of literal just like integral part, but reversed.
324 let fractional_part
= &parts
[1].chars().rev().collect
::<String
>();
325 let _
= Self::do_lint(fractional_part
)
326 .map(|fractional_group_size
| {
327 let consistent
= Self::parts_consistent(integral_group_size
,
328 fractional_group_size
,
332 WarningType
::InconsistentDigitGrouping
.display(&digit_info
.grouping_hint(),
337 .map_err(|warning_type
| warning_type
.display(&digit_info
.grouping_hint(),
342 .map_err(|warning_type
| warning_type
.display(&digit_info
.grouping_hint(), cx
, &lit
.span
));
350 /// Given the sizes of the digit groups of both integral and fractional
351 /// parts, and the length
352 /// of both parts, determine if the digits have been grouped consistently.
353 fn parts_consistent(int_group_size
: usize, frac_group_size
: usize, int_size
: usize, frac_size
: usize) -> bool
{
354 match (int_group_size
, frac_group_size
) {
355 // No groups on either side of decimal point - trivially consistent.
357 // Integral part has grouped digits, fractional part does not.
358 (_
, 0) => frac_size
<= int_group_size
,
359 // Fractional part has grouped digits, integral part does not.
360 (0, _
) => int_size
<= frac_group_size
,
361 // Both parts have grouped digits. Groups should be the same size.
362 (_
, _
) => int_group_size
== frac_group_size
,
366 /// Performs lint on `digits` (no decimal point) and returns the group
367 /// size on success or `WarningType` when emitting a warning.
368 fn do_lint(digits
: &str) -> Result
<usize, WarningType
> {
369 // Grab underscore indices with respect to the units digit.
370 let underscore_positions
: Vec
<usize> = digits
374 .filter_map(|(idx
, digit
)| if digit
== '_' { Some(idx) }
else { None }
)
377 if underscore_positions
.is_empty() {
378 // Check if literal needs underscores.
379 if digits
.len() > 5 {
380 Err(WarningType
::UnreadableLiteral
)
385 // Check consistency and the sizes of the groups.
386 let group_size
= underscore_positions
[0];
387 let consistent
= underscore_positions
389 .all(|ps
| ps
[1] - ps
[0] == group_size
+ 1)
390 // number of digits to the left of the last group cannot be bigger than group size.
391 && (digits
.len() - underscore_positions
.last()
392 .expect("there's at least one element") <= group_size
+ 1);
395 return Err(WarningType
::InconsistentDigitGrouping
);
396 } else if group_size
> 4 {
397 return Err(WarningType
::LargeDigitGroups
);
404 #[derive(Copy, Clone)]
405 pub struct LiteralRepresentation
{
409 impl LintPass
for LiteralRepresentation
{
410 fn get_lints(&self) -> LintArray
{
411 lint_array
!(DECIMAL_LITERAL_REPRESENTATION
)
415 impl EarlyLintPass
for LiteralRepresentation
{
416 fn check_expr(&mut self, cx
: &EarlyContext
, expr
: &Expr
) {
417 if in_external_macro(cx
, expr
.span
) {
421 if let ExprKind
::Lit(ref lit
) = expr
.node
{
422 self.check_lit(cx
, lit
)
427 impl LiteralRepresentation
{
428 pub fn new(threshold
: u64) -> Self {
433 fn check_lit(&self, cx
: &EarlyContext
, lit
: &Lit
) {
434 // Lint integral literals.
436 if let LitKind
::Int(..) = lit
.node
;
437 if let Some(src
) = snippet_opt(cx
, lit
.span
);
438 if let Some(firstch
) = src
.chars().next();
439 if char::to_digit(firstch
, 10).is_some();
441 let digit_info
= DigitInfo
::new(&src
, false);
442 if digit_info
.radix
== Radix
::Decimal
{
443 let val
= digit_info
.digits
445 .filter(|&c
| c
!= '_'
)
447 .parse
::<u128
>().unwrap();
448 if val
< u128
::from(self.threshold
) {
451 let hex
= format
!("{:#X}", val
);
452 let digit_info
= DigitInfo
::new(&hex
[..], false);
453 let _
= Self::do_lint(digit_info
.digits
).map_err(|warning_type
| {
454 warning_type
.display(&digit_info
.grouping_hint(), cx
, &lit
.span
)
461 fn do_lint(digits
: &str) -> Result
<(), WarningType
> {
462 if digits
.len() == 1 {
463 // Lint for 1 digit literals, if someone really sets the threshold that low
464 if digits
== "1" || digits
== "2" || digits
== "4" || digits
== "8" || digits
== "3" || digits
== "7"
467 return Err(WarningType
::DecimalRepresentation
);
469 } else if digits
.len() < 4 {
470 // Lint for Literals with a hex-representation of 2 or 3 digits
471 let f
= &digits
[0..1]; // first digit
472 let s
= &digits
[1..]; // suffix
474 if ((f
.eq("1") || f
.eq("2") || f
.eq("4") || f
.eq("8")) && s
.chars().all(|c
| c
== '
0'
))
475 // Powers of 2 minus 1
476 || ((f
.eq("1") || f
.eq("3") || f
.eq("7") || f
.eq("F")) && s
.chars().all(|c
| c
== 'F'
))
478 return Err(WarningType
::DecimalRepresentation
);
481 // Lint for Literals with a hex-representation of 4 digits or more
482 let f
= &digits
[0..1]; // first digit
483 let m
= &digits
[1..digits
.len() - 1]; // middle digits, except last
484 let s
= &digits
[1..]; // suffix
485 // Powers of 2 with a margin of +15/-16
486 if ((f
.eq("1") || f
.eq("2") || f
.eq("4") || f
.eq("8")) && m
.chars().all(|c
| c
== '
0'
))
487 || ((f
.eq("1") || f
.eq("3") || f
.eq("7") || f
.eq("F")) && m
.chars().all(|c
| c
== 'F'
))
488 // Lint for representations with only 0s and Fs, while allowing 7 as the first
490 || ((f
.eq("7") || f
.eq("F")) && s
.chars().all(|c
| c
== '
0'
|| c
== 'F'
))
492 return Err(WarningType
::DecimalRepresentation
);