rust/clippy_lints/src/literal_representation.rs

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//! Lints concerned with the grouping of digits with underscores in integral or
//! floating-point literal expressions.
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use crate::utils::{
in_macro,
numeric_literal::{NumericLiteral, Radix},
snippet_opt, span_lint_and_sugg,
};
use if_chain::if_chain;
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use rustc_ast::ast::{Expr, ExprKind, Lit, LitKind};
use rustc_errors::Applicability;
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use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
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declare_clippy_lint! {
/// **What it does:** Warns if a long integral or floating-point constant does
/// not contain underscores.
///
/// **Why is this bad?** Reading long numbers is difficult without separators.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// // Bad
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/// let x: u64 = 61864918973511;
///
/// // Good
/// let x: u64 = 61_864_918_973_511;
/// ```
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pub UNREADABLE_LITERAL,
pedantic,
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"long integer literal without underscores"
}
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declare_clippy_lint! {
/// **What it does:** Warns for mistyped suffix in literals
///
/// **Why is this bad?** This is most probably a typo
///
/// **Known problems:**
/// - Recommends a signed suffix, even though the number might be too big and an unsigned
/// suffix is required
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/// - Does not match on `_127` since that is a valid grouping for decimal and octal numbers
///
/// **Example:**
///
/// ```rust
/// // Probably mistyped
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/// 2_32;
///
/// // Good
/// 2_i32;
/// ```
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pub MISTYPED_LITERAL_SUFFIXES,
correctness,
"mistyped literal suffix"
}
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declare_clippy_lint! {
/// **What it does:** Warns if an integral or floating-point constant is
/// grouped inconsistently with underscores.
///
/// **Why is this bad?** Readers may incorrectly interpret inconsistently
/// grouped digits.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// // Bad
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/// let x: u64 = 618_64_9189_73_511;
///
/// // Good
/// let x: u64 = 61_864_918_973_511;
/// ```
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pub INCONSISTENT_DIGIT_GROUPING,
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style,
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"integer literals with digits grouped inconsistently"
}
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declare_clippy_lint! {
/// **What it does:** Warns if the digits of an integral or floating-point
/// constant are grouped into groups that
/// are too large.
///
/// **Why is this bad?** Negatively impacts readability.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
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/// let x: u64 = 6186491_8973511;
/// ```
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pub LARGE_DIGIT_GROUPS,
pedantic,
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"grouping digits into groups that are too large"
}
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declare_clippy_lint! {
/// **What it does:** Warns if there is a better representation for a numeric literal.
///
/// **Why is this bad?** Especially for big powers of 2 a hexadecimal representation is more
/// readable than a decimal representation.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// `255` => `0xFF`
/// `65_535` => `0xFFFF`
/// `4_042_322_160` => `0xF0F0_F0F0`
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pub DECIMAL_LITERAL_REPRESENTATION,
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restriction,
"using decimal representation when hexadecimal would be better"
}
enum WarningType {
UnreadableLiteral,
InconsistentDigitGrouping,
LargeDigitGroups,
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DecimalRepresentation,
MistypedLiteralSuffix,
}
impl WarningType {
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fn display(&self, suggested_format: String, cx: &EarlyContext<'_>, span: rustc_span::Span) {
match self {
Self::MistypedLiteralSuffix => span_lint_and_sugg(
cx,
MISTYPED_LITERAL_SUFFIXES,
span,
"mistyped literal suffix",
"did you mean to write",
suggested_format,
Applicability::MaybeIncorrect,
),
Self::UnreadableLiteral => span_lint_and_sugg(
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cx,
UNREADABLE_LITERAL,
span,
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"long literal lacking separators",
"consider",
suggested_format,
Applicability::MachineApplicable,
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),
Self::LargeDigitGroups => span_lint_and_sugg(
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cx,
LARGE_DIGIT_GROUPS,
span,
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"digit groups should be smaller",
"consider",
suggested_format,
Applicability::MachineApplicable,
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),
Self::InconsistentDigitGrouping => span_lint_and_sugg(
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cx,
INCONSISTENT_DIGIT_GROUPING,
span,
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"digits grouped inconsistently by underscores",
"consider",
suggested_format,
Applicability::MachineApplicable,
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),
Self::DecimalRepresentation => span_lint_and_sugg(
cx,
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DECIMAL_LITERAL_REPRESENTATION,
span,
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"integer literal has a better hexadecimal representation",
"consider",
suggested_format,
Applicability::MachineApplicable,
),
};
}
}
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declare_lint_pass!(LiteralDigitGrouping => [
UNREADABLE_LITERAL,
INCONSISTENT_DIGIT_GROUPING,
LARGE_DIGIT_GROUPS,
MISTYPED_LITERAL_SUFFIXES,
]);
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impl EarlyLintPass for LiteralDigitGrouping {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if in_external_macro(cx.sess(), expr.span) {
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return;
}
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if let ExprKind::Lit(ref lit) = expr.kind {
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Self::check_lit(cx, lit)
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}
}
}
// Length of each UUID hyphenated group in hex digits.
const UUID_GROUP_LENS: [usize; 5] = [8, 4, 4, 4, 12];
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impl LiteralDigitGrouping {
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fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
if_chain! {
if let Some(src) = snippet_opt(cx, lit.span);
if let Some(mut num_lit) = NumericLiteral::from_lit(&src, &lit);
then {
if !Self::check_for_mistyped_suffix(cx, lit.span, &mut num_lit) {
return;
}
if Self::is_literal_uuid_formatted(&mut num_lit) {
return;
}
let result = (|| {
let integral_group_size = Self::get_group_size(num_lit.integer.split('_'))?;
if let Some(fraction) = num_lit.fraction {
let fractional_group_size = Self::get_group_size(fraction.rsplit('_'))?;
let consistent = Self::parts_consistent(integral_group_size,
fractional_group_size,
num_lit.integer.len(),
fraction.len());
if !consistent {
return Err(WarningType::InconsistentDigitGrouping);
};
}
Ok(())
})();
if let Err(warning_type) = result {
let should_warn = match warning_type {
| WarningType::UnreadableLiteral
| WarningType::InconsistentDigitGrouping
| WarningType::LargeDigitGroups => {
!in_macro(lit.span)
}
WarningType::DecimalRepresentation | WarningType::MistypedLiteralSuffix => {
true
}
};
if should_warn {
warning_type.display(num_lit.format(), cx, lit.span)
}
}
}
}
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}
// Returns `false` if the check fails
fn check_for_mistyped_suffix(
cx: &EarlyContext<'_>,
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span: rustc_span::Span,
num_lit: &mut NumericLiteral<'_>,
) -> bool {
if num_lit.suffix.is_some() {
return true;
}
let (part, mistyped_suffixes, missing_char) = if let Some((_, exponent)) = &mut num_lit.exponent {
(exponent, &["32", "64"][..], 'f')
} else if let Some(fraction) = &mut num_lit.fraction {
(fraction, &["32", "64"][..], 'f')
} else {
(&mut num_lit.integer, &["8", "16", "32", "64"][..], 'i')
};
let mut split = part.rsplit('_');
let last_group = split.next().expect("At least one group");
if split.next().is_some() && mistyped_suffixes.contains(&last_group) {
*part = &part[..part.len() - last_group.len()];
let mut sugg = num_lit.format();
sugg.push('_');
sugg.push(missing_char);
sugg.push_str(last_group);
WarningType::MistypedLiteralSuffix.display(sugg, cx, span);
false
} else {
true
}
}
/// Checks whether the numeric literal matches the formatting of a UUID.
///
/// Returns `true` if the radix is hexadecimal, and the groups match the
/// UUID format of 8-4-4-4-12.
fn is_literal_uuid_formatted(num_lit: &mut NumericLiteral<'_>) -> bool {
if num_lit.radix != Radix::Hexadecimal {
return false;
}
// UUIDs should not have a fraction
if num_lit.fraction.is_some() {
return false;
}
let group_sizes: Vec<usize> = num_lit.integer.split('_').map(str::len).collect();
if UUID_GROUP_LENS.len() == group_sizes.len() {
UUID_GROUP_LENS.iter().zip(&group_sizes).all(|(&a, &b)| a == b)
} else {
false
}
}
/// Given the sizes of the digit groups of both integral and fractional
/// parts, and the length
/// of both parts, determine if the digits have been grouped consistently.
#[must_use]
fn parts_consistent(
int_group_size: Option<usize>,
frac_group_size: Option<usize>,
int_size: usize,
frac_size: usize,
) -> bool {
match (int_group_size, frac_group_size) {
// No groups on either side of decimal point - trivially consistent.
(None, None) => true,
// Integral part has grouped digits, fractional part does not.
(Some(int_group_size), None) => frac_size <= int_group_size,
// Fractional part has grouped digits, integral part does not.
(None, Some(frac_group_size)) => int_size <= frac_group_size,
// Both parts have grouped digits. Groups should be the same size.
(Some(int_group_size), Some(frac_group_size)) => int_group_size == frac_group_size,
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}
}
/// Returns the size of the digit groups (or None if ungrouped) if successful,
/// otherwise returns a `WarningType` for linting.
fn get_group_size<'a>(groups: impl Iterator<Item = &'a str>) -> Result<Option<usize>, WarningType> {
let mut groups = groups.map(str::len);
let first = groups.next().expect("At least one group");
if let Some(second) = groups.next() {
if !groups.all(|x| x == second) || first > second {
Err(WarningType::InconsistentDigitGrouping)
} else if second > 4 {
Err(WarningType::LargeDigitGroups)
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} else {
Ok(Some(second))
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}
} else if first > 5 {
Err(WarningType::UnreadableLiteral)
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} else {
Ok(None)
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}
}
}
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#[allow(clippy::module_name_repetitions)]
#[derive(Copy, Clone)]
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pub struct DecimalLiteralRepresentation {
threshold: u64,
}
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impl_lint_pass!(DecimalLiteralRepresentation => [DECIMAL_LITERAL_REPRESENTATION]);
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impl EarlyLintPass for DecimalLiteralRepresentation {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if in_external_macro(cx.sess(), expr.span) {
return;
}
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if let ExprKind::Lit(ref lit) = expr.kind {
self.check_lit(cx, lit)
}
}
}
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impl DecimalLiteralRepresentation {
#[must_use]
pub fn new(threshold: u64) -> Self {
Self { threshold }
}
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fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
// Lint integral literals.
if_chain! {
if let LitKind::Int(val, _) = lit.kind;
if let Some(src) = snippet_opt(cx, lit.span);
if let Some(num_lit) = NumericLiteral::from_lit(&src, &lit);
if num_lit.radix == Radix::Decimal;
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if val >= u128::from(self.threshold);
then {
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let hex = format!("{:#X}", val);
let num_lit = NumericLiteral::new(&hex, num_lit.suffix, false);
let _ = Self::do_lint(num_lit.integer).map_err(|warning_type| {
warning_type.display(num_lit.format(), cx, lit.span)
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});
}
}
}
fn do_lint(digits: &str) -> Result<(), WarningType> {
if digits.len() == 1 {
// Lint for 1 digit literals, if someone really sets the threshold that low
if digits == "1"
|| digits == "2"
|| digits == "4"
|| digits == "8"
|| digits == "3"
|| digits == "7"
|| digits == "F"
{
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return Err(WarningType::DecimalRepresentation);
}
} else if digits.len() < 4 {
// Lint for Literals with a hex-representation of 2 or 3 digits
let f = &digits[0..1]; // first digit
let s = &digits[1..]; // suffix
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// Powers of 2
if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && s.chars().all(|c| c == '0'))
// Powers of 2 minus 1
|| ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && s.chars().all(|c| c == 'F'))
{
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return Err(WarningType::DecimalRepresentation);
}
} else {
// Lint for Literals with a hex-representation of 4 digits or more
let f = &digits[0..1]; // first digit
let m = &digits[1..digits.len() - 1]; // middle digits, except last
let s = &digits[1..]; // suffix
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// Powers of 2 with a margin of +15/-16
if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && m.chars().all(|c| c == '0'))
|| ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && m.chars().all(|c| c == 'F'))
// Lint for representations with only 0s and Fs, while allowing 7 as the first
// digit
|| ((f.eq("7") || f.eq("F")) && s.chars().all(|c| c == '0' || c == 'F'))
{
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return Err(WarningType::DecimalRepresentation);
}
}
Ok(())
}
}