mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
615 lines
20 KiB
Rust
615 lines
20 KiB
Rust
//! Lints concerned with the grouping of digits with underscores in integral or
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//! floating-point literal expressions.
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use crate::utils::{in_macro, snippet_opt, span_lint_and_sugg};
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use if_chain::if_chain;
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use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
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use rustc::{declare_lint_pass, impl_lint_pass};
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use rustc_errors::Applicability;
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use rustc_session::declare_tool_lint;
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use syntax::ast::*;
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declare_clippy_lint! {
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/// **What it does:** Warns if a long integral or floating-point constant does
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/// not contain underscores.
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///
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/// **Why is this bad?** Reading long numbers is difficult without separators.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let x: u64 = 61864918973511;
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/// ```
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pub UNREADABLE_LITERAL,
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style,
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"long integer literal without underscores"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns for mistyped suffix in literals
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///
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/// **Why is this bad?** This is most probably a typo
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///
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/// **Known problems:**
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/// - Recommends a signed suffix, even though the number might be too big and an unsigned
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/// suffix is required
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/// - Does not match on `_128` since that is a valid grouping for decimal and octal numbers
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///
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/// **Example:**
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///
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/// ```rust
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/// 2_32;
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/// ```
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pub MISTYPED_LITERAL_SUFFIXES,
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correctness,
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"mistyped literal suffix"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns if an integral or floating-point constant is
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/// grouped inconsistently with underscores.
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///
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/// **Why is this bad?** Readers may incorrectly interpret inconsistently
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/// grouped digits.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let x: u64 = 618_64_9189_73_511;
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/// ```
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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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}
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declare_clippy_lint! {
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/// **What it does:** Warns if the digits of an integral or floating-point
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/// constant are grouped into groups that
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/// are too large.
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///
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/// **Why is this bad?** Negatively impacts readability.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let x: u64 = 6186491_8973511;
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/// ```
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pub LARGE_DIGIT_GROUPS,
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pedantic,
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"grouping digits into groups that are too large"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns if there is a better representation for a numeric literal.
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///
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/// **Why is this bad?** Especially for big powers of 2 a hexadecimal representation is more
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/// readable than a decimal representation.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// `255` => `0xFF`
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/// `65_535` => `0xFFFF`
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/// `4_042_322_160` => `0xF0F0_F0F0`
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pub DECIMAL_LITERAL_REPRESENTATION,
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restriction,
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"using decimal representation when hexadecimal would be better"
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}
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#[derive(Debug, PartialEq)]
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pub(super) enum Radix {
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Binary,
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Octal,
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Decimal,
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Hexadecimal,
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}
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impl Radix {
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/// Returns a reasonable digit group size for this radix.
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#[must_use]
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fn suggest_grouping(&self) -> usize {
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match *self {
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Self::Binary | Self::Hexadecimal => 4,
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Self::Octal | Self::Decimal => 3,
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}
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}
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}
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/// A helper method to format numeric literals with digit grouping.
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/// `lit` must be a valid numeric literal without suffix.
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pub fn format_numeric_literal(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
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NumericLiteral::new(lit, type_suffix, float).format()
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}
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#[derive(Debug)]
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pub(super) struct NumericLiteral<'a> {
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/// Which radix the literal was represented in.
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radix: Radix,
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/// The radix prefix, if present.
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prefix: Option<&'a str>,
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/// The integer part of the number.
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integer: &'a str,
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/// The fraction part of the number.
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fraction: Option<&'a str>,
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/// The character used as exponent seperator (b'e' or b'E') and the exponent part.
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exponent: Option<(char, &'a str)>,
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/// The type suffix, including preceding underscore if present.
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suffix: Option<&'a str>,
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}
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impl<'a> NumericLiteral<'a> {
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fn from_lit(src: &'a str, lit: &Lit) -> Option<NumericLiteral<'a>> {
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if lit.kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
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let (unsuffixed, suffix) = split_suffix(&src, &lit.kind);
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let float = if let LitKind::Float(..) = lit.kind { true } else { false };
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Some(NumericLiteral::new(unsuffixed, suffix, float))
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} else {
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None
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}
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}
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#[must_use]
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fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
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// Determine delimiter for radix prefix, if present, and radix.
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let radix = if lit.starts_with("0x") {
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Radix::Hexadecimal
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} else if lit.starts_with("0b") {
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Radix::Binary
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} else if lit.starts_with("0o") {
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Radix::Octal
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} else {
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Radix::Decimal
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};
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// Grab part of the literal after prefix, if present.
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let (prefix, mut sans_prefix) = if let Radix::Decimal = radix {
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(None, lit)
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} else {
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let (p, s) = lit.split_at(2);
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(Some(p), s)
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};
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if suffix.is_some() && sans_prefix.ends_with('_') {
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// The '_' before the suffix isn't part of the digits
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sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
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}
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let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
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Self {
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radix,
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prefix,
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integer,
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fraction,
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exponent,
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suffix,
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}
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}
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fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(char, &str)>) {
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let mut integer = digits;
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let mut fraction = None;
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let mut exponent = None;
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if float {
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for (i, c) in digits.char_indices() {
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match c {
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'.' => {
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integer = &digits[..i];
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fraction = Some(&digits[i + 1..]);
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},
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'e' | 'E' => {
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if integer.len() > i {
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integer = &digits[..i];
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} else {
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fraction = Some(&digits[integer.len() + 1..i]);
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};
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exponent = Some((c, &digits[i + 1..]));
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break;
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},
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_ => {},
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}
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}
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}
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(integer, fraction, exponent)
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}
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/// Returns literal formatted in a sensible way.
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fn format(&self) -> String {
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let mut output = String::new();
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if let Some(prefix) = self.prefix {
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output.push_str(prefix);
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}
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let group_size = self.radix.suggest_grouping();
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Self::group_digits(
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&mut output,
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self.integer,
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group_size,
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true,
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self.radix == Radix::Hexadecimal,
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);
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if let Some(fraction) = self.fraction {
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output.push('.');
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Self::group_digits(&mut output, fraction, group_size, false, false);
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}
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if let Some((separator, exponent)) = self.exponent {
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output.push(separator);
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Self::group_digits(&mut output, exponent, group_size, true, false);
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}
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if let Some(suffix) = self.suffix {
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output.push('_');
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output.push_str(suffix);
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}
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output
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}
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fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
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debug_assert!(group_size > 0);
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let mut digits = input.chars().filter(|&c| c != '_');
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let first_group_size;
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if partial_group_first {
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first_group_size = (digits.clone().count() - 1) % group_size + 1;
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if pad {
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for _ in 0..group_size - first_group_size {
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output.push('0');
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}
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}
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} else {
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first_group_size = group_size;
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}
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for _ in 0..first_group_size {
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if let Some(digit) = digits.next() {
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output.push(digit);
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}
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}
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for (c, i) in digits.zip((0..group_size).cycle()) {
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if i == 0 {
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output.push('_');
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}
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output.push(c);
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}
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}
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}
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fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
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debug_assert!(lit_kind.is_numeric());
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if let Some(suffix_length) = lit_suffix_length(lit_kind) {
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let (unsuffixed, suffix) = src.split_at(src.len() - suffix_length);
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(unsuffixed, Some(suffix))
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} else {
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(src, None)
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}
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}
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fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
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debug_assert!(lit_kind.is_numeric());
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let suffix = match lit_kind {
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LitKind::Int(_, int_lit_kind) => match int_lit_kind {
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LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
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LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
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LitIntType::Unsuffixed => None,
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},
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LitKind::Float(_, float_lit_kind) => match float_lit_kind {
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LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
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LitFloatType::Unsuffixed => None,
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},
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_ => None,
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};
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suffix.map(str::len)
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}
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enum WarningType {
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UnreadableLiteral,
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InconsistentDigitGrouping,
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LargeDigitGroups,
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DecimalRepresentation,
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MistypedLiteralSuffix,
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}
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impl WarningType {
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fn display(&self, suggested_format: String, cx: &EarlyContext<'_>, span: rustc_span::Span) {
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match self {
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Self::MistypedLiteralSuffix => span_lint_and_sugg(
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cx,
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MISTYPED_LITERAL_SUFFIXES,
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span,
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"mistyped literal suffix",
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"did you mean to write",
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suggested_format,
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Applicability::MaybeIncorrect,
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),
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Self::UnreadableLiteral => span_lint_and_sugg(
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cx,
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UNREADABLE_LITERAL,
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span,
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"long literal lacking separators",
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"consider",
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suggested_format,
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Applicability::MachineApplicable,
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),
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Self::LargeDigitGroups => span_lint_and_sugg(
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cx,
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LARGE_DIGIT_GROUPS,
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span,
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"digit groups should be smaller",
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"consider",
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suggested_format,
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Applicability::MachineApplicable,
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),
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Self::InconsistentDigitGrouping => span_lint_and_sugg(
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cx,
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INCONSISTENT_DIGIT_GROUPING,
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span,
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"digits grouped inconsistently by underscores",
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"consider",
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suggested_format,
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Applicability::MachineApplicable,
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),
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Self::DecimalRepresentation => span_lint_and_sugg(
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cx,
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DECIMAL_LITERAL_REPRESENTATION,
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span,
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"integer literal has a better hexadecimal representation",
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"consider",
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suggested_format,
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Applicability::MachineApplicable,
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),
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};
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}
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}
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declare_lint_pass!(LiteralDigitGrouping => [
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UNREADABLE_LITERAL,
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INCONSISTENT_DIGIT_GROUPING,
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LARGE_DIGIT_GROUPS,
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MISTYPED_LITERAL_SUFFIXES,
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]);
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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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}
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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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}
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}
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}
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impl LiteralDigitGrouping {
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fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
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if_chain! {
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if let Some(src) = snippet_opt(cx, lit.span);
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if let Some(mut num_lit) = NumericLiteral::from_lit(&src, &lit);
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then {
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if !Self::check_for_mistyped_suffix(cx, lit.span, &mut num_lit) {
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return;
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}
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let result = (|| {
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let integral_group_size = Self::get_group_size(num_lit.integer.split('_'))?;
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if let Some(fraction) = num_lit.fraction {
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let fractional_group_size = Self::get_group_size(fraction.rsplit('_'))?;
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let consistent = Self::parts_consistent(integral_group_size,
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fractional_group_size,
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num_lit.integer.len(),
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fraction.len());
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if !consistent {
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return Err(WarningType::InconsistentDigitGrouping);
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};
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}
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Ok(())
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})();
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if let Err(warning_type) = result {
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let should_warn = match warning_type {
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| WarningType::UnreadableLiteral
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| WarningType::InconsistentDigitGrouping
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| WarningType::LargeDigitGroups => {
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!in_macro(lit.span)
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}
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WarningType::DecimalRepresentation | WarningType::MistypedLiteralSuffix => {
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true
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}
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};
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if should_warn {
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warning_type.display(num_lit.format(), cx, lit.span)
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}
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}
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}
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}
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}
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// Returns `false` if the check fails
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fn check_for_mistyped_suffix(
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cx: &EarlyContext<'_>,
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span: rustc_span::Span,
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num_lit: &mut NumericLiteral<'_>,
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) -> bool {
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if num_lit.suffix.is_some() {
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return true;
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}
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let (part, mistyped_suffixes, missing_char) = if let Some((_, exponent)) = &mut num_lit.exponent {
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(exponent, &["32", "64"][..], 'f')
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} else if let Some(fraction) = &mut num_lit.fraction {
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(fraction, &["32", "64"][..], 'f')
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} else {
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(&mut num_lit.integer, &["8", "16", "32", "64"][..], 'i')
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};
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let mut split = part.rsplit('_');
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let last_group = split.next().expect("At least one group");
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if split.next().is_some() && mistyped_suffixes.contains(&last_group) {
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*part = &part[..part.len() - last_group.len()];
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let mut sugg = num_lit.format();
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sugg.push('_');
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sugg.push(missing_char);
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sugg.push_str(last_group);
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WarningType::MistypedLiteralSuffix.display(sugg, cx, span);
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false
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} else {
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true
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}
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}
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/// Given the sizes of the digit groups of both integral and fractional
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/// parts, and the length
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/// of both parts, determine if the digits have been grouped consistently.
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#[must_use]
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fn parts_consistent(
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int_group_size: Option<usize>,
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frac_group_size: Option<usize>,
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int_size: usize,
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frac_size: usize,
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) -> bool {
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match (int_group_size, frac_group_size) {
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// No groups on either side of decimal point - trivially consistent.
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(None, None) => true,
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// Integral part has grouped digits, fractional part does not.
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(Some(int_group_size), None) => frac_size <= int_group_size,
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// Fractional part has grouped digits, integral part does not.
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(None, Some(frac_group_size)) => int_size <= frac_group_size,
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// Both parts have grouped digits. Groups should be the same size.
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(Some(int_group_size), Some(frac_group_size)) => int_group_size == frac_group_size,
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}
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}
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/// Returns the size of the digit groups (or None if ungrouped) if successful,
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/// otherwise returns a `WarningType` for linting.
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fn get_group_size<'a>(groups: impl Iterator<Item = &'a str>) -> Result<Option<usize>, WarningType> {
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let mut groups = groups.map(str::len);
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let first = groups.next().expect("At least one group");
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if let Some(second) = groups.next() {
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if !groups.all(|x| x == second) || first > second {
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Err(WarningType::InconsistentDigitGrouping)
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} else if second > 4 {
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Err(WarningType::LargeDigitGroups)
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} else {
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Ok(Some(second))
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}
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} else if first > 5 {
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Err(WarningType::UnreadableLiteral)
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} else {
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Ok(None)
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}
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}
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}
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#[allow(clippy::module_name_repetitions)]
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#[derive(Copy, Clone)]
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pub struct DecimalLiteralRepresentation {
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threshold: u64,
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}
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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) {
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return;
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}
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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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}
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}
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}
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impl DecimalLiteralRepresentation {
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#[must_use]
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pub fn new(threshold: u64) -> Self {
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Self { threshold }
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}
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fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
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// Lint integral literals.
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if_chain! {
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if let LitKind::Int(val, _) = lit.kind;
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if let Some(src) = snippet_opt(cx, lit.span);
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if let Some(num_lit) = NumericLiteral::from_lit(&src, &lit);
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if num_lit.radix == Radix::Decimal;
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if val >= u128::from(self.threshold);
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then {
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let hex = format!("{:#X}", val);
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let num_lit = NumericLiteral::new(&hex, num_lit.suffix, false);
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let _ = Self::do_lint(num_lit.integer).map_err(|warning_type| {
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warning_type.display(num_lit.format(), cx, lit.span)
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});
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}
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}
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}
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fn do_lint(digits: &str) -> Result<(), WarningType> {
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if digits.len() == 1 {
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// Lint for 1 digit literals, if someone really sets the threshold that low
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if digits == "1"
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|| digits == "2"
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|| digits == "4"
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|| digits == "8"
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|| digits == "3"
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|| digits == "7"
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|| digits == "F"
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{
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return Err(WarningType::DecimalRepresentation);
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}
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} else if digits.len() < 4 {
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// Lint for Literals with a hex-representation of 2 or 3 digits
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let f = &digits[0..1]; // first digit
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let s = &digits[1..]; // suffix
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// Powers of 2
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if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && s.chars().all(|c| c == '0'))
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// Powers of 2 minus 1
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|| ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && s.chars().all(|c| c == 'F'))
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{
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return Err(WarningType::DecimalRepresentation);
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}
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} else {
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// Lint for Literals with a hex-representation of 4 digits or more
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let f = &digits[0..1]; // first digit
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let m = &digits[1..digits.len() - 1]; // middle digits, except last
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let s = &digits[1..]; // suffix
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// Powers of 2 with a margin of +15/-16
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if ((f.eq("1") || f.eq("2") || f.eq("4") || f.eq("8")) && m.chars().all(|c| c == '0'))
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|| ((f.eq("1") || f.eq("3") || f.eq("7") || f.eq("F")) && m.chars().all(|c| c == 'F'))
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// Lint for representations with only 0s and Fs, while allowing 7 as the first
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// digit
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|| ((f.eq("7") || f.eq("F")) && s.chars().all(|c| c == '0' || c == 'F'))
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{
|
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return Err(WarningType::DecimalRepresentation);
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}
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}
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Ok(())
|
|
}
|
|
}
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