src/tools/clippy/clippy_lints/src/literal_representation.rs - third_party/rust - Git at Google

 //! Lints concerned with the grouping of digits with underscores in integral or
 //! floating-point literal expressions.

 use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::numeric_literal::{NumericLiteral, Radix};
 use clippy_utils::source::snippet_opt;
 use rustc_ast::ast::{Expr, ExprKind, LitKind};
 use rustc_ast::token;
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_session::impl_lint_pass;
 use rustc_span::Span;
 use std::iter;

 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.
     ///
     /// ### Example
     /// ```no_run
     /// # let _: u64 =
     /// 61864918973511
     /// # ;
     /// ```
     ///
     /// Use instead:
     /// ```no_run
     /// # let _: u64 =
     /// 61_864_918_973_511
     /// # ;
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub UNREADABLE_LITERAL,
     pedantic,
     "long literal without underscores"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Warns for mistyped suffix in literals
     ///
     /// ### Why is this bad?
     /// This is most probably a typo
     ///
     /// ### Known problems
     /// - Does not match on integers too large to fit in the corresponding unsigned type
     /// - Does not match on `_127` since that is a valid grouping for decimal and octal numbers
     ///
     /// ### Example
     /// ```ignore
     /// `2_32` => `2_i32`
     /// `250_8 => `250_u8`
     /// ```
     #[clippy::version = "1.30.0"]
     pub MISTYPED_LITERAL_SUFFIXES,
     correctness,
     "mistyped literal suffix"
 }

 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.
     ///
     /// ### Example
     /// ```no_run
     /// # let _: u64 =
     /// 618_64_9189_73_511
     /// # ;
     /// ```
     ///
     /// Use instead:
     /// ```no_run
     /// # let _: u64 =
     /// 61_864_918_973_511
     /// # ;
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub INCONSISTENT_DIGIT_GROUPING,
     style,
     "integer literals with digits grouped inconsistently"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Warns if hexadecimal or binary literals are not grouped
     /// by nibble or byte.
     ///
     /// ### Why is this bad?
     /// Negatively impacts readability.
     ///
     /// ### Example
     /// ```no_run
     /// let x: u32 = 0xFFF_FFF;
     /// let y: u8 = 0b01_011_101;
     /// ```
     #[clippy::version = "1.49.0"]
     pub UNUSUAL_BYTE_GROUPINGS,
     style,
     "binary or hex literals that aren't grouped by four"
 }

 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.
     ///
     /// ### Example
     /// ```no_run
     /// let x: u64 = 6186491_8973511;
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub LARGE_DIGIT_GROUPS,
     pedantic,
     "grouping digits into groups that are too large"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Warns if there is a better representation for a numeric literal.
     ///
     /// ### Why restrict this?
     /// Especially for big powers of 2, a hexadecimal representation is usually more
     /// readable than a decimal representation.
     ///
     /// ### Example
     /// ```text
     /// `255` => `0xFF`
     /// `65_535` => `0xFFFF`
     /// `4_042_322_160` => `0xF0F0_F0F0`
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub DECIMAL_LITERAL_REPRESENTATION,
     restriction,
     "using decimal representation when hexadecimal would be better"
 }

 enum WarningType {
     UnreadableLiteral,
     InconsistentDigitGrouping,
     LargeDigitGroups,
     DecimalRepresentation,
     MistypedLiteralSuffix,
     UnusualByteGroupings,
 }

 impl WarningType {
     fn display(&self, suggested_format: String, cx: &EarlyContext<'_>, 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(
                 cx,
                 UNREADABLE_LITERAL,
                 span,
                 "long literal lacking separators",
                 "consider",
                 suggested_format,
                 Applicability::MachineApplicable,
             ),
             Self::LargeDigitGroups => span_lint_and_sugg(
                 cx,
                 LARGE_DIGIT_GROUPS,
                 span,
                 "digit groups should be smaller",
                 "consider",
                 suggested_format,
                 Applicability::MachineApplicable,
             ),
             Self::InconsistentDigitGrouping => span_lint_and_sugg(
                 cx,
                 INCONSISTENT_DIGIT_GROUPING,
                 span,
                 "digits grouped inconsistently by underscores",
                 "consider",
                 suggested_format,
                 Applicability::MachineApplicable,
             ),
             Self::DecimalRepresentation => span_lint_and_sugg(
                 cx,
                 DECIMAL_LITERAL_REPRESENTATION,
                 span,
                 "integer literal has a better hexadecimal representation",
                 "consider",
                 suggested_format,
                 Applicability::MachineApplicable,
             ),
             Self::UnusualByteGroupings => span_lint_and_sugg(
                 cx,
                 UNUSUAL_BYTE_GROUPINGS,
                 span,
                 "digits of hex, binary or octal literal not in groups of equal size",
                 "consider",
                 suggested_format,
                 Applicability::MachineApplicable,
             ),
         };
     }
 }

 pub struct LiteralDigitGrouping {
     lint_fraction_readability: bool,
 }

 impl_lint_pass!(LiteralDigitGrouping => [
     UNREADABLE_LITERAL,
     INCONSISTENT_DIGIT_GROUPING,
     LARGE_DIGIT_GROUPS,
     MISTYPED_LITERAL_SUFFIXES,
     UNUSUAL_BYTE_GROUPINGS,
 ]);

 impl EarlyLintPass for LiteralDigitGrouping {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
         if let ExprKind::Lit(lit) = expr.kind
             && !in_external_macro(cx.sess(), expr.span)
         {
             self.check_lit(cx, lit, expr.span);
         }
     }
 }

 // Length of each UUID hyphenated group in hex digits.
 const UUID_GROUP_LENS: [usize; 5] = [8, 4, 4, 4, 12];

 impl LiteralDigitGrouping {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
             lint_fraction_readability: conf.unreadable_literal_lint_fractions,
         }
     }

     fn check_lit(&self, cx: &EarlyContext<'_>, lit: token::Lit, span: Span) {
         if let Some(src) = snippet_opt(cx, span)
             && let Ok(lit_kind) = LitKind::from_token_lit(lit)
             && let Some(mut num_lit) = NumericLiteral::from_lit_kind(&src, &lit_kind)
         {
             if !Self::check_for_mistyped_suffix(cx, span, &mut num_lit) {
                 return;
             }

             if Self::is_literal_uuid_formatted(&num_lit) {
                 return;
             }

             let result = (|| {
                 let integral_group_size = Self::get_group_size(num_lit.integer.split('_'), num_lit.radix, true)?;
                 if let Some(fraction) = num_lit.fraction {
                     let fractional_group_size =
                         Self::get_group_size(fraction.rsplit('_'), num_lit.radix, self.lint_fraction_readability)?;

                     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::UnusualByteGroupings
                     | WarningType::LargeDigitGroups => !span.from_expansion(),
                     WarningType::DecimalRepresentation | WarningType::MistypedLiteralSuffix => true,
                 };
                 if should_warn {
                     warning_type.display(num_lit.format(), cx, span);
                 }
             }
         }
     }

     // Returns `false` if the check fails
     fn check_for_mistyped_suffix(cx: &EarlyContext<'_>, span: Span, num_lit: &mut NumericLiteral<'_>) -> bool {
         if num_lit.suffix.is_some() {
             return true;
         }

         let (part, mistyped_suffixes, is_float) = if let Some((_, exponent)) = &mut num_lit.exponent {
             (exponent, &["32", "64"][..], true)
         } else if num_lit.fraction.is_some() {
             return true;
         } else {
             (&mut num_lit.integer, &["8", "16", "32", "64"][..], false)
         };

         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) {
             let main_part = &part[..part.len() - last_group.len()];
             let missing_char;
             if is_float {
                 missing_char = 'f';
             } else {
                 let radix = match num_lit.radix {
                     Radix::Binary => 2,
                     Radix::Octal => 8,
                     Radix::Decimal => 10,
                     Radix::Hexadecimal => 16,
                 };
                 if let Ok(int) = u64::from_str_radix(&main_part.replace('_', ""), radix) {
                     missing_char = match (last_group, int) {
                         ("8", i) if i8::try_from(i).is_ok() => 'i',
                         ("16", i) if i16::try_from(i).is_ok() => 'i',
                         ("32", i) if i32::try_from(i).is_ok() => 'i',
                         ("64", i) if i64::try_from(i).is_ok() => 'i',
                         ("8", u) if u8::try_from(u).is_ok() => 'u',
                         ("16", u) if u16::try_from(u).is_ok() => 'u',
                         ("32", u) if u32::try_from(u).is_ok() => 'u',
                         ("64", _) => 'u',
                         _ => {
                             return true;
                         },
                     }
                 } else {
                     return true;
                 }
             }
             *part = main_part;
             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: &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() {
             iter::zip(&UUID_GROUP_LENS, &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,
         }
     }

     /// 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>,
         radix: Radix,
         lint_unreadable: bool,
     ) -> Result<Option<usize>, WarningType> {
         let mut groups = groups.map(str::len);

         let first = groups.next().expect("At least one group");

         if radix == Radix::Binary || radix == Radix::Octal || radix == Radix::Hexadecimal {
             if let Some(second_size) = groups.next() {
                 if !groups.all(|i| i == second_size) || first > second_size {
                     return Err(WarningType::UnusualByteGroupings);
                 }
             }
         }

         if let Some(second) = groups.next() {
             if !groups.all(|x| x == second) || first > second {
                 Err(WarningType::InconsistentDigitGrouping)
             } else if second > 4 {
                 Err(WarningType::LargeDigitGroups)
             } else {
                 Ok(Some(second))
             }
         } else if first > 5 && lint_unreadable {
             Err(WarningType::UnreadableLiteral)
         } else {
             Ok(None)
         }
     }
 }

 #[expect(clippy::module_name_repetitions)]
 pub struct DecimalLiteralRepresentation {
     threshold: u64,
 }

 impl_lint_pass!(DecimalLiteralRepresentation => [DECIMAL_LITERAL_REPRESENTATION]);

 impl EarlyLintPass for DecimalLiteralRepresentation {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
         if let ExprKind::Lit(lit) = expr.kind
             && !in_external_macro(cx.sess(), expr.span)
         {
             self.check_lit(cx, lit, expr.span);
         }
     }
 }

 impl DecimalLiteralRepresentation {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
             threshold: conf.literal_representation_threshold,
         }
     }
     fn check_lit(&self, cx: &EarlyContext<'_>, lit: token::Lit, span: Span) {
         // Lint integral literals.
         if let Ok(lit_kind) = LitKind::from_token_lit(lit)
             && let LitKind::Int(val, _) = lit_kind
             && let Some(src) = snippet_opt(cx, span)
             && let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit_kind)
             && num_lit.radix == Radix::Decimal
             && val >= u128::from(self.threshold)
         {
             let hex = format!("{val:#X}");
             let num_lit = NumericLiteral::new(&hex, num_lit.suffix, false);
             let _: Result<(), ()> = Self::do_lint(num_lit.integer).map_err(|warning_type| {
                 warning_type.display(num_lit.format(), cx, span);
             });
         }
     }

     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"
             {
                 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

             // 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'))
             {
                 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

             // 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'))
             {
                 return Err(WarningType::DecimalRepresentation);
             }
         }

         Ok(())
     }
 }
	//! Lints concerned with the grouping of digits with underscores in integral or
	//! floating-point literal expressions.

	use clippy_config::Conf;
	use clippy_utils::diagnostics::span_lint_and_sugg;
	use clippy_utils::numeric_literal::{NumericLiteral, Radix};
	use clippy_utils::source::snippet_opt;
	use rustc_ast::ast::{Expr, ExprKind, LitKind};
	use rustc_ast::token;
	use rustc_errors::Applicability;
	use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
	use rustc_middle::lint::in_external_macro;
	use rustc_session::impl_lint_pass;
	use rustc_span::Span;
	use std::iter;

	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.
	///
	/// ### Example
	/// ```no_run
	/// # let _: u64 =
	/// 61864918973511
	/// # ;
	/// ```
	///
	/// Use instead:
	/// ```no_run
	/// # let _: u64 =
	/// 61_864_918_973_511
	/// # ;
	/// ```
	#[clippy::version = "pre 1.29.0"]
	pub UNREADABLE_LITERAL,
	pedantic,
	"long literal without underscores"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Warns for mistyped suffix in literals
	///
	/// ### Why is this bad?
	/// This is most probably a typo
	///
	/// ### Known problems
	/// - Does not match on integers too large to fit in the corresponding unsigned type
	/// - Does not match on `_127` since that is a valid grouping for decimal and octal numbers
	///
	/// ### Example
	/// ```ignore
	/// `2_32` => `2_i32`
	/// `250_8 => `250_u8`
	/// ```
	#[clippy::version = "1.30.0"]
	pub MISTYPED_LITERAL_SUFFIXES,
	correctness,
	"mistyped literal suffix"
	}

	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.
	///
	/// ### Example
	/// ```no_run
	/// # let _: u64 =
	/// 618_64_9189_73_511
	/// # ;
	/// ```
	///
	/// Use instead:
	/// ```no_run
	/// # let _: u64 =
	/// 61_864_918_973_511
	/// # ;
	/// ```
	#[clippy::version = "pre 1.29.0"]
	pub INCONSISTENT_DIGIT_GROUPING,
	style,
	"integer literals with digits grouped inconsistently"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Warns if hexadecimal or binary literals are not grouped
	/// by nibble or byte.
	///
	/// ### Why is this bad?
	/// Negatively impacts readability.
	///
	/// ### Example
	/// ```no_run
	/// let x: u32 = 0xFFF_FFF;
	/// let y: u8 = 0b01_011_101;
	/// ```
	#[clippy::version = "1.49.0"]
	pub UNUSUAL_BYTE_GROUPINGS,
	style,
	"binary or hex literals that aren't grouped by four"
	}

	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.
	///
	/// ### Example
	/// ```no_run
	/// let x: u64 = 6186491_8973511;
	/// ```
	#[clippy::version = "pre 1.29.0"]
	pub LARGE_DIGIT_GROUPS,
	pedantic,
	"grouping digits into groups that are too large"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Warns if there is a better representation for a numeric literal.
	///
	/// ### Why restrict this?
	/// Especially for big powers of 2, a hexadecimal representation is usually more
	/// readable than a decimal representation.
	///
	/// ### Example
	/// ```text
	/// `255` => `0xFF`
	/// `65_535` => `0xFFFF`
	/// `4_042_322_160` => `0xF0F0_F0F0`
	/// ```
	#[clippy::version = "pre 1.29.0"]
	pub DECIMAL_LITERAL_REPRESENTATION,
	restriction,
	"using decimal representation when hexadecimal would be better"
	}

	enum WarningType {
	UnreadableLiteral,
	InconsistentDigitGrouping,
	LargeDigitGroups,
	DecimalRepresentation,
	MistypedLiteralSuffix,
	UnusualByteGroupings,
	}

	impl WarningType {
	fn display(&self, suggested_format: String, cx: &EarlyContext<'_>, 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(
	cx,
	UNREADABLE_LITERAL,
	span,
	"long literal lacking separators",
	"consider",
	suggested_format,
	Applicability::MachineApplicable,
	),
	Self::LargeDigitGroups => span_lint_and_sugg(
	cx,
	LARGE_DIGIT_GROUPS,
	span,
	"digit groups should be smaller",
	"consider",
	suggested_format,
	Applicability::MachineApplicable,
	),
	Self::InconsistentDigitGrouping => span_lint_and_sugg(
	cx,
	INCONSISTENT_DIGIT_GROUPING,
	span,
	"digits grouped inconsistently by underscores",
	"consider",
	suggested_format,
	Applicability::MachineApplicable,
	),
	Self::DecimalRepresentation => span_lint_and_sugg(
	cx,
	DECIMAL_LITERAL_REPRESENTATION,
	span,
	"integer literal has a better hexadecimal representation",
	"consider",
	suggested_format,
	Applicability::MachineApplicable,
	),
	Self::UnusualByteGroupings => span_lint_and_sugg(
	cx,
	UNUSUAL_BYTE_GROUPINGS,
	span,
	"digits of hex, binary or octal literal not in groups of equal size",
	"consider",
	suggested_format,
	Applicability::MachineApplicable,
	),
	};
	}
	}

	pub struct LiteralDigitGrouping {
	lint_fraction_readability: bool,
	}

	impl_lint_pass!(LiteralDigitGrouping => [
	UNREADABLE_LITERAL,
	INCONSISTENT_DIGIT_GROUPING,
	LARGE_DIGIT_GROUPS,
	MISTYPED_LITERAL_SUFFIXES,
	UNUSUAL_BYTE_GROUPINGS,
	]);

	impl EarlyLintPass for LiteralDigitGrouping {
	fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
	if let ExprKind::Lit(lit) = expr.kind
	&& !in_external_macro(cx.sess(), expr.span)
	{
	self.check_lit(cx, lit, expr.span);
	}
	}
	}

	// Length of each UUID hyphenated group in hex digits.
	const UUID_GROUP_LENS: [usize; 5] = [8, 4, 4, 4, 12];

	impl LiteralDigitGrouping {
	pub fn new(conf: &'static Conf) -> Self {
	Self {
	lint_fraction_readability: conf.unreadable_literal_lint_fractions,
	}
	}

	fn check_lit(&self, cx: &EarlyContext<'_>, lit: token::Lit, span: Span) {
	if let Some(src) = snippet_opt(cx, span)
	&& let Ok(lit_kind) = LitKind::from_token_lit(lit)
	&& let Some(mut num_lit) = NumericLiteral::from_lit_kind(&src, &lit_kind)
	{
	if !Self::check_for_mistyped_suffix(cx, span, &mut num_lit) {
	return;
	}

	if Self::is_literal_uuid_formatted(&num_lit) {
	return;
	}

	let result = (\|\| {
	let integral_group_size = Self::get_group_size(num_lit.integer.split('_'), num_lit.radix, true)?;
	if let Some(fraction) = num_lit.fraction {
	let fractional_group_size =
	Self::get_group_size(fraction.rsplit('_'), num_lit.radix, self.lint_fraction_readability)?;

	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::UnusualByteGroupings
	\| WarningType::LargeDigitGroups => !span.from_expansion(),
	WarningType::DecimalRepresentation \| WarningType::MistypedLiteralSuffix => true,
	};
	if should_warn {
	warning_type.display(num_lit.format(), cx, span);
	}
	}
	}
	}

	// Returns `false` if the check fails
	fn check_for_mistyped_suffix(cx: &EarlyContext<'_>, span: Span, num_lit: &mut NumericLiteral<'_>) -> bool {
	if num_lit.suffix.is_some() {
	return true;
	}

	let (part, mistyped_suffixes, is_float) = if let Some((_, exponent)) = &mut num_lit.exponent {
	(exponent, &["32", "64"][..], true)
	} else if num_lit.fraction.is_some() {
	return true;
	} else {
	(&mut num_lit.integer, &["8", "16", "32", "64"][..], false)
	};

	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) {
	let main_part = &part[..part.len() - last_group.len()];
	let missing_char;
	if is_float {
	missing_char = 'f';
	} else {
	let radix = match num_lit.radix {
	Radix::Binary => 2,
	Radix::Octal => 8,
	Radix::Decimal => 10,
	Radix::Hexadecimal => 16,
	};
	if let Ok(int) = u64::from_str_radix(&main_part.replace('_', ""), radix) {
	missing_char = match (last_group, int) {
	("8", i) if i8::try_from(i).is_ok() => 'i',
	("16", i) if i16::try_from(i).is_ok() => 'i',
	("32", i) if i32::try_from(i).is_ok() => 'i',
	("64", i) if i64::try_from(i).is_ok() => 'i',
	("8", u) if u8::try_from(u).is_ok() => 'u',
	("16", u) if u16::try_from(u).is_ok() => 'u',
	("32", u) if u32::try_from(u).is_ok() => 'u',
	("64", _) => 'u',
	_ => {
	return true;
	},
	}
	} else {
	return true;
	}
	}
	*part = main_part;
	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: &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() {
	iter::zip(&UUID_GROUP_LENS, &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,
	}
	}

	/// 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>,
	radix: Radix,
	lint_unreadable: bool,
	) -> Result<Option<usize>, WarningType> {
	let mut groups = groups.map(str::len);

	let first = groups.next().expect("At least one group");

	if radix == Radix::Binary \|\| radix == Radix::Octal \|\| radix == Radix::Hexadecimal {
	if let Some(second_size) = groups.next() {
	if !groups.all(\|i\| i == second_size) \|\| first > second_size {
	return Err(WarningType::UnusualByteGroupings);
	}
	}
	}

	if let Some(second) = groups.next() {
	if !groups.all(\|x\| x == second) \|\| first > second {
	Err(WarningType::InconsistentDigitGrouping)
	} else if second > 4 {
	Err(WarningType::LargeDigitGroups)
	} else {
	Ok(Some(second))
	}
	} else if first > 5 && lint_unreadable {
	Err(WarningType::UnreadableLiteral)
	} else {
	Ok(None)
	}
	}
	}

	#[expect(clippy::module_name_repetitions)]
	pub struct DecimalLiteralRepresentation {
	threshold: u64,
	}

	impl_lint_pass!(DecimalLiteralRepresentation => [DECIMAL_LITERAL_REPRESENTATION]);

	impl EarlyLintPass for DecimalLiteralRepresentation {
	fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
	if let ExprKind::Lit(lit) = expr.kind
	&& !in_external_macro(cx.sess(), expr.span)
	{
	self.check_lit(cx, lit, expr.span);
	}
	}
	}

	impl DecimalLiteralRepresentation {
	pub fn new(conf: &'static Conf) -> Self {
	Self {
	threshold: conf.literal_representation_threshold,
	}
	}
	fn check_lit(&self, cx: &EarlyContext<'_>, lit: token::Lit, span: Span) {
	// Lint integral literals.
	if let Ok(lit_kind) = LitKind::from_token_lit(lit)
	&& let LitKind::Int(val, _) = lit_kind
	&& let Some(src) = snippet_opt(cx, span)
	&& let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit_kind)
	&& num_lit.radix == Radix::Decimal
	&& val >= u128::from(self.threshold)
	{
	let hex = format!("{val:#X}");
	let num_lit = NumericLiteral::new(&hex, num_lit.suffix, false);
	let _: Result<(), ()> = Self::do_lint(num_lit.integer).map_err(\|warning_type\| {
	warning_type.display(num_lit.format(), cx, span);
	});
	}
	}

	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"
	{
	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

	// 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'))
	{
	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

	// 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'))
	{
	return Err(WarningType::DecimalRepresentation);
	}
	}

	Ok(())
	}
	}