498 lines
16 KiB
Rust
498 lines
16 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::{
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in_macro,
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numeric_literal::{NumericLiteral, Radix},
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snippet_opt, span_lint_and_sugg,
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};
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use if_chain::if_chain;
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use rustc_ast::ast::{Expr, ExprKind, Lit, LitKind};
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use rustc_errors::Applicability;
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use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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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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/// // Bad
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/// let x: u64 = 61864918973511;
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///
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/// // Good
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/// let x: u64 = 61_864_918_973_511;
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/// ```
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pub UNREADABLE_LITERAL,
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pedantic,
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"long 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 `_127` 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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/// // Probably mistyped
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/// 2_32;
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///
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/// // Good
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/// 2_i32;
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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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/// // Bad
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/// let x: u64 = 618_64_9189_73_511;
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///
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/// // Good
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/// let x: u64 = 61_864_918_973_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 hexadecimal or binary literals are not grouped
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/// by nibble or byte.
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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: u32 = 0xFFF_FFF;
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/// let y: u8 = 0b01_011_101;
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/// ```
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pub UNUSUAL_BYTE_GROUPINGS,
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style,
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"binary or hex literals that aren't grouped by four"
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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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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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UnusualByteGroupings,
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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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Self::UnusualByteGroupings => span_lint_and_sugg(
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cx,
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UNUSUAL_BYTE_GROUPINGS,
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span,
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"digits of hex or binary literal not grouped by four",
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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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#[allow(clippy::module_name_repetitions)]
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#[derive(Copy, Clone)]
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pub struct LiteralDigitGrouping {
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lint_fraction_readability: bool,
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}
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impl_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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UNUSUAL_BYTE_GROUPINGS,
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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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// Length of each UUID hyphenated group in hex digits.
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const UUID_GROUP_LENS: [usize; 5] = [8, 4, 4, 4, 12];
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impl LiteralDigitGrouping {
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pub fn new(lint_fraction_readability: bool) -> Self {
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Self {
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lint_fraction_readability,
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}
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}
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fn check_lit(self, 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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if Self::is_literal_uuid_formatted(&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('_'), num_lit.radix, true)?;
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if let Some(fraction) = num_lit.fraction {
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let fractional_group_size = Self::get_group_size(
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fraction.rsplit('_'),
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num_lit.radix,
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self.lint_fraction_readability)?;
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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::UnusualByteGroupings
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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 num_lit.fraction.is_some() {
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(&mut num_lit.integer, &["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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/// Checks whether the numeric literal matches the formatting of a UUID.
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///
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/// Returns `true` if the radix is hexadecimal, and the groups match the
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/// UUID format of 8-4-4-4-12.
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fn is_literal_uuid_formatted(num_lit: &mut NumericLiteral<'_>) -> bool {
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if num_lit.radix != Radix::Hexadecimal {
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return false;
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}
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// UUIDs should not have a fraction
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if num_lit.fraction.is_some() {
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return false;
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}
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let group_sizes: Vec<usize> = num_lit.integer.split('_').map(str::len).collect();
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if UUID_GROUP_LENS.len() == group_sizes.len() {
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UUID_GROUP_LENS.iter().zip(&group_sizes).all(|(&a, &b)| a == b)
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} else {
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false
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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>(
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groups: impl Iterator<Item = &'a str>,
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radix: Radix,
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lint_unreadable: bool,
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) -> 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 (radix == Radix::Binary || radix == Radix::Hexadecimal) && groups.any(|i| i != 4 && i != 2) {
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return Err(WarningType::UnusualByteGroupings);
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}
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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 && lint_unreadable {
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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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}
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}
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