533 lines
18 KiB
Rust
533 lines
18 KiB
Rust
use clippy_utils::consts::{constant, Constant};
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use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
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use clippy_utils::higher;
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use clippy_utils::msrvs::{self, Msrv};
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use clippy_utils::source::{snippet, snippet_opt, snippet_with_applicability};
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use clippy_utils::sugg::Sugg;
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use clippy_utils::{get_parent_expr, in_constant, is_integer_const, path_to_local};
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use if_chain::if_chain;
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use rustc_ast::ast::RangeLimits;
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use rustc_errors::Applicability;
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use rustc_hir::{BinOpKind, Expr, ExprKind, HirId};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::source_map::{Span, Spanned};
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use std::cmp::Ordering;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for exclusive ranges where 1 is added to the
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/// upper bound, e.g., `x..(y+1)`.
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///
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/// ### Why is this bad?
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/// The code is more readable with an inclusive range
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/// like `x..=y`.
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///
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/// ### Known problems
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/// Will add unnecessary pair of parentheses when the
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/// expression is not wrapped in a pair but starts with an opening parenthesis
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/// and ends with a closing one.
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/// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
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///
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/// Also in many cases, inclusive ranges are still slower to run than
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/// exclusive ranges, because they essentially add an extra branch that
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/// LLVM may fail to hoist out of the loop.
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///
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/// This will cause a warning that cannot be fixed if the consumer of the
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/// range only accepts a specific range type, instead of the generic
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/// `RangeBounds` trait
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/// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
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///
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/// ### Example
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/// ```rust
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/// # let x = 0;
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/// # let y = 1;
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/// for i in x..(y+1) {
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/// // ..
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/// }
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// # let x = 0;
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/// # let y = 1;
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/// for i in x..=y {
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/// // ..
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/// }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub RANGE_PLUS_ONE,
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pedantic,
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"`x..(y+1)` reads better as `x..=y`"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for inclusive ranges where 1 is subtracted from
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/// the upper bound, e.g., `x..=(y-1)`.
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///
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/// ### Why is this bad?
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/// The code is more readable with an exclusive range
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/// like `x..y`.
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///
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/// ### Known problems
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/// This will cause a warning that cannot be fixed if
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/// the consumer of the range only accepts a specific range type, instead of
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/// the generic `RangeBounds` trait
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/// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
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///
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/// ### Example
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/// ```rust
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/// # let x = 0;
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/// # let y = 1;
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/// for i in x..=(y-1) {
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/// // ..
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/// }
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// # let x = 0;
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/// # let y = 1;
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/// for i in x..y {
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/// // ..
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/// }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub RANGE_MINUS_ONE,
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pedantic,
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"`x..=(y-1)` reads better as `x..y`"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for range expressions `x..y` where both `x` and `y`
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/// are constant and `x` is greater or equal to `y`.
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///
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/// ### Why is this bad?
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/// Empty ranges yield no values so iterating them is a no-op.
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/// Moreover, trying to use a reversed range to index a slice will panic at run-time.
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///
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/// ### Example
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/// ```rust,no_run
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/// fn main() {
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/// (10..=0).for_each(|x| println!("{}", x));
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///
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/// let arr = [1, 2, 3, 4, 5];
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/// let sub = &arr[3..1];
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// fn main() {
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/// (0..=10).rev().for_each(|x| println!("{}", x));
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///
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/// let arr = [1, 2, 3, 4, 5];
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/// let sub = &arr[1..3];
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/// }
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/// ```
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#[clippy::version = "1.45.0"]
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pub REVERSED_EMPTY_RANGES,
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correctness,
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"reversing the limits of range expressions, resulting in empty ranges"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for expressions like `x >= 3 && x < 8` that could
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/// be more readably expressed as `(3..8).contains(x)`.
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///
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/// ### Why is this bad?
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/// `contains` expresses the intent better and has less
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/// failure modes (such as fencepost errors or using `||` instead of `&&`).
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///
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/// ### Example
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/// ```rust
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/// // given
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/// let x = 6;
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///
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/// assert!(x >= 3 && x < 8);
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/// ```
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/// Use instead:
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/// ```rust
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///# let x = 6;
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/// assert!((3..8).contains(&x));
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/// ```
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#[clippy::version = "1.49.0"]
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pub MANUAL_RANGE_CONTAINS,
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style,
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"manually reimplementing {`Range`, `RangeInclusive`}`::contains`"
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}
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pub struct Ranges {
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msrv: Msrv,
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}
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impl Ranges {
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#[must_use]
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pub fn new(msrv: Msrv) -> Self {
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Self { msrv }
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}
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}
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impl_lint_pass!(Ranges => [
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RANGE_PLUS_ONE,
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RANGE_MINUS_ONE,
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REVERSED_EMPTY_RANGES,
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MANUAL_RANGE_CONTAINS,
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]);
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impl<'tcx> LateLintPass<'tcx> for Ranges {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let ExprKind::Binary(ref op, l, r) = expr.kind {
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if self.msrv.meets(msrvs::RANGE_CONTAINS) {
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check_possible_range_contains(cx, op.node, l, r, expr, expr.span);
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}
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}
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check_exclusive_range_plus_one(cx, expr);
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check_inclusive_range_minus_one(cx, expr);
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check_reversed_empty_range(cx, expr);
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}
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extract_msrv_attr!(LateContext);
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}
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fn check_possible_range_contains(
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cx: &LateContext<'_>,
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op: BinOpKind,
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left: &Expr<'_>,
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right: &Expr<'_>,
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expr: &Expr<'_>,
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span: Span,
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) {
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if in_constant(cx, expr.hir_id) {
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return;
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}
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let combine_and = match op {
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BinOpKind::And | BinOpKind::BitAnd => true,
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BinOpKind::Or | BinOpKind::BitOr => false,
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_ => return,
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};
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// value, name, order (higher/lower), inclusiveness
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if let (Some(l), Some(r)) = (check_range_bounds(cx, left), check_range_bounds(cx, right)) {
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// we only lint comparisons on the same name and with different
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// direction
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if l.id != r.id || l.ord == r.ord {
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return;
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}
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let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l.expr), &l.val, &r.val);
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if combine_and && ord == Some(r.ord) {
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// order lower bound and upper bound
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let (l_span, u_span, l_inc, u_inc) = if r.ord == Ordering::Less {
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(l.val_span, r.val_span, l.inc, r.inc)
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} else {
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(r.val_span, l.val_span, r.inc, l.inc)
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};
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// we only lint inclusive lower bounds
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if !l_inc {
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return;
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}
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let (range_type, range_op) = if u_inc {
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("RangeInclusive", "..=")
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} else {
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("Range", "..")
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};
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let mut applicability = Applicability::MachineApplicable;
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let name = snippet_with_applicability(cx, l.name_span, "_", &mut applicability);
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let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
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let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
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let space = if lo.ends_with('.') { " " } else { "" };
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span_lint_and_sugg(
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cx,
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MANUAL_RANGE_CONTAINS,
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span,
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&format!("manual `{range_type}::contains` implementation"),
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"use",
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format!("({lo}{space}{range_op}{hi}).contains(&{name})"),
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applicability,
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);
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} else if !combine_and && ord == Some(l.ord) {
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// `!_.contains(_)`
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// order lower bound and upper bound
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let (l_span, u_span, l_inc, u_inc) = if l.ord == Ordering::Less {
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(l.val_span, r.val_span, l.inc, r.inc)
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} else {
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(r.val_span, l.val_span, r.inc, l.inc)
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};
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if l_inc {
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return;
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}
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let (range_type, range_op) = if u_inc {
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("Range", "..")
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} else {
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("RangeInclusive", "..=")
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};
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let mut applicability = Applicability::MachineApplicable;
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let name = snippet_with_applicability(cx, l.name_span, "_", &mut applicability);
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let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
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let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
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let space = if lo.ends_with('.') { " " } else { "" };
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span_lint_and_sugg(
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cx,
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MANUAL_RANGE_CONTAINS,
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span,
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&format!("manual `!{range_type}::contains` implementation"),
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"use",
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format!("!({lo}{space}{range_op}{hi}).contains(&{name})"),
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applicability,
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);
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}
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}
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// If the LHS is the same operator, we have to recurse to get the "real" RHS, since they have
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// the same operator precedence
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if_chain! {
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if let ExprKind::Binary(ref lhs_op, _left, new_lhs) = left.kind;
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if op == lhs_op.node;
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let new_span = Span::new(new_lhs.span.lo(), right.span.hi(), expr.span.ctxt(), expr.span.parent());
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if let Some(snip) = &snippet_opt(cx, new_span);
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// Do not continue if we have mismatched number of parens, otherwise the suggestion is wrong
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if snip.matches('(').count() == snip.matches(')').count();
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then {
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check_possible_range_contains(cx, op, new_lhs, right, expr, new_span);
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}
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}
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}
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struct RangeBounds<'a> {
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val: Constant,
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expr: &'a Expr<'a>,
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id: HirId,
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name_span: Span,
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val_span: Span,
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ord: Ordering,
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inc: bool,
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}
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// Takes a binary expression such as x <= 2 as input
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// Breaks apart into various pieces, such as the value of the number,
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// hir id of the variable, and direction/inclusiveness of the operator
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fn check_range_bounds<'a>(cx: &'a LateContext<'_>, ex: &'a Expr<'_>) -> Option<RangeBounds<'a>> {
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if let ExprKind::Binary(ref op, l, r) = ex.kind {
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let (inclusive, ordering) = match op.node {
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BinOpKind::Gt => (false, Ordering::Greater),
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BinOpKind::Ge => (true, Ordering::Greater),
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BinOpKind::Lt => (false, Ordering::Less),
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BinOpKind::Le => (true, Ordering::Less),
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_ => return None,
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};
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if let Some(id) = path_to_local(l) {
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if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
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return Some(RangeBounds {
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val: c,
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expr: r,
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id,
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name_span: l.span,
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val_span: r.span,
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ord: ordering,
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inc: inclusive,
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});
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}
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} else if let Some(id) = path_to_local(r) {
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if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
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return Some(RangeBounds {
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val: c,
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expr: l,
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id,
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name_span: r.span,
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val_span: l.span,
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ord: ordering.reverse(),
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inc: inclusive,
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});
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}
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}
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}
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None
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}
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// exclusive range plus one: `x..(y+1)`
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fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
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if_chain! {
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if expr.span.can_be_used_for_suggestions();
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if let Some(higher::Range {
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start,
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end: Some(end),
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limits: RangeLimits::HalfOpen
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}) = higher::Range::hir(expr);
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if let Some(y) = y_plus_one(cx, end);
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then {
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let span = expr.span;
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span_lint_and_then(
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cx,
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RANGE_PLUS_ONE,
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span,
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"an inclusive range would be more readable",
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|diag| {
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let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").maybe_par().to_string());
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let end = Sugg::hir(cx, y, "y").maybe_par();
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if let Some(is_wrapped) = &snippet_opt(cx, span) {
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if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
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diag.span_suggestion(
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span,
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"use",
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format!("({start}..={end})"),
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Applicability::MaybeIncorrect,
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);
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} else {
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diag.span_suggestion(
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span,
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"use",
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format!("{start}..={end}"),
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Applicability::MachineApplicable, // snippet
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);
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}
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}
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},
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);
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}
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}
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}
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// inclusive range minus one: `x..=(y-1)`
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fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
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if_chain! {
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if expr.span.can_be_used_for_suggestions();
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if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::Range::hir(expr);
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if let Some(y) = y_minus_one(cx, end);
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then {
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span_lint_and_then(
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cx,
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RANGE_MINUS_ONE,
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expr.span,
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"an exclusive range would be more readable",
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|diag| {
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let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").maybe_par().to_string());
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let end = Sugg::hir(cx, y, "y").maybe_par();
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diag.span_suggestion(
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expr.span,
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"use",
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format!("{start}..{end}"),
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Applicability::MachineApplicable, // snippet
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);
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},
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);
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}
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}
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}
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fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
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fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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matches!(
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get_parent_expr(cx, expr),
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Some(Expr {
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kind: ExprKind::Index(..),
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..
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})
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)
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}
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fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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let mut cur_expr = expr;
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while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
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match higher::ForLoop::hir(parent_expr) {
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Some(higher::ForLoop { arg, .. }) if arg.hir_id == expr.hir_id => return true,
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_ => cur_expr = parent_expr,
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}
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}
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false
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}
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fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
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match limits {
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RangeLimits::HalfOpen => ordering != Ordering::Less,
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RangeLimits::Closed => ordering == Ordering::Greater,
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}
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}
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if_chain! {
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if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::Range::hir(expr);
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let ty = cx.typeck_results().expr_ty(start);
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if let ty::Int(_) | ty::Uint(_) = ty.kind();
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if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
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if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
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if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
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if is_empty_range(limits, ordering);
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then {
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if inside_indexing_expr(cx, expr) {
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// Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
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if ordering != Ordering::Equal {
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span_lint(
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cx,
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REVERSED_EMPTY_RANGES,
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expr.span,
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"this range is reversed and using it to index a slice will panic at run-time",
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);
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}
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// ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
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} else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
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span_lint_and_then(
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cx,
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REVERSED_EMPTY_RANGES,
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expr.span,
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"this range is empty so it will yield no values",
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|diag| {
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if ordering != Ordering::Equal {
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let start_snippet = snippet(cx, start.span, "_");
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let end_snippet = snippet(cx, end.span, "_");
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let dots = match limits {
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RangeLimits::HalfOpen => "..",
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RangeLimits::Closed => "..="
|
|
};
|
|
|
|
diag.span_suggestion(
|
|
expr.span,
|
|
"consider using the following if you are attempting to iterate over this \
|
|
range in reverse",
|
|
format!("({end_snippet}{dots}{start_snippet}).rev()"),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
}
|
|
},
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
|
|
match expr.kind {
|
|
ExprKind::Binary(
|
|
Spanned {
|
|
node: BinOpKind::Add, ..
|
|
},
|
|
lhs,
|
|
rhs,
|
|
) => {
|
|
if is_integer_const(cx, lhs, 1) {
|
|
Some(rhs)
|
|
} else if is_integer_const(cx, rhs, 1) {
|
|
Some(lhs)
|
|
} else {
|
|
None
|
|
}
|
|
},
|
|
_ => None,
|
|
}
|
|
}
|
|
|
|
fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
|
|
match expr.kind {
|
|
ExprKind::Binary(
|
|
Spanned {
|
|
node: BinOpKind::Sub, ..
|
|
},
|
|
lhs,
|
|
rhs,
|
|
) if is_integer_const(cx, rhs, 1) => Some(lhs),
|
|
_ => None,
|
|
}
|
|
}
|