1 use clippy_utils::consts::{constant, Constant};
2 use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
3 use clippy_utils::source::{snippet, snippet_opt, snippet_with_applicability};
4 use clippy_utils::sugg::Sugg;
5 use clippy_utils::{get_parent_expr, in_constant, is_integer_const, meets_msrv, msrvs, path_to_local};
6 use clippy_utils::{higher, SpanlessEq};
7 use if_chain::if_chain;
8 use rustc_ast::ast::RangeLimits;
9 use rustc_errors::Applicability;
10 use rustc_hir::{BinOpKind, Expr, ExprKind, HirId, PathSegment, QPath};
11 use rustc_lint::{LateContext, LateLintPass};
13 use rustc_semver::RustcVersion;
14 use rustc_session::{declare_tool_lint, impl_lint_pass};
15 use rustc_span::source_map::{Span, Spanned};
17 use std::cmp::Ordering;
19 declare_clippy_lint! {
21 /// Checks for zipping a collection with the range of
24 /// ### Why is this bad?
25 /// The code is better expressed with `.enumerate()`.
29 /// # let x = vec![1];
30 /// let _ = x.iter().zip(0..x.len());
35 /// # let x = vec![1];
36 /// let _ = x.iter().enumerate();
38 #[clippy::version = "pre 1.29.0"]
39 pub RANGE_ZIP_WITH_LEN,
41 "zipping iterator with a range when `enumerate()` would do"
44 declare_clippy_lint! {
46 /// Checks for exclusive ranges where 1 is added to the
47 /// upper bound, e.g., `x..(y+1)`.
49 /// ### Why is this bad?
50 /// The code is more readable with an inclusive range
53 /// ### Known problems
54 /// Will add unnecessary pair of parentheses when the
55 /// expression is not wrapped in a pair but starts with an opening parenthesis
56 /// and ends with a closing one.
57 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
59 /// Also in many cases, inclusive ranges are still slower to run than
60 /// exclusive ranges, because they essentially add an extra branch that
61 /// LLVM may fail to hoist out of the loop.
63 /// This will cause a warning that cannot be fixed if the consumer of the
64 /// range only accepts a specific range type, instead of the generic
65 /// `RangeBounds` trait
66 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
72 /// for i in x..(y+1) {
85 #[clippy::version = "pre 1.29.0"]
88 "`x..(y+1)` reads better as `x..=y`"
91 declare_clippy_lint! {
93 /// Checks for inclusive ranges where 1 is subtracted from
94 /// the upper bound, e.g., `x..=(y-1)`.
96 /// ### Why is this bad?
97 /// The code is more readable with an exclusive range
100 /// ### Known problems
101 /// This will cause a warning that cannot be fixed if
102 /// the consumer of the range only accepts a specific range type, instead of
103 /// the generic `RangeBounds` trait
104 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
110 /// for i in x..=(y-1) {
123 #[clippy::version = "pre 1.29.0"]
126 "`x..=(y-1)` reads better as `x..y`"
129 declare_clippy_lint! {
131 /// Checks for range expressions `x..y` where both `x` and `y`
132 /// are constant and `x` is greater or equal to `y`.
134 /// ### Why is this bad?
135 /// Empty ranges yield no values so iterating them is a no-op.
136 /// Moreover, trying to use a reversed range to index a slice will panic at run-time.
141 /// (10..=0).for_each(|x| println!("{}", x));
143 /// let arr = [1, 2, 3, 4, 5];
144 /// let sub = &arr[3..1];
150 /// (0..=10).rev().for_each(|x| println!("{}", x));
152 /// let arr = [1, 2, 3, 4, 5];
153 /// let sub = &arr[1..3];
156 #[clippy::version = "1.45.0"]
157 pub REVERSED_EMPTY_RANGES,
159 "reversing the limits of range expressions, resulting in empty ranges"
162 declare_clippy_lint! {
164 /// Checks for expressions like `x >= 3 && x < 8` that could
165 /// be more readably expressed as `(3..8).contains(x)`.
167 /// ### Why is this bad?
168 /// `contains` expresses the intent better and has less
169 /// failure modes (such as fencepost errors or using `||` instead of `&&`).
176 /// assert!(x >= 3 && x < 8);
181 /// assert!((3..8).contains(&x));
183 #[clippy::version = "1.49.0"]
184 pub MANUAL_RANGE_CONTAINS,
186 "manually reimplementing {`Range`, `RangeInclusive`}`::contains`"
190 msrv: Option<RustcVersion>,
195 pub fn new(msrv: Option<RustcVersion>) -> Self {
200 impl_lint_pass!(Ranges => [
204 REVERSED_EMPTY_RANGES,
205 MANUAL_RANGE_CONTAINS,
208 impl<'tcx> LateLintPass<'tcx> for Ranges {
209 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
211 ExprKind::MethodCall(path, args, _) => {
212 check_range_zip_with_len(cx, path, args, expr.span);
214 ExprKind::Binary(ref op, l, r) => {
215 if meets_msrv(self.msrv, msrvs::RANGE_CONTAINS) {
216 check_possible_range_contains(cx, op.node, l, r, expr, expr.span);
222 check_exclusive_range_plus_one(cx, expr);
223 check_inclusive_range_minus_one(cx, expr);
224 check_reversed_empty_range(cx, expr);
226 extract_msrv_attr!(LateContext);
229 fn check_possible_range_contains(
230 cx: &LateContext<'_>,
237 if in_constant(cx, expr.hir_id) {
241 let combine_and = match op {
242 BinOpKind::And | BinOpKind::BitAnd => true,
243 BinOpKind::Or | BinOpKind::BitOr => false,
246 // value, name, order (higher/lower), inclusiveness
247 if let (Some(l), Some(r)) = (check_range_bounds(cx, left), check_range_bounds(cx, right)) {
248 // we only lint comparisons on the same name and with different
250 if l.id != r.id || l.ord == r.ord {
253 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l.expr), &l.val, &r.val);
254 if combine_and && ord == Some(r.ord) {
255 // order lower bound and upper bound
256 let (l_span, u_span, l_inc, u_inc) = if r.ord == Ordering::Less {
257 (l.val_span, r.val_span, l.inc, r.inc)
259 (r.val_span, l.val_span, r.inc, l.inc)
261 // we only lint inclusive lower bounds
265 let (range_type, range_op) = if u_inc {
266 ("RangeInclusive", "..=")
270 let mut applicability = Applicability::MachineApplicable;
271 let name = snippet_with_applicability(cx, l.name_span, "_", &mut applicability);
272 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
273 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
274 let space = if lo.ends_with('.') { " " } else { "" };
277 MANUAL_RANGE_CONTAINS,
279 &format!("manual `{}::contains` implementation", range_type),
281 format!("({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
284 } else if !combine_and && ord == Some(l.ord) {
286 // order lower bound and upper bound
287 let (l_span, u_span, l_inc, u_inc) = if l.ord == Ordering::Less {
288 (l.val_span, r.val_span, l.inc, r.inc)
290 (r.val_span, l.val_span, r.inc, l.inc)
295 let (range_type, range_op) = if u_inc {
298 ("RangeInclusive", "..=")
300 let mut applicability = Applicability::MachineApplicable;
301 let name = snippet_with_applicability(cx, l.name_span, "_", &mut applicability);
302 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
303 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
304 let space = if lo.ends_with('.') { " " } else { "" };
307 MANUAL_RANGE_CONTAINS,
309 &format!("manual `!{}::contains` implementation", range_type),
311 format!("!({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
317 // If the LHS is the same operator, we have to recurse to get the "real" RHS, since they have
318 // the same operator precedence
320 if let ExprKind::Binary(ref lhs_op, _left, new_lhs) = left.kind;
321 if op == lhs_op.node;
322 let new_span = Span::new(new_lhs.span.lo(), right.span.hi(), expr.span.ctxt(), expr.span.parent());
323 if let Some(snip) = &snippet_opt(cx, new_span);
324 // Do not continue if we have mismatched number of parens, otherwise the suggestion is wrong
325 if snip.matches('(').count() == snip.matches(')').count();
327 check_possible_range_contains(cx, op, new_lhs, right, expr, new_span);
332 struct RangeBounds<'a> {
342 // Takes a binary expression such as x <= 2 as input
343 // Breaks apart into various pieces, such as the value of the number,
344 // hir id of the variable, and direction/inclusiveness of the operator
345 fn check_range_bounds<'a>(cx: &'a LateContext<'_>, ex: &'a Expr<'_>) -> Option<RangeBounds<'a>> {
346 if let ExprKind::Binary(ref op, l, r) = ex.kind {
347 let (inclusive, ordering) = match op.node {
348 BinOpKind::Gt => (false, Ordering::Greater),
349 BinOpKind::Ge => (true, Ordering::Greater),
350 BinOpKind::Lt => (false, Ordering::Less),
351 BinOpKind::Le => (true, Ordering::Less),
354 if let Some(id) = path_to_local(l) {
355 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
356 return Some(RangeBounds {
366 } else if let Some(id) = path_to_local(r) {
367 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
368 return Some(RangeBounds {
374 ord: ordering.reverse(),
383 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
385 if path.ident.as_str() == "zip";
386 if let [iter, zip_arg] = args;
388 if let ExprKind::MethodCall(iter_path, iter_args, _) = iter.kind;
389 if iter_path.ident.name == sym::iter;
390 // range expression in `.zip()` call: `0..x.len()`
391 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::Range::hir(zip_arg);
392 if is_integer_const(cx, start, 0);
394 if let ExprKind::MethodCall(len_path, len_args, _) = end.kind;
395 if len_path.ident.name == sym::len && len_args.len() == 1;
396 // `.iter()` and `.len()` called on same `Path`
397 if let ExprKind::Path(QPath::Resolved(_, iter_path)) = iter_args[0].kind;
398 if let ExprKind::Path(QPath::Resolved(_, len_path)) = len_args[0].kind;
399 if SpanlessEq::new(cx).eq_path_segments(iter_path.segments, len_path.segments);
404 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
405 snippet(cx, iter_args[0].span, "_"))
411 // exclusive range plus one: `x..(y+1)`
412 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
414 if let Some(higher::Range {
417 limits: RangeLimits::HalfOpen
418 }) = higher::Range::hir(expr);
419 if let Some(y) = y_plus_one(cx, end);
421 let span = if expr.span.from_expansion() {
433 "an inclusive range would be more readable",
435 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").maybe_par().to_string());
436 let end = Sugg::hir(cx, y, "y").maybe_par();
437 if let Some(is_wrapped) = &snippet_opt(cx, span) {
438 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
439 diag.span_suggestion(
442 format!("({}..={})", start, end),
443 Applicability::MaybeIncorrect,
446 diag.span_suggestion(
449 format!("{}..={}", start, end),
450 Applicability::MachineApplicable, // snippet
460 // inclusive range minus one: `x..=(y-1)`
461 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
463 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::Range::hir(expr);
464 if let Some(y) = y_minus_one(cx, end);
470 "an exclusive range would be more readable",
472 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").maybe_par().to_string());
473 let end = Sugg::hir(cx, y, "y").maybe_par();
474 diag.span_suggestion(
477 format!("{}..{}", start, end),
478 Applicability::MachineApplicable, // snippet
486 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
487 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
489 get_parent_expr(cx, expr),
491 kind: ExprKind::Index(..),
497 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
498 let mut cur_expr = expr;
499 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
500 match higher::ForLoop::hir(parent_expr) {
501 Some(higher::ForLoop { arg, .. }) if arg.hir_id == expr.hir_id => return true,
502 _ => cur_expr = parent_expr,
509 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
511 RangeLimits::HalfOpen => ordering != Ordering::Less,
512 RangeLimits::Closed => ordering == Ordering::Greater,
517 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::Range::hir(expr);
518 let ty = cx.typeck_results().expr_ty(start);
519 if let ty::Int(_) | ty::Uint(_) = ty.kind();
520 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
521 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
522 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
523 if is_empty_range(limits, ordering);
525 if inside_indexing_expr(cx, expr) {
526 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
527 if ordering != Ordering::Equal {
530 REVERSED_EMPTY_RANGES,
532 "this range is reversed and using it to index a slice will panic at run-time",
535 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
536 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
539 REVERSED_EMPTY_RANGES,
541 "this range is empty so it will yield no values",
543 if ordering != Ordering::Equal {
544 let start_snippet = snippet(cx, start.span, "_");
545 let end_snippet = snippet(cx, end.span, "_");
546 let dots = match limits {
547 RangeLimits::HalfOpen => "..",
548 RangeLimits::Closed => "..="
551 diag.span_suggestion(
553 "consider using the following if you are attempting to iterate over this \
555 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
556 Applicability::MaybeIncorrect,
566 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
570 node: BinOpKind::Add, ..
575 if is_integer_const(cx, lhs, 1) {
577 } else if is_integer_const(cx, rhs, 1) {
587 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
591 node: BinOpKind::Sub, ..
595 ) if is_integer_const(cx, rhs, 1) => Some(lhs),