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, single_segment_path};
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, PathSegment, QPath};
11 use rustc_lint::{LateContext, LateLintPass, LintContext};
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 rustc_span::symbol::Ident;
18 use std::cmp::Ordering;
20 declare_clippy_lint! {
22 /// Checks for zipping a collection with the range of
25 /// ### Why is this bad?
26 /// The code is better expressed with `.enumerate()`.
30 /// # let x = vec![1];
31 /// x.iter().zip(0..x.len());
33 /// Could be written as
35 /// # let x = vec![1];
36 /// 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)).
70 /// for x..(y+1) { .. }
72 /// Could be written as
76 #[clippy::version = "pre 1.29.0"]
79 "`x..(y+1)` reads better as `x..=y`"
82 declare_clippy_lint! {
84 /// Checks for inclusive ranges where 1 is subtracted from
85 /// the upper bound, e.g., `x..=(y-1)`.
87 /// ### Why is this bad?
88 /// The code is more readable with an exclusive range
91 /// ### Known problems
92 /// This will cause a warning that cannot be fixed if
93 /// the consumer of the range only accepts a specific range type, instead of
94 /// the generic `RangeBounds` trait
95 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
99 /// for x..=(y-1) { .. }
101 /// Could be written as
105 #[clippy::version = "pre 1.29.0"]
108 "`x..=(y-1)` reads better as `x..y`"
111 declare_clippy_lint! {
113 /// Checks for range expressions `x..y` where both `x` and `y`
114 /// are constant and `x` is greater or equal to `y`.
116 /// ### Why is this bad?
117 /// Empty ranges yield no values so iterating them is a no-op.
118 /// Moreover, trying to use a reversed range to index a slice will panic at run-time.
123 /// (10..=0).for_each(|x| println!("{}", x));
125 /// let arr = [1, 2, 3, 4, 5];
126 /// let sub = &arr[3..1];
132 /// (0..=10).rev().for_each(|x| println!("{}", x));
134 /// let arr = [1, 2, 3, 4, 5];
135 /// let sub = &arr[1..3];
138 #[clippy::version = "1.45.0"]
139 pub REVERSED_EMPTY_RANGES,
141 "reversing the limits of range expressions, resulting in empty ranges"
144 declare_clippy_lint! {
146 /// Checks for expressions like `x >= 3 && x < 8` that could
147 /// be more readably expressed as `(3..8).contains(x)`.
149 /// ### Why is this bad?
150 /// `contains` expresses the intent better and has less
151 /// failure modes (such as fencepost errors or using `||` instead of `&&`).
158 /// assert!(x >= 3 && x < 8);
163 /// assert!((3..8).contains(&x));
165 #[clippy::version = "1.49.0"]
166 pub MANUAL_RANGE_CONTAINS,
168 "manually reimplementing {`Range`, `RangeInclusive`}`::contains`"
172 msrv: Option<RustcVersion>,
177 pub fn new(msrv: Option<RustcVersion>) -> Self {
182 impl_lint_pass!(Ranges => [
186 REVERSED_EMPTY_RANGES,
187 MANUAL_RANGE_CONTAINS,
190 impl<'tcx> LateLintPass<'tcx> for Ranges {
191 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
193 ExprKind::MethodCall(path, _, args, _) => {
194 check_range_zip_with_len(cx, path, args, expr.span);
196 ExprKind::Binary(ref op, l, r) => {
197 if meets_msrv(self.msrv.as_ref(), &msrvs::RANGE_CONTAINS) {
198 check_possible_range_contains(cx, op.node, l, r, expr);
204 check_exclusive_range_plus_one(cx, expr);
205 check_inclusive_range_minus_one(cx, expr);
206 check_reversed_empty_range(cx, expr);
208 extract_msrv_attr!(LateContext);
211 fn check_possible_range_contains(cx: &LateContext<'_>, op: BinOpKind, l: &Expr<'_>, r: &Expr<'_>, expr: &Expr<'_>) {
212 if in_constant(cx, expr.hir_id) {
216 let span = expr.span;
217 let combine_and = match op {
218 BinOpKind::And | BinOpKind::BitAnd => true,
219 BinOpKind::Or | BinOpKind::BitOr => false,
222 // value, name, order (higher/lower), inclusiveness
223 if let (Some((lval, lname, name_span, lval_span, lord, linc)), Some((rval, rname, _, rval_span, rord, rinc))) =
224 (check_range_bounds(cx, l), check_range_bounds(cx, r))
226 // we only lint comparisons on the same name and with different
228 if lname != rname || lord == rord {
231 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l), &lval, &rval);
232 if combine_and && ord == Some(rord) {
233 // order lower bound and upper bound
234 let (l_span, u_span, l_inc, u_inc) = if rord == Ordering::Less {
235 (lval_span, rval_span, linc, rinc)
237 (rval_span, lval_span, rinc, linc)
239 // we only lint inclusive lower bounds
243 let (range_type, range_op) = if u_inc {
244 ("RangeInclusive", "..=")
248 let mut applicability = Applicability::MachineApplicable;
249 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
250 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
251 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
252 let space = if lo.ends_with('.') { " " } else { "" };
255 MANUAL_RANGE_CONTAINS,
257 &format!("manual `{}::contains` implementation", range_type),
259 format!("({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
262 } else if !combine_and && ord == Some(lord) {
264 // order lower bound and upper bound
265 let (l_span, u_span, l_inc, u_inc) = if lord == Ordering::Less {
266 (lval_span, rval_span, linc, rinc)
268 (rval_span, lval_span, rinc, linc)
273 let (range_type, range_op) = if u_inc {
276 ("RangeInclusive", "..=")
278 let mut applicability = Applicability::MachineApplicable;
279 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
280 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
281 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
282 let space = if lo.ends_with('.') { " " } else { "" };
285 MANUAL_RANGE_CONTAINS,
287 &format!("manual `!{}::contains` implementation", range_type),
289 format!("!({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
296 fn check_range_bounds(cx: &LateContext<'_>, ex: &Expr<'_>) -> Option<(Constant, Ident, Span, Span, Ordering, bool)> {
297 if let ExprKind::Binary(ref op, l, r) = ex.kind {
298 let (inclusive, ordering) = match op.node {
299 BinOpKind::Gt => (false, Ordering::Greater),
300 BinOpKind::Ge => (true, Ordering::Greater),
301 BinOpKind::Lt => (false, Ordering::Less),
302 BinOpKind::Le => (true, Ordering::Less),
305 if let Some(id) = match_ident(l) {
306 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
307 return Some((c, id, l.span, r.span, ordering, inclusive));
309 } else if let Some(id) = match_ident(r) {
310 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
311 return Some((c, id, r.span, l.span, ordering.reverse(), inclusive));
318 fn match_ident(e: &Expr<'_>) -> Option<Ident> {
319 if let ExprKind::Path(ref qpath) = e.kind {
320 if let Some(seg) = single_segment_path(qpath) {
321 if seg.args.is_none() {
322 return Some(seg.ident);
329 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
331 if path.ident.as_str() == "zip";
332 if let [iter, zip_arg] = args;
334 if let ExprKind::MethodCall(iter_path, _, iter_args, _) = iter.kind;
335 if iter_path.ident.name == sym::iter;
336 // range expression in `.zip()` call: `0..x.len()`
337 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::Range::hir(zip_arg);
338 if is_integer_const(cx, start, 0);
340 if let ExprKind::MethodCall(len_path, _, len_args, _) = end.kind;
341 if len_path.ident.name == sym::len && len_args.len() == 1;
342 // `.iter()` and `.len()` called on same `Path`
343 if let ExprKind::Path(QPath::Resolved(_, iter_path)) = iter_args[0].kind;
344 if let ExprKind::Path(QPath::Resolved(_, len_path)) = len_args[0].kind;
345 if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
350 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
351 snippet(cx, iter_args[0].span, "_"))
357 // exclusive range plus one: `x..(y+1)`
358 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
360 if let Some(higher::Range {
363 limits: RangeLimits::HalfOpen
364 }) = higher::Range::hir(expr);
365 if let Some(y) = y_plus_one(cx, end);
367 let span = if expr.span.from_expansion() {
379 "an inclusive range would be more readable",
381 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
382 let end = Sugg::hir(cx, y, "y");
383 if let Some(is_wrapped) = &snippet_opt(cx, span) {
384 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
385 diag.span_suggestion(
388 format!("({}..={})", start, end),
389 Applicability::MaybeIncorrect,
392 diag.span_suggestion(
395 format!("{}..={}", start, end),
396 Applicability::MachineApplicable, // snippet
406 // inclusive range minus one: `x..=(y-1)`
407 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
409 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::Range::hir(expr);
410 if let Some(y) = y_minus_one(cx, end);
416 "an exclusive range would be more readable",
418 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
419 let end = Sugg::hir(cx, y, "y");
420 diag.span_suggestion(
423 format!("{}..{}", start, end),
424 Applicability::MachineApplicable, // snippet
432 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
433 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
435 get_parent_expr(cx, expr),
437 kind: ExprKind::Index(..),
443 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
444 let mut cur_expr = expr;
445 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
446 match higher::ForLoop::hir(parent_expr) {
447 Some(higher::ForLoop { arg, .. }) if arg.hir_id == expr.hir_id => return true,
448 _ => cur_expr = parent_expr,
455 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
457 RangeLimits::HalfOpen => ordering != Ordering::Less,
458 RangeLimits::Closed => ordering == Ordering::Greater,
463 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::Range::hir(expr);
464 let ty = cx.typeck_results().expr_ty(start);
465 if let ty::Int(_) | ty::Uint(_) = ty.kind();
466 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
467 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
468 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
469 if is_empty_range(limits, ordering);
471 if inside_indexing_expr(cx, expr) {
472 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
473 if ordering != Ordering::Equal {
476 REVERSED_EMPTY_RANGES,
478 "this range is reversed and using it to index a slice will panic at run-time",
481 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
482 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
485 REVERSED_EMPTY_RANGES,
487 "this range is empty so it will yield no values",
489 if ordering != Ordering::Equal {
490 let start_snippet = snippet(cx, start.span, "_");
491 let end_snippet = snippet(cx, end.span, "_");
492 let dots = match limits {
493 RangeLimits::HalfOpen => "..",
494 RangeLimits::Closed => "..="
497 diag.span_suggestion(
499 "consider using the following if you are attempting to iterate over this \
501 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
502 Applicability::MaybeIncorrect,
512 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
516 node: BinOpKind::Add, ..
521 if is_integer_const(cx, lhs, 1) {
523 } else if is_integer_const(cx, rhs, 1) {
533 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
537 node: BinOpKind::Sub, ..
541 ) if is_integer_const(cx, rhs, 1) => Some(lhs),