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 pub RANGE_ZIP_WITH_LEN,
40 "zipping iterator with a range when `enumerate()` would do"
43 declare_clippy_lint! {
45 /// Checks for exclusive ranges where 1 is added to the
46 /// upper bound, e.g., `x..(y+1)`.
48 /// ### Why is this bad?
49 /// The code is more readable with an inclusive range
52 /// ### Known problems
53 /// Will add unnecessary pair of parentheses when the
54 /// expression is not wrapped in a pair but starts with a opening parenthesis
55 /// and ends with a closing one.
56 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
58 /// Also in many cases, inclusive ranges are still slower to run than
59 /// exclusive ranges, because they essentially add an extra branch that
60 /// LLVM may fail to hoist out of the loop.
62 /// This will cause a warning that cannot be fixed if the consumer of the
63 /// range only accepts a specific range type, instead of the generic
64 /// `RangeBounds` trait
65 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
69 /// for x..(y+1) { .. }
71 /// Could be written as
77 "`x..(y+1)` reads better as `x..=y`"
80 declare_clippy_lint! {
82 /// Checks for inclusive ranges where 1 is subtracted from
83 /// the upper bound, e.g., `x..=(y-1)`.
85 /// ### Why is this bad?
86 /// The code is more readable with an exclusive range
89 /// ### Known problems
90 /// This will cause a warning that cannot be fixed if
91 /// the consumer of the range only accepts a specific range type, instead of
92 /// the generic `RangeBounds` trait
93 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
97 /// for x..=(y-1) { .. }
99 /// Could be written as
105 "`x..=(y-1)` reads better as `x..y`"
108 declare_clippy_lint! {
110 /// Checks for range expressions `x..y` where both `x` and `y`
111 /// are constant and `x` is greater or equal to `y`.
113 /// ### Why is this bad?
114 /// Empty ranges yield no values so iterating them is a no-op.
115 /// Moreover, trying to use a reversed range to index a slice will panic at run-time.
120 /// (10..=0).for_each(|x| println!("{}", x));
122 /// let arr = [1, 2, 3, 4, 5];
123 /// let sub = &arr[3..1];
129 /// (0..=10).rev().for_each(|x| println!("{}", x));
131 /// let arr = [1, 2, 3, 4, 5];
132 /// let sub = &arr[1..3];
135 pub REVERSED_EMPTY_RANGES,
137 "reversing the limits of range expressions, resulting in empty ranges"
140 declare_clippy_lint! {
142 /// Checks for expressions like `x >= 3 && x < 8` that could
143 /// be more readably expressed as `(3..8).contains(x)`.
145 /// ### Why is this bad?
146 /// `contains` expresses the intent better and has less
147 /// failure modes (such as fencepost errors or using `||` instead of `&&`).
154 /// assert!(x >= 3 && x < 8);
159 /// assert!((3..8).contains(&x));
161 pub MANUAL_RANGE_CONTAINS,
163 "manually reimplementing {`Range`, `RangeInclusive`}`::contains`"
167 msrv: Option<RustcVersion>,
172 pub fn new(msrv: Option<RustcVersion>) -> Self {
177 impl_lint_pass!(Ranges => [
181 REVERSED_EMPTY_RANGES,
182 MANUAL_RANGE_CONTAINS,
185 impl<'tcx> LateLintPass<'tcx> for Ranges {
186 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
188 ExprKind::MethodCall(path, _, args, _) => {
189 check_range_zip_with_len(cx, path, args, expr.span);
191 ExprKind::Binary(ref op, l, r) => {
192 if meets_msrv(self.msrv.as_ref(), &msrvs::RANGE_CONTAINS) {
193 check_possible_range_contains(cx, op.node, l, r, expr);
199 check_exclusive_range_plus_one(cx, expr);
200 check_inclusive_range_minus_one(cx, expr);
201 check_reversed_empty_range(cx, expr);
203 extract_msrv_attr!(LateContext);
206 fn check_possible_range_contains(cx: &LateContext<'_>, op: BinOpKind, l: &Expr<'_>, r: &Expr<'_>, expr: &Expr<'_>) {
207 if in_constant(cx, expr.hir_id) {
211 let span = expr.span;
212 let combine_and = match op {
213 BinOpKind::And | BinOpKind::BitAnd => true,
214 BinOpKind::Or | BinOpKind::BitOr => false,
217 // value, name, order (higher/lower), inclusiveness
218 if let (Some((lval, lname, name_span, lval_span, lord, linc)), Some((rval, rname, _, rval_span, rord, rinc))) =
219 (check_range_bounds(cx, l), check_range_bounds(cx, r))
221 // we only lint comparisons on the same name and with different
223 if lname != rname || lord == rord {
226 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l), &lval, &rval);
227 if combine_and && ord == Some(rord) {
228 // order lower bound and upper bound
229 let (l_span, u_span, l_inc, u_inc) = if rord == Ordering::Less {
230 (lval_span, rval_span, linc, rinc)
232 (rval_span, lval_span, rinc, linc)
234 // we only lint inclusive lower bounds
238 let (range_type, range_op) = if u_inc {
239 ("RangeInclusive", "..=")
243 let mut applicability = Applicability::MachineApplicable;
244 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
245 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
246 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
247 let space = if lo.ends_with('.') { " " } else { "" };
250 MANUAL_RANGE_CONTAINS,
252 &format!("manual `{}::contains` implementation", range_type),
254 format!("({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
257 } else if !combine_and && ord == Some(lord) {
259 // order lower bound and upper bound
260 let (l_span, u_span, l_inc, u_inc) = if lord == Ordering::Less {
261 (lval_span, rval_span, linc, rinc)
263 (rval_span, lval_span, rinc, linc)
268 let (range_type, range_op) = if u_inc {
271 ("RangeInclusive", "..=")
273 let mut applicability = Applicability::MachineApplicable;
274 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
275 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
276 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
277 let space = if lo.ends_with('.') { " " } else { "" };
280 MANUAL_RANGE_CONTAINS,
282 &format!("manual `!{}::contains` implementation", range_type),
284 format!("!({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
291 fn check_range_bounds(cx: &LateContext<'_>, ex: &Expr<'_>) -> Option<(Constant, Ident, Span, Span, Ordering, bool)> {
292 if let ExprKind::Binary(ref op, l, r) = ex.kind {
293 let (inclusive, ordering) = match op.node {
294 BinOpKind::Gt => (false, Ordering::Greater),
295 BinOpKind::Ge => (true, Ordering::Greater),
296 BinOpKind::Lt => (false, Ordering::Less),
297 BinOpKind::Le => (true, Ordering::Less),
300 if let Some(id) = match_ident(l) {
301 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
302 return Some((c, id, l.span, r.span, ordering, inclusive));
304 } else if let Some(id) = match_ident(r) {
305 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
306 return Some((c, id, r.span, l.span, ordering.reverse(), inclusive));
313 fn match_ident(e: &Expr<'_>) -> Option<Ident> {
314 if let ExprKind::Path(ref qpath) = e.kind {
315 if let Some(seg) = single_segment_path(qpath) {
316 if seg.args.is_none() {
317 return Some(seg.ident);
324 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
326 if path.ident.as_str() == "zip";
327 if let [iter, zip_arg] = args;
329 if let ExprKind::MethodCall(iter_path, _, iter_args, _) = iter.kind;
330 if iter_path.ident.name == sym::iter;
331 // range expression in `.zip()` call: `0..x.len()`
332 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg);
333 if is_integer_const(cx, start, 0);
335 if let ExprKind::MethodCall(len_path, _, len_args, _) = end.kind;
336 if len_path.ident.name == sym::len && len_args.len() == 1;
337 // `.iter()` and `.len()` called on same `Path`
338 if let ExprKind::Path(QPath::Resolved(_, iter_path)) = iter_args[0].kind;
339 if let ExprKind::Path(QPath::Resolved(_, len_path)) = len_args[0].kind;
340 if SpanlessEq::new(cx).eq_path_segments(iter_path.segments, len_path.segments);
345 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
346 snippet(cx, iter_args[0].span, "_"))
352 // exclusive range plus one: `x..(y+1)`
353 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
355 if let Some(higher::Range {
358 limits: RangeLimits::HalfOpen
359 }) = higher::range(expr);
360 if let Some(y) = y_plus_one(cx, end);
362 let span = if expr.span.from_expansion() {
374 "an inclusive range would be more readable",
376 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
377 let end = Sugg::hir(cx, y, "y");
378 if let Some(is_wrapped) = &snippet_opt(cx, span) {
379 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
380 diag.span_suggestion(
383 format!("({}..={})", start, end),
384 Applicability::MaybeIncorrect,
387 diag.span_suggestion(
390 format!("{}..={}", start, end),
391 Applicability::MachineApplicable, // snippet
401 // inclusive range minus one: `x..=(y-1)`
402 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
404 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(expr);
405 if let Some(y) = y_minus_one(cx, end);
411 "an exclusive range would be more readable",
413 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
414 let end = Sugg::hir(cx, y, "y");
415 diag.span_suggestion(
418 format!("{}..{}", start, end),
419 Applicability::MachineApplicable, // snippet
427 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
428 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
430 get_parent_expr(cx, expr),
432 kind: ExprKind::Index(..),
438 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
439 let mut cur_expr = expr;
440 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
441 match higher::for_loop(parent_expr) {
442 Some((_, args, _, _)) if args.hir_id == expr.hir_id => return true,
443 _ => cur_expr = parent_expr,
450 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
452 RangeLimits::HalfOpen => ordering != Ordering::Less,
453 RangeLimits::Closed => ordering == Ordering::Greater,
458 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(expr);
459 let ty = cx.typeck_results().expr_ty(start);
460 if let ty::Int(_) | ty::Uint(_) = ty.kind();
461 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
462 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
463 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
464 if is_empty_range(limits, ordering);
466 if inside_indexing_expr(cx, expr) {
467 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
468 if ordering != Ordering::Equal {
471 REVERSED_EMPTY_RANGES,
473 "this range is reversed and using it to index a slice will panic at run-time",
476 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
477 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
480 REVERSED_EMPTY_RANGES,
482 "this range is empty so it will yield no values",
484 if ordering != Ordering::Equal {
485 let start_snippet = snippet(cx, start.span, "_");
486 let end_snippet = snippet(cx, end.span, "_");
487 let dots = match limits {
488 RangeLimits::HalfOpen => "..",
489 RangeLimits::Closed => "..="
492 diag.span_suggestion(
494 "consider using the following if you are attempting to iterate over this \
496 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
497 Applicability::MaybeIncorrect,
507 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
511 node: BinOpKind::Add, ..
516 if is_integer_const(cx, lhs, 1) {
518 } else if is_integer_const(cx, rhs, 1) {
528 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
532 node: BinOpKind::Sub, ..
536 ) if is_integer_const(cx, rhs, 1) => Some(lhs),