1 use crate::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, 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! {
21 /// **What it does:** Checks for zipping a collection with the range of
24 /// **Why is this bad?** The code is better expressed with `.enumerate()`.
26 /// **Known problems:** None.
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! {
44 /// **What it does:** Checks for exclusive ranges where 1 is added to the
45 /// upper bound, e.g., `x..(y+1)`.
47 /// **Why is this bad?** The code is more readable with an inclusive range
50 /// **Known problems:** Will add unnecessary pair of parentheses when the
51 /// expression is not wrapped in a pair but starts with a opening parenthesis
52 /// and ends with a closing one.
53 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
55 /// Also in many cases, inclusive ranges are still slower to run than
56 /// exclusive ranges, because they essentially add an extra branch that
57 /// LLVM may fail to hoist out of the loop.
59 /// This will cause a warning that cannot be fixed if the consumer of the
60 /// range only accepts a specific range type, instead of the generic
61 /// `RangeBounds` trait
62 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
66 /// for x..(y+1) { .. }
68 /// Could be written as
74 "`x..(y+1)` reads better as `x..=y`"
77 declare_clippy_lint! {
78 /// **What it does:** Checks for inclusive ranges where 1 is subtracted from
79 /// the upper bound, e.g., `x..=(y-1)`.
81 /// **Why is this bad?** The code is more readable with an exclusive range
84 /// **Known problems:** This will cause a warning that cannot be fixed if
85 /// the consumer of the range only accepts a specific range type, instead of
86 /// the generic `RangeBounds` trait
87 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
91 /// for x..=(y-1) { .. }
93 /// Could be written as
99 "`x..=(y-1)` reads better as `x..y`"
102 declare_clippy_lint! {
103 /// **What it does:** Checks for range expressions `x..y` where both `x` and `y`
104 /// are constant and `x` is greater or equal to `y`.
106 /// **Why is this bad?** Empty ranges yield no values so iterating them is a no-op.
107 /// Moreover, trying to use a reversed range to index a slice will panic at run-time.
109 /// **Known problems:** None.
115 /// (10..=0).for_each(|x| println!("{}", x));
117 /// let arr = [1, 2, 3, 4, 5];
118 /// let sub = &arr[3..1];
124 /// (0..=10).rev().for_each(|x| println!("{}", x));
126 /// let arr = [1, 2, 3, 4, 5];
127 /// let sub = &arr[1..3];
130 pub REVERSED_EMPTY_RANGES,
132 "reversing the limits of range expressions, resulting in empty ranges"
135 declare_clippy_lint! {
136 /// **What it does:** Checks for expressions like `x >= 3 && x < 8` that could
137 /// be more readably expressed as `(3..8).contains(x)`.
139 /// **Why is this bad?** `contains` expresses the intent better and has less
140 /// failure modes (such as fencepost errors or using `||` instead of `&&`).
142 /// **Known problems:** None.
150 /// assert!(x >= 3 && x < 8);
155 /// assert!((3..8).contains(&x));
157 pub MANUAL_RANGE_CONTAINS,
159 "manually reimplementing {`Range`, `RangeInclusive`}`::contains`"
162 const MANUAL_RANGE_CONTAINS_MSRV: RustcVersion = RustcVersion::new(1, 35, 0);
165 msrv: Option<RustcVersion>,
170 pub fn new(msrv: Option<RustcVersion>) -> Self {
175 impl_lint_pass!(Ranges => [
179 REVERSED_EMPTY_RANGES,
180 MANUAL_RANGE_CONTAINS,
183 impl<'tcx> LateLintPass<'tcx> for Ranges {
184 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
186 ExprKind::MethodCall(path, _, args, _) => {
187 check_range_zip_with_len(cx, path, args, expr.span);
189 ExprKind::Binary(ref op, l, r) => {
190 if meets_msrv(self.msrv.as_ref(), &MANUAL_RANGE_CONTAINS_MSRV) {
191 check_possible_range_contains(cx, op.node, l, r, expr);
197 check_exclusive_range_plus_one(cx, expr);
198 check_inclusive_range_minus_one(cx, expr);
199 check_reversed_empty_range(cx, expr);
201 extract_msrv_attr!(LateContext);
204 fn check_possible_range_contains(cx: &LateContext<'_>, op: BinOpKind, l: &Expr<'_>, r: &Expr<'_>, expr: &Expr<'_>) {
205 if in_constant(cx, expr.hir_id) {
209 let span = expr.span;
210 let combine_and = match op {
211 BinOpKind::And | BinOpKind::BitAnd => true,
212 BinOpKind::Or | BinOpKind::BitOr => false,
215 // value, name, order (higher/lower), inclusiveness
216 if let (Some((lval, lname, name_span, lval_span, lord, linc)), Some((rval, rname, _, rval_span, rord, rinc))) =
217 (check_range_bounds(cx, l), check_range_bounds(cx, r))
219 // we only lint comparisons on the same name and with different
221 if lname != rname || lord == rord {
224 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l), &lval, &rval);
225 if combine_and && ord == Some(rord) {
226 // order lower bound and upper bound
227 let (l_span, u_span, l_inc, u_inc) = if rord == Ordering::Less {
228 (lval_span, rval_span, linc, rinc)
230 (rval_span, lval_span, rinc, linc)
232 // we only lint inclusive lower bounds
236 let (range_type, range_op) = if u_inc {
237 ("RangeInclusive", "..=")
241 let mut applicability = Applicability::MachineApplicable;
242 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
243 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
244 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
245 let space = if lo.ends_with('.') { " " } else { "" };
248 MANUAL_RANGE_CONTAINS,
250 &format!("manual `{}::contains` implementation", range_type),
252 format!("({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
255 } else if !combine_and && ord == Some(lord) {
257 // order lower bound and upper bound
258 let (l_span, u_span, l_inc, u_inc) = if lord == Ordering::Less {
259 (lval_span, rval_span, linc, rinc)
261 (rval_span, lval_span, rinc, linc)
266 let (range_type, range_op) = if u_inc {
269 ("RangeInclusive", "..=")
271 let mut applicability = Applicability::MachineApplicable;
272 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
273 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
274 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
275 let space = if lo.ends_with('.') { " " } else { "" };
278 MANUAL_RANGE_CONTAINS,
280 &format!("manual `!{}::contains` implementation", range_type),
282 format!("!({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
289 fn check_range_bounds(cx: &LateContext<'_>, ex: &Expr<'_>) -> Option<(Constant, Ident, Span, Span, Ordering, bool)> {
290 if let ExprKind::Binary(ref op, l, r) = ex.kind {
291 let (inclusive, ordering) = match op.node {
292 BinOpKind::Gt => (false, Ordering::Greater),
293 BinOpKind::Ge => (true, Ordering::Greater),
294 BinOpKind::Lt => (false, Ordering::Less),
295 BinOpKind::Le => (true, Ordering::Less),
298 if let Some(id) = match_ident(l) {
299 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
300 return Some((c, id, l.span, r.span, ordering, inclusive));
302 } else if let Some(id) = match_ident(r) {
303 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
304 return Some((c, id, r.span, l.span, ordering.reverse(), inclusive));
311 fn match_ident(e: &Expr<'_>) -> Option<Ident> {
312 if let ExprKind::Path(ref qpath) = e.kind {
313 if let Some(seg) = single_segment_path(qpath) {
314 if seg.args.is_none() {
315 return Some(seg.ident);
322 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
324 if path.ident.as_str() == "zip";
325 if let [iter, zip_arg] = args;
327 if let ExprKind::MethodCall(iter_path, _, iter_args, _) = iter.kind;
328 if iter_path.ident.name == sym::iter;
329 // range expression in `.zip()` call: `0..x.len()`
330 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg);
331 if is_integer_const(cx, start, 0);
333 if let ExprKind::MethodCall(len_path, _, len_args, _) = end.kind;
334 if len_path.ident.name == sym!(len) && len_args.len() == 1;
335 // `.iter()` and `.len()` called on same `Path`
336 if let ExprKind::Path(QPath::Resolved(_, iter_path)) = iter_args[0].kind;
337 if let ExprKind::Path(QPath::Resolved(_, len_path)) = len_args[0].kind;
338 if SpanlessEq::new(cx).eq_path_segments(iter_path.segments, len_path.segments);
343 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
344 snippet(cx, iter_args[0].span, "_"))
350 // exclusive range plus one: `x..(y+1)`
351 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
353 if let Some(higher::Range {
356 limits: RangeLimits::HalfOpen
357 }) = higher::range(expr);
358 if let Some(y) = y_plus_one(cx, end);
360 let span = if expr.span.from_expansion() {
372 "an inclusive range would be more readable",
374 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
375 let end = Sugg::hir(cx, y, "y");
376 if let Some(is_wrapped) = &snippet_opt(cx, span) {
377 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
378 diag.span_suggestion(
381 format!("({}..={})", start, end),
382 Applicability::MaybeIncorrect,
385 diag.span_suggestion(
388 format!("{}..={}", start, end),
389 Applicability::MachineApplicable, // snippet
399 // inclusive range minus one: `x..=(y-1)`
400 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
402 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(expr);
403 if let Some(y) = y_minus_one(cx, end);
409 "an exclusive range would be more readable",
411 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
412 let end = Sugg::hir(cx, y, "y");
413 diag.span_suggestion(
416 format!("{}..{}", start, end),
417 Applicability::MachineApplicable, // snippet
425 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
426 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
428 get_parent_expr(cx, expr),
430 kind: ExprKind::Index(..),
436 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
437 let mut cur_expr = expr;
438 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
439 match higher::for_loop(parent_expr) {
440 Some((_, args, _, _)) if args.hir_id == expr.hir_id => return true,
441 _ => cur_expr = parent_expr,
448 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
450 RangeLimits::HalfOpen => ordering != Ordering::Less,
451 RangeLimits::Closed => ordering == Ordering::Greater,
456 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(expr);
457 let ty = cx.typeck_results().expr_ty(start);
458 if let ty::Int(_) | ty::Uint(_) = ty.kind();
459 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
460 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
461 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
462 if is_empty_range(limits, ordering);
464 if inside_indexing_expr(cx, expr) {
465 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
466 if ordering != Ordering::Equal {
469 REVERSED_EMPTY_RANGES,
471 "this range is reversed and using it to index a slice will panic at run-time",
474 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
475 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
478 REVERSED_EMPTY_RANGES,
480 "this range is empty so it will yield no values",
482 if ordering != Ordering::Equal {
483 let start_snippet = snippet(cx, start.span, "_");
484 let end_snippet = snippet(cx, end.span, "_");
485 let dots = match limits {
486 RangeLimits::HalfOpen => "..",
487 RangeLimits::Closed => "..="
490 diag.span_suggestion(
492 "consider using the following if you are attempting to iterate over this \
494 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
495 Applicability::MaybeIncorrect,
505 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
509 node: BinOpKind::Add, ..
514 if is_integer_const(cx, lhs, 1) {
516 } else if is_integer_const(cx, rhs, 1) {
526 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
530 node: BinOpKind::Sub, ..
534 ) if is_integer_const(cx, rhs, 1) => Some(lhs),