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! {
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`"
163 msrv: Option<RustcVersion>,
168 pub fn new(msrv: Option<RustcVersion>) -> Self {
173 impl_lint_pass!(Ranges => [
177 REVERSED_EMPTY_RANGES,
178 MANUAL_RANGE_CONTAINS,
181 impl<'tcx> LateLintPass<'tcx> for Ranges {
182 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
184 ExprKind::MethodCall(path, _, args, _) => {
185 check_range_zip_with_len(cx, path, args, expr.span);
187 ExprKind::Binary(ref op, l, r) => {
188 if meets_msrv(self.msrv.as_ref(), &msrvs::RANGE_CONTAINS) {
189 check_possible_range_contains(cx, op.node, l, r, expr);
195 check_exclusive_range_plus_one(cx, expr);
196 check_inclusive_range_minus_one(cx, expr);
197 check_reversed_empty_range(cx, expr);
199 extract_msrv_attr!(LateContext);
202 fn check_possible_range_contains(cx: &LateContext<'_>, op: BinOpKind, l: &Expr<'_>, r: &Expr<'_>, expr: &Expr<'_>) {
203 if in_constant(cx, expr.hir_id) {
207 let span = expr.span;
208 let combine_and = match op {
209 BinOpKind::And | BinOpKind::BitAnd => true,
210 BinOpKind::Or | BinOpKind::BitOr => false,
213 // value, name, order (higher/lower), inclusiveness
214 if let (Some((lval, lname, name_span, lval_span, lord, linc)), Some((rval, rname, _, rval_span, rord, rinc))) =
215 (check_range_bounds(cx, l), check_range_bounds(cx, r))
217 // we only lint comparisons on the same name and with different
219 if lname != rname || lord == rord {
222 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l), &lval, &rval);
223 if combine_and && ord == Some(rord) {
224 // order lower bound and upper bound
225 let (l_span, u_span, l_inc, u_inc) = if rord == Ordering::Less {
226 (lval_span, rval_span, linc, rinc)
228 (rval_span, lval_span, rinc, linc)
230 // we only lint inclusive lower bounds
234 let (range_type, range_op) = if u_inc {
235 ("RangeInclusive", "..=")
239 let mut applicability = Applicability::MachineApplicable;
240 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
241 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
242 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
243 let space = if lo.ends_with('.') { " " } else { "" };
246 MANUAL_RANGE_CONTAINS,
248 &format!("manual `{}::contains` implementation", range_type),
250 format!("({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
253 } else if !combine_and && ord == Some(lord) {
255 // order lower bound and upper bound
256 let (l_span, u_span, l_inc, u_inc) = if lord == Ordering::Less {
257 (lval_span, rval_span, linc, rinc)
259 (rval_span, lval_span, rinc, linc)
264 let (range_type, range_op) = if u_inc {
267 ("RangeInclusive", "..=")
269 let mut applicability = Applicability::MachineApplicable;
270 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
271 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
272 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
273 let space = if lo.ends_with('.') { " " } else { "" };
276 MANUAL_RANGE_CONTAINS,
278 &format!("manual `!{}::contains` implementation", range_type),
280 format!("!({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
287 fn check_range_bounds(cx: &LateContext<'_>, ex: &Expr<'_>) -> Option<(Constant, Ident, Span, Span, Ordering, bool)> {
288 if let ExprKind::Binary(ref op, l, r) = ex.kind {
289 let (inclusive, ordering) = match op.node {
290 BinOpKind::Gt => (false, Ordering::Greater),
291 BinOpKind::Ge => (true, Ordering::Greater),
292 BinOpKind::Lt => (false, Ordering::Less),
293 BinOpKind::Le => (true, Ordering::Less),
296 if let Some(id) = match_ident(l) {
297 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
298 return Some((c, id, l.span, r.span, ordering, inclusive));
300 } else if let Some(id) = match_ident(r) {
301 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
302 return Some((c, id, r.span, l.span, ordering.reverse(), inclusive));
309 fn match_ident(e: &Expr<'_>) -> Option<Ident> {
310 if let ExprKind::Path(ref qpath) = e.kind {
311 if let Some(seg) = single_segment_path(qpath) {
312 if seg.args.is_none() {
313 return Some(seg.ident);
320 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
322 if path.ident.as_str() == "zip";
323 if let [iter, zip_arg] = args;
325 if let ExprKind::MethodCall(iter_path, _, iter_args, _) = iter.kind;
326 if iter_path.ident.name == sym::iter;
327 // range expression in `.zip()` call: `0..x.len()`
328 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg);
329 if is_integer_const(cx, start, 0);
331 if let ExprKind::MethodCall(len_path, _, len_args, _) = end.kind;
332 if len_path.ident.name == sym!(len) && len_args.len() == 1;
333 // `.iter()` and `.len()` called on same `Path`
334 if let ExprKind::Path(QPath::Resolved(_, iter_path)) = iter_args[0].kind;
335 if let ExprKind::Path(QPath::Resolved(_, len_path)) = len_args[0].kind;
336 if SpanlessEq::new(cx).eq_path_segments(iter_path.segments, len_path.segments);
341 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
342 snippet(cx, iter_args[0].span, "_"))
348 // exclusive range plus one: `x..(y+1)`
349 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
351 if let Some(higher::Range {
354 limits: RangeLimits::HalfOpen
355 }) = higher::range(expr);
356 if let Some(y) = y_plus_one(cx, end);
358 let span = if expr.span.from_expansion() {
370 "an inclusive range would be more readable",
372 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
373 let end = Sugg::hir(cx, y, "y");
374 if let Some(is_wrapped) = &snippet_opt(cx, span) {
375 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
376 diag.span_suggestion(
379 format!("({}..={})", start, end),
380 Applicability::MaybeIncorrect,
383 diag.span_suggestion(
386 format!("{}..={}", start, end),
387 Applicability::MachineApplicable, // snippet
397 // inclusive range minus one: `x..=(y-1)`
398 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
400 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(expr);
401 if let Some(y) = y_minus_one(cx, end);
407 "an exclusive range would be more readable",
409 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
410 let end = Sugg::hir(cx, y, "y");
411 diag.span_suggestion(
414 format!("{}..{}", start, end),
415 Applicability::MachineApplicable, // snippet
423 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
424 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
426 get_parent_expr(cx, expr),
428 kind: ExprKind::Index(..),
434 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
435 let mut cur_expr = expr;
436 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
437 match higher::for_loop(parent_expr) {
438 Some((_, args, _, _)) if args.hir_id == expr.hir_id => return true,
439 _ => cur_expr = parent_expr,
446 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
448 RangeLimits::HalfOpen => ordering != Ordering::Less,
449 RangeLimits::Closed => ordering == Ordering::Greater,
454 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(expr);
455 let ty = cx.typeck_results().expr_ty(start);
456 if let ty::Int(_) | ty::Uint(_) = ty.kind();
457 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
458 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
459 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
460 if is_empty_range(limits, ordering);
462 if inside_indexing_expr(cx, expr) {
463 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
464 if ordering != Ordering::Equal {
467 REVERSED_EMPTY_RANGES,
469 "this range is reversed and using it to index a slice will panic at run-time",
472 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
473 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
476 REVERSED_EMPTY_RANGES,
478 "this range is empty so it will yield no values",
480 if ordering != Ordering::Equal {
481 let start_snippet = snippet(cx, start.span, "_");
482 let end_snippet = snippet(cx, end.span, "_");
483 let dots = match limits {
484 RangeLimits::HalfOpen => "..",
485 RangeLimits::Closed => "..="
488 diag.span_suggestion(
490 "consider using the following if you are attempting to iterate over this \
492 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
493 Applicability::MaybeIncorrect,
503 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
507 node: BinOpKind::Add, ..
512 if is_integer_const(cx, lhs, 1) {
514 } else if is_integer_const(cx, rhs, 1) {
524 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
528 node: BinOpKind::Sub, ..
532 ) if is_integer_const(cx, rhs, 1) => Some(lhs),