1 use crate::consts::{constant, Constant};
2 use if_chain::if_chain;
3 use rustc_ast::ast::RangeLimits;
4 use rustc_errors::Applicability;
5 use rustc_hir::{BinOpKind, Expr, ExprKind, PathSegment, QPath};
6 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
9 use rustc_span::source_map::{Span, Spanned};
10 use rustc_span::symbol::Ident;
11 use std::cmp::Ordering;
13 use crate::utils::sugg::Sugg;
15 get_parent_expr, is_integer_const, single_segment_path, snippet, snippet_opt, snippet_with_applicability,
16 span_lint, span_lint_and_sugg, span_lint_and_then,
18 use crate::utils::{higher, SpanlessEq};
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 declare_lint_pass!(Ranges => [
166 REVERSED_EMPTY_RANGES,
167 MANUAL_RANGE_CONTAINS,
170 impl<'tcx> LateLintPass<'tcx> for Ranges {
171 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
173 ExprKind::MethodCall(ref path, _, ref args, _) => {
174 check_range_zip_with_len(cx, path, args, expr.span);
176 ExprKind::Binary(ref op, ref l, ref r) => {
177 check_possible_range_contains(cx, op.node, l, r, expr.span);
182 check_exclusive_range_plus_one(cx, expr);
183 check_inclusive_range_minus_one(cx, expr);
184 check_reversed_empty_range(cx, expr);
188 fn check_possible_range_contains(cx: &LateContext<'_>, op: BinOpKind, l: &Expr<'_>, r: &Expr<'_>, span: Span) {
189 let combine_and = match op {
190 BinOpKind::And | BinOpKind::BitAnd => true,
191 BinOpKind::Or | BinOpKind::BitOr => false,
194 // value, name, order (higher/lower), inclusiveness
195 if let (Some((lval, lname, name_span, lval_span, lord, linc)), Some((rval, rname, _, rval_span, rord, rinc))) =
196 (check_range_bounds(cx, l), check_range_bounds(cx, r))
198 // we only lint comparisons on the same name and with different
200 if lname != rname || lord == rord {
203 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l), &lval, &rval);
204 if combine_and && ord == Some(rord) {
205 // order lower bound and upper bound
206 let (l_span, u_span, l_inc, u_inc) = if rord == Ordering::Less {
207 (lval_span, rval_span, linc, rinc)
209 (rval_span, lval_span, rinc, linc)
211 // we only lint inclusive lower bounds
215 let (range_type, range_op) = if u_inc {
216 ("RangeInclusive", "..=")
220 let mut applicability = Applicability::MachineApplicable;
221 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
222 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
223 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
226 MANUAL_RANGE_CONTAINS,
228 &format!("manual `{}::contains` implementation", range_type),
230 format!("({}{}{}).contains(&{})", lo, range_op, hi, name),
233 } else if !combine_and && ord == Some(lord) {
235 // order lower bound and upper bound
236 let (l_span, u_span, l_inc, u_inc) = if lord == Ordering::Less {
237 (lval_span, rval_span, linc, rinc)
239 (rval_span, lval_span, rinc, linc)
244 let (range_type, range_op) = if u_inc {
247 ("RangeInclusive", "..=")
249 let mut applicability = Applicability::MachineApplicable;
250 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
251 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
252 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
255 MANUAL_RANGE_CONTAINS,
257 &format!("manual `!{}::contains` implementation", range_type),
259 format!("!({}{}{}).contains(&{})", lo, range_op, hi, name),
266 fn check_range_bounds(cx: &LateContext<'_>, ex: &Expr<'_>) -> Option<(Constant, Ident, Span, Span, Ordering, bool)> {
267 if let ExprKind::Binary(ref op, ref l, ref r) = ex.kind {
268 let (inclusive, ordering) = match op.node {
269 BinOpKind::Gt => (false, Ordering::Greater),
270 BinOpKind::Ge => (true, Ordering::Greater),
271 BinOpKind::Lt => (false, Ordering::Less),
272 BinOpKind::Le => (true, Ordering::Less),
275 if let Some(id) = match_ident(l) {
276 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
277 return Some((c, id, l.span, r.span, ordering, inclusive));
279 } else if let Some(id) = match_ident(r) {
280 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
281 return Some((c, id, r.span, l.span, ordering.reverse(), inclusive));
288 fn match_ident(e: &Expr<'_>) -> Option<Ident> {
289 if let ExprKind::Path(ref qpath) = e.kind {
290 if let Some(seg) = single_segment_path(qpath) {
291 if seg.args.is_none() {
292 return Some(seg.ident);
299 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
300 let name = path.ident.as_str();
301 if name == "zip" && args.len() == 2 {
302 let iter = &args[0].kind;
303 let zip_arg = &args[1];
306 if let ExprKind::MethodCall(ref iter_path, _, ref iter_args, _) = *iter;
307 if iter_path.ident.name == sym!(iter);
308 // range expression in `.zip()` call: `0..x.len()`
309 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg);
310 if is_integer_const(cx, start, 0);
312 if let ExprKind::MethodCall(ref len_path, _, ref len_args, _) = end.kind;
313 if len_path.ident.name == sym!(len) && len_args.len() == 1;
314 // `.iter()` and `.len()` called on same `Path`
315 if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].kind;
316 if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].kind;
317 if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
322 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
323 snippet(cx, iter_args[0].span, "_"))
330 // exclusive range plus one: `x..(y+1)`
331 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
333 if let Some(higher::Range {
336 limits: RangeLimits::HalfOpen
337 }) = higher::range(expr);
338 if let Some(y) = y_plus_one(cx, end);
340 let span = if expr.span.from_expansion() {
352 "an inclusive range would be more readable",
354 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
355 let end = Sugg::hir(cx, y, "y");
356 if let Some(is_wrapped) = &snippet_opt(cx, span) {
357 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
358 diag.span_suggestion(
361 format!("({}..={})", start, end),
362 Applicability::MaybeIncorrect,
365 diag.span_suggestion(
368 format!("{}..={}", start, end),
369 Applicability::MachineApplicable, // snippet
379 // inclusive range minus one: `x..=(y-1)`
380 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
382 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(expr);
383 if let Some(y) = y_minus_one(cx, end);
389 "an exclusive range would be more readable",
391 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
392 let end = Sugg::hir(cx, y, "y");
393 diag.span_suggestion(
396 format!("{}..{}", start, end),
397 Applicability::MachineApplicable, // snippet
405 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
406 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
408 get_parent_expr(cx, expr),
410 kind: ExprKind::Index(..),
416 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
417 let mut cur_expr = expr;
418 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
419 match higher::for_loop(parent_expr) {
420 Some((_, args, _)) if args.hir_id == expr.hir_id => return true,
421 _ => cur_expr = parent_expr,
428 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
430 RangeLimits::HalfOpen => ordering != Ordering::Less,
431 RangeLimits::Closed => ordering == Ordering::Greater,
436 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(expr);
437 let ty = cx.typeck_results().expr_ty(start);
438 if let ty::Int(_) | ty::Uint(_) = ty.kind();
439 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
440 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
441 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
442 if is_empty_range(limits, ordering);
444 if inside_indexing_expr(cx, expr) {
445 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
446 if ordering != Ordering::Equal {
449 REVERSED_EMPTY_RANGES,
451 "this range is reversed and using it to index a slice will panic at run-time",
454 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
455 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
458 REVERSED_EMPTY_RANGES,
460 "this range is empty so it will yield no values",
462 if ordering != Ordering::Equal {
463 let start_snippet = snippet(cx, start.span, "_");
464 let end_snippet = snippet(cx, end.span, "_");
465 let dots = match limits {
466 RangeLimits::HalfOpen => "..",
467 RangeLimits::Closed => "..="
470 diag.span_suggestion(
472 "consider using the following if you are attempting to iterate over this \
474 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
475 Applicability::MaybeIncorrect,
485 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
489 node: BinOpKind::Add, ..
494 if is_integer_const(cx, lhs, 1) {
496 } else if is_integer_const(cx, rhs, 1) {
506 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
510 node: BinOpKind::Sub, ..
514 ) if is_integer_const(cx, rhs, 1) => Some(lhs),