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};
11 use rustc_span::symbol::Ident;
12 use std::cmp::Ordering;
14 use crate::utils::sugg::Sugg;
16 get_parent_expr, is_integer_const, single_segment_path, snippet, snippet_opt, snippet_with_applicability,
17 span_lint, span_lint_and_sugg, span_lint_and_then,
19 use crate::utils::{higher, SpanlessEq};
21 declare_clippy_lint! {
22 /// **What it does:** Checks for zipping a collection with the range of
25 /// **Why is this bad?** The code is better expressed with `.enumerate()`.
27 /// **Known problems:** None.
31 /// # let x = vec![1];
32 /// x.iter().zip(0..x.len());
34 /// Could be written as
36 /// # let x = vec![1];
37 /// x.iter().enumerate();
39 pub RANGE_ZIP_WITH_LEN,
41 "zipping iterator with a range when `enumerate()` would do"
44 declare_clippy_lint! {
45 /// **What it does:** Checks for exclusive ranges where 1 is added to the
46 /// upper bound, e.g., `x..(y+1)`.
48 /// **Why is this bad?** The code is more readable with an inclusive range
51 /// **Known problems:** Will add unnecessary pair of parentheses when the
52 /// expression is not wrapped in a pair but starts with a opening parenthesis
53 /// and ends with a closing one.
54 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
56 /// Also in many cases, inclusive ranges are still slower to run than
57 /// exclusive ranges, because they essentially add an extra branch that
58 /// LLVM may fail to hoist out of the loop.
60 /// This will cause a warning that cannot be fixed if the consumer of the
61 /// range only accepts a specific range type, instead of the generic
62 /// `RangeBounds` trait
63 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
67 /// for x..(y+1) { .. }
69 /// Could be written as
75 "`x..(y+1)` reads better as `x..=y`"
78 declare_clippy_lint! {
79 /// **What it does:** Checks for inclusive ranges where 1 is subtracted from
80 /// the upper bound, e.g., `x..=(y-1)`.
82 /// **Why is this bad?** The code is more readable with an exclusive range
85 /// **Known problems:** This will cause a warning that cannot be fixed if
86 /// the consumer of the range only accepts a specific range type, instead of
87 /// the generic `RangeBounds` trait
88 /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
92 /// for x..=(y-1) { .. }
94 /// Could be written as
100 "`x..=(y-1)` reads better as `x..y`"
103 declare_clippy_lint! {
104 /// **What it does:** Checks for range expressions `x..y` where both `x` and `y`
105 /// are constant and `x` is greater or equal to `y`.
107 /// **Why is this bad?** Empty ranges yield no values so iterating them is a no-op.
108 /// Moreover, trying to use a reversed range to index a slice will panic at run-time.
110 /// **Known problems:** None.
116 /// (10..=0).for_each(|x| println!("{}", x));
118 /// let arr = [1, 2, 3, 4, 5];
119 /// let sub = &arr[3..1];
125 /// (0..=10).rev().for_each(|x| println!("{}", x));
127 /// let arr = [1, 2, 3, 4, 5];
128 /// let sub = &arr[1..3];
131 pub REVERSED_EMPTY_RANGES,
133 "reversing the limits of range expressions, resulting in empty ranges"
136 declare_clippy_lint! {
137 /// **What it does:** Checks for expressions like `x >= 3 && x < 8` that could
138 /// be more readably expressed as `(3..8).contains(x)`.
140 /// **Why is this bad?** `contains` expresses the intent better and has less
141 /// failure modes (such as fencepost errors or using `||` instead of `&&`).
143 /// **Known problems:** None.
151 /// assert!(x >= 3 && x < 8);
156 /// assert!((3..8).contains(&x));
158 pub MANUAL_RANGE_CONTAINS,
160 "manually reimplementing {`Range`, `RangeInclusive`}`::contains`"
163 declare_lint_pass!(Ranges => [
167 REVERSED_EMPTY_RANGES,
168 MANUAL_RANGE_CONTAINS,
171 impl<'tcx> LateLintPass<'tcx> for Ranges {
172 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
174 ExprKind::MethodCall(ref path, _, ref args, _) => {
175 check_range_zip_with_len(cx, path, args, expr.span);
177 ExprKind::Binary(ref op, ref l, ref r) => {
178 check_possible_range_contains(cx, op.node, l, r, expr.span);
183 check_exclusive_range_plus_one(cx, expr);
184 check_inclusive_range_minus_one(cx, expr);
185 check_reversed_empty_range(cx, expr);
189 fn check_possible_range_contains(cx: &LateContext<'_>, op: BinOpKind, l: &Expr<'_>, r: &Expr<'_>, span: Span) {
190 let combine_and = match op {
191 BinOpKind::And | BinOpKind::BitAnd => true,
192 BinOpKind::Or | BinOpKind::BitOr => false,
195 // value, name, order (higher/lower), inclusiveness
196 if let (Some((lval, lname, name_span, lval_span, lord, linc)), Some((rval, rname, _, rval_span, rord, rinc))) =
197 (check_range_bounds(cx, l), check_range_bounds(cx, r))
199 // we only lint comparisons on the same name and with different
201 if lname != rname || lord == rord {
204 let ord = Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(l), &lval, &rval);
205 if combine_and && ord == Some(rord) {
206 // order lower bound and upper bound
207 let (l_span, u_span, l_inc, u_inc) = if rord == Ordering::Less {
208 (lval_span, rval_span, linc, rinc)
210 (rval_span, lval_span, rinc, linc)
212 // we only lint inclusive lower bounds
216 let (range_type, range_op) = if u_inc {
217 ("RangeInclusive", "..=")
221 let mut applicability = Applicability::MachineApplicable;
222 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
223 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
224 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
225 let space = if lo.ends_with('.') { " " } else { "" };
228 MANUAL_RANGE_CONTAINS,
230 &format!("manual `{}::contains` implementation", range_type),
232 format!("({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
235 } else if !combine_and && ord == Some(lord) {
237 // order lower bound and upper bound
238 let (l_span, u_span, l_inc, u_inc) = if lord == Ordering::Less {
239 (lval_span, rval_span, linc, rinc)
241 (rval_span, lval_span, rinc, linc)
246 let (range_type, range_op) = if u_inc {
249 ("RangeInclusive", "..=")
251 let mut applicability = Applicability::MachineApplicable;
252 let name = snippet_with_applicability(cx, name_span, "_", &mut applicability);
253 let lo = snippet_with_applicability(cx, l_span, "_", &mut applicability);
254 let hi = snippet_with_applicability(cx, u_span, "_", &mut applicability);
255 let space = if lo.ends_with('.') { " " } else { "" };
258 MANUAL_RANGE_CONTAINS,
260 &format!("manual `!{}::contains` implementation", range_type),
262 format!("!({}{}{}{}).contains(&{})", lo, space, range_op, hi, name),
269 fn check_range_bounds(cx: &LateContext<'_>, ex: &Expr<'_>) -> Option<(Constant, Ident, Span, Span, Ordering, bool)> {
270 if let ExprKind::Binary(ref op, ref l, ref r) = ex.kind {
271 let (inclusive, ordering) = match op.node {
272 BinOpKind::Gt => (false, Ordering::Greater),
273 BinOpKind::Ge => (true, Ordering::Greater),
274 BinOpKind::Lt => (false, Ordering::Less),
275 BinOpKind::Le => (true, Ordering::Less),
278 if let Some(id) = match_ident(l) {
279 if let Some((c, _)) = constant(cx, cx.typeck_results(), r) {
280 return Some((c, id, l.span, r.span, ordering, inclusive));
282 } else if let Some(id) = match_ident(r) {
283 if let Some((c, _)) = constant(cx, cx.typeck_results(), l) {
284 return Some((c, id, r.span, l.span, ordering.reverse(), inclusive));
291 fn match_ident(e: &Expr<'_>) -> Option<Ident> {
292 if let ExprKind::Path(ref qpath) = e.kind {
293 if let Some(seg) = single_segment_path(qpath) {
294 if seg.args.is_none() {
295 return Some(seg.ident);
302 fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args: &[Expr<'_>], span: Span) {
303 let name = path.ident.as_str();
304 if name == "zip" && args.len() == 2 {
305 let iter = &args[0].kind;
306 let zip_arg = &args[1];
309 if let ExprKind::MethodCall(ref iter_path, _, ref iter_args, _) = *iter;
310 if iter_path.ident.name == sym::iter;
311 // range expression in `.zip()` call: `0..x.len()`
312 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg);
313 if is_integer_const(cx, start, 0);
315 if let ExprKind::MethodCall(ref len_path, _, ref len_args, _) = end.kind;
316 if len_path.ident.name == sym!(len) && len_args.len() == 1;
317 // `.iter()` and `.len()` called on same `Path`
318 if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].kind;
319 if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].kind;
320 if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
325 &format!("it is more idiomatic to use `{}.iter().enumerate()`",
326 snippet(cx, iter_args[0].span, "_"))
333 // exclusive range plus one: `x..(y+1)`
334 fn check_exclusive_range_plus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
336 if let Some(higher::Range {
339 limits: RangeLimits::HalfOpen
340 }) = higher::range(expr);
341 if let Some(y) = y_plus_one(cx, end);
343 let span = if expr.span.from_expansion() {
355 "an inclusive range would be more readable",
357 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
358 let end = Sugg::hir(cx, y, "y");
359 if let Some(is_wrapped) = &snippet_opt(cx, span) {
360 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
361 diag.span_suggestion(
364 format!("({}..={})", start, end),
365 Applicability::MaybeIncorrect,
368 diag.span_suggestion(
371 format!("{}..={}", start, end),
372 Applicability::MachineApplicable, // snippet
382 // inclusive range minus one: `x..=(y-1)`
383 fn check_inclusive_range_minus_one(cx: &LateContext<'_>, expr: &Expr<'_>) {
385 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(expr);
386 if let Some(y) = y_minus_one(cx, end);
392 "an exclusive range would be more readable",
394 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
395 let end = Sugg::hir(cx, y, "y");
396 diag.span_suggestion(
399 format!("{}..{}", start, end),
400 Applicability::MachineApplicable, // snippet
408 fn check_reversed_empty_range(cx: &LateContext<'_>, expr: &Expr<'_>) {
409 fn inside_indexing_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
411 get_parent_expr(cx, expr),
413 kind: ExprKind::Index(..),
419 fn is_for_loop_arg(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
420 let mut cur_expr = expr;
421 while let Some(parent_expr) = get_parent_expr(cx, cur_expr) {
422 match higher::for_loop(parent_expr) {
423 Some((_, args, _)) if args.hir_id == expr.hir_id => return true,
424 _ => cur_expr = parent_expr,
431 fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
433 RangeLimits::HalfOpen => ordering != Ordering::Less,
434 RangeLimits::Closed => ordering == Ordering::Greater,
439 if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(expr);
440 let ty = cx.typeck_results().expr_ty(start);
441 if let ty::Int(_) | ty::Uint(_) = ty.kind();
442 if let Some((start_idx, _)) = constant(cx, cx.typeck_results(), start);
443 if let Some((end_idx, _)) = constant(cx, cx.typeck_results(), end);
444 if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
445 if is_empty_range(limits, ordering);
447 if inside_indexing_expr(cx, expr) {
448 // Avoid linting `N..N` as it has proven to be useful, see #5689 and #5628 ...
449 if ordering != Ordering::Equal {
452 REVERSED_EMPTY_RANGES,
454 "this range is reversed and using it to index a slice will panic at run-time",
457 // ... except in for loop arguments for backwards compatibility with `reverse_range_loop`
458 } else if ordering != Ordering::Equal || is_for_loop_arg(cx, expr) {
461 REVERSED_EMPTY_RANGES,
463 "this range is empty so it will yield no values",
465 if ordering != Ordering::Equal {
466 let start_snippet = snippet(cx, start.span, "_");
467 let end_snippet = snippet(cx, end.span, "_");
468 let dots = match limits {
469 RangeLimits::HalfOpen => "..",
470 RangeLimits::Closed => "..="
473 diag.span_suggestion(
475 "consider using the following if you are attempting to iterate over this \
477 format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
478 Applicability::MaybeIncorrect,
488 fn y_plus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
492 node: BinOpKind::Add, ..
497 if is_integer_const(cx, lhs, 1) {
499 } else if is_integer_const(cx, rhs, 1) {
509 fn y_minus_one<'t>(cx: &LateContext<'_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
513 node: BinOpKind::Sub, ..
517 ) if is_integer_const(cx, rhs, 1) => Some(lhs),