1 use if_chain::if_chain;
3 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
4 use rustc::{declare_lint_pass, declare_tool_lint};
5 use rustc_errors::Applicability;
6 use syntax::ast::RangeLimits;
7 use syntax::source_map::Spanned;
9 use crate::utils::sugg::Sugg;
10 use crate::utils::{get_trait_def_id, higher, implements_trait, SpanlessEq};
11 use crate::utils::{is_integer_const, paths, snippet, snippet_opt, span_lint, span_lint_and_then};
13 declare_clippy_lint! {
14 /// **What it does:** Checks for calling `.step_by(0)` on iterators,
15 /// which never terminates.
17 /// **Why is this bad?** This very much looks like an oversight, since with
18 /// `loop { .. }` there is an obvious better way to endlessly loop.
20 /// **Known problems:** None.
24 /// for x in (5..5).step_by(0) {
28 pub ITERATOR_STEP_BY_ZERO,
30 "using `Iterator::step_by(0)`, which produces an infinite iterator"
33 declare_clippy_lint! {
34 /// **What it does:** Checks for zipping a collection with the range of
37 /// **Why is this bad?** The code is better expressed with `.enumerate()`.
39 /// **Known problems:** None.
43 /// # let x = vec![1];
44 /// x.iter().zip(0..x.len());
46 /// Could be written as
48 /// # let x = vec![1];
49 /// x.iter().enumerate();
51 pub RANGE_ZIP_WITH_LEN,
53 "zipping iterator with a range when `enumerate()` would do"
56 declare_clippy_lint! {
57 /// **What it does:** Checks for exclusive ranges where 1 is added to the
58 /// upper bound, e.g., `x..(y+1)`.
60 /// **Why is this bad?** The code is more readable with an inclusive range
63 /// **Known problems:** Will add unnecessary pair of parentheses when the
64 /// expression is not wrapped in a pair but starts with a opening parenthesis
65 /// and ends with a closing one.
66 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
70 /// for x..(y+1) { .. }
72 /// Could be written as
78 "`x..(y+1)` reads better as `x..=y`"
81 declare_clippy_lint! {
82 /// **What it does:** Checks for inclusive ranges where 1 is subtracted from
83 /// the upper bound, e.g., `x..=(y-1)`.
85 /// **Why is this bad?** The code is more readable with an exclusive range
88 /// **Known problems:** None.
92 /// for x..=(y-1) { .. }
94 /// Could be written as
100 "`x..=(y-1)` reads better as `x..y`"
103 declare_lint_pass!(Ranges => [
104 ITERATOR_STEP_BY_ZERO,
110 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Ranges {
111 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
112 if let ExprKind::MethodCall(ref path, _, ref args) = expr.kind {
113 let name = path.ident.as_str();
115 // Range with step_by(0).
116 if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
117 use crate::consts::{constant, Constant};
118 if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
121 ITERATOR_STEP_BY_ZERO,
123 "Iterator::step_by(0) will panic at runtime",
126 } else if name == "zip" && args.len() == 2 {
127 let iter = &args[0].kind;
128 let zip_arg = &args[1];
131 if let ExprKind::MethodCall(ref iter_path, _, ref iter_args ) = *iter;
132 if iter_path.ident.name == sym!(iter);
133 // range expression in `.zip()` call: `0..x.len()`
134 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(cx, zip_arg);
135 if is_integer_const(cx, start, 0);
137 if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.kind;
138 if len_path.ident.name == sym!(len) && len_args.len() == 1;
139 // `.iter()` and `.len()` called on same `Path`
140 if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].kind;
141 if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].kind;
142 if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
147 &format!("It is more idiomatic to use {}.iter().enumerate()",
148 snippet(cx, iter_args[0].span, "_")));
154 check_exclusive_range_plus_one(cx, expr);
155 check_inclusive_range_minus_one(cx, expr);
159 // exclusive range plus one: `x..(y+1)`
160 fn check_exclusive_range_plus_one(cx: &LateContext<'_, '_>, expr: &Expr) {
162 if let Some(higher::Range {
165 limits: RangeLimits::HalfOpen
166 }) = higher::range(cx, expr);
167 if let Some(y) = y_plus_one(cx, end);
169 let span = if expr.span.from_expansion() {
181 "an inclusive range would be more readable",
183 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
184 let end = Sugg::hir(cx, y, "y");
185 if let Some(is_wrapped) = &snippet_opt(cx, span) {
186 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
190 format!("({}..={})", start, end),
191 Applicability::MaybeIncorrect,
197 format!("{}..={}", start, end),
198 Applicability::MachineApplicable, // snippet
208 // inclusive range minus one: `x..=(y-1)`
209 fn check_inclusive_range_minus_one(cx: &LateContext<'_, '_>, expr: &Expr) {
211 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(cx, expr);
212 if let Some(y) = y_minus_one(cx, end);
218 "an exclusive range would be more readable",
220 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
221 let end = Sugg::hir(cx, y, "y");
225 format!("{}..{}", start, end),
226 Applicability::MachineApplicable, // snippet
234 fn has_step_by(cx: &LateContext<'_, '_>, expr: &Expr) -> bool {
235 // No need for `walk_ptrs_ty` here because `step_by` moves `self`, so it
236 // can't be called on a borrowed range.
237 let ty = cx.tables.expr_ty_adjusted(expr);
239 get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
242 fn y_plus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr) -> Option<&'t Expr> {
246 node: BinOpKind::Add, ..
251 if is_integer_const(cx, lhs, 1) {
253 } else if is_integer_const(cx, rhs, 1) {
263 fn y_minus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr) -> Option<&'t Expr> {
267 node: BinOpKind::Sub, ..
271 ) if is_integer_const(cx, rhs, 1) => Some(lhs),