1 use if_chain::if_chain;
2 use rustc::declare_lint_pass;
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc_errors::Applicability;
6 use rustc_session::declare_tool_lint;
7 use syntax::ast::RangeLimits;
8 use syntax::source_map::Spanned;
10 use crate::utils::sugg::Sugg;
11 use crate::utils::{get_trait_def_id, higher, implements_trait, SpanlessEq};
12 use crate::utils::{is_integer_const, paths, snippet, snippet_opt, span_lint, span_lint_and_then};
14 declare_clippy_lint! {
15 /// **What it does:** Checks for calling `.step_by(0)` on iterators,
16 /// which never terminates.
18 /// **Why is this bad?** This very much looks like an oversight, since with
19 /// `loop { .. }` there is an obvious better way to endlessly loop.
21 /// **Known problems:** None.
25 /// for x in (5..5).step_by(0) {
29 pub ITERATOR_STEP_BY_ZERO,
31 "using `Iterator::step_by(0)`, which produces an infinite iterator"
34 declare_clippy_lint! {
35 /// **What it does:** Checks for zipping a collection with the range of
38 /// **Why is this bad?** The code is better expressed with `.enumerate()`.
40 /// **Known problems:** None.
44 /// # let x = vec![1];
45 /// x.iter().zip(0..x.len());
47 /// Could be written as
49 /// # let x = vec![1];
50 /// x.iter().enumerate();
52 pub RANGE_ZIP_WITH_LEN,
54 "zipping iterator with a range when `enumerate()` would do"
57 declare_clippy_lint! {
58 /// **What it does:** Checks for exclusive ranges where 1 is added to the
59 /// upper bound, e.g., `x..(y+1)`.
61 /// **Why is this bad?** The code is more readable with an inclusive range
64 /// **Known problems:** Will add unnecessary pair of parentheses when the
65 /// expression is not wrapped in a pair but starts with a opening parenthesis
66 /// and ends with a closing one.
67 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
71 /// for x..(y+1) { .. }
73 /// Could be written as
79 "`x..(y+1)` reads better as `x..=y`"
82 declare_clippy_lint! {
83 /// **What it does:** Checks for inclusive ranges where 1 is subtracted from
84 /// the upper bound, e.g., `x..=(y-1)`.
86 /// **Why is this bad?** The code is more readable with an exclusive range
89 /// **Known problems:** None.
93 /// for x..=(y-1) { .. }
95 /// Could be written as
101 "`x..=(y-1)` reads better as `x..y`"
104 declare_lint_pass!(Ranges => [
105 ITERATOR_STEP_BY_ZERO,
111 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Ranges {
112 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
113 if let ExprKind::MethodCall(ref path, _, ref args) = expr.kind {
114 let name = path.ident.as_str();
116 // Range with step_by(0).
117 if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
118 use crate::consts::{constant, Constant};
119 if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
122 ITERATOR_STEP_BY_ZERO,
124 "Iterator::step_by(0) will panic at runtime",
127 } else if name == "zip" && args.len() == 2 {
128 let iter = &args[0].kind;
129 let zip_arg = &args[1];
132 if let ExprKind::MethodCall(ref iter_path, _, ref iter_args ) = *iter;
133 if iter_path.ident.name == sym!(iter);
134 // range expression in `.zip()` call: `0..x.len()`
135 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(cx, zip_arg);
136 if is_integer_const(cx, start, 0);
138 if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.kind;
139 if len_path.ident.name == sym!(len) && len_args.len() == 1;
140 // `.iter()` and `.len()` called on same `Path`
141 if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].kind;
142 if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].kind;
143 if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
148 &format!("It is more idiomatic to use {}.iter().enumerate()",
149 snippet(cx, iter_args[0].span, "_")));
155 check_exclusive_range_plus_one(cx, expr);
156 check_inclusive_range_minus_one(cx, expr);
160 // exclusive range plus one: `x..(y+1)`
161 fn check_exclusive_range_plus_one(cx: &LateContext<'_, '_>, expr: &Expr) {
163 if let Some(higher::Range {
166 limits: RangeLimits::HalfOpen
167 }) = higher::range(cx, expr);
168 if let Some(y) = y_plus_one(cx, end);
170 let span = if expr.span.from_expansion() {
182 "an inclusive range would be more readable",
184 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
185 let end = Sugg::hir(cx, y, "y");
186 if let Some(is_wrapped) = &snippet_opt(cx, span) {
187 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
191 format!("({}..={})", start, end),
192 Applicability::MaybeIncorrect,
198 format!("{}..={}", start, end),
199 Applicability::MachineApplicable, // snippet
209 // inclusive range minus one: `x..=(y-1)`
210 fn check_inclusive_range_minus_one(cx: &LateContext<'_, '_>, expr: &Expr) {
212 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(cx, expr);
213 if let Some(y) = y_minus_one(cx, end);
219 "an exclusive range would be more readable",
221 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
222 let end = Sugg::hir(cx, y, "y");
226 format!("{}..{}", start, end),
227 Applicability::MachineApplicable, // snippet
235 fn has_step_by(cx: &LateContext<'_, '_>, expr: &Expr) -> bool {
236 // No need for `walk_ptrs_ty` here because `step_by` moves `self`, so it
237 // can't be called on a borrowed range.
238 let ty = cx.tables.expr_ty_adjusted(expr);
240 get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
243 fn y_plus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr) -> Option<&'t Expr> {
247 node: BinOpKind::Add, ..
252 if is_integer_const(cx, lhs, 1) {
254 } else if is_integer_const(cx, rhs, 1) {
264 fn y_minus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr) -> Option<&'t Expr> {
268 node: BinOpKind::Sub, ..
272 ) if is_integer_const(cx, rhs, 1) => Some(lhs),