1 use if_chain::if_chain;
3 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
4 use rustc::{declare_tool_lint, lint_array};
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_literal, 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 /// x.iter().zip(0..x.len())
45 pub RANGE_ZIP_WITH_LEN,
47 "zipping iterator with a range when `enumerate()` would do"
50 declare_clippy_lint! {
51 /// **What it does:** Checks for exclusive ranges where 1 is added to the
52 /// upper bound, e.g., `x..(y+1)`.
54 /// **Why is this bad?** The code is more readable with an inclusive range
57 /// **Known problems:** Will add unnecessary pair of parentheses when the
58 /// expression is not wrapped in a pair but starts with a opening parenthesis
59 /// and ends with a closing one.
60 /// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
64 /// for x..(y+1) { .. }
68 "`x..(y+1)` reads better as `x..=y`"
71 declare_clippy_lint! {
72 /// **What it does:** Checks for inclusive ranges where 1 is subtracted from
73 /// the upper bound, e.g., `x..=(y-1)`.
75 /// **Why is this bad?** The code is more readable with an exclusive range
78 /// **Known problems:** None.
82 /// for x..=(y-1) { .. }
86 "`x..=(y-1)` reads better as `x..y`"
89 #[derive(Copy, Clone)]
92 impl LintPass for Pass {
93 fn get_lints(&self) -> LintArray {
95 ITERATOR_STEP_BY_ZERO,
102 fn name(&self) -> &'static str {
107 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
108 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
109 if let ExprKind::MethodCall(ref path, _, ref args) = expr.node {
110 let name = path.ident.as_str();
112 // Range with step_by(0).
113 if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
114 use crate::consts::{constant, Constant};
115 if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
118 ITERATOR_STEP_BY_ZERO,
120 "Iterator::step_by(0) will panic at runtime",
123 } else if name == "zip" && args.len() == 2 {
124 let iter = &args[0].node;
125 let zip_arg = &args[1];
128 if let ExprKind::MethodCall(ref iter_path, _, ref iter_args ) = *iter;
129 if iter_path.ident.name == "iter";
130 // range expression in `.zip()` call: `0..x.len()`
131 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(cx, zip_arg);
132 if is_integer_literal(start, 0);
134 if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.node;
135 if len_path.ident.name == "len" && len_args.len() == 1;
136 // `.iter()` and `.len()` called on same `Path`
137 if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].node;
138 if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].node;
139 if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
144 &format!("It is more idiomatic to use {}.iter().enumerate()",
145 snippet(cx, iter_args[0].span, "_")));
151 // exclusive range plus one: `x..(y+1)`
153 if let Some(higher::Range {
156 limits: RangeLimits::HalfOpen
157 }) = higher::range(cx, expr);
158 if let Some(y) = y_plus_one(end);
164 .map(|info| info.call_site)
165 .unwrap_or(expr.span);
170 "an inclusive range would be more readable",
172 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
173 let end = Sugg::hir(cx, y, "y");
174 if let Some(is_wrapped) = &snippet_opt(cx, span) {
175 if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
179 format!("({}..={})", start, end),
180 Applicability::MaybeIncorrect,
186 format!("{}..={}", start, end),
187 Applicability::MachineApplicable, // snippet
196 // inclusive range minus one: `x..=(y-1)`
198 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(cx, expr);
199 if let Some(y) = y_minus_one(end);
205 "an exclusive range would be more readable",
207 let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
208 let end = Sugg::hir(cx, y, "y");
212 format!("{}..{}", start, end),
213 Applicability::MachineApplicable, // snippet
222 fn has_step_by(cx: &LateContext<'_, '_>, expr: &Expr) -> bool {
223 // No need for `walk_ptrs_ty` here because `step_by` moves `self`, so it
224 // can't be called on a borrowed range.
225 let ty = cx.tables.expr_ty_adjusted(expr);
227 get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
230 fn y_plus_one(expr: &Expr) -> Option<&Expr> {
234 node: BinOpKind::Add, ..
239 if is_integer_literal(lhs, 1) {
241 } else if is_integer_literal(rhs, 1) {
251 fn y_minus_one(expr: &Expr) -> Option<&Expr> {
255 node: BinOpKind::Sub, ..
259 ) if is_integer_literal(rhs, 1) => Some(lhs),