3 use syntax::ast::RangeLimits;
4 use syntax::codemap::Spanned;
5 use utils::{is_integer_literal, paths, snippet, span_lint, span_lint_and_then};
6 use utils::{get_trait_def_id, higher, implements_trait};
9 /// **What it does:** Checks for calling `.step_by(0)` on iterators,
10 /// which never terminates.
12 /// **Why is this bad?** This very much looks like an oversight, since with
13 /// `loop { .. }` there is an obvious better way to endlessly loop.
15 /// **Known problems:** None.
19 /// for x in (5..5).step_by(0) { .. }
21 declare_clippy_lint! {
22 pub ITERATOR_STEP_BY_ZERO,
24 "using `Iterator::step_by(0)`, which produces an infinite iterator"
27 /// **What it does:** Checks for zipping a collection with the range of
30 /// **Why is this bad?** The code is better expressed with `.enumerate()`.
32 /// **Known problems:** None.
36 /// x.iter().zip(0..x.len())
38 declare_clippy_lint! {
39 pub RANGE_ZIP_WITH_LEN,
41 "zipping iterator with a range when `enumerate()` would do"
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:** None.
54 /// for x..(y+1) { .. }
56 declare_clippy_lint! {
59 "`x..(y+1)` reads better as `x..=y`"
62 /// **What it does:** Checks for inclusive ranges where 1 is subtracted from
63 /// the upper bound, e.g. `x..=(y-1)`.
65 /// **Why is this bad?** The code is more readable with an exclusive range
68 /// **Known problems:** None.
72 /// for x..=(y-1) { .. }
74 declare_clippy_lint! {
77 "`x..=(y-1)` reads better as `x..y`"
80 #[derive(Copy, Clone)]
83 impl LintPass for Pass {
84 fn get_lints(&self) -> LintArray {
85 lint_array!(ITERATOR_STEP_BY_ZERO, RANGE_ZIP_WITH_LEN, RANGE_PLUS_ONE, RANGE_MINUS_ONE)
89 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
90 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
91 if let ExprMethodCall(ref path, _, ref args) = expr.node {
92 let name = path.name.as_str();
94 // Range with step_by(0).
95 if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
96 use consts::{constant, Constant};
97 if let Some((Constant::Int(0), _)) = constant(cx, &args[1]) {
100 ITERATOR_STEP_BY_ZERO,
102 "Iterator::step_by(0) will panic at runtime",
105 } else if name == "zip" && args.len() == 2 {
106 let iter = &args[0].node;
107 let zip_arg = &args[1];
110 if let ExprMethodCall(ref iter_path, _, ref iter_args ) = *iter;
111 if iter_path.name == "iter";
112 // range expression in .zip() call: 0..x.len()
113 if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(cx, zip_arg);
114 if is_integer_literal(start, 0);
116 if let ExprMethodCall(ref len_path, _, ref len_args) = end.node;
117 if len_path.name == "len" && len_args.len() == 1;
118 // .iter() and .len() called on same Path
119 if let ExprPath(QPath::Resolved(_, ref iter_path)) = iter_args[0].node;
120 if let ExprPath(QPath::Resolved(_, ref len_path)) = len_args[0].node;
121 if iter_path.segments == len_path.segments;
126 &format!("It is more idiomatic to use {}.iter().enumerate()",
127 snippet(cx, iter_args[0].span, "_")));
133 // exclusive range plus one: x..(y+1)
135 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::HalfOpen }) = higher::range(cx, expr);
136 if let Some(y) = y_plus_one(end);
142 "an inclusive range would be more readable",
144 let start = start.map_or("".to_owned(), |x| Sugg::hir(cx, x, "x").to_string());
145 let end = Sugg::hir(cx, y, "y");
146 db.span_suggestion(expr.span,
148 format!("{}..={}", start, end));
154 // inclusive range minus one: x..=(y-1)
156 if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(cx, expr);
157 if let Some(y) = y_minus_one(end);
163 "an exclusive range would be more readable",
165 let start = start.map_or("".to_owned(), |x| Sugg::hir(cx, x, "x").to_string());
166 let end = Sugg::hir(cx, y, "y");
167 db.span_suggestion(expr.span,
169 format!("{}..{}", start, end));
177 fn has_step_by(cx: &LateContext, expr: &Expr) -> bool {
178 // No need for walk_ptrs_ty here because step_by moves self, so it
179 // can't be called on a borrowed range.
180 let ty = cx.tables.expr_ty_adjusted(expr);
182 get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
185 fn y_plus_one(expr: &Expr) -> Option<&Expr> {
187 ExprBinary(Spanned { node: BiAdd, .. }, ref lhs, ref rhs) => if is_integer_literal(lhs, 1) {
189 } else if is_integer_literal(rhs, 1) {
198 fn y_minus_one(expr: &Expr) -> Option<&Expr> {
200 ExprBinary(Spanned { node: BiSub, .. }, ref lhs, ref rhs) if is_integer_literal(rhs, 1) => Some(lhs),