3 use utils::{in_macro, implements_trait, is_copy, multispan_sugg, snippet, span_lint, span_lint_and_then, SpanlessEq};
5 /// **What it does:** Checks for equal operands to comparison, logical and
6 /// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
7 /// `||`, `&`, `|`, `^`, `-` and `/`).
9 /// **Why is this bad?** This is usually just a typo or a copy and paste error.
11 /// **Known problems:** False negatives: We had some false positives regarding
12 /// calls (notably [racer](https://github.com/phildawes/racer) had one instance
13 /// of `x.pop() && x.pop()`), so we removed matching any function or method
14 /// calls. We may introduce a whitelist of known pure functions in the future.
23 "equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)"
26 /// **What it does:** Checks for arguments to `==` which have their address
27 /// taken to satisfy a bound
28 /// and suggests to dereference the other argument instead
30 /// **Why is this bad?** It is more idiomatic to dereference the other argument.
32 /// **Known problems:** None
41 "taking a reference to satisfy the type constraints on `==`"
44 #[derive(Copy, Clone)]
47 impl LintPass for EqOp {
48 fn get_lints(&self) -> LintArray {
49 lint_array!(EQ_OP, OP_REF)
53 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EqOp {
54 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
55 if let ExprBinary(ref op, ref left, ref right) = e.node {
56 if is_valid_operator(op) && SpanlessEq::new(cx).ignore_fn().eq_expr(left, right) && !in_macro(e.span) {
61 &format!("equal expressions as operands to `{}`", op.node.as_str()),
65 let (trait_id, requires_ref) = match op.node {
66 BiAdd => (cx.tcx.lang_items().add_trait(), false),
67 BiSub => (cx.tcx.lang_items().sub_trait(), false),
68 BiMul => (cx.tcx.lang_items().mul_trait(), false),
69 BiDiv => (cx.tcx.lang_items().div_trait(), false),
70 BiRem => (cx.tcx.lang_items().rem_trait(), false),
71 // don't lint short circuiting ops
72 BiAnd | BiOr => return,
73 BiBitXor => (cx.tcx.lang_items().bitxor_trait(), false),
74 BiBitAnd => (cx.tcx.lang_items().bitand_trait(), false),
75 BiBitOr => (cx.tcx.lang_items().bitor_trait(), false),
76 BiShl => (cx.tcx.lang_items().shl_trait(), false),
77 BiShr => (cx.tcx.lang_items().shr_trait(), false),
78 BiNe | BiEq => (cx.tcx.lang_items().eq_trait(), true),
79 BiLt | BiLe | BiGe | BiGt => (cx.tcx.lang_items().ord_trait(), true),
81 if let Some(trait_id) = trait_id {
82 #[allow(match_same_arms)]
83 match (&left.node, &right.node) {
84 // do not suggest to dereference literals
85 (&ExprLit(..), _) | (_, &ExprLit(..)) => {},
87 (&ExprAddrOf(_, ref l), &ExprAddrOf(_, ref r)) => {
88 let lty = cx.tables.expr_ty(l);
89 let rty = cx.tables.expr_ty(r);
90 let lcpy = is_copy(cx, lty);
91 let rcpy = is_copy(cx, rty);
92 // either operator autorefs or both args are copyable
93 if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty]) {
98 "needlessly taken reference of both operands",
100 let lsnip = snippet(cx, l.span, "...").to_string();
101 let rsnip = snippet(cx, r.span, "...").to_string();
104 "use the values directly".to_string(),
105 vec![(left.span, lsnip), (right.span, rsnip)],
109 } else if lcpy && !rcpy && implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right)]) {
110 span_lint_and_then(cx, OP_REF, e.span, "needlessly taken reference of left operand", |db| {
111 let lsnip = snippet(cx, l.span, "...").to_string();
112 db.span_suggestion(left.span, "use the left value directly", lsnip);
114 } else if !lcpy && rcpy && implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty]) {
119 "needlessly taken reference of right operand",
121 let rsnip = snippet(cx, r.span, "...").to_string();
122 db.span_suggestion(right.span, "use the right value directly", rsnip);
128 (&ExprAddrOf(_, ref l), _) => {
129 let lty = cx.tables.expr_ty(l);
130 let lcpy = is_copy(cx, lty);
131 if (requires_ref || lcpy) && implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right)]) {
132 span_lint_and_then(cx, OP_REF, e.span, "needlessly taken reference of left operand", |db| {
133 let lsnip = snippet(cx, l.span, "...").to_string();
134 db.span_suggestion(left.span, "use the left value directly", lsnip);
139 (_, &ExprAddrOf(_, ref r)) => {
140 let rty = cx.tables.expr_ty(r);
141 let rcpy = is_copy(cx, rty);
142 if (requires_ref || rcpy) && implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty]) {
143 span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |db| {
144 let rsnip = snippet(cx, r.span, "...").to_string();
145 db.span_suggestion(right.span, "use the right value directly", rsnip);
157 fn is_valid_operator(op: &BinOp) -> bool {
159 BiSub | BiDiv | BiEq | BiLt | BiLe | BiGt | BiGe | BiNe | BiAnd | BiOr | BiBitXor | BiBitAnd | BiBitOr => true,