1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
use rustc::hir;
use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
use rustc::lint::*;
use syntax::ast;
use utils::{get_trait_def_id, implements_trait, snippet_opt, span_lint_and_then, SpanlessEq};
use utils::{higher, sugg};
declare_restriction_lint! {
pub ASSIGN_OPS,
"any compound assignment operation"
}
declare_lint! {
pub ASSIGN_OP_PATTERN,
Warn,
"assigning the result of an operation on a variable to that same variable"
}
declare_lint! {
pub MISREFACTORED_ASSIGN_OP,
Warn,
"having a variable on both sides of an assign op"
}
#[derive(Copy, Clone, Default)]
pub struct AssignOps;
impl LintPass for AssignOps {
fn get_lints(&self) -> LintArray {
lint_array!(ASSIGN_OPS, ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
match expr.node {
hir::ExprAssignOp(op, ref lhs, ref rhs) => {
span_lint_and_then(cx, ASSIGN_OPS, expr.span, "assign operation detected", |db| {
let lhs = &sugg::Sugg::hir(cx, lhs, "..");
let rhs = &sugg::Sugg::hir(cx, rhs, "..");
db.span_suggestion(
expr.span,
"replace it with",
format!("{} = {}", lhs, sugg::make_binop(higher::binop(op.node), lhs, rhs)),
);
});
if let hir::ExprBinary(binop, ref l, ref r) = rhs.node {
if op.node == binop.node {
let lint = |assignee: &hir::Expr, rhs_other: &hir::Expr| {
span_lint_and_then(
cx,
MISREFACTORED_ASSIGN_OP,
expr.span,
"variable appears on both sides of an assignment operation",
|db| if let (Some(snip_a), Some(snip_r)) =
(snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span))
{
let a = &sugg::Sugg::hir(cx, assignee, "..");
let r = &sugg::Sugg::hir(cx, rhs, "..");
let long = format!("{} = {}", snip_a, sugg::make_binop(higher::binop(op.node), a, r));
db.span_suggestion(
expr.span,
&format!("Did you mean {} = {} {} {} or {}? Consider replacing it with",
snip_a, snip_a, op.node.as_str(), snip_r,
long),
format!("{} {}= {}", snip_a, op.node.as_str(), snip_r)
);
db.span_suggestion(
expr.span,
"or",
long
);
},
);
};
if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, l) {
lint(lhs, r);
}
if is_commutative(op.node) && SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, r) {
lint(lhs, l);
}
}
}
},
hir::ExprAssign(ref assignee, ref e) => {
if let hir::ExprBinary(op, ref l, ref r) = e.node {
#[allow(cyclomatic_complexity)]
let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
let ty = cx.tables.expr_ty(assignee);
let rty = cx.tables.expr_ty(rhs);
macro_rules! ops {
($op:expr,
$cx:expr,
$ty:expr,
$rty:expr,
$($trait_name:ident:$full_trait_name:ident),+) => {
match $op {
$(hir::$full_trait_name => {
let [krate, module] = ::utils::paths::OPS_MODULE;
let path = [krate, module, concat!(stringify!($trait_name), "Assign")];
let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
trait_id
} else {
return;
};
let parent_fn = cx.tcx.hir.get_parent(e.id);
let parent_impl = cx.tcx.hir.get_parent(parent_fn);
if_chain! {
if parent_impl != ast::CRATE_NODE_ID;
if let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl);
if let hir::Item_::ItemImpl(_, _, _, _, Some(ref trait_ref), _, _) =
item.node;
if trait_ref.path.def.def_id() == trait_id;
then { return; }
}
implements_trait($cx, $ty, trait_id, &[$rty])
},)*
_ => false,
}
}
}
if ops!(
op.node,
cx,
ty,
rty,
Add: BiAdd,
Sub: BiSub,
Mul: BiMul,
Div: BiDiv,
Rem: BiRem,
And: BiAnd,
Or: BiOr,
BitAnd: BiBitAnd,
BitOr: BiBitOr,
BitXor: BiBitXor,
Shr: BiShr,
Shl: BiShl
) {
span_lint_and_then(
cx,
ASSIGN_OP_PATTERN,
expr.span,
"manual implementation of an assign operation",
|db| if let (Some(snip_a), Some(snip_r)) =
(snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
{
db.span_suggestion(
expr.span,
"replace it with",
format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
);
},
);
}
};
let mut visitor = ExprVisitor {
assignee: assignee,
counter: 0,
cx: cx
};
walk_expr(&mut visitor, e);
if visitor.counter == 1 {
if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, l) {
lint(assignee, r);
}
if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, r) {
match op.node {
hir::BiAdd |
hir::BiMul |
hir::BiAnd |
hir::BiOr |
hir::BiBitXor |
hir::BiBitAnd |
hir::BiBitOr => {
lint(assignee, l);
},
_ => {},
}
}
}
}
},
_ => {},
}
}
}
fn is_commutative(op: hir::BinOp_) -> bool {
use rustc::hir::BinOp_::*;
match op {
BiAdd | BiMul | BiAnd | BiOr | BiBitXor | BiBitAnd | BiBitOr | BiEq | BiNe => true,
BiSub | BiDiv | BiRem | BiShl | BiShr | BiLt | BiLe | BiGe | BiGt => false,
}
}
struct ExprVisitor<'a, 'tcx: 'a> {
assignee: &'a hir::Expr,
counter: u8,
cx: &'a LateContext<'a, 'tcx>,
}
impl<'a, 'tcx: 'a> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
if SpanlessEq::new(self.cx).ignore_fn().eq_expr(self.assignee, &expr) {
self.counter += 1;
}
walk_expr(self, expr);
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}