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
use rustc::lint::*;
use rustc::hir::{ExprAddrOf, Expr, MutImmutable, Pat, PatKind, BindingMode};
use rustc::ty;
use utils::{span_lint, in_macro};
declare_lint! {
pub NEEDLESS_BORROW,
Warn,
"taking a reference that is going to be automatically dereferenced"
}
#[derive(Copy,Clone)]
pub struct NeedlessBorrow;
impl LintPass for NeedlessBorrow {
fn get_lints(&self) -> LintArray {
lint_array!(NEEDLESS_BORROW)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBorrow {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
if in_macro(cx, e.span) {
return;
}
if let ExprAddrOf(MutImmutable, ref inner) = e.node {
if let ty::TyRef(..) = cx.tcx.tables().expr_ty(inner).sty {
if let Some(&ty::adjustment::Adjust::DerefRef { autoderefs, autoref, .. }) =
cx.tcx.tables.borrow().adjustments.get(&e.id).map(|a| &a.kind) {
if autoderefs > 1 && autoref.is_some() {
span_lint(cx,
NEEDLESS_BORROW,
e.span,
"this expression borrows a reference that is immediately dereferenced by the \
compiler");
}
}
}
}
}
fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat) {
if in_macro(cx, pat.span) {
return;
}
if_let_chain! {[
let PatKind::Binding(BindingMode::BindByRef(MutImmutable), _, _, _) = pat.node,
let ty::TyRef(_, ref tam) = cx.tcx.tables().pat_ty(pat).sty,
tam.mutbl == MutImmutable,
let ty::TyRef(_, ref tam) = tam.ty.sty,
tam.mutbl == MutImmutable,
], {
span_lint(cx, NEEDLESS_BORROW, pat.span, "this pattern creates a reference to a reference")
}}
}
}