Skip to content

Commit da0578a

Browse files
lengyijunlengyijun
committed
borrow_deref_ref
1 parent a3bf9d1 commit da0578a

31 files changed

+279
-64
lines changed

‎CHANGELOG.md

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2887,6 +2887,7 @@ Released 2018-09-13
28872887
[`blocks_in_if_conditions`]: https://rust-lang.github.io/rust-clippy/master/index.html#blocks_in_if_conditions
28882888
[`bool_assert_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#bool_assert_comparison
28892889
[`bool_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#bool_comparison
2890+
[`borrow_deref_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#borrow_deref_ref
28902891
[`borrow_interior_mutable_const`]: https://rust-lang.github.io/rust-clippy/master/index.html#borrow_interior_mutable_const
28912892
[`borrowed_box`]: https://rust-lang.github.io/rust-clippy/master/index.html#borrowed_box
28922893
[`box_collection`]: https://rust-lang.github.io/rust-clippy/master/index.html#box_collection

‎clippy_lints/src/borrow_deref_ref.rs

Lines changed: 113 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,113 @@
1+
use crate::reference::DEREF_ADDROF;
2+
use clippy_utils::diagnostics::span_lint_and_then;
3+
use clippy_utils::source::snippet_opt;
4+
use clippy_utils::ty::implements_trait;
5+
use clippy_utils::{get_parent_expr, is_lint_allowed};
6+
use rustc_hir::{ExprKind, UnOp};
7+
use rustc_lint::{LateContext, LateLintPass};
8+
use rustc_middle::mir::Mutability;
9+
use rustc_middle::ty;
10+
use rustc_session::{declare_lint_pass, declare_tool_lint};
11+
12+
declare_clippy_lint! {
13+
/// ### What it does
14+
/// Checks for `&*(&T)`.
15+
///
16+
/// ### Why is this bad?
17+
/// When people deref on an immutable reference `&T`, they may expect return `&U`.
18+
/// Accutually `&* (&T)` is still `&T`.
19+
/// if you want to deref explicitly, `&** (&T)` is what you need.
20+
/// If you want to reborrow, `&T` is enough (`&T` is Copy).
21+
///
22+
/// ### Known problems
23+
/// false negative on such code:
24+
/// ```
25+
/// let x = &12;
26+
/// let addr_x = &x as *const _ as usize;
27+
/// let addr_y = &&*x as *const _ as usize; // assert ok now, and lint triggerd.
28+
/// // But if we fix it, assert will fail.
29+
/// assert_ne!(addr_x, addr_y);
30+
/// ```
31+
///
32+
/// ### Example
33+
/// ```rust
34+
/// let s = &String::new();
35+
///
36+
/// // Bad
37+
/// let a: &String = &* s;
38+
/// foo(&*s);
39+
///
40+
/// // Good
41+
/// let a: &String = s;
42+
/// foo(&**s);
43+
///
44+
/// fn foo(_: &str){ }
45+
/// ```
46+
#[clippy::version = "1.59.0"]
47+
pub BORROW_DEREF_REF,
48+
complexity,
49+
"deref on an immutable reference returns the same type as itself"
50+
}
51+
52+
declare_lint_pass!(BorrowDerefRef => [BORROW_DEREF_REF]);
53+
54+
impl LateLintPass<'_> for BorrowDerefRef {
55+
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx rustc_hir::Expr<'_>) {
56+
if_chain! {
57+
if !e.span.from_expansion();
58+
if let ExprKind::AddrOf(_, Mutability::Not, addrof_target) = e.kind;
59+
if !addrof_target.span.from_expansion();
60+
if let ExprKind::Unary(UnOp::Deref, deref_target) = addrof_target.kind;
61+
if !deref_target.span.from_expansion();
62+
if !matches!(deref_target.kind, ExprKind::Unary(UnOp::Deref, ..) );
63+
let ref_ty = cx.typeck_results().expr_ty(deref_target);
64+
if let ty::Ref(_, inner_ty, Mutability::Not) = ref_ty.kind();
65+
then{
66+
67+
if let Some(parent_expr) = get_parent_expr(cx, e){
68+
if matches!(deref_target.kind, ExprKind::Path(..) | ExprKind::Field(..)) {
69+
if matches!(parent_expr.kind, ExprKind::AddrOf(_, Mutability::Mut, _)) {
70+
return;
71+
}
72+
if matches!(parent_expr.kind, ExprKind::Unary(UnOp::Deref, ..)) &&
73+
!is_lint_allowed(cx, DEREF_ADDROF, parent_expr.hir_id) {
74+
return;
75+
}
76+
}
77+
}
78+
79+
span_lint_and_then(
80+
cx,
81+
BORROW_DEREF_REF,
82+
e.span,
83+
"deref on an immutable reference",
84+
|diag| {
85+
diag.help(
86+
&format!(
87+
"consider using `{}` if you would like to reborrow",
88+
&snippet_opt(cx, deref_target.span).unwrap(),
89+
)
90+
);
91+
92+
// has deref trait -> give 2 help
93+
// doesn't have deref trait -> give 1 help
94+
if let Some(deref_trait_id) = cx.tcx.lang_items().deref_trait(){
95+
if !implements_trait(cx, inner_ty, deref_trait_id, &[]) {
96+
return;
97+
}
98+
}
99+
100+
diag.help(
101+
&format!(
102+
"consider using `&**{}` if you would like to deref",
103+
&snippet_opt(cx, deref_target.span).unwrap(),
104+
)
105+
);
106+
107+
}
108+
);
109+
110+
}
111+
}
112+
}
113+
}

‎clippy_lints/src/checked_conversions.rs

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -319,7 +319,7 @@ fn get_implementing_type<'a>(path: &QPath<'_>, candidates: &'a [&str], function:
319319
if let QPath::TypeRelative(ty, path) = &path;
320320
if path.ident.name.as_str() == function;
321321
if let TyKind::Path(QPath::Resolved(None, tp)) = &ty.kind;
322-
if let [int] = &*tp.segments;
322+
if let [int] = tp.segments;
323323
then {
324324
let name = &int.ident.name.as_str();
325325
candidates.iter().find(|c| name == *c).copied()
@@ -333,7 +333,7 @@ fn get_implementing_type<'a>(path: &QPath<'_>, candidates: &'a [&str], function:
333333
fn int_ty_to_sym<'tcx>(path: &QPath<'_>) -> Option<&'tcx str> {
334334
if_chain! {
335335
if let QPath::Resolved(_, path) = *path;
336-
if let [ty] = &*path.segments;
336+
if let [ty] = path.segments;
337337
then {
338338
let name = &ty.ident.name.as_str();
339339
INTS.iter().find(|c| name == *c).copied()

‎clippy_lints/src/enum_variants.rs

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -154,8 +154,8 @@ fn check_variant(
154154
}
155155
}
156156
let first = &def.variants[0].ident.name.as_str();
157-
let mut pre = &first[..str_utils::camel_case_until(&*first).byte_index];
158-
let mut post = &first[str_utils::camel_case_start(&*first).byte_index..];
157+
let mut pre = &first[..str_utils::camel_case_until(first).byte_index];
158+
let mut post = &first[str_utils::camel_case_start(first).byte_index..];
159159
for var in def.variants {
160160
let name = var.ident.name.as_str();
161161

‎clippy_lints/src/eval_order_dependence.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -121,7 +121,7 @@ impl<'a, 'tcx> DivergenceVisitor<'a, 'tcx> {
121121
self.visit_expr(if_expr);
122122
}
123123
// make sure top level arm expressions aren't linted
124-
self.maybe_walk_expr(&*arm.body);
124+
self.maybe_walk_expr(arm.body);
125125
}
126126
},
127127
_ => walk_expr(self, e),

‎clippy_lints/src/format.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -54,7 +54,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat {
5454
span_useless_format_empty(cx, call_site, "String::new()".to_owned(), applicability);
5555
} else {
5656
if_chain! {
57-
if let [e] = &*format_args.format_string_parts;
57+
if let [e] = format_args.format_string_parts;
5858
if let ExprKind::Lit(lit) = &e.kind;
5959
if let Some(s_src) = snippet_opt(cx, lit.span);
6060
then {

‎clippy_lints/src/let_if_seq.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -68,7 +68,7 @@ impl<'tcx> LateLintPass<'tcx> for LetIfSeq {
6868
if let hir::ExprKind::If(hir::Expr { kind: hir::ExprKind::DropTemps(cond), ..}, then, else_) = if_.kind;
6969
if !is_local_used(cx, *cond, canonical_id);
7070
if let hir::ExprKind::Block(then, _) = then.kind;
71-
if let Some(value) = check_assign(cx, canonical_id, &*then);
71+
if let Some(value) = check_assign(cx, canonical_id, then);
7272
if !is_local_used(cx, value, canonical_id);
7373
then {
7474
let span = stmt.span.to(if_.span);

‎clippy_lints/src/lib.register_all.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -21,6 +21,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
2121
LintId::of(bool_assert_comparison::BOOL_ASSERT_COMPARISON),
2222
LintId::of(booleans::LOGIC_BUG),
2323
LintId::of(booleans::NONMINIMAL_BOOL),
24+
LintId::of(borrow_deref_ref::BORROW_DEREF_REF),
2425
LintId::of(casts::CAST_REF_TO_MUT),
2526
LintId::of(casts::CHAR_LIT_AS_U8),
2627
LintId::of(casts::FN_TO_NUMERIC_CAST),

‎clippy_lints/src/lib.register_complexity.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,7 @@
55
store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec![
66
LintId::of(attrs::DEPRECATED_CFG_ATTR),
77
LintId::of(booleans::NONMINIMAL_BOOL),
8+
LintId::of(borrow_deref_ref::BORROW_DEREF_REF),
89
LintId::of(casts::CHAR_LIT_AS_U8),
910
LintId::of(casts::UNNECESSARY_CAST),
1011
LintId::of(derivable_impls::DERIVABLE_IMPLS),

‎clippy_lints/src/lib.register_lints.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -59,6 +59,7 @@ store.register_lints(&[
5959
bool_assert_comparison::BOOL_ASSERT_COMPARISON,
6060
booleans::LOGIC_BUG,
6161
booleans::NONMINIMAL_BOOL,
62+
borrow_deref_ref::BORROW_DEREF_REF,
6263
bytecount::NAIVE_BYTECOUNT,
6364
cargo_common_metadata::CARGO_COMMON_METADATA,
6465
case_sensitive_file_extension_comparisons::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,

0 commit comments

Comments
 (0)