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Simplify casting logic of the invalid_reference_casting lint
1 parent e577dcd commit b97d311

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3 files changed

+93
-105
lines changed

3 files changed

+93
-105
lines changed

‎compiler/rustc_lint/src/reference_casting.rs

+38-80
Original file line numberDiff line numberDiff line change
@@ -104,99 +104,57 @@ fn is_operation_we_care_about<'tcx>(
104104
deref_assign_or_addr_of(e).or_else(|| ptr_write(cx, e))
105105
}
106106

107-
fn is_cast_from_const_to_mut<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> bool {
108-
let e = e.peel_blocks();
107+
fn is_cast_from_const_to_mut<'tcx>(cx: &LateContext<'tcx>, orig_expr: &'tcx Expr<'tcx>) -> bool {
108+
let mut had_at_least_one_cast = false;
109+
let mut need_check_freeze = false;
110+
let mut e = orig_expr;
109111

110-
fn from_casts<'tcx>(
111-
cx: &LateContext<'tcx>,
112-
e: &'tcx Expr<'tcx>,
113-
need_check_freeze: &mut bool,
114-
) -> Option<&'tcx Expr<'tcx>> {
115-
// <expr> as *mut ...
116-
let mut e = if let ExprKind::Cast(e, t) = e.kind
117-
&& let ty::RawPtr(TypeAndMut { mutbl: Mutability::Mut, .. }) = cx.typeck_results().node_type(t.hir_id).kind() {
118-
e
119-
// <expr>.cast_mut()
112+
let end_ty = cx.typeck_results().node_type(orig_expr.hir_id);
113+
114+
// Bail out early if the end type is **not** a mutable pointer.
115+
if !matches!(end_ty.kind(), ty::RawPtr(TypeAndMut { ty: _, mutbl: Mutability::Mut })) {
116+
return false;
117+
}
118+
119+
loop {
120+
e = e.peel_blocks();
121+
// <expr> as ...
122+
e = if let ExprKind::Cast(expr, _) = e.kind {
123+
had_at_least_one_cast = true;
124+
expr
125+
// <expr>.cast(), <expr>.cast_mut() or <expr>.cast_const()
120126
} else if let ExprKind::MethodCall(_, expr, [], _) = e.kind
121127
&& let Some(def_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
122-
&& cx.tcx.is_diagnostic_item(sym::ptr_cast_mut, def_id) {
128+
&& matches!(
129+
cx.tcx.get_diagnostic_name(def_id),
130+
Some(sym::ptr_cast | sym::const_ptr_cast | sym::ptr_cast_mut | sym::ptr_cast_const)
131+
)
132+
{
133+
had_at_least_one_cast = true;
123134
expr
124-
// UnsafeCell::raw_get(<expr>)
135+
// ptr::from_ref(<expr>), UnsafeCell::raw_get(<expr>) or mem::transmute<_, _>(<expr>)
125136
} else if let ExprKind::Call(path, [arg]) = e.kind
126137
&& let ExprKind::Path(ref qpath) = path.kind
127138
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
128-
&& cx.tcx.is_diagnostic_item(sym::unsafe_cell_raw_get, def_id)
139+
&& matches!(
140+
cx.tcx.get_diagnostic_name(def_id),
141+
Some(sym::ptr_from_ref | sym::unsafe_cell_raw_get | sym::transmute)
142+
)
129143
{
130-
*need_check_freeze = true;
144+
if cx.tcx.is_diagnostic_item(sym::unsafe_cell_raw_get, def_id) {
145+
need_check_freeze = true;
146+
}
147+
had_at_least_one_cast = true;
131148
arg
149+
} else if had_at_least_one_cast {
150+
break;
132151
} else {
133-
return None;
152+
return false;
134153
};
135-
136-
let mut had_at_least_one_cast = false;
137-
loop {
138-
e = e.peel_blocks();
139-
// <expr> as *mut/const ... or <expr> as <uint>
140-
e = if let ExprKind::Cast(expr, t) = e.kind
141-
&& matches!(cx.typeck_results().node_type(t.hir_id).kind(), ty::RawPtr(_) | ty::Uint(_)) {
142-
had_at_least_one_cast = true;
143-
expr
144-
// <expr>.cast(), <expr>.cast_mut() or <expr>.cast_const()
145-
} else if let ExprKind::MethodCall(_, expr, [], _) = e.kind
146-
&& let Some(def_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
147-
&& matches!(
148-
cx.tcx.get_diagnostic_name(def_id),
149-
Some(sym::ptr_cast | sym::const_ptr_cast | sym::ptr_cast_mut | sym::ptr_cast_const)
150-
)
151-
{
152-
had_at_least_one_cast = true;
153-
expr
154-
// ptr::from_ref(<expr>) or UnsafeCell::raw_get(<expr>)
155-
} else if let ExprKind::Call(path, [arg]) = e.kind
156-
&& let ExprKind::Path(ref qpath) = path.kind
157-
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
158-
&& matches!(
159-
cx.tcx.get_diagnostic_name(def_id),
160-
Some(sym::ptr_from_ref | sym::unsafe_cell_raw_get)
161-
)
162-
{
163-
if cx.tcx.is_diagnostic_item(sym::unsafe_cell_raw_get, def_id) {
164-
*need_check_freeze = true;
165-
}
166-
return Some(arg);
167-
} else if had_at_least_one_cast {
168-
return Some(e);
169-
} else {
170-
return None;
171-
};
172-
}
173154
}
174155

175-
fn from_transmute<'tcx>(
176-
cx: &LateContext<'tcx>,
177-
e: &'tcx Expr<'tcx>,
178-
) -> Option<&'tcx Expr<'tcx>> {
179-
// mem::transmute::<_, *mut _>(<expr>)
180-
if let ExprKind::Call(path, [arg]) = e.kind
181-
&& let ExprKind::Path(ref qpath) = path.kind
182-
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
183-
&& cx.tcx.is_diagnostic_item(sym::transmute, def_id)
184-
&& let ty::RawPtr(TypeAndMut { mutbl: Mutability::Mut, .. }) = cx.typeck_results().node_type(e.hir_id).kind() {
185-
Some(arg)
186-
} else {
187-
None
188-
}
189-
}
190-
191-
let mut need_check_freeze = false;
192-
let Some(e) = from_casts(cx, e, &mut need_check_freeze).or_else(|| from_transmute(cx, e))
193-
else {
194-
return false;
195-
};
196-
197-
let e = e.peel_blocks();
198-
let node_type = cx.typeck_results().node_type(e.hir_id);
199-
if let ty::Ref(_, inner_ty, Mutability::Not) = node_type.kind() {
156+
let start_ty = cx.typeck_results().node_type(e.hir_id);
157+
if let ty::Ref(_, inner_ty, Mutability::Not) = start_ty.kind() {
200158
// If an UnsafeCell method is involved we need to additionaly check the
201159
// inner type for the presence of the Freeze trait (ie does NOT contain
202160
// an UnsafeCell), since in that case we would incorrectly lint on valid casts.

‎tests/ui/lint/reference_casting.rs

+6
Original file line numberDiff line numberDiff line change
@@ -36,6 +36,8 @@ unsafe fn ref_to_mut() {
3636
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
3737
let _num = &mut *std::mem::transmute::<_, *mut i32>(num);
3838
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
39+
let _num = &mut *(std::mem::transmute::<_, *mut i32>(num) as *mut i32);
40+
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
3941
let _num = &mut *std::cell::UnsafeCell::raw_get(
4042
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
4143
num as *const i32 as *const std::cell::UnsafeCell<i32>
@@ -52,6 +54,8 @@ unsafe fn ref_to_mut() {
5254
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
5355
let _num = &mut *(num as *const _ as usize as *mut i32);
5456
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
57+
let _num = &mut *(std::mem::transmute::<_, *mut _>(num as *const i32) as *mut i32);
58+
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
5559

5660
static NUM: &'static i32 = &2;
5761
let num = NUM as *const i32 as *mut i32;
@@ -95,6 +99,8 @@ unsafe fn assign_to_ref() {
9599
//~^ ERROR assigning to `&T` is undefined behavior
96100
*std::mem::transmute::<_, *mut i32>(num) += 1;
97101
//~^ ERROR assigning to `&T` is undefined behavior
102+
*(std::mem::transmute::<_, *mut i32>(num) as *mut i32) += 1;
103+
//~^ ERROR assigning to `&T` is undefined behavior
98104
std::ptr::write(
99105
//~^ ERROR assigning to `&T` is undefined behavior
100106
std::mem::transmute::<*const i32, *mut i32>(num),

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