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Auto merge of #5949 - rail-rain:fix_fp_borrow_interior_mutable_const,…
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… r=oli-obk

Fix fp in `borrow_interior_mutable_const`

fixes #5796

changelog: fix false positive in `borrow_interior_mutable_const` when referencing a field behind a pointer.
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@bors
bors committed Aug 26, 2020
2 parents 23db542 + ce8915c commit 9ef4479
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Showing 3 changed files with 64 additions and 18 deletions.
15 changes: 14 additions & 1 deletion clippy_lints/src/non_copy_const.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -211,8 +211,21 @@ impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
needs_check_adjustment = false;
},
ExprKind::Field(..) => {
dereferenced_expr = parent_expr;
needs_check_adjustment = true;

// Check whether implicit dereferences happened;
// if so, no need to go further up
// because of the same reason as the `ExprKind::Unary` case.
if cx
.typeck_results()
.expr_adjustments(dereferenced_expr)
.iter()
.any(|adj| matches!(adj.kind, Adjust::Deref(_)))
{
break;
}

dereferenced_expr = parent_expr;
},
ExprKind::Index(e, _) if ptr::eq(&**e, cur_expr) => {
// `e[i]` => desugared to `*Index::index(&e, i)`,
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35 changes: 34 additions & 1 deletion tests/ui/borrow_interior_mutable_const.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
#![allow(clippy::declare_interior_mutable_const, clippy::ref_in_deref)]

use std::borrow::Cow;
use std::cell::Cell;
use std::cell::{Cell, UnsafeCell};
use std::fmt::Display;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Once;
Expand Down Expand Up @@ -30,6 +30,37 @@ impl Trait<u32> for u64 {
const ATOMIC: AtomicUsize = AtomicUsize::new(9);
}

// This is just a pointer that can be safely dereferended,
// it's semantically the same as `&'static T`;
// but it isn't allowed to make a static reference from an arbitrary integer value at the moment.
// For more information, please see the issue #5918.
pub struct StaticRef<T> {
ptr: *const T,
}

impl<T> StaticRef<T> {
/// Create a new `StaticRef` from a raw pointer
///
/// ## Safety
///
/// Callers must pass in a reference to statically allocated memory which
/// does not overlap with other values.
pub const unsafe fn new(ptr: *const T) -> StaticRef<T> {
StaticRef { ptr }
}
}

impl<T> std::ops::Deref for StaticRef<T> {
type Target = T;

fn deref(&self) -> &'static T {
unsafe { &*self.ptr }
}
}

// use a tuple to make sure referencing a field behind a pointer isn't linted.
const CELL_REF: StaticRef<(UnsafeCell<u32>,)> = unsafe { StaticRef::new(std::ptr::null()) };

fn main() {
ATOMIC.store(1, Ordering::SeqCst); //~ ERROR interior mutability
assert_eq!(ATOMIC.load(Ordering::SeqCst), 5); //~ ERROR interior mutability
Expand Down Expand Up @@ -82,4 +113,6 @@ fn main() {
assert_eq!(u64::ATOMIC.load(Ordering::SeqCst), 9); //~ ERROR interior mutability

assert_eq!(NO_ANN.to_string(), "70"); // should never lint this.

let _ = &CELL_REF.0;
}
32 changes: 16 additions & 16 deletions tests/ui/borrow_interior_mutable_const.stderr
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:34:5
--> $DIR/borrow_interior_mutable_const.rs:65:5
|
LL | ATOMIC.store(1, Ordering::SeqCst); //~ ERROR interior mutability
| ^^^^^^
Expand All @@ -8,119 +8,119 @@ LL | ATOMIC.store(1, Ordering::SeqCst); //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:35:16
--> $DIR/borrow_interior_mutable_const.rs:66:16
|
LL | assert_eq!(ATOMIC.load(Ordering::SeqCst), 5); //~ ERROR interior mutability
| ^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:38:22
--> $DIR/borrow_interior_mutable_const.rs:69:22
|
LL | let _once_ref = &ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:39:25
--> $DIR/borrow_interior_mutable_const.rs:70:25
|
LL | let _once_ref_2 = &&ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:40:27
--> $DIR/borrow_interior_mutable_const.rs:71:27
|
LL | let _once_ref_4 = &&&&ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:41:26
--> $DIR/borrow_interior_mutable_const.rs:72:26
|
LL | let _once_mut = &mut ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:52:14
--> $DIR/borrow_interior_mutable_const.rs:83:14
|
LL | let _ = &ATOMIC_TUPLE; //~ ERROR interior mutability
| ^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:53:14
--> $DIR/borrow_interior_mutable_const.rs:84:14
|
LL | let _ = &ATOMIC_TUPLE.0; //~ ERROR interior mutability
| ^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:54:19
--> $DIR/borrow_interior_mutable_const.rs:85:19
|
LL | let _ = &(&&&&ATOMIC_TUPLE).0; //~ ERROR interior mutability
| ^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:55:14
--> $DIR/borrow_interior_mutable_const.rs:86:14
|
LL | let _ = &ATOMIC_TUPLE.0[0]; //~ ERROR interior mutability
| ^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:56:13
--> $DIR/borrow_interior_mutable_const.rs:87:13
|
LL | let _ = ATOMIC_TUPLE.0[0].load(Ordering::SeqCst); //~ ERROR interior mutability
| ^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:62:13
--> $DIR/borrow_interior_mutable_const.rs:93:13
|
LL | let _ = ATOMIC_TUPLE.0[0]; //~ ERROR interior mutability
| ^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:67:5
--> $DIR/borrow_interior_mutable_const.rs:98:5
|
LL | CELL.set(2); //~ ERROR interior mutability
| ^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:68:16
--> $DIR/borrow_interior_mutable_const.rs:99:16
|
LL | assert_eq!(CELL.get(), 6); //~ ERROR interior mutability
| ^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:81:5
--> $DIR/borrow_interior_mutable_const.rs:112:5
|
LL | u64::ATOMIC.store(5, Ordering::SeqCst); //~ ERROR interior mutability
| ^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here

error: a `const` item with interior mutability should not be borrowed
--> $DIR/borrow_interior_mutable_const.rs:82:16
--> $DIR/borrow_interior_mutable_const.rs:113:16
|
LL | assert_eq!(u64::ATOMIC.load(Ordering::SeqCst), 9); //~ ERROR interior mutability
| ^^^^^^^^^^^
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