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consider assignments of union field of ManuallyDrop type safe

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This commit is contained in:
Ralf Jung 2020-10-18 13:53:54 +02:00
parent 3d3c8c5e0d
commit 3ac1df8b99
4 changed files with 35 additions and 56 deletions
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6
src/test/ui/union/union-unsafe.rs
View file

@ -18,7 +18,7 @@ union U4<T: Copy> {
fn generic_noncopy<T: Default>() {
let mut u3 = U3 { a: ManuallyDrop::new(T::default()) };
u3.a = ManuallyDrop::new(T::default()); //~ ERROR assignment to non-`Copy` union field is unsafe
u3.a = ManuallyDrop::new(T::default()); // OK (assignment does not drop)
*u3.a = T::default(); //~ ERROR access to union field is unsafe
}
@ -41,7 +41,7 @@ fn main() {
// let U1 { .. } = u1; // OK
let mut u2 = U2 { a: ManuallyDrop::new(String::from("old")) }; // OK
u2.a = ManuallyDrop::new(String::from("new")); //~ ERROR assignment to non-`Copy` union
u2.a = ManuallyDrop::new(String::from("new")); // OK (assignment does not drop)
*u2.a = String::from("new"); //~ ERROR access to union field is unsafe
let mut u3 = U3 { a: ManuallyDrop::new(0) }; // OK
@ -49,6 +49,6 @@ fn main() {
*u3.a = 1; //~ ERROR access to union field is unsafe
let mut u3 = U3 { a: ManuallyDrop::new(String::from("old")) }; // OK
u3.a = ManuallyDrop::new(String::from("new")); //~ ERROR assignment to non-`Copy` union
u3.a = ManuallyDrop::new(String::from("new")); // OK (assignment does not drop)
*u3.a = String::from("new"); //~ ERROR access to union field is unsafe
}

26
src/test/ui/union/union-unsafe.stderr
View file

@ -1,11 +1,3 @@
error[E0133]: assignment to non-`Copy` union field is unsafe and requires unsafe function or block
--> $DIR/union-unsafe.rs:21:5
|
LL | u3.a = ManuallyDrop::new(T::default());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to non-`Copy` union field
|
= note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
error[E0133]: access to union field is unsafe and requires unsafe function or block
--> $DIR/union-unsafe.rs:22:6
|
@ -46,14 +38,6 @@ LL | if let U1 { a: 12 } = u1 {}
|
= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
error[E0133]: assignment to non-`Copy` union field is unsafe and requires unsafe function or block
--> $DIR/union-unsafe.rs:44:5
|
LL | u2.a = ManuallyDrop::new(String::from("new"));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to non-`Copy` union field
|
= note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
error[E0133]: access to union field is unsafe and requires unsafe function or block
--> $DIR/union-unsafe.rs:45:6
|
@ -70,14 +54,6 @@ LL | *u3.a = 1;
|
= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
error[E0133]: assignment to non-`Copy` union field is unsafe and requires unsafe function or block
--> $DIR/union-unsafe.rs:52:5
|
LL | u3.a = ManuallyDrop::new(String::from("new"));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to non-`Copy` union field
|
= note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
error[E0133]: access to union field is unsafe and requires unsafe function or block
--> $DIR/union-unsafe.rs:53:6
|
@ -86,6 +62,6 @@ LL | *u3.a = String::from("new");
|
= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
error: aborting due to 11 previous errors
error: aborting due to 8 previous errors
For more information about this error, try `rustc --explain E0133`.