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A value with a custom `Drop` implementation may be dropped during const-eval.
Erroneous code example:
```compile_fail,E0493
enum DropType {
A,
}
impl Drop for DropType {
fn drop(&mut self) {}
}
struct Foo {
field1: DropType,
}
static FOO: Foo = Foo { field1: (DropType::A, DropType::A).1 }; // error!
```
The problem here is that if the given type or one of its fields implements the
`Drop` trait, this `Drop` implementation cannot be called within a const
context since it may run arbitrary, non-const-checked code. To prevent this
issue, ensure all values with a custom `Drop` implementation escape the
initializer.
```
enum DropType {
A,
}
impl Drop for DropType {
fn drop(&mut self) {}
}
struct Foo {
field1: DropType,
}
static FOO: Foo = Foo { field1: DropType::A }; // We initialize all fields
// by hand.
```
|
