Problems with mutable static struct with a field of an associated type

help
1

Hello everyone,

The following code fails to compile with the message "mutable statics are not allowed to have destructors [E0397]" both on stable and nightly:

struct A;

trait Foo {
    type Associated;
}

impl Foo for A {
    type Associated = A;
}

struct Bar<T: Foo>(T::Associated);

static mut STATIC: Bar<A> = Bar(A);

Neither Bar nor the unit struct A implement Drop. When you replace the definition of Bar with struct Bar<T: Foo>(T) or struct Bar(A) everything works as expected (but of course these have a different intentions). Even if this is intended behaviour (which seems unlikely to me), the error message could definitely use some work.

2

This is a known issue: An associated type magically adds a destructor? · Issue #29821 · rust-lang/rust · GitHub

3

Thanks for the quick response!

4