Macro assert_not_impl_any

macro_rules! assert_not_impl_any {
    ($x:ty: $($t:path),+ $(,)?) => { ... };
}

Asserts that the type does not implement any of the given traits.

This can be used to ensure types do not implement auto traits such as Send and Sync, as well as traits with blanket impls.

This macro causes a compilation failure if any of the provided individual traits are implemented for the type. If you want to check that a combination of traits is not implemented you should invoke assert_not_impl_all! instead. For single traits both macros behave the same.

Examples

If u32 were to implement Into conversions for usize and for u8, the following would fail to compile:

assert_not_impl_any!(u32: Into<usize>, Into<u8>);

This is also good for simple one-off cases:

assert_not_impl_any!(&'static mut u8: Copy);

The following example fails to compile since u32 can be converted into u64 even though it can not be converted into a u16:

assert_not_impl_any!(u32: Into<u64>, Into<u16>);