Re: [PATCH v2] rust: assertions: add static_assert

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 3/20/25 12:19, Pierrick Bouvier wrote:
> On 3/20/25 04:55, Paolo Bonzini wrote:
>> Add a new assertion that is similar to "const { assert!(...) }" but can be used
>> outside functions and with older versions of Rust.  A similar macro is found in
>> Linux, whereas the "static_assertions" crate has a const_assert macro that
>> produces worse error messages.
>>
>> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
>> Supersedes: <20250320113356.799412-1-pbonzini@redhat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>>    rust/qemu-api/src/assertions.rs | 22 ++++++++++++++++++++++
>>    1 file changed, 22 insertions(+)
>>
>> diff --git a/rust/qemu-api/src/assertions.rs b/rust/qemu-api/src/assertions.rs
>> index 104dec39774..bba38cfda11 100644
>> --- a/rust/qemu-api/src/assertions.rs
>> +++ b/rust/qemu-api/src/assertions.rs
>> @@ -120,3 +120,25 @@ macro_rules! assert_match {
>>            );
>>        };
>>    }
>> +
>> +/// Assert at compile time that an expression is true.  This is similar
>> +/// to `const { assert!(...); }` but it works outside functions, as well as
>> +/// on versions of Rust before 1.79.
>> +///
>> +/// # Examples
>> +///
>> +/// ```
>> +/// # use qemu_api::static_assert;
>> +/// static_assert!("abc".len() == 3);
>> +/// ```
>> +///
>> +/// ```compile_fail
>> +/// # use qemu_api::static_assert;
>> +/// static_assert!("abc".len() == 2); // does not compile
>> +/// ```
>> +#[macro_export]
>> +macro_rules! static_assert {
>> +    ($x:expr) => {
>> +        const _: () = assert!($x);
>> +    };
>> +}
> 
> How about using something already done, and exhaustive for this?
> https://docs.rs/static_assertions/latest/static_assertions/
> 
> It provides a lot of convenient asserts related to types, traits, and
> configs, which will probably end up being introduced in QEMU Rust at
> some point.

Just saw it was mentioned "don't like this crate because of error 
messages". Well...