#### Note: this error code is no longer emitted by the compiler.

When using the `#[simd]` attribute on a tuple struct, the components of the
tuple struct must all be of a concrete, nongeneric type so the compiler can
reason about how to use SIMD with them. This error will occur if the types
are generic.

This will cause an error:

```
#![feature(repr_simd)]

#[repr(simd)]
struct Bad<T>(T, T, T, T);
```

This will not:

```
#![feature(repr_simd)]

#[repr(simd)]
struct Good(u32, u32, u32, u32);
```