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+#### 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);
+```