Understanding Rust Error E0439

Introduction to Rust Error E0439

Rust Error E0439 occurs when the length of the platform-intrinsic function simd_shuffle is not specified in the function name. The simd_shuffle function requires the inclusion of a length parameter in its name.

Example of Erroneous Code


extern "platform-intrinsic" {
    fn simd_shuffle<A,B>(a: A, b: A, c: [u32; 8]) -> B;
    // error: invalid `simd_shuffle`, needs length: `simd_shuffle`

The above code is missing the length for 'simd_shuffle' in its name, which leads to the Rust Error E0439.

Correcting the Erroneous Code

To fix the error, we must add the length parameter to the function name, as shown in the corrected code example below:


fn main() {
extern "platform-intrinsic" {fn simd_shauffle8<A,B>(a: A, b: A, c: [u32; 8]) -> B;

In this revised code, we have included the length parameter in the name of the simd_shuffle function ('simd_shuffle8'), successfully resolving Rust Error E0439.

Additional Considerations

It is important to ensure that the specified length parameter in the simd_shuffle function name corresponds to the length of the array passed as the last parameter. Mismatched lengths may cause unexpected behavior or other errors.