You declared a pattern as an argument in a foreign function declaration.

Erroneous code example:

extern {
    fn foo((a, b): (u32, u32)); // error: patterns aren't allowed in foreign
                                //        function declarations
}

Please replace the pattern argument with a regular one. Example:

struct SomeStruct {
    a: u32,
    b: u32,
}

extern {
    fn foo(s: SomeStruct); // ok!
}

Or:

extern {
    fn foo(a: (u32, u32)); // ok!
}