A pattern was declared as an argument in a foreign function declaration.
Erroneous code example:
```compile_fail
extern {
fn foo((a, b): (u32, u32)); // error: patterns aren't allowed in foreign
// function declarations
}
```
To fix this error, 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!
}
```