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1 A non-ident or non-wildcard pattern has been used as a parameter of a function
2 pointer type.
3
4 Erroneous code example:
5
6 ```compile_fail,E0561
7 type A1 = fn(mut param: u8); // error!
8 type A2 = fn(&param: u32); // error!
9 ```
10
11 When using an alias over a function type, you cannot e.g. denote a parameter as
12 being mutable.
13
14 To fix the issue, remove patterns (`_` is allowed though). Example:
15
16 ```
17 type A1 = fn(param: u8); // ok!
18 type A2 = fn(_: u32); // ok!
19 ```
20
21 You can also omit the parameter name:
22
23 ```
24 type A3 = fn(i16); // ok!
25 ```