src/doc/edition-guide/src/rust-2018/trait-fn-parameters.md


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# Anonymous trait function parameters deprecated

![Minimum Rust version: 1.31](https://img.shields.io/badge/Minimum%20Rust%20Version-1.31-brightgreen.svg)

## Summary

- [Trait function parameters] may use any irrefutable pattern when the function has a body.

[Trait function parameters]: https://doc.rust-lang.org/stable/reference/items/traits.html#parameter-patterns


## Details

In accordance with RFC [#1685](https://github.com/rust-lang/rfcs/pull/1685),
parameters in trait method declarations are no longer allowed to be anonymous.

For example, in the 2015 edition, this was allowed:

```rust
trait Foo {
    fn foo(&self, u8);
}
```

In the 2018 edition, all parameters must be given an argument name  (even if it's just
`_`):

```rust
trait Foo {
    fn foo(&self, baz: u8);
}
```