`dyn` Trait (RFC 2113)

[matthewjasper]

Looking to stabilise in 1.27.

• Add as (contextual) keyword
• Add to trait object documentation
• Use in examples

[Havvy]

We should keep this issue open for when dyn becomes mandatory in the Rust 2018 edition.

[ehuss]

We should keep this issue open for when dyn becomes mandatory in the Rust 2018 edition.

If this is referring to the keyword becoming strict, that should be done now. If this is something else, I'm curious what it means.