#[has_many(posts)] multiple applicable items in scope

[mfpiccolo]

Using #[has_many(posts)] on a User struct throws this error:

src/models/user.rs:12:19: 12:19 error: multiple applicable items in scope [E0034]
src/models/user.rs:12 #[has_many(posts)]
                                        ^
src/models/user.rs:12:1: 12:19 note: in this expansion of #[has_many] (defined in src/models/user.rs)
src/models/user.rs:12:19: 12:19 help: run `rustc --explain E0034` to see a detailed explanation
src/models/user.rs:12:19: 12:19 note: candidate #1 is defined in an impl of the trait `diesel::expression::Expression` for the type `diesel::expression::predicates::Eq<_, _>`
src/models/user.rs:12 #[has_many(posts)]
                                        ^
src/models/user.rs:12:1: 12:19 note: in this expansion of #[has_many] (defined in src/models/user.rs)
src/models/user.rs:12:19: 12:19 note: candidate #2 is defined in an impl of the trait `diesel::query_builder::update_statement::changeset::Changeset` for the type `diesel::expression::predicates::Eq<_, _>`
src/models/user.rs:12 #[has_many(posts)]
                                        ^
src/models/user.rs:12:1: 12:19 note: in this expansion of #[has_many] (defined in src/models/user.rs)
src/models/user.rs:12:19: 12:19 note: candidate #3 is defined in an impl of the trait `diesel::expression::Expression` for the type `&_`
src/models/user.rs:12 #[has_many(posts)]
                                        ^
src/models/user.rs:12:1: 12:19 note: in this expansion of #[has_many] (defined in src/models/user.rs)
src/models/user.rs:12:19: 12:19 note: candidate #4 is defined in an impl of the trait `diesel::query_builder::QueryFragment` for the type `_`
src/models/user.rs:12 #[has_many(posts)]
                                        ^
src/models/user.rs:12:1: 12:19 note: in this expansion of #[has_many] (defined in src/models/user.rs)
error: aborting due to previous error