Type Alias Parameter

pub type Parameter<'a> = &'a (dyn ToSql + Sync);

A shorthand for types that can be treated as SQL parameters.

A common use case for this type alias is when using dynamic bindings and you have to please the type checker:

let mut bindings = Vec::new();

// Without the `as Parameter` the compiler assumes the type to be `&i32`.
bindings.push(("age", &32 as Parameter));

// Which would cause problems when adding something that is not an integer.
bindings.push(("name", &"John" as Parameter));

let query = query_dyn!(
    "SELECT * FROM people WHERE age > $age AND name = $name",
    ..bindings
)?;

Alternatively we could just set the type on the container explicitly:

let mut bindings: Vec<(&str, Parameter)> = Vec::new();