Docs: update query!() documentation WRT casting parameters using _

[AleVul]

I have trouble using (or understanding how to use) sqlx::Type. I have derived it for a wrapper around a String.
As far as I understand, this should implement Encode and Decode traits for the wrapper type and as a consequence I should be able to pass an instance of the wrapper type to query! macro, but I get an error stating that the drivers expects an &str instead of the wrapper type.
The description on the Encode trait made me think that this is how it should work. If it is not please help me understand.

See this repo for a minimal example that leads to error.

[jplatte]

I had a look at the linked repo. You have this:

sqlx::query!("INSERT INTO foo (email) VALUES ($1)", email)

since your email variable has a type of Email which is not a type SQLx knows about, it will complain that it's not the right type for the email column. You need to use a type override to disable this check:

sqlx::query!("INSERT INTO foo (email) VALUES ($1)", email as _)

[AleVul]

@jplatte Thank you, that did the trick!
Though the description you linked to is somewhat misleading, I'm referring to this part

Casts to _ are forbidden for now as they produce rather nasty type errors.

Is it forbidden or not? Because I can definitely use it. Maybe an update to the docs is in order?

[jplatte]

Yeah, seems like it. I think first sentence after the codeblock applies (i.e. as _ is available since Rust 1.45).

[abonander]

Yeah, now we just treat as _ as a blanket override and remove it. That paragraph needs to be rewritten.

[abonander]

closed by #1619