Hello,
I’m being curious about why Ecto needs explicit casting when passing arguments to a query. I faced the following situation:

amount = %Amount{value: 1, type: "spa"}
Iris.Repo
|> Ecto.Adapters.SQL.query!("insert into prospect_overview(amount) values ($1)", [amount])

The Amount struct implements the behaviour Ecto.Type.
This example doesn’t work though, it require me to explicitly state the type:

amount = %Amount{value: 1, type: "spa"}
Iris.Repo
|> Ecto.Adapters.SQL.query!("insert into prospect_overview(amount) values ($1)", [type(Amount, amount)])

If amount was one of the basic types (string, integer, binaries, booleans, float and array of basic types), I don’t need to cast, however for everything else I need to.
While it totally make sense when using Ecto.Query DSL, since some things might need conversions (e.g. is_nil(something) becomes IS NULL in SQL, I can’t figure out why this is needed when passing params to a “string-based” query:

The struct can definitely implement some kind of protocol to request “auto casting” to the DB type, the basic types are detectable and covered. Shouldn’t the conversion be possible automatically?