Generic types are not handled properly in the `Type` proc-macro

[ivan770]

I have found these related issues/pull requests

#3195 seems to mention this issue, but in a different context.

Description

This codegen snippet omits generic types when generating the sqlx::Type impl: https://github.com/launchbadge/sqlx/blob/90797200eef8d7aa41ce0cd582fdd8560bfc0f24/sqlx-macros-core/src/derives/type.rs#L244-L263

The same file contains a valid codegen logic just above the previously mentioned code fragment: https://github.com/launchbadge/sqlx/blob/90797200eef8d7aa41ce0cd582fdd8560bfc0f24/sqlx-macros-core/src/derives/type.rs#L87-L110

Reproduction steps

1. Create a struct with a generic type
2. Derive sqlx::Type for it
3. Enable postgres-related features in sqlx

This should result in an error similar to this one:

error[E0107]: missing generics for struct `Test`
   --> [snip]
    |
118 | pub struct Test<OC: Serialize + DeserializeOwned + 'static> {
    |            ^^^^ expected 1 generic argument
    |
note: struct defined here, with 1 generic parameter: `OC`
   --> [snip]
    |
118 | pub struct Test<OC: Serialize + DeserializeOwned + 'static> {
    |            ^^^^ --
help: add missing generic argument
    |
118 | pub struct Test<OC><OC: Serialize + DeserializeOwned + 'static> {
    |                ++++

SQLx version

0.8.6

Enabled SQLx features

runtime-tokio-native-tls,postgres,chrono,json,macros,migrate,uuid

Database server and version

Postgres 16.9

Operating system

NixOS 25.05

Rust version

rustc 1.87.0 (17067e9ac 2025-05-09)