Field macro #[sqlx(flatten)] doesn't seem to work in this case

[UMR1352]

Bug Description

I have a struct defined as

#[derive(Debug, FromRow, Serialize)]
pub struct Building {
    pub name: String,
    pub key: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub description: Option<String>,
}

and I want to make another where some other field is included (in this case conf):

#[derive(Debug, FromRow, Serialize)]
pub struct BuildingWithConfig {
    #[sqlx(flatten)]
    pub building: Building,
    pub conf: JsonValue,
}

In my mind this would work, but it doesn't:

error[E0560]: struct `structure::BuildingWithConfig` has no field named `key`
   --> src/routes/map.rs:96:5
    |
96  | /     sqlx::query_as!(
97  | |         BuildingWithConfig,
98  | |         r#"
99  | | SELECT
...   |
110 | |         is_preview
111 | |     )
    | |_____^ `structure::BuildingWithConfig` does not have this field
    |
    = note: available fields are: `conf`, `building`

Using this query:

SELECT
    b.name,
    b.description,
    b.key,
    c.configuration AS conf
FROM buildings b
    JOIN component_configurations c ON 
        c.id = 'page-building-' || b.key

Info

• SQLx version: 0.6.3
• SQLx features enabled: [
  "runtime-tokio-rustls",
  "macros",
  "postgres",
  "migrate",
  "offline",
  "time",
  "chrono",
  "json",
  ]
• Database server and version: Postgres 14.6
• Operating system: 6.4.1-arch1-1
• rustc --version: 1.70

[saiintbrisson]

Hi! This is a duplicate of #2188.
TL;DR: The query_as! macro does not use the FromRow implementation, though it might change in the future (#514).