facet-kdl Compile Error Showcase

Using an unknown attribute like kdl::nonexistent produces a clear error
that points directly to the attribute and suggests valid options.

use facet::Facet;
use facet_kdl as kdl;

#[derive(Facet)]
struct Config {
    #[facet(kdl::nonexistent)]
    field: String,
}

fn main() {}

error: unknown extension attribute `nonexistent`
 --> src/main.rs:6:18
  |
6 |     #[facet(kdl::nonexistent)]
  |                  ^^^^^^^^^^^
error: could not compile test (bin "test") due to 1 previous error

Common typos like chld instead of child or proprty instead of property
are caught at compile time with helpful suggestions.

use facet::Facet;
use facet_kdl as kdl;

#[derive(Facet)]
struct Config {
    #[facet(kdl::chld)]
    nested: Inner,
}

#[derive(Facet)]
struct Inner {
    #[facet(kdl::proprty)]
    value: String,
}

fn main() {}

error: unknown extension attribute `chld`
 --> src/main.rs:6:18
  |
6 |     #[facet(kdl::chld)]
  |                  ^^^^
error: unknown extension attribute proprty
  --> src/main.rs:12:18
   |
12 |     #[facet(kdl::proprty)]
   |                  ^^^^^^^
error: could not compile test (bin "test") due to 2 previous errors

Passing arguments to attributes that don't accept them produces a clear error.

use facet::Facet;
use facet_kdl as kdl;

#[derive(Facet)]
struct Config {
    #[facet(kdl::child = "unexpected")]
    nested: Inner,
}

#[derive(Facet)]
struct Inner {
    value: String,
}

fn main() {}

error: kdl::child does not accept arguments
 --> src/main.rs:6:26
  |
6 |     #[facet(kdl::child = "unexpected")]
  |                          ^^^^^^^^^^^^
error: could not compile test (bin "test") due to 1 previous error

When extension attributes are used correctly, everything compiles smoothly.
This shows the intended usage pattern for KDL attributes.

use facet::Facet;
use facet_kdl as kdl;

#[derive(Facet)]
struct Config {
    #[facet(kdl::child)]
    server: Server,

    #[facet(kdl::property)]
    name: String,

    #[facet(kdl::argument)]
    version: u32,
}

#[derive(Facet)]
struct Server {
    #[facet(kdl::property)]
    host: String,

    #[facet(kdl::property)]
    port: u16,
}

fn main() {
    println!("Compiles successfully!");
}

Compilation successful! No errors.