Show bounds on variable with generic type

When I place the cursor over a variable defined with a generic type, I only get the name of the generic type, not its trait bounds (which is what I'm interested in, especially for types bounded by closure traits). For example, in a function defined like this:

pub fn run<F>(make_sessionizer: F)
where
    F: FnOnce(&Arc<Database>),
{
    // imagine many lines here...
    let sessionizer = make_sessionizer(Arc::new(Database));
    // ...
}

I would expect hovering above make_sessionizer to tell me how I can call the function, e.g. something like F: FnOnce(&Arc<Database>). What I actually get is make_sessionizer: F, which is technically correct, but not very useful on its own:

I use Emacs with Rustic, but I believe the contents of the popup entirely comes from rust-analyzer. For example (taken on slightly different code, but showing the same thing):

[Trace - 03:44:39 PM] Received response 'textDocument/hover - (6979)' in 887ms.
Result: {
  "range": {
    "end": {
      "character": 34,
      "line": 227
    },
    "start": {
      "character": 17,
      "line": 227
    }
  },
  "contents": {
    "value": "\n```rust\nmake_event_loader: F\n```",
    "kind": "markdown"
  }
}

Originally reported as brotzeit/rustic#311.

Start by tracing rust-analyzer's textDocument/hover handling for the reported variable type, using the captured response as the expected current behavior. Determine how generic type bounds are represented for hover content, then verify that hovering make_sessionizer presents its FnOnce(&Arc) bound rather than only F.