rc-buffer doesn't recognize Rc<String> in some cases

Summary

rc-buffer doesn't recognize Rc<Buffer> when used in function body.

If a local function variable has Rc<String> type, the lint should trigger, but it does not.

Lint Name

rc-buffer

Reproducer

I tried this code:

use std::collections::BTreeMap;
use std::rc::Rc;

fn main() {
    let mut bt = BTreeMap::<Rc<String>, u64>::new();
    let key: Rc<String> = Rc::from("foo".to_string());
    bt.insert(key, 12);
    println!("{:?}", bt.get(&"foo".to_string()));
}

I expected to see this happen:
clippy displays rc-buffer lint for lines 4 and 5 and suggests to use Rc<str> instead of Rc<String>.

Instead, this happened:
clippy returns no lint messages.

Version

rustc 1.59.0-nightly (48a5999fc 2021-12-01)
binary: rustc
commit-hash: 48a5999fceeea84a8971634355287faa349909d4
commit-date: 2021-12-01
host: x86_64-pc-windows-msvc
release: 1.59.0-nightly
LLVM version: 13.0.0

Start by reproducing the provided Rust example and then locate the rc-buffer lint implementation. Confirm that Rc local variables in function bodies are diagnosed and that the lint suggests Rc; add or update coverage for this reproducer.