restriction lint: implicit drop

What it does

detect all locations where drop is called implicitly and suggest turning it into an explicit drop.

possibly has a setting to only warn about locations where a needs_drop value is dropped.

Advantage

would be handy as a learning and debugging tool, allowing you to essentially desugar your code.

Drawbacks

non-trivial implementation for a lint that will never be used in production code.

Example

fn main() {
  let s = "Hello, World".to_string();
  println!("{s}");
}

Could be written as:

fn main() {
  let s = "Hello, World".to_string();
  println!("{s}");
  drop(s);
}

The issue does not name files, tests, or an entry point. Start by locating Clippy's lint registration and existing lints related to ownership or drops, then compare their handling with the example. Done means implicit drops are detected and an explicit drop suggestion is produced, with an optional needs_drop restriction if that scope is accepted.