lint against shadowing prelude types in the signature of public functions

What it does

warn if any item that shares a name with an item in the prelude is used without qualification in the signature of a public function.

Advantage

people might see the auto-generated documentation and think it is referring to the prelude type instead of another type.

Drawbacks

this pattern is extremely common in the rust ecosystem, especially with Result types.

Example

use std::io::Result;

fn unclear() -> Result<()> {
    Ok(())
}

Could be written as:

use std::io;

fn unclear() -> io::Result<()> {
    Ok(())
}

No implementation files or tests are named. Start by locating existing Clippy lints that inspect public function signatures and their UI tests, then trace how prelude names and qualified paths are represented. Done means the lint diagnoses unqualified shadowing in public signatures, handles the documented example, and has coverage for the intended behavior.