feature request: passing File::open value to where Write is expected

What it does

detects passing File::open value to place where Write is expected

Lint Name

file_is_not_writable

Category

suspicious

Advantage

• Remove "bad file descriptor" errors at runtime.

Drawbacks

none

Example

let file = File::open("config.txt"); // this handle is read-only
let buf_write = BufWriter::new(file);

Could be written as below when above 1.58.0:

let file = File::options().write(true).open("config.txt");
let buf_write = BufWriter::new(file);

when below 1.58.0:

let file = OpenOptions::new().write(true).open("config.txt");
let buf_write = BufWriter::new(file);

Start by locating the existing Clippy lint entry point for file_is_not_writable and review how suspicious lints inspect Rust expressions and types. Use the File::open and BufWriter examples as the behavior to cover, and consider the shown File::options and OpenOptions forms acceptable alternatives. Done means the lint detects the read-only handle passed where Write is expected without flagging writable opens.