add lint on File::read_to_string and File::read_to_end

[jmeyers35]

Adds lint verbose_file_reads which checks for use of File::read_to_end and File::read_to_string.

Closes #4916

changelog: add lint on File::{read_to_end, read_to_string}

[bors]

☔ The latest upstream changes (presumably #5230) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #5276) made this pull request unmergeable. Please resolve the merge conflicts.

[flip1995]

LGTM overall

[jmeyers35]

I'm guessing something like

    /// # use std::io::Read;
    /// # use std::fs::File;
    /// # fn main() -> std::io::Result<()> { 
    /// let mut f = File::open("foo.txt")?;
    /// let mut bytes = Vec::new();
    /// f.read_to_end(&mut bytes)?;
    /// # Ok(())
    /// # }

would make the doctest happy? (though wouldn't it then fail on /// let mut f = File::open("foo.txt")?; )?

[flip1995]

Just use .unwrap() here, instead of ?.

[flip1995]

@bors r+

[bors]

📌 Commit a4ba102 has been approved by flip1995

[bors]

⌛ Testing commit a4ba102 with merge fdce47b...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing fdce47b to master...