allow BufReader::peek to be called on unsized types

[lolbinarycat]

#128405

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[compiler-errors]

Suggested change

	where
	R: ?Sized,

[workingjubilee]

R is already ?Sized. What does this change?

[lolbinarycat]

@workingjubilee previously peek was in an impl block that was not ?Sized (the same one as new and with_capacity). it should be in a block with the same bounds as BufRead.

namely, this code should run now:

#![feature(bufreader_peek)]

use std::io::{Read, BufReader, stdin};

fn main() {
    let r1 = BufReader::new(stdin());
    let r2: Box<BufReader<dyn Read>> = Box::new(r1);
    println!("{:?}", r2.peek());
}

[workingjubilee]

OH, I see the block change now.

[workingjubilee]

@bors r+ rollup

[bors]

📌 Commit ae6f8a7 has been approved by workingjubilee

It is now in the queue for this repository.