Mut String += format_args!(…);

[matklad]

Previous discussion here:

Add an easier way to append `T: Display` to `String` to stdlib?

I am regularly annoyed when I need to append new formatted content to an existing buf: &mut String. I think the official way to do this is use std::fmt::Write; write!(buf, "{}", data).unwrap(); The problem with this is: You need to import Write It's hard to remember which Write should be imported there's unwrap that can't actually fire For this reason, I often just do buf += &format!("...") or buf += &data.to_string(), which is nicer to write, but is horrible semantics-wise. Do other fo…

Since then, I became even more convinced that this is a trivial papercut which is important to fix in stdlib.

I like += format_args!() solution because its a clear improvement with basically no downsides. We should go and do it.

I wouldn't want for us to stick with buf += format_args!() as a long-term (10 years from now) solution --- its a clever use of plumbing and a happy coincidence in library design, but it doesn't seem like a sufficiently good first class solution.

Potential long-term alternative is for rust to gain first-class string interpolation syntax, such that we could write

buf += f"Hello, {name}!"

where f"" desugars into something like format_args!.