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Comment by gamegoblin | Hacker News Reader

The methods on `String` should be a strict superset of the methods on `str` because `String` dereferences to `str`, thus `String` gets all of the `str` methods for free.

If you're familiar with say, `Vec<u8>` and `[u8]`, `String` and `str` are basically the same except they are contractually valid UTF bytes. So just like you can `push` and `extend` to a `Vec`, you can do the same to a `String`.

With regard to generic type parameters, if you want to code in Java or Go style, you can use dynamic dispatch trait objects to remove type parameters.

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> The methods on `String` should be a strict superset of the methods on `str` because `String` dereferences to `str`

I've found that sometimes this doesn't happen automatically (at least when passing as an argument; maybe not when calling methods). i.e., you have to explicitly call .as_str() in some situations. Even as someone who's comfortable with the String/&str distinction and moderately familiar with Rust, it's not clear to me where this is and isn't necessary. The compiler just tells me when I make the wrong guess.

Maybe read a bit on Deref: https://doc.rust-lang.org/std/ops/trait.Deref.html

Any time you have a &String reference, it triggers coercion to &str.

Unfortunately that is not always the case. This fails to compile, for example (and is fairly irritating):

    let my_str = "Hello".to_owned();
    match &my_str {
        "Hello" => (),
        _ => ()
    }

try &*my_str

Yes, that's the trivial "fix" to make it work, but that's not my point. In most other similar situations the compiler does that for me, but not here. It feels like something the compiler should be doing, not me.

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