Swap Subtree::token_trees from Vec to boxed slice
Performs one of the optimizations suggested in #16325, but a little bit more. Boxed slices guarantee `shrink_to_fit` aswell as saving a pointer width as no capacity has to be stored.
Most of the diff is:
- Changing `vec![]` to `Box::new([])`
- Changing initialize -> fill into fill -> into_boxed_slice
- Working around the lack of an owned iterator or automatic iteration over a `Box<[T]>`
I would like to use my own crate, [small-fixed-array](https://lib.rs/small-fixed-array), although I understand if it isn't mature enough for this. If I'm given the go ahead, I can rework this PR to use it instead.
Don't provide `add_missing_match_arms` assist when upmapping match arm list failed
Fixes#15310
We shouldn't provide the assist when we fail to find the original match arm list.
Note that this PR will temporarily make the assist not applicable when attribute macro operates on the match expression in question, just like the case in #15310, for most of the current stable toolchain users. This is because the sysroot-abi proc-macro-srv on the current stable [discards] spans for `Group` delimiters in some code paths, which the popular `proc-macro2` crate almost always calls, and it makes the identity of match arm list's brackets lost, leading to the upmapping failure. This has been fixed by #14960, which will land in the next stable, 1.71.
[discards]: 8ede3aae28/src/tools/rust-analyzer/crates/proc-macro-srv/src/abis/abi_sysroot/ra_server.rs (L231)
This makes code more readale and concise,
moving all format arguments like `format!("{}", foo)`
into the more compact `format!("{foo}")` form.
The change was automatically created with, so there are far less change
of an accidental typo.
```
cargo clippy --fix -- -A clippy::all -W clippy::uninlined_format_args
```
