performance: Speed up Method Completions By Taking Advantage of Orphan Rules
(Continues https://github.com/rust-lang/rust-analyzer/pull/16498)
This PR speeds up method completions by doing two things without regressing `analysis-stats`[^1]:
- Filter candidate traits prior to calling `iterate_path_candidates` by relying on orphan rules (see below for a slightly more in-depth explanation). When generating completions [on `slog::Logger`](5e9e59c312/common/src/ledger.rs (L78)) in `oxidecomputer/omicron` as a test, this PR halved my completion times—it's now 454ms cold and 281ms warm. Before this PR, it was 808ms cold and 579ms warm.
- Inline some of the method candidate checks into `is_valid_method_candidate` and remove some unnecessary visibility checks. This was suggested by `@Veykril` in [this comment](https://github.com/rust-lang/rust-analyzer/pull/16498#issuecomment-1929864427).
We filter candidate traits by taking advantage of orphan rules. For additional details, I'll rely on `@WaffleLapkin's` explanation [from Zulip](https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/Trait.20Checking/near/420942417):
> A type `A` can only implements traits which
> 1. Have a blanket implementation (`impl<T> Trait for T {}`)
> 2. Have implementation for `A` (`impl Trait for A {}`)
>
> Blanket implementation can only exist in `Trait`'s crate. Implementation for `A` can only exist in `A`'s or `Trait`'s crate.
Big thanks to Waffle for its keen observation!
---
I think some additional improvements are possible:
- `for_trait_and_self_ty` seemingly does not distinguish between `&T`, `&mut T`, or `T`, resulting in seemingly irrelevant traits like `tokio::io::AsyncWrite` being being included for, e.g., `&slog::Logger`. I don't know they're being considered due to the [autoref/autoderef behavior](a02a219773/crates/hir-ty/src/method_resolution.rs (L945-L962)), but I wonder if it'd make sense to filter by mutability earlier and not consider trait implementations that require `&mut T` when we only have a `&T`.
- The method completions [spend a _lot_ of time in unification](https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/Trait.20Checking/near/421072356), and while there might be low-hanging fruit there, it might make more sense to wait for the new trait solver in `rustc`. I dunno.
[^1]: The filtering occurs outside of typechecking, after all.
fix: Don't panic on synthetic syntax in inference diagnostics
Temporary fix for https://github.com/rust-lang/rust-analyzer/issues/16682
We ought to rethink how we attach diagnostics to things, as IDs don't work for `format_args` like that!
fix: panic when inlining callsites inside macros' parameters
Close#16660, #12429, #10695.
When `inline_into_callers` encounters callsites in macros parameters, it can lead to panics. Since there is no perfect way to handle macros, this PR directly filters out these cases.
Prioritise rustup sysroots over system ones
`get_path_for_executable` will now first check `$CARGO_HOME` before falling back to searching `$PATH`.
`rustup` is the recommended way to manage rust toolchains, therefore should be picked before the system toolchain.
Closes#16661
Document nvim 0.10 `inlay_hint`
It took me a few hours to figure out how to enable inlay type hints on Nvim 0.10 with `lspconfig`. `rustaceanvim` has already dropped support for them (https://github.com/mrcjkb/rustaceanvim/discussions/46#discussioncomment-7518669) and most other plugins, like `rust-tools`, are depreciated in favor of `rustaceanvim`.
This PR documents how to enable the inlay hints on Neovim 0.10 and later. I've tested this and changing the `on_attach` function is the only step that is required.
`get_path_for_executable` will now first check `$CARGO_HOME` before falling back to searching `$PATH`.
rustup is the recommended way to manage rust toolchains, therefore should be picked before the
system toolchain.
Add short flag -V for consistency with other rust tooling
Minor change to add the `-V` short flag to `rust-analyzer` to bring it in-line with other rust tooling such as:
> rustc -V
```bash
rustc 1.76.0 (07dca489a 2024-02-04)
```
> rustup -V
```bash
rustup 1.26.0 (5af9b9484 2023-04-05)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.76.0 (07dca489a 2024-02-04)`
```
> cargo -V
```bash
cargo 1.76.0 (c84b36747 2024-01-18)
```
