Remove client side proc-macro version check
The server already verifies versions due to ABI picking now so there shouldn't be a need for the client side check anymore
fix: Do not retry inlay hint requests
Should close https://github.com/rust-lang/rust-analyzer/issues/13372, retrying the way its currently implemented is not ideal as we do not adjust offsets in the requests, but doing that is a major PITA, so this should at least work around one of the more annoying issues stemming from it.
Add Cargo-style project discovery for Buck and Bazel Users
This feature requires the user to add a command that generates a `rust-project.json` from a set of files. Project discovery can be invoked in two ways:
1. At extension activation time, which includes the generated `rust-project.json` as part of the linkedProjects argument in `InitializeParams`.
2. Through a new command titled "rust-analyzer: Add current file to workspace", which makes use of a new, rust-analyzer-specific LSP request that adds the workspace without erasing any existing workspaces. Note that there is no mechanism to _remove_ workspaces other than "quit the rust-analyzer server".
Few notes:
- I think that the command-running functionality _could_ merit being placed into its own extension (and expose it via extension contribution points) to provide build-system idiomatic progress reporting and status handling, but I haven't (yet) made an extension that does this nor does Buck expose this sort of functionality.
- This approach would _just work_ for Bazel. I'll try and get the tool that's responsible for Buck integration open-sourced soon.
- On the testing side of things, I've used this in around my employer's Buck-powered monorepo and it's a nice experience. That being said, I can't think of an open-source repository where this can be tested in public, so you might need to trust me on this one.
I'd love to get feedback on:
- Naming of LSP extensions/new commands. I'm not too pleased with how "rust-analyzer: Add current file to workspace" is named, in that it's creating a _new_ workspace. I think that this command being added should be gated on `rust-analyzer.discoverProjectCommand` on being set, so I can add this in sequent commits.
- My Typescript. It's not particularly good.
- Suggestions on handling folders with _both_ Cargo and non-Cargo build systems and if I make activation a bit better.
(I previously tried to add this functionality entirely within rust-analyzer-the-LSP server itself, but matklad was right—an extension side approach is much, much easier.)
This feature requires the user to add a command that generates a
`rust-project.json` from a set of files. Project discovery can be invoked
in two ways:
1. At extension activation time, which includes the generated
`rust-project.json` as part of the linkedProjects argument in
InitializeParams
2. Through a new command titled "Add current file to workspace", which
makes use of a new, rust-analyzer specific LSP request that adds
the workspace without erasing any existing workspaces.
I think that the command-running functionality _could_ merit being
placed into its own extension (and expose it via extension contribution
points), if only provide build-system idiomatic progress reporting and
status handling, but I haven't (yet) made an extension that does this.
Handle trait alias definitions
Part of #2773
This PR adds a bunch of structs and enum variants for trait aliases. Trait aliases should be handled as an independent item because they are semantically distinct from traits.
I basically started by adding `TraitAlias{Id, Loc}` to `hir_def::item_tree` and iterated adding necessary stuffs until compiler stopped complaining what's missing. Let me know if there's still anything I need to add.
I'm opening up this PR for early review and stuff. I'm planning to add tests for IDE functionalities in this PR, but not type-related support, for which I put FIXME notes.
Beginning of MIR
This pull request introduces the initial implementation of MIR lowering and interpreting in Rust Analyzer.
The implementation of MIR has potential to bring several benefits:
- Executing a unit test without compiling it: This is my main goal. It can be useful for quickly testing code changes and print-debugging unit tests without the need for a full compilation (ideally in almost zero time, similar to languages like python and js). There is a probability that it goes nowhere, it might become slower than rustc, or it might need some unreasonable amount of memory, or we may fail to support a common pattern/function that make it unusable for most of the codes.
- Constant evaluation: MIR allows for easier and more correct constant evaluation, on par with rustc. If r-a wants to fully support the type system, it needs full const eval, which means arbitrary code execution, which needs MIR or something similar.
- Supporting more diagnostics: MIR can be used to detect errors, most famously borrow checker and lifetime errors, but also mutability errors and uninitialized variables, which can be difficult/impossible to detect in HIR.
- Lowering closures: With MIR we can find out closure capture modes, which is useful in detecting if a closure implements the `FnMut` or `Fn` traits, and calculating its size and data layout.
But the current PR implements no diagnostics and doesn't support closures. About const eval, I removed the old const eval code and it now uses the mir interpreter. Everything that is supported in stable rustc is either implemented or is super easy to implement. About interpreting unit tests, I added an experimental config, disabled by default, that shows a `pass` or `fail` on hover of unit tests (ideally it should be a button similar to `Run test` button, but I didn't figured out how to add them). Currently, no real world test works, due to missing features including closures, heap allocation, `dyn Trait` and ... so at this point it is only useful for me selecting what to implement next.
The implementation of MIR is based on the design of rustc, the data structures are almost copy paste (so it should be easy to migrate it to a possible future stable-mir), but the lowering and interpreting code is from me.
Rename `checkOnSave` settings to `check`
Now that flychecks can be triggered without saving the setting name doesn't make that much sense anymore. This PR renames it to just `check`, but keeps `checkOnSave` as the enabling setting.
feat: add the ability to limit the number of threads launched by `main_loop`
## Motivation
`main_loop` defaults to launch as many threads as cpus in one machine. When developing on multi-core remote servers on multiple projects, this will lead to thousands of idle threads being created. This is very annoying when one wants check whether his program under developing is running correctly via `htop`.
<img width="756" alt="image" src="https://user-images.githubusercontent.com/41831480/206656419-fa3f0dd2-e554-4f36-be1b-29d54739930c.png">
## Contribution
This patch introduce the configuration option `rust-analyzer.numThreads` to set the desired thread number used by the main thread pool.
This should have no effects on the performance as not all threads are actually used.
<img width="1325" alt="image" src="https://user-images.githubusercontent.com/41831480/206656834-fe625c4c-b993-4771-8a82-7427c297fd41.png">
## Demonstration
The following is a snippet of `lunarvim` configuration using my own build.
```lua
vim.list_extend(lvim.lsp.automatic_configuration.skipped_servers, { "rust_analyzer" })
require("lvim.lsp.manager").setup("rust_analyzer", {
cmd = { "env", "RA_LOG=debug", "RA_LOG_FILE=/tmp/ra-test.log",
"/home/jlhu/Projects/rust-analyzer/target/debug/rust-analyzer",
},
init_options = {
numThreads = 4,
},
settings = {
cachePriming = {
numThreads = 8,
},
},
})
```
## Limitations
The `numThreads` can only be modified via `initializationOptions` in early initialisation because everything has to wait until the thread pool starts including the dynamic settings modification support.
The `numThreads` also does not reflect the end results of how many threads is actually created, because I have not yet tracked down everything that spawns threads.
fix a bunch of clippy lints
fixes a bunch of clippy lints for fun and profit
i'm aware of this repo's position on clippy. The changes are split into separate commits so they can be reviewed separately
feat: Package Windows release artifacts as ZIP and add symbols file
Closes#13872Closes#7747
CC #10371
This allows us to ship a format that's easier to handle on Windows. As a bonus, we can also include the PDB, to get useful stack traces. Unfortunately, it adds a couple of dependencies to `xtask`, increasing the debug build times from 1.28 to 1.58 s (release from 1.60s to 2.20s) on my system.
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
```
Seems like these can be safely fixed. With one, I was particularly
surprised -- `Some(pats) => &**pats,` in body.rs?
```
cargo clippy --fix -- -A clippy::all -D clippy::explicit_auto_deref
```
I am not certain if this will improve performance,
but it seems having a .clone() without any need should be removed.
This was done with clippy, and manually reviewed:
```
cargo clippy --fix -- -A clippy::all -D clippy::redundant_clone
```
feat: Add an option to hide adjustment hints outside of `unsafe` blocks and functions
As the title suggests: this PR adds an option (namely `rust-analyzer.inlayHints.expressionAdjustmentHints.hideOutsideUnsafe`) that allows to hide adjustment hints outside of `unsafe` blocks and functions:
![2022-12-21_23-11](https://user-images.githubusercontent.com/38225716/208986376-d607de62-8290-4e16-b7fe-15b762dc5f60.png)
Requested by `@BoxyUwU` <3
Don't show runnable code lenses in libraries outside of the workspace
Addresses #13664. For now I'm just disabling runnable code lenses since the ones that display the number of references and implementations do work correctly with external code.
Also made a tiny TypeScript change to use the typed `sendNotification` overload.
Mega-sync from `rust-lang/rust`
This essentially implements `@oli-obk's` suggestion here https://github.com/rust-lang/rust-analyzer/pull/13459#issuecomment-1297285607, with `@eddyb's` help.
This PR is equivalent to 14 syncs (back and forth) between `rust-lang/rust` and `rust-lang/rust-analyzer`.
Working from this list (from bottom to top):
```
(x) a2a1d9954⬆️ rust-analyzer
(x) 79923c382⬆️ rust-analyzer
(x) c60b1f641⬆️ rust-analyzer
(x) 8807fc4cc⬆️ rust-analyzer
(x) a99a48e78⬆️ rust-analyzer
(x) 4f55ebbd4⬆️ rust-analyzer
(x) f5fde4df4⬆️ rust-analyzer
(x) 459bbb422⬆️ rust-analyzer
(x) 65e1dc4d9⬆️ rust-analyzer
(x) 3e358a682⬆️ rust-analyzer
(x) 31519bb39⬆️ rust-analyzer
(x) 8231fee46⬆️ rust-analyzer
(x) 22c8c9c40⬆️ rust-analyzer
(x) 9d2cb42a4⬆️ rust-analyzer
```
(This listed was assembled by doing a `git subtree push`, which made a branch, and looking at the new commits in that branch, picking only those that were `⬆️ rust-analyzer` commits)
We used the following commands to simulate merges in both directions:
```shell
TO_MERGE=22c8c9c40 # taken from the list above, bottom to top
git merge --no-edit --no-ff $TO_MERGE
git merge --no-edit --no-ff $(git -C ../rust log --pretty=format:'%cN | %s | %ad => %P' | rg -m1 -F "$(git show --no-patch --pretty=format:%ad $TO_MERGE)" | tee /dev/stderr | rg '.* => \S+ (\S+)$' --replace '$1')
```
We encountered no merge conflicts that Git wasn't able to solve by doing it this way.
Here's what the commit graph looks like (as shown in the Git Lens VSCode extension):
<img width="1345" alt="image" src="https://user-images.githubusercontent.com/7998310/203984523-7c1a690a-8224-416c-8015-ed6e49667066.png">
This PR closes#13459
## Does this unbreak `rust->ra` syncs?
Yes, here's how we tried:
In `rust-analyzer`:
* check out `subtree-fix` (this PR's branch)
* make a new branch off of it: `git checkout -b subtree-fix-merge-test`
* simulate this PR getting merged with `git merge master`
In `rust`:
* pull latest master
* make a new branch: `git checkout -b test-change`
* mess with rust-analyzer (I added a comment to `src/tools/rust-analyzer/Cargo.toml`)
* commit
* run `git subtree push -P src/tools/rust-analyzer ra-local final-sync` (this follows the [Clippy sync guide](https://doc.rust-lang.org/nightly/clippy/development/infrastructure/sync.html))
This created a `final-sync` branch in `rust-analyzer`.
In `rust-analyzer`:
* `git merge --no-ff final-sync` (this follows the [Clippy sync guide](https://doc.rust-lang.org/nightly/clippy/development/infrastructure/sync.html))
Now `git log` in `rust-analyzer` shows this:
```
commit 460128387e46ddfc2b95921b2d7f6e913a3d2b9f (HEAD -> subtree-fix-merge-test)
Merge: 0513fc02a 9ce6a734f
Author: Amos Wenger <amoswenger@gmail.com>
Date: Fri Nov 25 13:28:24 2022 +0100
Merge branch 'final-sync' into subtree-fix-merge-test
commit 0513fc02a08ea9de952983624bd0a00e98044b36
Merge: 38c98d1ff6918009fe
Author: Amos Wenger <amoswenger@gmail.com>
Date: Fri Nov 25 13:28:02 2022 +0100
Merge branch 'master' into subtree-fix-merge-test
commit 9ce6a734f37ef8e53689f1c6f427a9efafe846bd (final-sync)
Author: Amos Wenger <amoswenger@gmail.com>
Date: Fri Nov 25 13:26:26 2022 +0100
Mess with rust-analyzer just for fun
```
And `git diff 0513fc02a08ea9de952983624bd0a00e98044b36` shows this:
```patch
diff --git a/Cargo.toml b/Cargo.toml
index 286ef1e7d..c9e24cd19 100644
--- a/Cargo.toml
+++ b/Cargo.toml
`@@` -32,3 +32,5 `@@` debug = 0
# ungrammar = { path = "../ungrammar" }
# salsa = { path = "../salsa" }
+
+# lol, hi
```
## Does this unbreak `ra->rust` syncs?
Yes, here's how we tried.
From `rust`:
* `git checkout -b sync-from-ra`
* `git subtree pull -P src/tools/rust-analyzer ra-local subtree-fix-merge-test` (this is adapted from the [Clippy sync guide](https://doc.rust-lang.org/nightly/clippy/development/infrastructure/sync.html#performing-the-sync-from-clippy-to-rust-langrust), you would normally use `ra-upstream master` but we're simulating things here)
A commit editor pops up, there was no merge conflicts.
## How do we prevent this from happening again?
Like `@bjorn3` said in https://github.com/rust-lang/rust-analyzer/pull/13459#issuecomment-1293587848
> Whenever syncing from rust-analyzer -> rust you have to immediately sync the merge commit from rust -> rust-analyzer to prevent merge conflicts in the future.
But if we get it wrong again, at least now we have a not-so-painful way to fix it.
Fix: Handle empty `checkOnSave/target` values
This fixes a regression introduced by #13290, in which failing to set `checkOnSave/target` (or `checkOnSave/targets`) would lead to an invalid config.
[Fixes#13660]
Support multiple targets for checkOnSave (in conjunction with cargo 1.64.0+)
This PR adds support for the ability to pass multiple `--target` flags when using
`cargo` 1.64.0+.
## Questions
I needed to change the type of two configurations options, but I did not plurialize the names to
avoid too much churn, should I ?
## Zulip thread
https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/Issue.2013282.20.28supporting.20multiple.20targets.20with.201.2E64.2B.29
## Example
To see it working, on a macOS machine:
```sh
$ cd /tmp
$ cargo new cargo-multiple-targets-support-ra-test
$ cd !$
$ mkdir .cargo
$ echo '
[build]
target = [
"aarch64-apple-darwin",
"x86_64-apple-darwin",
]
' > .cargo/config.toml
$ echo '
fn main() {
#[cfg(all(target_arch = "aarch64", target_os = "macos"))]
{
let a = std::fs::read_to_string("/tmp/test-read");
}
#[cfg(all(target_arch = "x86_64", target_os = "macos"))]
{
let a = std::fs::read_to_string("/tmp/test-read");
}
#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
{
let a = std::fs::read_to_string("/tmp/test-read");
}
}
' > src/main.rs
# launch your favorite editor with the version of RA from this PR
#
# You should see warnings under the first two `let a = ...` but not the third
```
## Screen
![Two panes of a terminal emulator, on the left pane is the main.rs file described above, with warnings for the first two let a = declaration, on the right pane is a display of the .cargo/config.toml, an ls of the current files in the directory and a call to cargo build to show the same warnings as in the editor on the left pane](https://user-images.githubusercontent.com/7951708/192122707-7a00606a-e581-4534-b9d5-b81c92694e8e.png)
Helps with #13282
scip: Generate symbols for local crates.
Consider something like:
```
// a.rs
pub struct Foo { .. } // Foo is "local 1"
fn something() {
crate:🅱️:Bar::new() // Bar is "local 1", but of "b.rs"
}
// b.rs
pub struct Bar { .. } // "local 1"
```
Without this there's no way to disambiguate whether "local 1" references "Bar" or "Foo".
feat: add config for inserting must_use in `generate_enum_as_method`
Should fix#13312
Didn't add a test because I was not sure on how to add test for a specific configuration option, tried to look for the usages for other `AssistConfig` variants but couldn't find any in `tests`. If there is a way to test this, do point me towards it.
I tried to extract the formatting string as a common `template_string` and only have if-else for that, but it didn't compile :(
Also it seems these tests are failing:
```
test config::tests::generate_config_documentation ... FAILED
test config::tests::generate_package_json_config ... FAILED
```
Can you also point me to how to correct these 😅 ( I guess there is some command to automatically generate these? )
Implement invocation strategy config
Fixes https://github.com/rust-lang/rust-analyzer/issues/10793
This allows to change how we run build scripts (and `checkOnSave`), exposing two configs:
- `once`: run the specified command once in the project root (the working dir of the server)
- `per_workspace`: run the specified command per workspace in the corresponding workspace
This also applies to `checkOnSave` likewise, though `once_in_root` is useless there currently, due to https://github.com/rust-lang/cargo/issues/11007
The reason for that was that we were calculating the crate defmaps
of the file we are saving by accident causing us to get stuck waiting
on their expensive computation, while we only need the relevant crate
id.
The main change here should be that flags are not inhereted, so
$ rust-analyzer analysis-stats . -v -v
would do what it should do
We also no longer Don\'t
This fixes a typo first appearing in #94624
in which test-macro diagnostic uses "a" article twice.
Since I searched sources for " a a " sequences,
I also fixed the same issue in a few source files where I found it.
Signed-off-by: Petr Portnov <gh@progrm-jarvis.ru>
Amalgamate file changes for the same file ids in process_changes
When receiving multiple change events for a single file id where the last change is a delete the server panics, as it tries to access the file contents of a deleted file. This occurs due to the VFS changes and the in memory file contents being updated immediately, while `process_changes` processes the events afterwards in sequence which no longer works as it will only observe the final file contents. By folding these events together, we will no longer try to process these intermediate changes, as they aren't relevant anyways.
Potentially fixes https://github.com/rust-lang/rust-analyzer/issues/13236
When receiving multiple change events for a single file id where the
last change is a delete the server panics, as it tries to access the
file contents of a deleted file. This occurs due to the VFS changes and
the in memory file contents being updated immediately, while
`process_changes` processes the events afterwards in sequence which no
longer works as it will only observe the final file contents. By
folding these events together, we will no longer try to process these
intermediate changes, as they aren't relevant anyways.
Potentially fixes https://github.com/rust-lang/rust-analyzer/issues/13236
proc-macro ABI breakage still affects the tests when a new stable version
releases. Ideally we'd still be able to run the tests on the rust-analyzer
repo without having to update the proc-macro ABI, but for now just to
unblock CI we will ignore them here, as they are still run in upstream.
Add a new configuration settings to set env vars when running cargo, rustc, etc. commands: cargo.extraEnv and checkOnSave.extraEnv
It can be extremely useful to be able to set environment variables when rust-analyzer is running various cargo or rustc commands (such as `cargo check`, `cargo --print cfg` or `cargo metadata`): users may want to set custom `RUSTFLAGS`, change `PATH` to use a custom toolchain or set a different `CARGO_HOME`.
There is the existing `server.extraEnv` setting that allows env vars to be set when the rust-analyzer server is launched, but using this as the recommended mechanism to also configure cargo/rust has some drawbacks:
- It convolutes configuring the rust-analyzer server with configuring cargo/rustc (one may want to change the `PATH` for cargo/rustc without affecting the rust-analyzer server).
- The name `server.extraEnv` doesn't indicate that cargo/rustc will be affected but renaming it to `cargo.extraEnv` doesn't indicate that the rust-analyzer server would be affected.
- To make the setting useful, it needs to be dynamically reloaded without requiring that the entire extension is reloaded. It might be possible to do this, but it would require the client communicating to the server what the overwritten env vars were at first launch, which isn't easy to do.
This change adds two new configuration settings: `cargo.extraEnv` and `checkOnSave.extraEnv` that can be used to change the environment for the rust-analyzer server after launch (thus affecting any process that rust-analyzer invokes) and the `cargo check` command respectively. `cargo.extraEnv` supports dynamic changes by keeping track of the pre-change values of environment variables, thus it can undo changes made previously before applying the new configuration (and then requesting a workspace reload).
Allow configuration of annotation location.
I've added the ability to configure where lens annotations render relevant to the item they describe. Previously, these would render directly above the line the item is declared on. Now, there is the ability to render these annotations above the entire item (including doc comments, and attributes).
The names of the config options are up for debate, I did what seemed best to me but if anyone has better ideas let me know.
This is my first contribution so if I've missed anything please let me know.
Here's a preview of what the new option looks like:
<img width="577" alt="Screen Shot 2022-09-11 at 10 39 51 PM" src="https://user-images.githubusercontent.com/33100798/189570298-b4fcbf9c-ee49-4b79-aae6-1037ae4f26af.png">
closes https://github.com/rust-lang/rust-analyzer/issues/13218
Restructure `find_path` into a separate functions for modules and non-module items
Follow up to https://github.com/rust-lang/rust-analyzer/pull/13212
Also renames `prefer_core` imports config to `prefer_no_std` and changes the behavior of no_std path searching by preferring `core` paths `over` alloc
This PR turned into a slight rewrite, so it unfortunately does a few more things that I initially planned to (including a bug fix for enum variant paths)
Previously, annotations would only appear above the name of an item (function signature, struct declaration, etc).
Now, rust-analyzer can be configured to show annotations either above the name or above the whole item (including doc comments and attributes).
Make use of NoHash hashing for FileId and CrateId
Both of these are mere integers so there is nothing to hash here.
Ideally we would use this for `la_arena::Idx` too, but that doesn't work due to the orphan rule, and `la_arena` is unfortunately a public library so we can't really do much here... Unless we remove the trait restriction but I'd like not to
feat: Run test mod from anywhere in parent file
The "Run" feature of rust-analyzer is super useful, especially for running
individual tests or test-modules during development.
One common pattern in rust development is to develop tests in the same file as
production code, inside a module (usually called `test` or `tests`) marked with
`#[cfg(test)]`. Unforunately, this pattern is not well supported by r-a today,
as a test module won't show up as a runnable unless the cursor is inside it.
In my experience, it is quite common to want to run the tests associated with
some production code immediately after editing it, not only after editing the
tests themselves. As such it would be better if test modules were available
from the "Run" menu even when the cursor is outside the test module.
This change updates the filtration logic for runnables in
`handlers::handle_runnables` to special case `RunnableKind::TestMod`, making
test modules available regardless of the cursor location. Other `RunnableKind`s
are unnaffected.
Fixes#9589
The "Run" feature of rust-analyzer is super useful, especially for running
individual tests or test-modules during development.
One common pattern in rust development is to develop tests in the same file as
production code, inside a module (usually called `test` or `tests`) marked with
`#[cfg(test)]`. Unforunately, this pattern is not well supported by r-a today,
as a test module won't show up as a runnable unless the cursor is inside it.
In my experience, it is quite common to want to run the tests associated with
some production code immediately after editing it, not only after editing the
tests themselves. As such it would be better if test modules were available
from the "Run" menu even when the cursor is outside the test module.
This change updates the filtration logic for runnables in
`handlers::handle_runnables` to special case `RunnableKind::TestMod`, making
test modules available regardless of the cursor location. Other `RunnableKind`s
are unnaffected.
Fixes#9589
This PR will fix some typos detected by [typos].
There are also some other typos in the function names, variable names, and file
names, which I leave as they are. I'm more certain that typos in comments
should be fixed.
[typos]: https://github.com/crate-ci/typos
rust-analyzer's RUSTC_WRAPPER unconditionally succeeds `cargo check`
invocations tripping up build scripts using `cargo check` to probe for
successful compilations. To prevent this from happening the RUSTC_WRAPPER
now checks if it's run from a build script by looking for the
`CARGO_CFG_TARGET_ARCH` env var that cargo sets only when running build
scripts.
When r-a starts up, it starts switching the workspace before all vfs
events have been processed which causes us to switch workspace multiple
times until all vfs changes have been processed. This scales with the
size of the project and its dependencies. If workspace files from
dependencies as well as the sysroot get loaded, we shouldn't switch
the workspace as those have no impact on the project workspace.
feat: Only flycheck workspace that belongs to saved file
Supercedes https://github.com/rust-lang/rust-analyzer/pull/11038
There is still the problem that all the diagnostics are cleared, only clearing diagnostics of the relevant workspace isn't easily doable though I think, will have to dig into that
feat: Spawn a proc-macro-srv instance per workspace
cc https://github.com/rust-lang/rust-analyzer/issues/12855
The idea is to have each server be spawned with the appropriate toolchain, that way workspaces with differing toolchains shouldn't suffer from proc-macro abi mismatches.
Rationale: Merge commits will probably end up in
`rust-lang/rust-analyzer` when doing "rust=>ra" syncs anyway.
It could be changed to only check for merge commits in non-sync PRs,
but it's "probably not worth the hassle"
This adds an `in-rust-tree` feature that will be enabled when
rust-analyzer is built from `rust-lang/rust`. Due to the way
"git subtree" works, that test _will_ find merge commits and
fail, so we simply skip it.