perf: Speed up search for short associated functions, especially very common identifiers such as `new`
`@Veykril` said in https://github.com/rust-lang/rust-analyzer/pull/17908#issuecomment-2292958068 that people complain searches for `new()` are slow (they are right), so here I am to help!
The search is used by IDE features such as rename and find all references.
The search is slow because we need to verify each candidate, and that requires analyzing it; the key to speeding it up is to avoid the analysis where possible.
I did that with a bunch of tricks that exploits knowledge about the language and its possibilities. The first key insight is that associated methods may only be referenced in the form `ContainerName::func_name` (parentheses are not necessary!) (Rust doesn't include a way to `use Container::func_name`, and even if it will in the future most usages are likely to stay in that form.
Searching for `::` will help only a bit, but searching for `Container` can help considerably, since it is very rare that there will be two identical instances of both a container and a method of it.
However, things are not as simple as they sound. In Rust a container can be aliased in multiple ways, and even aliased from different files/modules. If we will try to resolve the alias, we will lose any gain from the textual search (although very common method names such as `new` will still benefit, most will suffer because there are more instances of a container name than its associated item).
This is where the key trick enters the picture. The key insight is that there is still a textual property: a container namer cannot be aliased, unless its name is mentioned in the alias declaration, or a name of alias of it is mentioned in the alias declaration.
This becomes a fixpoint algorithm: we expand our list of aliases as we collect more and more (possible) aliases, until we eventually reach a fixpoint. A fixpoint is not guaranteed (and we do have guards for the rare cases where it does not happen), but it is almost so: most types have very few aliases, if at all.
We do use some semantic information while analyzing aliases. It's a balance: too much semantic analysis, and the search will become slow. But too few of it, and we will bring many incorrect aliases to our list, and risk it expands and expands and never reach a fixpoint. At the end, based on benchmarks, it seems worth to do a lot to avoid adding an alias (but not too much), while it is worth to do a lot to avoid the need to semantically analyze func_name matches (but again, not too much).
After we collected our list of aliases, we filter matches based on this list. Only if a match can be real, we do semantic analysis for it.
The results are promising: searching for all references on `new()` in `base-db` in the rust-analyzer repository, which previously took around 60 seconds, now takes as least as two seconds and a half (roughly), while searching for `Vec::new()`, almost an upper bound to how much a symbol can be used, that used to take 7-9 minutes(!) now completes in 100-120 seconds, and with less than half of non-verified results (aka. false positives).
This is the less strictly correct (but faster) branch of this patch; it can miss some (rare) cases (there is a test for that - `goto_ref_on_short_associated_function_complicated_type_magic_can_confuse_our_logic()`). There is another branch that have no false negatives but is slower to search (`Vec::new()` never reaches a fixpoint in aliases collection there). I believe it is possible to create a strategy that will have the best of both worlds, but it will involve significant complexity and I didn't bother, especially considering that in the vast majority of the searches the other branch will be more than enough. But all in all, I decided to bring this branch (of course if the maintainers will agree), since our search is already not 100% accurate (it misses macros), and I believe there is value in the additional perf.
You can find the strict branch at https://github.com/ChayimFriedman2/rust-analyzer/tree/speedup-new-usages-strict.
Should fix#7404, I guess (will check now).
fix: run flycheck without rev_deps when target is specified
Since querying for a crate's target is a call to salsa and therefore blocking, flycheck task is now deferred out of main thread by using `GlobalState`s `deferred_task_queue`. Fixes#17829 and https://github.com/rust-lang/rustlings/issues/2071
The search is used by IDE features such as rename and find all references.
The search is slow because we need to verify each candidate, and that requires analyzing it; the key to speeding it up is to avoid the analysis where possible.
I did that with a bunch of tricks that exploits knowledge about the language and its possibilities. The first key insight is that associated methods may only be referenced in the form `ContainerName::func_name` (parentheses are not necessary!) (Rust doesn't include a way to `use Container::func_name`, and even if it will in the future most usages are likely to stay in that form.
Searching for `::` will help only a bit, but searching for `Container` can help considerably, since it is very rare that there will be two identical instances of both a container and a method of it.
However, things are not as simple as they sound. In Rust a container can be aliased in multiple ways, and even aliased from different files/modules. If we will try to resolve the alias, we will lose any gain from the textual search (although very common method names such as `new` will still benefit, most will suffer because there are more instances of a container name than its associated item).
This is where the key trick enters the picture. The key insight is that there is still a textual property: a container namer cannot be aliased, unless its name is mentioned in the alias declaration, or a name of alias of it is mentioned in the alias declaration.
This becomes a fixpoint algorithm: we expand our list of aliases as we collect more and more (possible) aliases, until we eventually reach a fixpoint. A fixpoint is not guaranteed (and we do have guards for the rare cases where it does not happen), but it is almost so: most types have very few aliases, if at all.
We do use some semantic information while analyzing aliases. It's a balance: too much semantic analysis, and the search will become slow. But too few of it, and we will bring many incorrect aliases to our list, and risk it expands and expands and never reach a fixpoint. At the end, based on benchmarks, it seems worth to do a lot to avoid adding an alias (but not too much), while it is worth to do a lot to avoid the need to semantically analyze func_name matches (but again, not too much).
After we collected our list of aliases, we filter matches based on this list. Only if a match can be real, we do semantic analysis for it.
The results are promising: searching for all references on `new()` in `base-db` in the rust-analyzer repository, which previously took around 60 seconds, now takes as least as two seconds and a half (roughly), while searching for `Vec::new()`, almost an upper bound to how much a symbol can be used, that used to take 7-9 minutes(!) now completes in 100-120 seconds, and with less than half of non-verified results (aka. false positives).
This is the less strictly correct (but faster) of this patch; it can miss some (rare) cases (there is a test for that - `goto_ref_on_short_associated_function_complicated_type_magic_can_confuse_our_logic()`). There is another branch that have no false negatives but is slower to search (`Vec::new()` never reaches a fixpoint in aliases collection there). I believe it is possible to create a strategy that will have the best of both worlds, but it will involve significant complexity and I didn't bother, especially considering that in the vast majority of the searches the other branch will be more than enough. But all in all, I decided to bring this branch (of course if the maintainers will agree), since our search is already not 100% accurate (it misses macros), and I believe there is value in the additional perf.
This avoids the need to analyze the file when we are not inside a macro call.
This is especially important for the optimization in the next commit(s), as there the common case will be to descent into macros but then not analyze.
fix: Wrong `Sized` predicate for `generic_predicates_for_param`
I found this gathers wrong `Self: Sized` bound while implementing object safety, though I couldn't find proper test for this.
If we call `generic_predicates_for_param` to `Bar` in the following code;
```rust
trait Foo<T: ?Sized> {}
trait Bar<T: Foo<Self> + ?Sized> {}
```
it returns `T: Sized` and `Self: Sized` bound, because normaly, the `?Sized` bound applied properly in L1059 with;
3723e5910c/crates/hir-ty/src/lower.rs (L1035-L1061)
But we filter them before it is lowered with that function here;
3723e5910c/crates/hir-ty/src/lower.rs (L1540-L1586)
So, the `?Sized` bounded params are not gathered into `ctx.unsized_types` and thus we are applying them implicit `Sized` bound here;
3723e5910c/crates/hir-ty/src/lower.rs (L1591-L1602)
Remove the ability to configure the user config path
Being able to do this makes little sense as this is effectively a cyclic dependency (and we do not want to fixpoint this really).
fix: Fix panics for semantic highlighting at startup
Without this we might try to process semantic highlighting requests before the database has entries for the given file resulting in a panic. There is no work to be done either way so delay this like we do with other request handlers.
internal: ServerStatusParams should consider 'prime caches' in quiescent status
Priming caches is a performance win, but it takes a lock on the salsa database and prevents rust-analyzer from responding to e.g. go-to-def requests.
This causes confusion for users, who see the spinner next to rust-analyzer in the VS Code footer stop, so they start attempting to navigate their code.
Instead, set the `quiescent` status in LSP to false during cache priming, so the VS Code spinner persists until we can respond to any LSP request.
Priming caches is a performance win, but it takes a lock on the salsa
database and prevents rust-analyzer from responding to e.g. go-to-def
requests.
This causes confusion for users, who see the spinner next to
rust-analyzer in the VS Code footer stop, so they start attempting to
navigate their code.
Instead, set the `quiescent` status in LSP to false during cache
priming, so the VS Code spinner persists until we can respond to any
LSP request.
fix: Panic when a TAIT exists in a RPIT
Fixes #17921
When there is a TAIT inside of a RPIT like;
```rust
trait Foo {}
type Bar = impl Foo;
fn foo<A>() -> impl Future<Output = Bar> { .. }
```
while inferencing `fn foo`, `insert_inference_vars_for_impl_trait` tries to substitute impl trait bounds of `Bar`, i.e. `Implemented(Foo)` with RPITs `placeholders`, and this causes panic
fa00326247/crates/hir-ty/src/infer.rs (L903-L905)
chore(config): remove `invocationLocation` in favor of `invocationStrategy`
These flags were added to help rust-analyzer integrate with repos requiring non-Cargo invocations. The consensus is that having two independent settings are no longer needed. This change removes `invocationLocation` in favor of `invocationStrategy` and changes the internal representation of `InvocationStrategy::Once` to hold the workspace root.
Closes#17848.
These flags were added to help rust-analyzer integrate with repos
requiring non-Cargo invocations. The consensus is that having two
independent settings are no longer needed. This change removes
`invocationLocation` in favor of `invocationStrategy` and changes
the internal representation of `InvocationStrategy::Once` to hold
the workspace root.
fix: Wrong BoundVar index when lowering impl trait parameter of parent generics
Fixes#17711
From the following test code;
```rust
//- minicore: deref
use core::ops::Deref;
struct Struct<'a, T>(&'a T);
trait Trait {}
impl<'a, T: Deref<Target = impl Trait>> Struct<'a, T> {
fn foo(&self) -> &Self { self }
fn bar(&self) {
let _ = self.foo();
}
}
```
when we call `register_obligations_for_call` for `let _ = self.foo();`,
07659783fd/crates/hir-ty/src/infer/expr.rs (L1939-L1952)
we are querying `generic_predicates` and it has `T: Deref<Target = impl Trait>` predicate from the parent `impl Struct`;
07659783fd/crates/hir-ty/src/lower.rs (L375-L399)
but as we can see above, lowering `TypeRef = impl Trait` doesn't take into account the parent generic parameters, so the `BoundVar` index here is `0`, as `fn foo` has no generic args other than parent's,
But this `BoundVar` is pointing at `'a` in `<'a, T: Deref<Target = impl Trait>>`.
So, in the first code reference `register_obligations_for_call`'s L:1948 - `.substitute(Interner, parameters)`, we are substituting `'a` with `Ty`, not `Lifetime` and this makes panic inside the chalk.
This PR fixes this wrong `BoundVar` index in such cases
