Merge #4947

4947: Replace `impls_in_trait` query with smarter use of `CrateImplDefs` r=matklad a=jonas-schievink

`impls_in_trait` was allocating a whopping ~400 MB of RAM when running analysis-stats on r-a itself.

Remove it, instead adding a query that computes a summary `CrateImplDefs` map for all transitive dependencies. This can probably still be made more efficient, but this already reduces the peak memory usage by 25% without much performance impact on analysis-stats.

**Before**:

```
Total: 34.962107188s, 2083mb allocated 2141mb resident
   422mb ImplsForTraitQuery (deps)
   250mb CrateDefMapQueryQuery
   147mb MacroArgQuery
   140mb TraitSolveQuery (deps)
    68mb InferQueryQuery (deps)
    62mb ImplDatumQuery (deps)
```

**After**:

```
Total: 35.261100358s, 1520mb allocated 1569mb resident
   250mb CrateDefMapQueryQuery
   147mb MacroArgQuery
   144mb TraitSolveQuery (deps)
    68mb InferQueryQuery (deps)
    61mb ImplDatumQuery (deps)
    45mb BodyQuery
    45mb ImplDatumQuery
```

Co-authored-by: Jonas Schievink <[email protected]>

1 files changed, 20 insertions, 8 deletions

diff --git a/crates/ra_hir_ty/src/traits/chalk.rs b/crates/ra_hir_ty/src/traits/chalk.rs
index a72a82f5a..2f35d6d49 100644
--- a/crates/ra_hir_ty/src/traits/chalk.rs
+++ b/crates/ra_hir_ty/src/traits/chalk.rs
@@ -74,14 +74,26 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         // Note: Since we're using impls_for_trait, only impls where the trait
         // can be resolved should ever reach Chalk. `impl_datum` relies on that
         // and will panic if the trait can't be resolved.
-        let mut result: Vec<_> = self
-            .db
-            .impls_for_trait(self.krate, trait_, self_ty_fp)
-            .iter()
-            .copied()
-            .map(Impl::ImplDef)
-            .map(|impl_| impl_.to_chalk(self.db))
-            .collect();
+        let in_deps = self.db.impls_from_deps(self.krate);
+        let in_self = self.db.impls_in_crate(self.krate);
+        let impl_maps = [in_deps, in_self];
+
+        let id_to_chalk = |id: hir_def::ImplId| Impl::ImplDef(id).to_chalk(self.db);
+
+        let mut result: Vec<_> = match self_ty_fp {
+            Some(fp) => impl_maps
+                .iter()
+                .flat_map(|crate_impl_defs| {
+                    crate_impl_defs.lookup_impl_defs_for_trait_and_ty(trait_, fp).map(id_to_chalk)
+                })
+                .collect(),
+            None => impl_maps
+                .iter()
+                .flat_map(|crate_impl_defs| {
+                    crate_impl_defs.lookup_impl_defs_for_trait(trait_).map(id_to_chalk)
+                })
+                .collect(),
+        };
 
         let arg: Option<Ty> =
             parameters.get(1).map(|p| from_chalk(self.db, p.assert_ty_ref(&Interner).clone()));