Merge #8318

8318: Use shrink_to_fit to reduce DefMap sizes r=jonas-schievink a=jonas-schievink

Especially `block_def_map` can overallocate when there's not a lot of items in the `DefMap`. This saves around 10 MB during analysis-stats. Not too much, but a cheap win.

bors r+

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

3 files changed, 25 insertions, 1 deletions

diff --git a/crates/hir_def/src/item_scope.rs b/crates/hir_def/src/item_scope.rs
index f3ebe7c72..4ddfd9ee6 100644
--- a/crates/hir_def/src/item_scope.rs
+++ b/crates/hir_def/src/item_scope.rs
@@ -285,6 +285,17 @@ impl ItemScope {
             buf.push('\n');
         }
     }
+
+    pub(crate) fn shrink_to_fit(&mut self) {
+        self.types.shrink_to_fit();
+        self.values.shrink_to_fit();
+        self.macros.shrink_to_fit();
+        self.unresolved.shrink_to_fit();
+        self.defs.shrink_to_fit();
+        self.impls.shrink_to_fit();
+        self.unnamed_trait_imports.shrink_to_fit();
+        self.legacy_macros.shrink_to_fit();
+    }
 }
 
 impl PerNs {
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 9e8e4e9ec..6a09ad420 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -409,6 +409,17 @@ impl DefMap {
             }
         }
     }
+
+    fn shrink_to_fit(&mut self) {
+        self.extern_prelude.shrink_to_fit();
+        self.exported_proc_macros.shrink_to_fit();
+        self.diagnostics.shrink_to_fit();
+        self.modules.shrink_to_fit();
+        for (_, module) in self.modules.iter_mut() {
+            module.children.shrink_to_fit();
+            module.scope.shrink_to_fit();
+        }
+    }
 }
 
 impl ModuleData {
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index c2e445b68..4ddc791ce 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -109,7 +109,9 @@ pub(super) fn collect_defs(
         }
     }
     collector.collect();
-    collector.finish()
+    let mut def_map = collector.finish();
+    def_map.shrink_to_fit();
+    def_map
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]