Merge #3584

3584: Switch to dynamic dispatch r=matklad a=matklad

Benches are in https://github.com/rust-analyzer/rust-analyzer/issues/1987#issuecomment-598807185

TL;DR: 

* 33% faster release build
* slightly worse/same perf
* no changes for debug build
* slightly smaller binary

cc @flodiebold I genuinely don't know if it is a good idea or not.

Co-authored-by: Aleksey Kladov <[email protected]>

2 files changed, 5 insertions, 8 deletions

diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 54b5591d3..6238de606 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -36,7 +36,7 @@ use crate::{
 };
 
 pub(super) fn lower(
-    db: &impl DefDatabase,
+    db: &dyn DefDatabase,
     def: DefWithBodyId,
     expander: Expander,
     params: Option<ast::ParamList>,
@@ -58,8 +58,8 @@ pub(super) fn lower(
     .collect(params, body)
 }
 
-struct ExprCollector<DB> {
-    db: DB,
+struct ExprCollector<'a> {
+    db: &'a dyn DefDatabase,
     def: DefWithBodyId,
     expander: Expander,
 
@@ -67,10 +67,7 @@ struct ExprCollector<DB> {
     source_map: BodySourceMap,
 }
 
-impl<'a, DB> ExprCollector<&'a DB>
-where
-    DB: DefDatabase,
-{
+impl ExprCollector<'_> {
     fn collect(
         mut self,
         param_list: Option<ast::ParamList>,
diff --git a/crates/ra_hir_def/src/body/scope.rs b/crates/ra_hir_def/src/body/scope.rs
index a58a7b21f..7c3db8869 100644
--- a/crates/ra_hir_def/src/body/scope.rs
+++ b/crates/ra_hir_def/src/body/scope.rs
@@ -45,7 +45,7 @@ pub struct ScopeData {
 }
 
 impl ExprScopes {
-    pub(crate) fn expr_scopes_query(db: &impl DefDatabase, def: DefWithBodyId) -> Arc<ExprScopes> {
+    pub(crate) fn expr_scopes_query(db: &dyn DefDatabase, def: DefWithBodyId) -> Arc<ExprScopes> {
         let body = db.body(def);
         Arc::new(ExprScopes::new(&*body))
     }