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]>

4 files changed, 16 insertions, 26 deletions

diff --git a/crates/ra_hir_def/src/nameres/collector.rs b/crates/ra_hir_def/src/nameres/collector.rs
index db9838cb5..7a042e69f 100644
--- a/crates/ra_hir_def/src/nameres/collector.rs
+++ b/crates/ra_hir_def/src/nameres/collector.rs
@@ -30,7 +30,7 @@ use crate::{
     TraitLoc, TypeAliasLoc, UnionLoc,
 };
 
-pub(super) fn collect_defs(db: &impl DefDatabase, mut def_map: CrateDefMap) -> CrateDefMap {
+pub(super) fn collect_defs(db: &dyn DefDatabase, mut def_map: CrateDefMap) -> CrateDefMap {
     let crate_graph = db.crate_graph();
 
     // populate external prelude
@@ -112,8 +112,8 @@ struct DeriveDirective {
 }
 
 /// Walks the tree of module recursively
-struct DefCollector<'a, DB> {
-    db: &'a DB,
+struct DefCollector<'a> {
+    db: &'a dyn DefDatabase,
     def_map: CrateDefMap,
     glob_imports: FxHashMap<LocalModuleId, Vec<(LocalModuleId, Visibility)>>,
     unresolved_imports: Vec<ImportDirective>,
@@ -124,10 +124,7 @@ struct DefCollector<'a, DB> {
     cfg_options: &'a CfgOptions,
 }
 
-impl<DB> DefCollector<'_, DB>
-where
-    DB: DefDatabase,
-{
+impl DefCollector<'_> {
     fn collect(&mut self) {
         let file_id = self.db.crate_graph()[self.def_map.krate].root_file_id;
         let raw_items = self.db.raw_items(file_id.into());
@@ -605,8 +602,8 @@ where
 }
 
 /// Walks a single module, populating defs, imports and macros
-struct ModCollector<'a, D> {
-    def_collector: D,
+struct ModCollector<'a, 'b> {
+    def_collector: &'a mut DefCollector<'b>,
     macro_depth: usize,
     module_id: LocalModuleId,
     file_id: HirFileId,
@@ -614,10 +611,7 @@ struct ModCollector<'a, D> {
     mod_dir: ModDir,
 }
 
-impl<DB> ModCollector<'_, &'_ mut DefCollector<'_, DB>>
-where
-    DB: DefDatabase,
-{
+impl ModCollector<'_, '_> {
     fn collect(&mut self, items: &[raw::RawItem]) {
         // Note: don't assert that inserted value is fresh: it's simply not true
         // for macros.
@@ -950,7 +944,7 @@ mod tests {
 
     use super::*;
 
-    fn do_collect_defs(db: &impl DefDatabase, def_map: CrateDefMap) -> CrateDefMap {
+    fn do_collect_defs(db: &dyn DefDatabase, def_map: CrateDefMap) -> CrateDefMap {
         let mut collector = DefCollector {
             db,
             def_map,
diff --git a/crates/ra_hir_def/src/nameres/mod_resolution.rs b/crates/ra_hir_def/src/nameres/mod_resolution.rs
index 14fb8ba3a..386c5cade 100644
--- a/crates/ra_hir_def/src/nameres/mod_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/mod_resolution.rs
@@ -40,12 +40,12 @@ impl ModDir {
 
     pub(super) fn resolve_declaration(
         &self,
-        db: &impl DefDatabase,
+        db: &dyn DefDatabase,
         file_id: HirFileId,
         name: &Name,
         attr_path: Option<&SmolStr>,
     ) -> Result<(FileId, ModDir), RelativePathBuf> {
-        let file_id = file_id.original_file(db);
+        let file_id = file_id.original_file(db.upcast());
 
         let mut candidate_files = Vec::new();
         match attr_to_path(attr_path) {
diff --git a/crates/ra_hir_def/src/nameres/path_resolution.rs b/crates/ra_hir_def/src/nameres/path_resolution.rs
index c058e70aa..35a0a0c98 100644
--- a/crates/ra_hir_def/src/nameres/path_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/path_resolution.rs
@@ -70,7 +70,7 @@ impl CrateDefMap {
 
     pub(crate) fn resolve_visibility(
         &self,
-        db: &impl DefDatabase,
+        db: &dyn DefDatabase,
         original_module: LocalModuleId,
         visibility: &RawVisibility,
     ) -> Option<Visibility> {
@@ -98,7 +98,7 @@ impl CrateDefMap {
     // the result.
     pub(super) fn resolve_path_fp_with_macro(
         &self,
-        db: &impl DefDatabase,
+        db: &dyn DefDatabase,
         mode: ResolveMode,
         original_module: LocalModuleId,
         path: &ModPath,
@@ -262,7 +262,7 @@ impl CrateDefMap {
 
     fn resolve_name_in_module(
         &self,
-        db: &impl DefDatabase,
+        db: &dyn DefDatabase,
         module: LocalModuleId,
         name: &Name,
         shadow: BuiltinShadowMode,
@@ -304,7 +304,7 @@ impl CrateDefMap {
         from_crate_root.or(from_extern_prelude)
     }
 
-    fn resolve_in_prelude(&self, db: &impl DefDatabase, name: &Name) -> PerNs {
+    fn resolve_in_prelude(&self, db: &dyn DefDatabase, name: &Name) -> PerNs {
         if let Some(prelude) = self.prelude {
             let keep;
             let def_map = if prelude.krate == self.krate {
diff --git a/crates/ra_hir_def/src/nameres/raw.rs b/crates/ra_hir_def/src/nameres/raw.rs
index ea3c00da8..0e4931f58 100644
--- a/crates/ra_hir_def/src/nameres/raw.rs
+++ b/crates/ra_hir_def/src/nameres/raw.rs
@@ -9,7 +9,6 @@ use std::{ops::Index, sync::Arc};
 
 use hir_expand::{
     ast_id_map::AstIdMap,
-    db::AstDatabase,
     hygiene::Hygiene,
     name::{AsName, Name},
 };
@@ -45,16 +44,13 @@ pub struct RawItems {
 }
 
 impl RawItems {
-    pub(crate) fn raw_items_query(
-        db: &(impl DefDatabase + AstDatabase),
-        file_id: HirFileId,
-    ) -> Arc<RawItems> {
+    pub(crate) fn raw_items_query(db: &dyn DefDatabase, file_id: HirFileId) -> Arc<RawItems> {
         let _p = profile("raw_items_query");
         let mut collector = RawItemsCollector {
             raw_items: RawItems::default(),
             source_ast_id_map: db.ast_id_map(file_id),
             file_id,
-            hygiene: Hygiene::new(db, file_id),
+            hygiene: Hygiene::new(db.upcast(), file_id),
         };
         if let Some(node) = db.parse_or_expand(file_id) {
             if let Some(source_file) = ast::SourceFile::cast(node.clone()) {