Remove all upcasts!

It turns out there were a lot redundant too.

crates/ide-db/src/lib.rs

@@ -52,11 +52,11 @@ use std::{fmt, mem::ManuallyDrop};
 
 use base_db::{
     CrateGraphBuilder, CratesMap, FileSourceRootInput, FileText, Files, RootQueryDb,
-    SourceDatabase, SourceRoot, SourceRootId, SourceRootInput, Upcast, query_group,
+    SourceDatabase, SourceRoot, SourceRootId, SourceRootInput, query_group,
 };
 use hir::{
     FilePositionWrapper, FileRangeWrapper,
-    db::{DefDatabase, ExpandDatabase, HirDatabase},
+    db::{DefDatabase, ExpandDatabase},
 };
 use triomphe::Arc;
 
@@ -116,39 +116,6 @@ impl fmt::Debug for RootDatabase {
     }
 }
 
-impl Upcast<dyn ExpandDatabase> for RootDatabase {
-    #[inline]
-    fn upcast(&self) -> &(dyn ExpandDatabase + 'static) {
-        self
-    }
-}
-
-impl Upcast<dyn DefDatabase> for RootDatabase {
-    #[inline]
-    fn upcast(&self) -> &(dyn DefDatabase + 'static) {
-        self
-    }
-}
-
-impl Upcast<dyn HirDatabase> for RootDatabase {
-    #[inline]
-    fn upcast(&self) -> &(dyn HirDatabase + 'static) {
-        self
-    }
-}
-
-impl Upcast<dyn RootQueryDb> for RootDatabase {
-    fn upcast(&self) -> &(dyn RootQueryDb + 'static) {
-        self
-    }
-}
-
-impl Upcast<dyn SourceDatabase> for RootDatabase {
-    fn upcast(&self) -> &(dyn SourceDatabase + 'static) {
-        self
-    }
-}
-
 #[salsa::db]
 impl SourceDatabase for RootDatabase {
     fn file_text(&self, file_id: vfs::FileId) -> FileText {

crates/ide-db/src/path_transform.rs

@@ -210,7 +210,7 @@ impl<'a> PathTransform<'a> {
             .flat_map(|it| it.lifetime_params(db))
             .zip(self.substs.lifetimes.clone())
             .filter_map(|(k, v)| {
-                Some((k.name(db).display(db.upcast(), target_edition).to_string(), v.lifetime()?))
+                Some((k.name(db).display(db, target_edition).to_string(), v.lifetime()?))
             })
             .collect();
         let ctx = Ctx {
@@ -325,7 +325,7 @@ impl Ctx<'_> {
                                 allow_unstable: true,
                             };
                             let found_path = self.target_module.find_path(
-                                self.source_scope.db.upcast(),
+                                self.source_scope.db,
                                 hir::ModuleDef::Trait(trait_ref),
                                 cfg,
                             )?;
@@ -384,8 +384,7 @@ impl Ctx<'_> {
                     prefer_absolute: false,
                     allow_unstable: true,
                 };
-                let found_path =
-                    self.target_module.find_path(self.source_scope.db.upcast(), def, cfg)?;
+                let found_path = self.target_module.find_path(self.source_scope.db, def, cfg)?;
                 let res = mod_path_to_ast(&found_path, self.target_edition).clone_for_update();
                 if let Some(args) = path.segment().and_then(|it| it.generic_arg_list()) {
                     if let Some(segment) = res.segment() {
@@ -425,7 +424,7 @@ impl Ctx<'_> {
                             allow_unstable: true,
                         };
                         let found_path = self.target_module.find_path(
-                            self.source_scope.db.upcast(),
+                            self.source_scope.db,
                             ModuleDef::from(adt),
                             cfg,
                         )?;

crates/ide-db/src/symbol_index.rs

@@ -27,7 +27,7 @@ use std::{
     ops::ControlFlow,
 };
 
-use base_db::{RootQueryDb, SourceDatabase, SourceRootId, Upcast};
+use base_db::{RootQueryDb, SourceDatabase, SourceRootId};
 use fst::{Automaton, Streamer, raw::IndexedValue};
 use hir::{
     Crate, Module,
@@ -97,7 +97,7 @@ impl Query {
 }
 
 #[query_group::query_group]
-pub trait SymbolsDatabase: HirDatabase + SourceDatabase + Upcast<dyn HirDatabase> {
+pub trait SymbolsDatabase: HirDatabase + SourceDatabase {
     /// The symbol index for a given module. These modules should only be in source roots that
     /// are inside local_roots.
     fn module_symbols(&self, module: Module) -> Arc<SymbolIndex>;
@@ -123,11 +123,11 @@ pub trait SymbolsDatabase: HirDatabase + SourceDatabase + Upcast<dyn HirDatabase
 fn library_symbols(db: &dyn SymbolsDatabase, source_root_id: SourceRootId) -> Arc<SymbolIndex> {
     let _p = tracing::info_span!("library_symbols").entered();
 
-    let mut symbol_collector = SymbolCollector::new(db.upcast());
+    let mut symbol_collector = SymbolCollector::new(db);
 
     db.source_root_crates(source_root_id)
         .iter()
-        .flat_map(|&krate| Crate::from(krate).modules(db.upcast()))
+        .flat_map(|&krate| Crate::from(krate).modules(db))
         // we specifically avoid calling other SymbolsDatabase queries here, even though they do the same thing,
         // as the index for a library is not going to really ever change, and we do not want to store each
         // the module or crate indices for those in salsa unless we need to.
@@ -139,12 +139,12 @@ fn library_symbols(db: &dyn SymbolsDatabase, source_root_id: SourceRootId) -> Ar
 fn module_symbols(db: &dyn SymbolsDatabase, module: Module) -> Arc<SymbolIndex> {
     let _p = tracing::info_span!("module_symbols").entered();
 
-    Arc::new(SymbolIndex::new(SymbolCollector::new_module(db.upcast(), module)))
+    Arc::new(SymbolIndex::new(SymbolCollector::new_module(db, module)))
 }
 
 pub fn crate_symbols(db: &dyn SymbolsDatabase, krate: Crate) -> Box<[Arc<SymbolIndex>]> {
     let _p = tracing::info_span!("crate_symbols").entered();
-    krate.modules(db.upcast()).into_iter().map(|module| db.module_symbols(module)).collect()
+    krate.modules(db).into_iter().map(|module| db.module_symbols(module)).collect()
 }
 
 // Feature: Workspace Symbol