Use `dyn Trait` for working with databse

It improves compile time in `--release` mode quite a bit, it doesn't
really slow things down and, conceptually, it seems closer to what we
want the physical architecture to look like (we don't want to
monomorphise EVERYTHING in a single leaf crate).

1 files changed, 16 insertions, 2 deletions

diff --git a/crates/ra_hir_ty/src/test_db.rs b/crates/ra_hir_ty/src/test_db.rs
index 0be2fea4b..5bbeabf51 100644
--- a/crates/ra_hir_ty/src/test_db.rs
+++ b/crates/ra_hir_ty/src/test_db.rs
@@ -6,8 +6,10 @@ use std::{
 };
 
 use hir_def::{db::DefDatabase, AssocItemId, ModuleDefId, ModuleId};
-use hir_expand::diagnostics::DiagnosticSink;
-use ra_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, RelativePath, SourceDatabase};
+use hir_expand::{db::AstDatabase, diagnostics::DiagnosticSink};
+use ra_db::{
+    salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, RelativePath, SourceDatabase, Upcast,
+};
 
 use crate::{db::HirDatabase, expr::ExprValidator};
 
@@ -25,6 +27,18 @@ pub struct TestDB {
     runtime: salsa::Runtime<TestDB>,
 }
 
+impl Upcast<dyn AstDatabase> for TestDB {
+    fn upcast(&self) -> &(dyn AstDatabase + 'static) {
+        &*self
+    }
+}
+
+impl Upcast<dyn DefDatabase> for TestDB {
+    fn upcast(&self) -> &(dyn DefDatabase + 'static) {
+        &*self
+    }
+}
+
 impl salsa::Database for TestDB {
     fn salsa_runtime(&self) -> &salsa::Runtime<TestDB> {
         &self.runtime