From 6f15a440ca3a670bf41926b584ecf4a98d03dc21 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Fri, 25 Jan 2019 18:35:16 -0500
Subject: [PATCH] make `dyn Trait` query implementations work

---
 components/salsa-macros/src/query_group.rs | 18 ++++++++++--
 tests/dyn_trait.rs                         | 32 ++++++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)
 create mode 100644 tests/dyn_trait.rs

diff --git a/components/salsa-macros/src/query_group.rs b/components/salsa-macros/src/query_group.rs
index 5a69bd05..ba5af0ed 100644
--- a/components/salsa-macros/src/query_group.rs
+++ b/components/salsa-macros/src/query_group.rs
@@ -243,7 +243,9 @@ pub(crate) fn query_group(args: TokenStream, input: TokenStream) -> TokenStream
         #trait_vis struct #group_struct { }
 
         impl<DB__> salsa::plumbing::QueryGroup<DB__> for #group_struct
-        where DB__: #trait_name
+        where
+            DB__: #trait_name,
+            DB__: salsa::Database,
         {
             type GroupStorage = #group_storage<DB__>;
             type GroupKey = #group_key;
@@ -288,6 +290,7 @@ pub(crate) fn query_group(args: TokenStream, input: TokenStream) -> TokenStream
             impl<DB> salsa::Query<DB> for #qt
             where
                 DB: #trait_name,
+                DB: salsa::Database,
             {
                 type Key = (#(#keys),*);
                 type Value = #value;
@@ -325,6 +328,7 @@ pub(crate) fn query_group(args: TokenStream, input: TokenStream) -> TokenStream
                 impl<DB> salsa::plumbing::QueryFunction<DB> for #qt
                 where
                     DB: #trait_name,
+                    DB: salsa::Database,
                 {
                     fn execute(db: &DB, #key_pattern: <Self as salsa::Query<DB>>::Key)
                         -> <Self as salsa::Query<DB>>::Value {
@@ -371,11 +375,19 @@ pub(crate) fn query_group(args: TokenStream, input: TokenStream) -> TokenStream
     // It would derive Default, but then all database structs would have to implement Default
     // as the derived version includes an unused `+ Default` constraint.
     output.extend(quote! {
-        #trait_vis struct #group_storage<DB__: #trait_name> {
+        #trait_vis struct #group_storage<DB__>
+        where
+            DB__: #trait_name,
+            DB__: salsa::Database,
+        {
             #storage_fields
         }
 
-        impl<DB__: #trait_name> Default for #group_storage<DB__> {
+        impl<DB__> Default for #group_storage<DB__>
+        where
+            DB__: #trait_name,
+            DB__: salsa::Database,
+        {
             #[inline]
             fn default() -> Self {
                 #group_storage {
diff --git a/tests/dyn_trait.rs b/tests/dyn_trait.rs
new file mode 100644
index 00000000..c232c303
--- /dev/null
+++ b/tests/dyn_trait.rs
@@ -0,0 +1,32 @@
+//! Test that you can implement a query using a `dyn Trait` setup.
+
+#[salsa::database(DynTraitStorage)]
+#[derive(Default)]
+struct DynTraitDatabase {
+    runtime: salsa::Runtime<DynTraitDatabase>,
+}
+
+impl salsa::Database for DynTraitDatabase {
+    fn salsa_runtime(&self) -> &salsa::Runtime<DynTraitDatabase> {
+        &self.runtime
+    }
+}
+
+#[salsa::query_group(DynTraitStorage)]
+trait DynTrait {
+    #[salsa::input]
+    fn input(&self, x: u32) -> u32;
+
+    fn output(&self, x: u32) -> u32;
+}
+
+fn output(db: &dyn DynTrait, x: u32) -> u32 {
+    db.input(x) * 2
+}
+
+#[test]
+fn dyn_trait() {
+    let mut query = DynTraitDatabase::default();
+    query.set_input(22, 23);
+    assert_eq!(query.output(22), 46);
+}