use GAT to elide StreamTrait lifetime (#1161)

Author: nappa85

src/database/connection.rs

@@ -34,15 +34,17 @@ pub trait ConnectionTrait: Sync {
 }
 
 /// Stream query results
-pub trait StreamTrait<'a>: Send + Sync {
+pub trait StreamTrait: Send + Sync {
     /// Create a stream for the [QueryResult]
-    type Stream: Stream<Item = Result<QueryResult, DbErr>> + Send;
+    type Stream<'a>: Stream<Item = Result<QueryResult, DbErr>> + Send
+    where
+        Self: 'a;
 
     /// Execute a [Statement] and return a stream of results
-    fn stream(
+    fn stream<'a>(
         &'a self,
         stmt: Statement,
-    ) -> Pin<Box<dyn Future<Output = Result<Self::Stream, DbErr>> + 'a + Send>>;
+    ) -> Pin<Box<dyn Future<Output = Result<Self::Stream<'a>, DbErr>> + 'a + Send>>;
 }
 
 /// Spawn database transaction

src/database/db_connection.rs

@@ -165,15 +165,15 @@ impl ConnectionTrait for DatabaseConnection {
 }
 
 #[async_trait::async_trait]
-impl<'a> StreamTrait<'a> for DatabaseConnection {
-    type Stream = crate::QueryStream;
+impl StreamTrait for DatabaseConnection {
+    type Stream<'a> = crate::QueryStream;
 
     #[instrument(level = "trace")]
     #[allow(unused_variables, unreachable_code)]
-    fn stream(
+    fn stream<'a>(
         &'a self,
         stmt: Statement,
-    ) -> Pin<Box<dyn Future<Output = Result<Self::Stream, DbErr>> + 'a + Send>> {
+    ) -> Pin<Box<dyn Future<Output = Result<Self::Stream<'a>, DbErr>> + 'a + Send>> {
         Box::pin(async move {
             Ok(match self {
                 #[cfg(feature = "sqlx-mysql")]

src/database/transaction.rs

@@ -388,16 +388,14 @@ impl ConnectionTrait for DatabaseTransaction {
     }
 }
 
-#[async_trait::async_trait]
-#[allow(unused_variables)]
-impl<'a> StreamTrait<'a> for DatabaseTransaction {
-    type Stream = TransactionStream<'a>;
+impl StreamTrait for DatabaseTransaction {
+    type Stream<'a> = TransactionStream<'a>;
 
     #[instrument(level = "trace")]
-    fn stream(
+    fn stream<'a>(
         &'a self,
         stmt: Statement,
-    ) -> Pin<Box<dyn Future<Output = Result<Self::Stream, DbErr>> + 'a + Send>> {
+    ) -> Pin<Box<dyn Future<Output = Result<Self::Stream<'a>, DbErr>> + 'a + Send>> {
         Box::pin(async move {
             let conn = self.conn.lock().await;
             Ok(crate::TransactionStream::build(

src/executor/select.rs

@@ -275,7 +275,7 @@ where
         db: &'a C,
     ) -> Result<impl Stream<Item = Result<E::Model, DbErr>> + 'b + Send, DbErr>
     where
-        C: ConnectionTrait + StreamTrait<'a> + Send,
+        C: ConnectionTrait + StreamTrait + Send,
     {
         self.into_model().stream(db).await
     }
@@ -329,7 +329,7 @@ where
         db: &'a C,
     ) -> Result<impl Stream<Item = Result<(E::Model, Option<F::Model>), DbErr>> + 'b, DbErr>
     where
-        C: ConnectionTrait + StreamTrait<'a> + Send,
+        C: ConnectionTrait + StreamTrait + Send,
     {
         self.into_model().stream(db).await
     }
@@ -367,7 +367,7 @@ where
         db: &'a C,
     ) -> Result<impl Stream<Item = Result<(E::Model, Option<F::Model>), DbErr>> + 'b + Send, DbErr>
     where
-        C: ConnectionTrait + StreamTrait<'a> + Send,
+        C: ConnectionTrait + StreamTrait + Send,
     {
         self.into_model().stream(db).await
     }
@@ -453,7 +453,7 @@ where
         db: &'a C,
     ) -> Result<Pin<Box<dyn Stream<Item = Result<S::Item, DbErr>> + 'b + Send>>, DbErr>
     where
-        C: ConnectionTrait + StreamTrait<'a> + Send,
+        C: ConnectionTrait + StreamTrait + Send,
         S: 'b,
         S::Item: Send,
     {
@@ -739,7 +739,7 @@ where
         db: &'a C,
     ) -> Result<Pin<Box<dyn Stream<Item = Result<S::Item, DbErr>> + 'b + Send>>, DbErr>
     where
-        C: ConnectionTrait + StreamTrait<'a> + Send,
+        C: ConnectionTrait + StreamTrait + Send,
         S: 'b,
         S::Item: Send,
     {