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fix: avoid where Self: 'a clause on GATs #106

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Merged
merged 4 commits into from
Sep 8, 2023
Merged

fix: avoid where Self: 'a clause on GATs #106

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b6adeb0
modify test to uncover existing bug
kmdreko Sep 5, 2023
b2abc7d
remove where Self: 'a on associated types
kmdreko Sep 5, 2023
8c0e1a7
document the dummy functions
kmdreko Sep 7, 2023
66636b2
add link
kmdreko Sep 7, 2023
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26 changes: 14 additions & 12 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -127,21 +127,13 @@ pub trait SimpleAsyncConnection {
#[async_trait::async_trait]
pub trait AsyncConnection: SimpleAsyncConnection + Sized + Send {
/// The future returned by `AsyncConnection::execute`
type ExecuteFuture<'conn, 'query>: Future<Output = QueryResult<usize>> + Send
where
Self: 'conn;
type ExecuteFuture<'conn, 'query>: Future<Output = QueryResult<usize>> + Send;
/// The future returned by `AsyncConnection::load`
type LoadFuture<'conn, 'query>: Future<Output = QueryResult<Self::Stream<'conn, 'query>>> + Send
where
Self: 'conn;
type LoadFuture<'conn, 'query>: Future<Output = QueryResult<Self::Stream<'conn, 'query>>> + Send;
/// The inner stream returned by `AsyncConnection::load`
type Stream<'conn, 'query>: Stream<Item = QueryResult<Self::Row<'conn, 'query>>> + Send
where
Self: 'conn;
type Stream<'conn, 'query>: Stream<Item = QueryResult<Self::Row<'conn, 'query>>> + Send;
/// The row type used by the stream returned by `AsyncConnection::load`
type Row<'conn, 'query>: Row<'conn, Self::Backend>
where
Self: 'conn;
type Row<'conn, 'query>: Row<'conn, Self::Backend>;

/// The backend this type connects to
type Backend: Backend;
Expand Down Expand Up @@ -341,4 +333,14 @@ pub trait AsyncConnection: SimpleAsyncConnection + Sized + Send {
fn transaction_state(
&mut self,
) -> &mut <Self::TransactionManager as TransactionManager<Self>>::TransactionStateData;

// These functions allow the associated types (`ExecuteFuture`, `LoadFuture`, etc.) to
// compile without a `where Self: '_` clause. This is needed the because bound causes
// lifetime issues when using `transaction()` with generic `AsyncConnection`s.
//
// See: https://github.com/rust-lang/rust/issues/87479
#[doc(hidden)]
fn _silence_lint_on_execute_future(_: Self::ExecuteFuture<'_, '_>) {}
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Can you add a comment to these function explaining why they exist + linking to the relevant rust issues?

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Comment and link added

#[doc(hidden)]
fn _silence_lint_on_load_future(_: Self::LoadFuture<'_, '_>) {}
}
12 changes: 4 additions & 8 deletions src/pooled_connection/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -181,14 +181,10 @@ where
C::Target: AsyncConnection,
{
type ExecuteFuture<'conn, 'query> =
<C::Target as AsyncConnection>::ExecuteFuture<'conn, 'query>
where C::Target: 'conn, C: 'conn;
type LoadFuture<'conn, 'query> = <C::Target as AsyncConnection>::LoadFuture<'conn, 'query>
where C::Target: 'conn, C: 'conn;
type Stream<'conn, 'query> = <C::Target as AsyncConnection>::Stream<'conn, 'query>
where C::Target: 'conn, C: 'conn;
type Row<'conn, 'query> = <C::Target as AsyncConnection>::Row<'conn, 'query>
where C::Target: 'conn, C: 'conn;
<C::Target as AsyncConnection>::ExecuteFuture<'conn, 'query>;
type LoadFuture<'conn, 'query> = <C::Target as AsyncConnection>::LoadFuture<'conn, 'query>;
type Stream<'conn, 'query> = <C::Target as AsyncConnection>::Stream<'conn, 'query>;
type Row<'conn, 'query> = <C::Target as AsyncConnection>::Row<'conn, 'query>;

type Backend = <C::Target as AsyncConnection>::Backend;

Expand Down
4 changes: 3 additions & 1 deletion tests/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,9 @@ mod pooling;
mod sync_wrapper;
mod type_check;

async fn transaction_test(conn: &mut TestConnection) -> QueryResult<()> {
async fn transaction_test<C: AsyncConnection<Backend = TestBackend>>(
conn: &mut C,
) -> QueryResult<()> {
let res = conn
.transaction::<i32, diesel::result::Error, _>(|conn| {
Box::pin(async move {
Expand Down