generalize MaybeOwnedConnection and clean up the connection file

sqlx-core/src/connection.rs

@@ -3,6 +3,7 @@ use std::convert::TryInto;
 use futures_core::future::BoxFuture;
 
 use crate::executor::Executor;
+use crate::maybe_owned::MaybeOwned;
 use crate::pool::{Pool, PoolConnection};
 use crate::transaction::Transaction;
 use crate::url::Url;
@@ -42,63 +43,32 @@ pub trait Connect: Connection {
         Self: Sized;
 }
 
-mod internal {
-    #[allow(dead_code)]
-    pub enum MaybeOwnedConnection<'c, C>
-    where
-        C: super::Connect,
-    {
-        Borrowed(&'c mut C),
-        Owned(super::PoolConnection<C>),
-    }
+pub(crate) enum ConnectionSource<'c, C>
+where
+    C: Connect,
+{
+    Connection(MaybeOwned<'c, PoolConnection<C>, C>),
 
     #[allow(dead_code)]
-    pub enum ConnectionSource<'c, C>
-    where
-        C: super::Connect,
-    {
-        Connection(MaybeOwnedConnection<'c, C>),
-        Pool(super::Pool<C>),
-    }
+    Pool(Pool<C>),
 }
 
-pub(crate) use self::internal::{ConnectionSource, MaybeOwnedConnection};
-
 impl<'c, C> ConnectionSource<'c, C>
 where
     C: Connect,
 {
     #[allow(dead_code)]
-    pub(crate) async fn resolve_by_ref(&mut self) -> crate::Result<&'_ mut C> {
+    pub(crate) async fn resolve(&mut self) -> crate::Result<&'_ mut C> {
         if let ConnectionSource::Pool(pool) = self {
-            *self =
-                ConnectionSource::Connection(MaybeOwnedConnection::Owned(pool.acquire().await?));
+            *self = ConnectionSource::Connection(MaybeOwned::Owned(pool.acquire().await?));
         }
 
         Ok(match self {
             ConnectionSource::Connection(conn) => match conn {
-                MaybeOwnedConnection::Borrowed(conn) => &mut *conn,
-                MaybeOwnedConnection::Owned(ref mut conn) => conn,
+                MaybeOwned::Borrowed(conn) => &mut *conn,
+                MaybeOwned::Owned(ref mut conn) => conn,
             },
             ConnectionSource::Pool(_) => unreachable!(),
         })
     }
 }
-
-impl<'c, C> From<&'c mut C> for MaybeOwnedConnection<'c, C>
-where
-    C: Connect,
-{
-    fn from(conn: &'c mut C) -> Self {
-        MaybeOwnedConnection::Borrowed(conn)
-    }
-}
-
-impl<'c, C> From<PoolConnection<C>> for MaybeOwnedConnection<'c, C>
-where
-    C: Connect,
-{
-    fn from(conn: PoolConnection<C>) -> Self {
-        MaybeOwnedConnection::Owned(conn)
-    }
-}

sqlx-core/src/cursor.rs

@@ -1,6 +1,5 @@
 use futures_core::future::BoxFuture;
 
-use crate::connection::{Connect, MaybeOwnedConnection};
 use crate::database::{Database, HasRow};
 use crate::executor::Execute;
 use crate::pool::Pool;
@@ -19,18 +18,17 @@ where
 {
     type Database: Database;
 
-    #[doc(hidden)]
     fn from_pool<E>(pool: &Pool<<Self::Database as Database>::Connection>, query: E) -> Self
     where
         Self: Sized,
         E: Execute<'q, Self::Database>;
 
-    #[doc(hidden)]
-    fn from_connection<E, C>(conn: C, query: E) -> Self
+    fn from_connection<E>(
+        connection: &'c mut <Self::Database as Database>::Connection,
+        query: E,
+    ) -> Self
     where
         Self: Sized,
-        <Self::Database as Database>::Connection: Connect,
-        C: Into<MaybeOwnedConnection<'c, <Self::Database as Database>::Connection>>,
         E: Execute<'q, Self::Database>;
 
     /// Fetch the next row in the result. Returns `None` if there are no more rows.

sqlx-core/src/executor.rs

@@ -24,7 +24,10 @@ where
     /// discarding any potential result rows.
     ///
     /// Returns the number of rows affected, or 0 if not applicable.
-    fn execute<'e, 'q, E: 'e>(&'e mut self, query: E) -> BoxFuture<'e, crate::Result<u64>>
+    fn execute<'e, 'q: 'e, 'c: 'e, E: 'e>(
+        &'c mut self,
+        query: E,
+    ) -> BoxFuture<'e, crate::Result<u64>>
     where
         E: Execute<'q, Self::Database>;
 
@@ -89,7 +92,10 @@ where
 {
     type Database = T::Database;
 
-    fn execute<'e, 'q, E: 'e>(&'e mut self, query: E) -> BoxFuture<'e, crate::Result<u64>>
+    fn execute<'e, 'q: 'e, 'c: 'e, E: 'e>(
+        &'c mut self,
+        query: E,
+    ) -> BoxFuture<'e, crate::Result<u64>>
     where
         E: Execute<'q, Self::Database>,
     {

sqlx-core/src/io/buf_stream.rs

@@ -45,6 +45,7 @@ where
         }
     }
 
+    #[cfg(feature = "postgres")]
     #[inline]
     pub fn buffer<'c>(&'c self) -> &'c [u8] {
         &self.rbuf[self.rbuf_rindex..]

sqlx-core/src/lib.rs

@@ -15,6 +15,8 @@ pub mod error;
 #[macro_use]
 mod io;
 
+mod maybe_owned;
+
 pub mod connection;
 pub mod cursor;
 pub mod database;

sqlx-core/src/maybe_owned.rs

@@ -0,0 +1,42 @@
+use core::borrow::{Borrow, BorrowMut};
+use core::ops::{Deref, DerefMut};
+
+pub(crate) enum MaybeOwned<'a, O, B = O> {
+    #[allow(dead_code)]
+    Borrowed(&'a mut B),
+
+    #[allow(dead_code)]
+    Owned(O),
+}
+
+impl<'a, O, B> From<&'a mut B> for MaybeOwned<'a, O, B> {
+    fn from(val: &'a mut B) -> Self {
+        MaybeOwned::Borrowed(val)
+    }
+}
+
+impl<'a, O, B> Deref for MaybeOwned<'a, O, B>
+where
+    O: Borrow<B>,
+{
+    type Target = B;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            MaybeOwned::Borrowed(val) => val,
+            MaybeOwned::Owned(ref val) => val.borrow(),
+        }
+    }
+}
+
+impl<'a, O, B> DerefMut for MaybeOwned<'a, O, B>
+where
+    O: BorrowMut<B>,
+{
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        match self {
+            MaybeOwned::Borrowed(val) => val,
+            MaybeOwned::Owned(ref mut val) => val.borrow_mut(),
+        }
+    }
+}

sqlx-core/src/mysql/cursor.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 
 use futures_core::future::BoxFuture;
 
-use crate::connection::{ConnectionSource, MaybeOwnedConnection};
+use crate::connection::ConnectionSource;
 use crate::cursor::Cursor;
 use crate::executor::Execute;
 use crate::mysql::protocol::{ColumnCount, ColumnDefinition, Row, Status, TypeId};
@@ -21,7 +21,6 @@ pub struct MySqlCursor<'c, 'q> {
 impl<'c, 'q> Cursor<'c, 'q> for MySqlCursor<'c, 'q> {
     type Database = MySql;
 
-    #[doc(hidden)]
     fn from_pool<E>(pool: &Pool<MySqlConnection>, query: E) -> Self
     where
         Self: Sized,
@@ -36,11 +35,9 @@ impl<'c, 'q> Cursor<'c, 'q> for MySqlCursor<'c, 'q> {
         }
     }
 
-    #[doc(hidden)]
-    fn from_connection<E, C>(conn: C, query: E) -> Self
+    fn from_connection<E>(conn: &'c mut MySqlConnection, query: E) -> Self
     where
         Self: Sized,
-        C: Into<MaybeOwnedConnection<'c, MySqlConnection>>,
         E: Execute<'q, MySql>,
     {
         Self {
@@ -60,7 +57,7 @@ impl<'c, 'q> Cursor<'c, 'q> for MySqlCursor<'c, 'q> {
 async fn next<'a, 'c: 'a, 'q: 'a>(
     cursor: &'a mut MySqlCursor<'c, 'q>,
 ) -> crate::Result<Option<MySqlRow<'a>>> {
-    let mut conn = cursor.source.resolve_by_ref().await?;
+    let mut conn = cursor.source.resolve().await?;
 
     // The first time [next] is called we need to actually execute our
     // contained query. We guard against this happening on _all_ next calls

sqlx-core/src/mysql/executor.rs

@@ -202,7 +202,10 @@ impl super::MySqlConnection {
 impl Executor for super::MySqlConnection {
     type Database = MySql;
 
-    fn execute<'e, 'q, E: 'e>(&'e mut self, query: E) -> BoxFuture<'e, crate::Result<u64>>
+    fn execute<'e, 'q: 'e, 'c: 'e, E: 'e>(
+        &'c mut self,
+        query: E,
+    ) -> BoxFuture<'e, crate::Result<u64>>
     where
         E: Execute<'q, Self::Database>,
     {

sqlx-core/src/pool/connection.rs

@@ -1,4 +1,5 @@
 use futures_core::future::BoxFuture;
+use std::borrow::{Borrow, BorrowMut};
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
 use std::time::Instant;
@@ -35,6 +36,24 @@ pub(super) struct Floating<'p, C> {
 
 const DEREF_ERR: &str = "(bug) connection already released to pool";
 
+impl<C> Borrow<C> for PoolConnection<C>
+where
+    C: Connect,
+{
+    fn borrow(&self) -> &C {
+        &*self
+    }
+}
+
+impl<C> BorrowMut<C> for PoolConnection<C>
+where
+    C: Connect,
+{
+    fn borrow_mut(&mut self) -> &mut C {
+        &mut *self
+    }
+}
+
 impl<C> Deref for PoolConnection<C>
 where
     C: Connect,

sqlx-core/src/pool/executor.rs

@@ -17,7 +17,10 @@ where
 {
     type Database = DB;
 
-    fn execute<'e, 'q, E: 'e>(&'e mut self, query: E) -> BoxFuture<'e, crate::Result<u64>>
+    fn execute<'e, 'q: 'e, 'c: 'e, E: 'e>(
+        &'c mut self,
+        query: E,
+    ) -> BoxFuture<'e, crate::Result<u64>>
     where
         E: Execute<'q, Self::Database>,
     {
@@ -65,7 +68,10 @@ where
 {
     type Database = C::Database;
 
-    fn execute<'e, 'q, E: 'e>(&'e mut self, query: E) -> BoxFuture<'e, crate::Result<u64>>
+    fn execute<'e, 'q: 'e, 'c: 'e, E: 'e>(
+        &'c mut self,
+        query: E,
+    ) -> BoxFuture<'e, crate::Result<u64>>
     where
         E: Execute<'q, Self::Database>,
     {

sqlx-core/src/postgres/cursor.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 
 use futures_core::future::BoxFuture;
 
-use crate::connection::{ConnectionSource, MaybeOwnedConnection};
+use crate::connection::ConnectionSource;
 use crate::cursor::Cursor;
 use crate::executor::Execute;
 use crate::pool::Pool;
@@ -22,7 +22,6 @@ pub struct PgCursor<'c, 'q> {
 impl<'c, 'q> Cursor<'c, 'q> for PgCursor<'c, 'q> {
     type Database = Postgres;
 
-    #[doc(hidden)]
     fn from_pool<E>(pool: &Pool<PgConnection>, query: E) -> Self
     where
         Self: Sized,
@@ -36,11 +35,9 @@ impl<'c, 'q> Cursor<'c, 'q> for PgCursor<'c, 'q> {
         }
     }
 
-    #[doc(hidden)]
-    fn from_connection<E, C>(conn: C, query: E) -> Self
+    fn from_connection<E>(conn: &'c mut PgConnection, query: E) -> Self
     where
         Self: Sized,
-        C: Into<MaybeOwnedConnection<'c, PgConnection>>,
         E: Execute<'q, Postgres>,
     {
         Self {
@@ -128,7 +125,7 @@ async fn get_or_describe(
 async fn next<'a, 'c: 'a, 'q: 'a>(
     cursor: &'a mut PgCursor<'c, 'q>,
 ) -> crate::Result<Option<PgRow<'a>>> {
-    let mut conn = cursor.source.resolve_by_ref().await?;
+    let mut conn = cursor.source.resolve().await?;
 
     // The first time [next] is called we need to actually execute our
     // contained query. We guard against this happening on _all_ next calls

sqlx-core/src/postgres/executor.rs

@@ -368,7 +368,10 @@ impl PgConnection {
 impl Executor for super::PgConnection {
     type Database = Postgres;
 
-    fn execute<'e, 'q, E: 'e>(&'e mut self, query: E) -> BoxFuture<'e, crate::Result<u64>>
+    fn execute<'e, 'q: 'e, 'c: 'e, E: 'e>(
+        &'c mut self,
+        query: E,
+    ) -> BoxFuture<'e, crate::Result<u64>>
     where
         E: Execute<'q, Self::Database>,
     {

sqlx-core/src/url.rs

@@ -29,6 +29,7 @@ impl<'s> TryFrom<&'s String> for Url {
 }
 
 impl Url {
+    #[allow(dead_code)]
     pub(crate) fn as_str(&self) -> &str {
         self.0.as_str()
     }