refactor: remove several blanket impls to allow more customization

sqlx-core/src/decode.rs

@@ -2,7 +2,6 @@
 
 use crate::database::{Database, HasValueRef};
 use crate::error::BoxDynError;
-use crate::value::ValueRef;
 
 /// A type that can be decoded from the database.
 ///
@@ -62,17 +61,24 @@ pub trait Decode<'r, DB: Database>: Sized {
     fn decode(value: <DB as HasValueRef<'r>>::ValueRef) -> Result<Self, BoxDynError>;
 }
 
-// implement `Decode` for Option<T> for all SQL types
-impl<'r, DB, T> Decode<'r, DB> for Option<T>
-where
-    DB: Database,
-    T: Decode<'r, DB>,
-{
-    fn decode(value: <DB as HasValueRef<'r>>::ValueRef) -> Result<Self, BoxDynError> {
+#[allow(unused_macros)]
+macro_rules! impl_decode_for_option {
+    ($DB:ident) => {
+        impl<'r, T> crate::decode::Decode<'r, $DB> for Option<T>
+        where
+            T: crate::decode::Decode<'r, $DB>,
+        {
+            fn decode(
+                value: <$DB as crate::database::HasValueRef<'r>>::ValueRef,
+            ) -> Result<Self, crate::error::BoxDynError> {
+                use crate::value::ValueRef;
+
                 if value.is_null() {
                     Ok(None)
                 } else {
                     Ok(Some(T::decode(value)?))
                 }
             }
+        }
+    };
 }

sqlx-core/src/encode.rs

@@ -45,22 +45,32 @@ pub trait Encode<'q, DB: Database> {
     }
 }
 
-impl<'q, T, DB: Database> Encode<'q, DB> for &'_ T
-where
-    T: Encode<'q, DB>,
-{
+// de-generified using macros because Any doesn't want this
+#[allow(unused_macros)]
+macro_rules! impl_encode_for_ref {
+    ($DB:ident) => {
+        impl<'q, T> crate::encode::Encode<'q, $DB> for &'_ T
+        where
+            T: crate::encode::Encode<'q, $DB>,
+        {
             #[inline]
-    fn encode(self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull {
-        <T as Encode<DB>>::encode_by_ref(self, buf)
+            fn encode(
+                self,
+                buf: &mut <$DB as crate::database::HasArguments<'q>>::ArgumentBuffer,
+            ) -> crate::encode::IsNull {
+                <T as crate::encode::Encode<$DB>>::encode_by_ref(self, buf)
             }
 
             #[inline]
-    fn encode_by_ref(&self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull {
-        <&T as Encode<DB>>::encode(self, buf)
+            fn encode_by_ref(
+                &self,
+                buf: &mut <$DB as crate::database::HasArguments<'q>>::ArgumentBuffer,
+            ) -> crate::encode::IsNull {
+                <&T as crate::encode::Encode<$DB>>::encode(self, buf)
             }
 
             #[inline]
-    fn produces(&self) -> Option<DB::TypeInfo> {
+            fn produces(&self) -> Option<<$DB as crate::database::Database>::TypeInfo> {
                 (**self).produces()
             }
 
@@ -68,8 +78,11 @@ where
             fn size_hint(&self) -> usize {
                 (**self).size_hint()
             }
+        }
+    };
 }
 
+// de-generified using macros because MSSQL has a different concept of how nullable encoding works
 #[allow(unused_macros)]
 macro_rules! impl_encode_for_option {
     ($DB:ident) => {

sqlx-core/src/mssql/mod.rs

@@ -31,5 +31,10 @@ impl_into_arguments_for_arguments!(MssqlArguments);
 impl_executor_for_pool_connection!(Mssql, MssqlConnection, MssqlRow);
 impl_executor_for_transaction!(Mssql, MssqlRow);
 
+// required because of `Any`
+impl_type_for_ref_and_option!(Mssql);
+impl_encode_for_ref!(Mssql);
+impl_decode_for_option!(Mssql);
+
 // FIXME: RPC NULL parameter values / results
 // FIXME: RPC Empty String parameter values

sqlx-core/src/mysql/mod.rs

@@ -31,6 +31,11 @@ impl_into_arguments_for_arguments!(MySqlArguments);
 impl_executor_for_pool_connection!(MySql, MySqlConnection, MySqlRow);
 impl_executor_for_transaction!(MySql, MySqlRow);
 
+// required because of `Any`
+impl_type_for_ref_and_option!(MySql);
+impl_encode_for_ref!(MySql);
+impl_decode_for_option!(MySql);
+
 // required because some databases have a different handling
 // of NULL
 impl_encode_for_option!(MySql);

sqlx-core/src/mysql/types/bytes.rs

@@ -46,7 +46,7 @@ impl Type<MySql> for Vec<u8> {
     }
 
     fn compatible(ty: &MySqlTypeInfo) -> bool {
-        <&[u8] as Type<MySql>>::compatible(ty)
+        <[u8] as Type<MySql>>::compatible(ty)
     }
 }
 

sqlx-core/src/postgres/mod.rs

@@ -34,6 +34,11 @@ impl_into_arguments_for_arguments!(PgArguments);
 impl_executor_for_pool_connection!(Postgres, PgConnection, PgRow);
 impl_executor_for_transaction!(Postgres, PgRow);
 
+// required because of `Any`
+impl_type_for_ref_and_option!(Postgres);
+impl_encode_for_ref!(Postgres);
+impl_decode_for_option!(Postgres);
+
 // required because some databases have a different handling
 // of NULL
 impl_encode_for_option!(Postgres);

sqlx-core/src/postgres/types/array.rs

@@ -37,7 +37,6 @@ impl<'q, T> Encode<'q, Postgres> for Vec<T>
 where
     for<'a> &'a [T]: Encode<'q, Postgres>,
     T: Encode<'q, Postgres>,
-    Self: Type<Postgres>,
 {
     #[inline]
     fn encode_by_ref(&self, buf: &mut PgArgumentBuffer) -> IsNull {
@@ -48,7 +47,6 @@ where
 impl<'q, T> Encode<'q, Postgres> for &'_ [T]
 where
     T: Encode<'q, Postgres> + Type<Postgres>,
-    Self: Type<Postgres>,
 {
     fn encode_by_ref(&self, buf: &mut PgArgumentBuffer) -> IsNull {
         buf.extend(&1_i32.to_be_bytes()); // number of dimensions
@@ -77,7 +75,6 @@ where
 impl<'r, T> Decode<'r, Postgres> for Vec<T>
 where
     T: for<'a> Decode<'a, Postgres> + Type<Postgres>,
-    Self: Type<Postgres>,
 {
     fn decode(value: PgValueRef<'r>) -> Result<Self, BoxDynError> {
         let element_type_info = T::type_info();

sqlx-core/src/postgres/types/mod.rs

@@ -171,7 +171,7 @@ pub use range::PgRange;
 pub use record::{PgRecordDecoder, PgRecordEncoder};
 
 // Type::compatible impl appropriate for arrays
-fn array_compatible<E: Type<Postgres>>(ty: &PgTypeInfo) -> bool {
+fn array_compatible<E: ?Sized + Type<Postgres>>(ty: &PgTypeInfo) -> bool {
     // we require the declared type to be an _array_ with an
     // element type that is acceptable
     if let PgTypeKind::Array(element) = &ty.kind() {

sqlx-core/src/postgres/types/str.rs

@@ -28,7 +28,7 @@ impl Type<Postgres> for [&'_ str] {
     }
 
     fn compatible(ty: &PgTypeInfo) -> bool {
-        array_compatible::<&str>(ty)
+        array_compatible::<str>(ty)
     }
 }
 
@@ -64,11 +64,11 @@ impl<'r> Decode<'r, Postgres> for &'r str {
 
 impl Type<Postgres> for String {
     fn type_info() -> PgTypeInfo {
-        <&str as Type<Postgres>>::type_info()
+        <str as Type<Postgres>>::type_info()
     }
 
     fn compatible(ty: &PgTypeInfo) -> bool {
-        <&str as Type<Postgres>>::compatible(ty)
+        <str as Type<Postgres>>::compatible(ty)
     }
 }
 

sqlx-core/src/sqlite/mod.rs

@@ -35,6 +35,11 @@ impl_into_arguments_for_arguments!(SqliteArguments<'q>);
 impl_executor_for_pool_connection!(Sqlite, SqliteConnection, SqliteRow);
 impl_executor_for_transaction!(Sqlite, SqliteRow);
 
+// required because of `Any`
+impl_type_for_ref_and_option!(Sqlite);
+impl_encode_for_ref!(Sqlite);
+impl_decode_for_option!(Sqlite);
+
 // required because some databases have a different handling
 // of NULL
 impl_encode_for_option!(Sqlite);

sqlx-core/src/sqlite/types/bytes.rs

@@ -29,7 +29,7 @@ impl<'r> Decode<'r, Sqlite> for &'r [u8] {
 
 impl Type<Sqlite> for Vec<u8> {
     fn type_info() -> SqliteTypeInfo {
-        <&[u8] as Type<Sqlite>>::type_info()
+        <[u8] as Type<Sqlite>>::type_info()
     }
 }
 

sqlx-core/src/sqlite/types/str.rs

@@ -29,7 +29,7 @@ impl<'r> Decode<'r, Sqlite> for &'r str {
 
 impl Type<Sqlite> for String {
     fn type_info() -> SqliteTypeInfo {
-        <&str as Type<Sqlite>>::type_info()
+        <str as Type<Sqlite>>::type_info()
     }
 }
 

sqlx-core/src/types/mod.rs

@@ -69,24 +69,30 @@ pub trait Type<DB: Database> {
     }
 }
 
-// for references, the underlying SQL type is identical
-impl<T: ?Sized + Type<DB>, DB: Database> Type<DB> for &'_ T {
-    fn type_info() -> DB::TypeInfo {
-        <T as Type<DB>>::type_info()
+// de-generified using macros because Any doesn't want this
+#[allow(unused_macros)]
+macro_rules! impl_type_for_ref_and_option {
+    ($DB:ident) => {
+        // for references, the underlying SQL type is identical
+        impl<T: ?Sized + crate::types::Type<$DB>> crate::types::Type<$DB> for &'_ T {
+            fn type_info() -> <$DB as crate::database::Database>::TypeInfo {
+                <T as crate::types::Type<$DB>>::type_info()
             }
 
-    fn compatible(ty: &DB::TypeInfo) -> bool {
-        <T as Type<DB>>::compatible(ty)
-    }
-}
-
-// for optionals, the underlying SQL type is identical
-impl<T: Type<DB>, DB: Database> Type<DB> for Option<T> {
-    fn type_info() -> DB::TypeInfo {
-        <T as Type<DB>>::type_info()
-    }
-
-    fn compatible(ty: &DB::TypeInfo) -> bool {
-        <T as Type<DB>>::compatible(ty)
+            fn compatible(ty: &<$DB as crate::database::Database>::TypeInfo) -> bool {
+                <T as crate::types::Type<$DB>>::compatible(ty)
             }
+        }
+
+        // for optionals, the underlying SQL type is identical
+        impl<T: crate::types::Type<$DB>> crate::types::Type<$DB> for Option<T> {
+            fn type_info() -> <$DB as crate::database::Database>::TypeInfo {
+                <T as crate::types::Type<$DB>>::type_info()
+            }
+
+            fn compatible(ty: &<$DB as crate::database::Database>::TypeInfo) -> bool {
+                <T as crate::types::Type<$DB>>::compatible(ty)
+            }
+        }
+    };
 }