Change the order of generic arguments for InsertValues

This commit changes to order of generic arguments for the `InsertValues`
trait. This allows us to generate a sound impl of that trait via
`#[derive(MultiConnection)]` that will be accepted by future rust
compiler versions as well. This works as the backend type is this case
local, while the table type is generic. By having first the backend type
and then the table type we first have the local type, which is allowed
according to the rust coherence rules.

This is no breaking change as `InsertValues` is not part of the public
API: https://docs.diesel.rs/2.1.x/diesel/index.html?search=insertvalues

This fixes #4035

diesel/src/insertable.rs

@@ -115,7 +115,7 @@ where
     }
 }
 
-pub trait InsertValues<T: Table, DB: Backend>: QueryFragment<DB> {
+pub trait InsertValues<DB: Backend, T: Table>: QueryFragment<DB> {
     fn column_names(&self, out: AstPass<'_, '_, DB>) -> QueryResult<()>;
 }
 
@@ -154,7 +154,7 @@ impl<T> Default for DefaultableColumnInsertValue<T> {
     }
 }
 
-impl<Col, Expr, DB> InsertValues<Col::Table, DB>
+impl<Col, Expr, DB> InsertValues<DB, Col::Table>
     for DefaultableColumnInsertValue<ColumnInsertValue<Col, Expr>>
 where
     DB: Backend + SqlDialect<InsertWithDefaultKeyword = sql_dialect::default_keyword_for_insert::IsoSqlDefaultKeyword>,
@@ -168,7 +168,7 @@ where
     }
 }
 
-impl<Col, Expr, DB> InsertValues<Col::Table, DB> for ColumnInsertValue<Col, Expr>
+impl<Col, Expr, DB> InsertValues<DB, Col::Table> for ColumnInsertValue<Col, Expr>
 where
     DB: Backend,
     Col: Column,
@@ -218,7 +218,7 @@ where
 }
 
 #[cfg(feature = "sqlite")]
-impl<Col, Expr> InsertValues<Col::Table, crate::sqlite::Sqlite>
+impl<Col, Expr> InsertValues<crate::sqlite::Sqlite, Col::Table>
     for DefaultableColumnInsertValue<ColumnInsertValue<Col, Expr>>
 where
     Col: Column,

diesel/src/query_builder/insert_statement/insert_with_default_for_sqlite.rs

@@ -235,7 +235,7 @@ where
     T: Table + Copy + QueryId + 'static,
     T::FromClause: QueryFragment<Sqlite>,
     Op: Copy + QueryId + QueryFragment<Sqlite>,
-    V: InsertValues<T, Sqlite> + CanInsertInSingleQuery<Sqlite> + QueryId,
+    V: InsertValues<Sqlite, T> + CanInsertInSingleQuery<Sqlite> + QueryId,
 {
     fn execute((Yes, query): Self, conn: &mut C) -> QueryResult<usize> {
         conn.transaction(|conn| {

diesel/src/query_builder/insert_statement/mod.rs

@@ -455,7 +455,7 @@ impl<T, Tab, DB> QueryFragment<DB> for ValuesClause<T, Tab>
 where
     DB: Backend,
     Tab: Table,
-    T: InsertValues<Tab, DB>,
+    T: InsertValues<DB, Tab>,
     DefaultValues: QueryFragment<DB>,
 {
     fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {

diesel/src/type_impls/tuples.rs

@@ -156,11 +156,11 @@ macro_rules! tuple_impls {
             }
 
             #[allow(unused_assignments)]
-            impl<$($T,)+ Tab, __DB> InsertValues<Tab, __DB> for ($($T,)+)
+            impl<$($T,)+ Tab, __DB> InsertValues<__DB, Tab> for ($($T,)+)
             where
                 Tab: Table,
                 __DB: Backend,
-                $($T: InsertValues<Tab, __DB>,)+
+                $($T: InsertValues<__DB, Tab>,)+
             {
                 fn column_names(&self, mut out: AstPass<'_, '_, __DB>) -> QueryResult<()> {
                     let mut needs_comma = false;

diesel_derives/src/multiconnection.rs

@@ -1195,7 +1195,7 @@ fn generate_querybuilder(connection_types: &[ConnectionVariant]) -> TokenStream
         let ty = c.ty;
         quote::quote! {
             super::backend::MultiBackend::#ident(_) => {
-                <Self as diesel::insertable::InsertValues<Col::Table, <#ty as diesel::connection::Connection>::Backend>>::column_names(
+                <Self as diesel::insertable::InsertValues<<#ty as diesel::connection::Connection>::Backend, Col::Table>>::column_names(
                     &self,
                     out.cast_database(
                         super::bind_collector::MultiBindCollector::#lower_ident,
@@ -1214,7 +1214,7 @@ fn generate_querybuilder(connection_types: &[ConnectionVariant]) -> TokenStream
     let insert_values_backend_bounds = connection_types.iter().map(|c| {
         let ty = c.ty;
         quote::quote! {
-            diesel::insertable::DefaultableColumnInsertValue<diesel::insertable::ColumnInsertValue<Col, Expr>>: diesel::insertable::InsertValues<Col::Table, <#ty as diesel::connection::Connection>::Backend>
+            diesel::insertable::DefaultableColumnInsertValue<diesel::insertable::ColumnInsertValue<Col, Expr>>: diesel::insertable::InsertValues<<#ty as diesel::connection::Connection>::Backend, Col::Table>
         }
     });
 
@@ -1405,7 +1405,7 @@ fn generate_querybuilder(connection_types: &[ConnectionVariant]) -> TokenStream
             }
         }
 
-        impl<Col, Expr> diesel::insertable::InsertValues<Col::Table, super::multi_connection_impl::backend::MultiBackend>
+        impl<Col, Expr> diesel::insertable::InsertValues<super::multi_connection_impl::backend::MultiBackend, Col::Table>
             for diesel::insertable::DefaultableColumnInsertValue<diesel::insertable::ColumnInsertValue<Col, Expr>>
         where
             Col: diesel::prelude::Column,