orm: allow using connections, that were explicitly casted to orm.Connection too (#17427)

cmd/tools/vtest-self.v

@@ -127,6 +127,7 @@ const (
 		'vlib/orm/orm_fn_calls_test.v',
 		'vlib/orm/orm_last_id_test.v',
 		'vlib/orm/orm_string_interpolation_in_where_test.v',
+		'vlib/orm/orm_interface_test.v',
 		'vlib/db/sqlite/sqlite_test.v',
 		'vlib/db/sqlite/sqlite_orm_test.v',
 		'vlib/db/sqlite/sqlite_vfs_lowlevel_test.v',
@@ -197,6 +198,7 @@ const (
 		'vlib/orm/orm_fn_calls_test.v',
 		'vlib/orm/orm_last_id_test.v',
 		'vlib/orm/orm_string_interpolation_in_where_test.v',
+		'vlib/orm/orm_interface_test.v',
 		'vlib/v/tests/orm_sub_struct_test.v',
 		'vlib/v/tests/orm_sub_array_struct_test.v',
 		'vlib/v/tests/orm_joined_tables_select_test.v',

vlib/orm/orm_interface_test.v

@@ -0,0 +1,31 @@
+import db.sqlite
+import orm
+
+struct User {
+	id   int    [primary; sql: serial]
+	name string
+}
+
+fn test_orm_interface() {
+	sqlite_db := sqlite.connect(':memory:') or { panic(err) }
+	db := orm.Connection(sqlite_db)
+
+	sql db {
+		create table User
+	}
+
+	user := User{
+		name: 'test'
+	}
+
+	sql db {
+		insert user into User
+	}
+
+	users := sql db {
+		select from User
+	}
+
+	assert users.len == 1
+	assert users.first().name == user.name
+}

vlib/v/gen/c/sql.v

@@ -15,11 +15,19 @@ fn (mut g Gen) sql_stmt(node ast.SqlStmt) {
 	conn := g.new_tmp_var()
 	g.writeln('')
 	g.writeln('// orm')
-	g.write('orm__Connection ${conn} = (orm__Connection){._')
+	g.write('orm__Connection ${conn} = ')
+
 	db_expr_ctype_name := g.typ(node.db_expr_type)
-	g.write('${db_expr_ctype_name} = &')
+
-	g.expr(node.db_expr)
+	if db_expr_ctype_name == 'orm__Connection' {
-	g.writeln(', ._typ = _orm__Connection_${db_expr_ctype_name}_index};')
+		g.expr(node.db_expr)
+		g.writeln(';')
+	} else {
+		g.write('(orm__Connection){._${db_expr_ctype_name} = &')
+		g.expr(node.db_expr)
+		g.writeln(', ._typ = _orm__Connection_${db_expr_ctype_name}_index};')
+	}
+
 	for line in node.lines {
 		g.sql_stmt_line(line, conn, node.or_expr)
 	}
@@ -534,14 +542,21 @@ fn (mut g Gen) sql_select_expr(node ast.SqlExpr) {
 	conn := g.new_tmp_var()
 	g.writeln('')
 	g.writeln('// orm')
-	g.write('orm__Connection ${conn} = (orm__Connection){._')
+	g.write('orm__Connection ${conn} = ')
 	db_expr_type := g.get_db_type(node.db_expr) or {
 		verror('sql orm error - unknown db type for ${node.db_expr}')
 	}
 	db_expr_ctype_name := g.typ(db_expr_type)
-	g.write('${db_expr_ctype_name} = &')
+
-	g.expr(node.db_expr)
+	if db_expr_ctype_name == 'orm__Connection' {
-	g.writeln(', ._typ = _orm__Connection_${db_expr_ctype_name}_index};')
+		g.expr(node.db_expr)
+		g.writeln(';')
+	} else {
+		g.write('(orm__Connection){._${db_expr_ctype_name} = &')
+		g.expr(node.db_expr)
+		g.writeln(', ._typ = _orm__Connection_${db_expr_ctype_name}_index};')
+	}
+
 	g.sql_select(node, conn, left, node.or_expr)
 }