Fix local bind body not being desugared

In Go `for i, val := range arr` creates a *copy*
so it was changing some temporary value.

desugarer.go

@@ -302,8 +302,8 @@ func desugar(astPtr *astNode, objLevel int) (err error) {
 		return unimplErr
 
 	case *astLocal:
-		for _, bind := range ast.binds {
+		for i := range ast.binds {
-			err = desugar(&bind.body, objLevel)
+			err = desugar(&ast.binds[i].body, objLevel)
 			if err != nil {
 				return
 			}