/execute @s /fill and /setblock command on a command block doesn't work.

For example: In a repeating or any other command block command block type: /execute playername ~~~ fill ~30 ~30 ~30 ~~~ air 

Activate the command using redstone.

 

Expected result: Cleared a 30×30×30 area

Current result: The command block says syntax error in the command block menu.