"Is block replaceable?" option for blocks and plants

Some vanilla blocks, such as snow layer and dead bush, can be replaced just by placing a block instead of having to break them first. (This behavior is also applied by choosing certain materials, but this can't be done for plant elements)
The required code is

@Override
		public boolean isReplaceable(IBlockAccess worldIn, BlockPos pos)
    	{
       		return true;
    	}