expression : '{' commalist '}'
                  | kw_array '[' commalist ']'

def p_array(self,t):
    """expression : '{' commalist '}'
                  | kw_array '[' commalist ']'
    """
    if len(t)==4: t[0] = ArrayLit(t[2].children)
    elif len(t)==5: t[0] = ArrayLit(t[3].children)
    else: raise NotImplementedError('unk_len',len(t)) # pragma: no cover