function to return uint256 requires all code paths to return uint256

[ethers]

if there is a single return that not uint256, for example return(0), the contract function never returns uint256.

In the example below, since there is a single return(0) where uint256 was forgotten, the function never returns uint256 even when x is 2,3,4...

if x==1:
  return(0)
if x==2:
  return(-1:uint256)
if x==3:
  return(-1:uint256)
if x==4:
  return(-1:uint256)