Solidity : Unsafe type inference

Solidity supports type inference: the type of i in var i = 42; is the smallest integer type sufficient to store the right-hand side value (uint8). Consider a common for-loop pattern:

for (var i = 0; i < array.length; i++) { /* ... */ }

The type of i is inferred to uint8. If array.length is bigger than 255, an overflow will occur. Explicitly define the type when declaring integer variables:

for (uint256 i = 0; i < array.length; i++) { /* ... */ }