Replaceasserts with require

[emizzle]

See comment #144 (comment).

[markspanbroek]

There is a semantic difference between require() and assert(). Preconditions such as requirements on a function's input are handled by require(), Things that a programmer thinks should never happen are handled by assert().
This semantic difference is for example used by echidna for fuzzing. They use require() to ensure that fuzzed input values match expected ranges, and then check that assertions don't happen.

Also I expect there to be a good reason why asserts eat up all the gas; maybe to ensure that exceptions are not caught and then handled elsewhere. It could be a security property that ensures that execution really stops.

[0x-r4bbit]

@markspanbroek you're not wrong, and we're probably entering the space of bike shedding here.
I'd extend the definition of where/when to use require to "use for conditions that depend on external factors the code doesn't control", which is user inputs as you've described, but also external calls like transferring tokens.
This also allows for providing proper custom errors (which asserts don't allow for).

Assertions are more appropriate for internal checks and typically used for cases when there's a serious internal error to your code.

Ultimately it's your decision, but I at least wanted to bring it up.

[markspanbroek]

Ah, good point @0x-r4bbit, the call to the ERC20 contract can indeed be seen as an external call which the code doesn't control. Using require() does make sense there. I read the description of this issue as "we're going to replace all asserts with requires".