Safe maths are not correctly applied in compiled contracts

[Robbepop]

For asserting that overflow checks are enabled in Rust compiled smart contracts we include the following lines into Cargo.toml files:

[profile.release]
overflow-checks = true

However, when inspecting the compiled Incrementer example found here we can clearly see that it deterministically underflows and overflows when given certain values. E.g. when the current value of a deployed Incrementer contract is -42 and we decrease it by 2^32-1 we receive -41 as result but instead we expect it to trap.

Thanks to @TriplEight for reporting this bug. 🎉

[SkymanOne]

Overflow checks have been disabled in #1831

ERROR: Overflow checks must be disabled. Cargo contract makes sure that no unchecked arithmetic is used.