Overflowing panics when debug asserts enabled or overflow checks?

[albertlarsan68]

Location

Methods and functions that deal with integers (non exhaustive):

• https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.position
• https://doc.rust-lang.org/stable/std/iter/struct.Enumerate.html#method.next
• https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.count
• https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.enumerate
• https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.sum
• https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.product

Summary

The documentation in these items says clearly "If debug assertions are enabled, a panic is guaranteed".
However, the configuration can be made so that a panic doesn't occur, even though the debug assertions are enabled (through disabling the overflow checks), as shown by this godbolt, while a panic is generated when oveflow checks are enabled (godbolt).
Thus, the documentation is not accurate: while it is true that most of the time that debug assertions are enabled, the overflow checks are also enabled, this is definitly not always true.
The solution would either be to adapt the implementation to the documentation, or the other way round.

[lolbinarycat]

I believe -Coverflow-checks was added after this documentation was written, the solution is to change "when debug assertions are enabled" to "when overflow checks are enabled".

[izarma]

@rustbot claim