Enforcing the MAX_MONEY invariant is quite involved because it means
multiple things:
- Constructing amounts is now fallible
- Converting from unsigned to signed is now infallible
- Taking the absolute value is now infallible
- Integer overflow is illuminated in various places
Details:
- Update from_sat to check the invariant
- Fix all docs including examples
- Use the unchecked constructor in test code
- Comment any other use of the unchecked constructor
- Deprecate unchecked_abs
- Fail serde (using the horrible string error variant)
- Try not to use the unchecked constructor in rustdocs, no need to encourage unsuspecting users to use it.
- Use ? in rustdoc examples (required by Rust API guidlines)
- Remove TryFrom<Amount> for SignedAmount because the conversion is now infallible. Add a From impl.
- Fix the arbitrary impls
- Maintain correct formatting
- Remove private check_max function as its no longer needed
We would like to return an error when doing math ops on amount types.
We cannot however use the stdlib `Result` or `Option` because we want to
implement ops on the result type.
Add an `AmountOpResult` type. Return this type from all math operations
on `Amount` and `SignedAmount`.
Implement `core::iter::Sum` for the new type to allow summing iterators
of amounts - somewhat ugly to use, see tests for example usage.
Amount add and sub now enforce the MAX_MONEY invariant when doing
addition and subtraction. We need to tell kani to assume we don't
overflow before doing actual tests.
Note also that `ops::Add` calls through to `checked_add` and
`ops::Sub` calls through to `checked_sub` so separate kani tests for
these are unnecessary.
Tobin C. Harding
Fmt Bot