A minimal implementation of Rust's Result type. Used for contract
methods that return Results, to maintain their distinction from methods
that simply either return a value or throw.
Why is this needed?
This is used by ContractSpec and
AssembledTransaction when
parsing values return by contracts.
Contract methods can be implemented to return simple values, in which case
they can also throw errors. This matches JavaScript's most idiomatic
workflow, using try...catch blocks.
But Rust also gives the flexibility of returning Result types. And Soroban
contracts further support this with the #[contracterror] macro. Should
JavaScript calls to such methods ignore all of that, and just flatten this
extra info down to the same try...catch flow as other methods? We're not
sure.
For now, we've added this minimal implementation of Rust's Result logic,
which exports the Result interface and its associated implementations,
Ok and Err. This allows ContractSpec and AssembledTransaction to
work together to duplicate the contract's Rust logic, always returning
Result types for contract methods that are implemented to do so.
In the future, if this feels too un-idiomatic for JavaScript, we can always
remove this and flatten all JS calls to try...catch. Easier to remove this
logic later than it would be to add it.