Also, this commit makes `apply_term` automatically re-intern the
program since it isn't safe to apply any term onto a UPLC program. In
particular, terms that introduce new let-bindings (via lambdas) will
mess with the already generated DeBruijn indices.
The problem doesn't occur for pure constant terms like Data. So we
still have a safe and fast version 'apply_data' when needed.
This is very very rough at the moment. But it does a couple of thing:
1. The 'ArgVia' now contains an Expr/TypedExpr which should unify to a Fuzzer. This is to avoid having to introduce custom logic to handle fuzzer referencing. So this now accepts function call, field access etc.. so long as they unify to the right thing.
2. I've done quite a lot of cleanup in aiken-project mostly around the tests and the naming surrounding them. What we used to call 'Script' is now called 'Test' and is an enum between UnitTest (ex-Script) and PropertyTest. I've moved some boilerplate and relevant function under those module Impl.
3. I've completed the end-to-end pipeline of:
- Compiling the property test
- Compiling the fuzzer
- Generating an initial seed
- Running property tests sequentially, threading the seed through each step.
An interesting finding is that, I had to wrap the prop test in a similar wrapper that we use for validator, to ensure we convert primitive types wrapped in Data back to UPLC terms. This is necessary because the fuzzer return a ProtoPair (and soon an Array) which holds 'Data'.
At the moment, we do nothing with the size, though the size should ideally grow after each iteration (up to a certain cap).
In addition, there are a couple of todo/fixme that I left in the code as reminders of what's left to do beyond the obvious (error and success reporting, testing, etc..)
We've been wrongly representing large ints as BigInt, causing them to
behave differently in the VM through builtins like 'serialise_data'.
Indeed, we expect anything that fits in 8 bytes to be encoded as Major
Type 0 or 1. But we were switching to encoding as Major type 6
(tagged, PosBigInt, NegBigInt) for much smaller values! Anything
outside of the range [-2^32, 2^32-1] would be treated as big int
(positive or negative).
Why? Because we checked whether a value i would fit in an i64, and if
it didn't we treated it as big int. But the reality is more subtle...
Fortunately, Rust has i128 and the minicbor library implements TryFrom
which enforces that the value fits in a range of [-2^64, 2^64 - 1], so
we're back on track easily.
