- We now consistently desugar an expect in the last position as
`Void`. Regardless of the pattern. Desugaring to a boolean value is
deemed too confusing.
- This commit also removes the desugaring for let-binding. It's only
ever allowed for _expect_ which then behaves like a side effect.
- We also now allow tests to return either `Bool` or `Void`. A test
that returns `Void` is treated the same as a test returning `True`.
The spirit here is to make it easier to discover this syntax. People
have different intuition about it and the single pipe may not be the
most obvious one.
It is however the recommended syntax, and the formatter will rewrite
any of the other to it.
- Doesn't allow pattern-matching on G1/G2 elements and strings,
because the use cases for those is unclear and it adds complexity to
the feature.
- We still _parse_ patterns on G1/G2 elements and strings, but emit an
error in those cases.
- The syntax is the same as for bytearray literals (i.e. supports hex,
utf-8 strings or plain arrays of bytes).
We've never been using those 'expected' tokens captured during
parsing, which is lame because they contain useful information!
This is much better than merely showing our infamous
"Try removing it!"
This commit introduces a new feature into
the parser, typechecker, and formatter.
The work for code gen will be in the next commit.
I was able to leverage some existing infrastructure
by making using of `AssignmentPattern`. A new field
`is` was introduced into `IfBranch`. This field holds
a generic `Option<Is>` meaning a new generic has to be
introduced into `IfBranch`. When used in `UntypedExpr`,
`IfBranch` must use `AssignmentPattern`. When used in
`TypedExpr`, `IfBranch` must use `TypedPattern`.
The parser was updated such that we can support this
kind of psuedo grammar:
`if <expr:condition> [is [<pattern>: ]<annotation>]`
This can be read as, when parsing an `if` expression,
always expect an expression after the keyword `if`. And then
optionally there may be this `is` stuff, and within that you
may optionally expect a pattern followed by a colon. We will
always expect an annotation.
This first expression is still saved as the field
`condition` in `IfBranch`. If `pattern` is not there
AND `expr:condition` is `UntypedExpr::Var` we can set
the pattern to be `Pattern::Var` with the same name. From
there shadowing should allow this syntax sugar to feel
kinda magical within the `IfBranch` block that follow.
The typechecker doesn't need to be aware of the sugar
described above. The typechecker looks at `branch.is`
and if it's `Some(is)` then it'll use `infer_assignment`
for some help. Because of the way that `is` can inject
variables into the scope of the branch's block and since
it's basically just like how `expect` works minus the error
we get to re-use that helper method.
It's important to note that in the typechecker, if `is`
is `Some(_)` then we do not enforce that `condition` is
of type `Bool`. This is because the bool itself will be
whether or not the `is` itself holds true given a PlutusData
payload.
When `is` is None, we do exactly what was being done
previously so that plain `if` expressions remain unaffected
with no semantic changes.
The formatter had to be made aware of the new changes with
some simple changes that need no further explanation.
This is mainly a syntactic trick/sugar, but it's been pretty annoying
to me for a while that we can't simply pattern-match/destructure
single-variant constructors directly from the args list. A classic
example is when writing property tests:
```ak
test foo(params via both(bytearray(), int())) {
let (bytes, ix) = params
...
}
```
Now can be replaced simply with:
```
test foo((bytes, ix) via both(bytearray(), int())) {
...
}
```
If feels natural, especially coming from the JavaScript, Haskell or
Rust worlds and is mostly convenient. Behind the scene, the compiler
does nothing more than re-writing the AST as the first form, with
pre-generated arg names. Then, we fully rely on the existing
type-checking capabilities and thus, works in a seamless way as if we
were just pattern matching inline.
There's no reasons for this to be a property of only ArgName::Named to begin with. And now, with the extra indirection introduced for arg_name, it may leads to subtle issues when patterns args are used in validators.
I slightly altered the way we parse import definitions to ensure we
merge imports from the same modules (that aren't aliased) together.
This prevents an annoying warning with duplicated import lines and
makes it just more convenient overall.
As a trade-off, we can no longer interleave import definitions with
other definitions. This should be a minor setback only since the
formatter was already ensuring that all import definitions would be
grouped at the top.
---
Note that, I originally attempted to implement this in the formatter
instead of the parser. As it felt more appropriate there. However, the
formatter operates on (unmutable) borrowed definitions, which makes it
annoyingly hard to perform any AST manipulations. The `Document`
returns by the format carries a lifetime that prevents the creation of
intermediate local values.
So instead, slightly tweaking the parser felt like the right thing to
do.
While we agree on the idea of having some ways of emitting events, the
design hasn't been completely fleshed out and it is unclear whether
events should have a well-defined format independent of the framework
/ compiler and what this format should be.
So we need more time discussing and agreeing about what use case we
are actually trying to solve with that.
Irrespective of that, some cleanup was also needed on the UPLC side
anyway since the PR introduced a lot of needless duplications.
Refactor get_uplc_type to account for constr types that don't exactly resolve to a uplc type
Check arg_stack in uplc generator has only 1 argument at the end of the generation
warning fixes
Before this commit, we would parse 'Pair' as a user-defined
data-types, and thus piggybacking on that whole record system. While
perhaps handy for some things, it's also semantically wrong and
induces a lot more complexity in codegen which now needs to
systematically distinguish every data-type access between pairs, and
others.
So it's better to have it as a separate expression, and handle it
similar to tuples (since it's fundamentally a 2-tuple with a special
serialization).
And a few more tests along the way for others. Note that it is important here that we try to parse for a 'Pair' BEFORE we try to parse for a constructor pattern. Because the latter would swallow any Pair pattern.
The main trick here was transforming Assignment
to contain `Vec<UntypedPattern, Option<Annotation>>`
in a field called patterns. This then meant that I
could remove the `pattern` and `annotation` field
from `Assignment`. The parser handles `=` and `<-`
just fine because in the future `=` with multi
patterns will mean some kind of optimization on tuples.
But, since we don't have that optimization yet, when
someone uses multi patterns with an `=` there will be an
error returned from the type checker right where `infer_seq`
looks for `backpassing`. From there the rest of the work
was in `Project::backpassing` where I only needed to rework
some things to work with a list of patterns instead of just one.
The 3rd kind of assignment kind (Bind) is gone and now reflected through a boolean parameter. Note that this parameter is completely erased by the type-checker so that the rest of the pipeline (i.e. code-generation) doesn't have to make any assumption. They simply can't see a backpassing let or expect.
We'll piggyback on the tracing capabilities of the VM to provide labelling for prop tests. To ensure we do not interfere with normal traces, we only count traces that starts with a NUL byte as label. That convention is assumed to be known of the companion fuzz library that should then provide the labelling capabilities as a dedicated function.
Somehow, these have always been right-associative, when the natural thing to expect is left-associativity. It now matters when trying to crawl down binary tree to display them properly.
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..)
The parameter is special as it takes no annotation but a 'via' keyword followed by an expression that should unify to a Fuzzer<a>, where Fuzzer<a> = fn(Seed) -> (Seed, a). The current commit only allow name identifiers for now. Ultimately, this may allow full expressions.
Note that the formatter rewrite parens-block sequences as curly-block
sequences anyway. Albeit weird looking syntax, they are valid
nonetheless.
I also clarified a bit the hints and description of the
'illegal::return' error as it would mistakenly say 'function' instead
of 'block'.
rvcas