- 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).
The original goal for this commit was to allow casting from Data on
patterns without annotation. For example, given some custom type
'OrderDatum':
```
expect OrderDatum { requested_handle, destination, .. }: OrderDatum = datum
```
would work fine, but:
```
expect OrderDatum { requested_handle, destination, .. } = datum
```
Yet, the annotation feels unnecessary at this point because type can
be inferred from the pattern itself. So this commit allows, whenever
possible (ie when the pattern is neither a discard nor a var), to
infer the type from a pattern.
Along the way, I also found a couple of weird behaviours surrounding
this kind of assignments, in particular in combination with let. I'll
highlight those in the next PR (#979).
Currently, pattern-matching on 'Pair' is handled by treating Pair as a
record, which comes as slightly odd given that it isn't actually a
record and isn't user-defined. Thus now, every use of a record must
distinguish between Pairs and other kind of records -- which screams
for another variant constructor instead.
We cannot use `Tuple` either for this, because then we have no ways to
tell 2-tuples apart from pairs, which is the whole point here. So the
most sensical thing to do is to define a new pattern `Pair` which is
akin to tuples, but simpler since we know the number of elements and
it's always 2.
is_assignment was a bit confusing to me since we do actually categorize expect as 'assignment'. So this is more about whether this is a *let* assignment. Hence 'is_let'.
The typed-AST produced as a result of type-checking the program will
no longer contain unused let-bindings. They still raise warnings in
the code so that developers are aware that they are being ignore.
This is mainly done to prevent mistakes for people coming from an
imperative background who may think that things like:
```
let _ = foo(...)
```
should have some side-effects. It does not, and it's similar to
assigned variables that are never used / evaluated. We now properly
strip those elements from the AST when encountered and raise proper
warnings, even for discarded values.
There's arguably no use case ever for that in the context of on-chain
Plutus. Strings are really just meant to be used for tracing. They
aren't meant to be manipulated as heavily as in classic programming
languages.
I decided to invert how I'm doing it. I'm passing
in a new argument to unify in environment called
allow_cast: bool and essentially at various
unification sites I can control whether or not I
want to allow casting to even occur. So we can
assume it's false by default always and then we
turn it on in a few places vs. just opening the
flood gates and locking it down at various sites
as they come up# Please enter the commit message
for your changes. Lines starting
This is a bit annoying as we are forced to use #[related] here which isn't quite what we want.
Ideally, this would use #[diagnostic_source] but, there's a bug upstream. See: zkat/miette#172.
## Before
```
× Checking
╰─▶ Unexpected labeled argument
t
╭─[/Users/mati/Devel/OpenSource/time_lock_aiken/validators/time_lock.ak:13:1]
13 │ let now = when context.transaction.validity_range.lower_bound.bound_type is {
14 │ Finite { t } -> t
· ─
15 │ NegativeInfinity -> 0
╰────
```
## After
```
× Type-checking
╰─▶ Unexpected labeled argument 't'
╭─[../stdlib/validators/tmp.ak:10:1]
10 │ let now = when context.transaction.validity_range.lower_bound.bound_type is {
11 │ interval.Finite { t } -> t
· ─
12 │ interval.NegativeInfinity -> 0
╰────
help: The constructor 'Finite' does not have any labeled field. Its fields
must therefore be matched only by position.
Perhaps, try the following:
╰─▶ interval.Finite(t)
```
KtorZ