It is now possible to leave a hole in a type annotation and have the compiler fill-in the expected type of us.
This is a pretty useful debugging tool when playing with complex functions.
Before that commit, the type-checker would allow unsafe list patterns
such as:
```
let [x] = xs
when xs is {
[x] -> ...
[x, ..] -> ...
}
```
This is quite unsafe and can lead to confusing situations. Now at
least the compiler warns about this. It isn't perfect though,
especially in the presence of clause guards. But that's a start.
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
* you cannot cast FROM Data with a `let`
* you cannot cast FROM Data by passing
Data to none Data when calling a function
* you MUST use `assert` to cast from data
* you can cast INTO Data with a `let`
* you can cast INTO Data by passing none Data
to Data when calling a function
* You cannot assert cast Data without an
annotation
## Before
```
× Type-checking
╰─▶ Unknown module field 'ValidityRaneg' in module 'aiken/transaction'
```
## After
```
× Type-checking
╰─▶ Unknown import 'ValidityRaneg' from module 'aiken/transaction'
╭─[../stdlib/validators/tmp.ak:2:1]
2 │ use aiken/interval.{Interval, IntervalBound, IntervalBoundType}
3 │ use aiken/transaction.{ScriptContext, ValidityRaneg}
· ─────────────
4 │
╰────
help: Did you mean to import 'ValidityRange'?
```
## 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)
```
## Before
```
× Checking
╰─▶ Unknown variable
Finite
╭─[../stdlib/validators/tmp.ak:10:1]
10 │ let now = when context.transaction.validity_range.lower_bound.bound_type is {
11 │ Finite { t } -> t
· ────────────
12 │ NegativeInfinity -> 0
╰────
```
## After
```
× Type-checking
╰─▶ Unknown data-type constructor 'Finite'
╭─[../stdlib/validators/tmp.ak:10:1]
10 │ let now = when context.transaction.validity_range.lower_bound.bound_type is {
11 │ Finite { t } -> t
· ────────────
12 │ NegativeInfinity -> 0
╰────
help: Did you forget to import it?
Data-type constructors are not automatically imported, even if their type is
imported. So, if a module `aiken/pet` defines the following type:
┍━ aiken/pet.ak ━━━━━━━━
│ pub type Pet {
│ Cat
│ Dog
│ }
You must import its constructors explicitly to use them, or prefix them
with the module's name.
┍━ foo.ak ━━━━━━━━
│ use aiken/pet.{Pet, Dog}
│
│ fn foo(pet : Pet) {
│ when pet is {
│ pet.Cat -> // ...
│ Dog -> // ...
│ }
│ }
```
rvcas