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KacperFKorban opened this issue Feb 6, 2025 · 0 comments · Fixed by #22543
Closed

Support "Applied Constructor Types" #22542

KacperFKorban opened this issue Feb 6, 2025 · 0 comments · Fixed by #22543
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@KacperFKorban
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area:experimental:modularity Issues related to the modularity extension. itype:enhancement

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@KacperFKorban
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Example

Under modularity, it should be possible to have a shorter way for writing precise types of class applications (for classes with tracked parameters)

For example, it should be possible to write the following code:

import scala.language.experimental.modularity

class Box(tracked val v: Any)

val c: C(42) /* ≡ C { val v: 42 } */ = C(42)
@KacperFKorban KacperFKorban added area:experimental:modularity Issues related to the modularity extension. itype:enhancement labels Feb 6, 2025
@KacperFKorban KacperFKorban self-assigned this Feb 6, 2025
@KacperFKorban KacperFKorban mentioned this issue Feb 6, 2025
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odersky pushed a commit to dotty-staging/dotty that referenced this issue May 12, 2025
@KacperFKorban @mbovel @odersky
Implement applied constructor types (scala#22543)
7952eba 
closes scala#22542 

Introduce new syntax to make classes with `tracked` parameters
easier to use. The new syntax is essentially the ability to use an
application
of a class constructor as a type, we call such types applied constructor
types.

With this new feature the following example compiles correctly and the
type in
the comment is the resulting type of the applied constructor types.

```scala
import scala.language.experimental.modularity

class C(tracked val v: Any)

val c: C(42) /* C { val v: 42 } */ = C(42)
```

### Syntax change

```
SimpleType        ::=  SimpleLiteral
                    |  ‘?’ TypeBounds
---                 |  SimpleType1
+++                 |  SimpleType1 {ParArgumentExprs}
```

A `SimpleType` can now optionally be followed by `ParArgumentExprs`.

---------

Co-authored-by: Matt Bovel <[email protected]>
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area:experimental:modularity Issues related to the modularity extension. itype:enhancement
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Implement applied constructor types dotty-staging/dotty
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