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Minimal support for dependent case classes
This lets us write:
trait A:
type B
case class CC(a: A, b: a.B)
Pattern matching works but isn't dependent yet:
x match
case CC(a, b) =>
val a1: A = a
// Dependent pattern matching is not currently supported
// val b1: a1.B = b
val b1 = b // Type is CC#a.B
(for my usecase this isn't a problem, I'm working on a type constraint API
which lets me write things like `case class CC(a: Int, b: Int
GreaterThan[a.type])`)
Because case class pattern matching relies on the product selectors `_N`, making
it dependent is a bit tricky, currently we generate:
case class CC(a: A, b: a.B):
def _1: A = a
def _2: a.B = b
So the type of `_2` is not obviously related to the type of `_1`, we probably
need to change what we generate into:
case class CC(a: A, b: a.B):
@uncheckedStable def _1: a.type = a
def _2: _1.B = b
But this can be done in a separate PR.
Fixes #8073.- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| import scala.deriving.Mirror | ||
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| trait A: | ||
| type B | ||
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| object Test: | ||
| case class CC(a: A, b: a.B) | ||
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| def test1(): Unit = | ||
| val generic = summon[Mirror.Of[CC]] | ||
| // No language syntax for type projection of a singleton type | ||
| // summon[generic.MirroredElemTypes =:= (A, CC#a.B)] | ||
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| val aa: A { type B = Int } = new A { type B = Int } | ||
| val x: CC { val a: aa.type } = CC(aa, 1).asInstanceOf[CC { val a: aa.type }] // manual `tracked` | ||
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| val dependent = summon[Mirror.Of[x.type]] | ||
| summon[dependent.MirroredElemTypes =:= (A, x.a.B)] | ||
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| assert(CC(aa, 1) == generic.fromProduct((aa, 1))) | ||
| assert(CC(aa, 1) == dependent.fromProduct((aa, 1))) | ||
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| x match | ||
| case CC(a, b) => | ||
| val a1: A = a | ||
| // Dependent pattern matching is not currently supported | ||
| // val b1: a1.B = b | ||
| val b1 = b // Type is CC#a.B | ||
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| end test1 | ||
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| case class CCPoly[T <: A](a: T, b: a.B) | ||
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| def test2(): Unit = | ||
| val generic = summon[Mirror.Of[CCPoly[A]]] | ||
| // No language syntax for type projection of a singleton type | ||
| // summon[generic.MirroredElemTypes =:= (A, CCPoly[A]#a.B)] | ||
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| val aa: A { type B = Int } = new A { type B = Int } | ||
| val x: CCPoly[aa.type] = CCPoly(aa, 1) | ||
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| val dependent = summon[Mirror.Of[x.type]] | ||
| summon[dependent.MirroredElemTypes =:= (aa.type, x.a.B)] | ||
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| assert(CCPoly[A](aa, 1) == generic.fromProduct((aa, 1))) | ||
| assert(CCPoly[A](aa, 1) == dependent.fromProduct((aa, 1))) | ||
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| x match | ||
| case CCPoly(a, b) => | ||
| val a1: A = a | ||
| // Dependent pattern matching is not currently supported | ||
| // val b1: a1.B = b | ||
| val b1 = b // Type is CC#a.B | ||
|
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| end test2 | ||
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| enum Enum: | ||
| case EC(a: A, b: a.B) | ||
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| def test3(): Unit = | ||
| val generic = summon[Mirror.Of[Enum.EC]] | ||
| // No language syntax for type projection of a singleton type | ||
| // summon[generic.MirroredElemTypes =:= (A, Enum.EC#a.B)] | ||
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| val aa: A { type B = Int } = new A { type B = Int } | ||
| val x: Enum.EC { val a: aa.type } = Enum.EC(aa, 1).asInstanceOf[Enum.EC { val a: aa.type }] // manual `tracked` | ||
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| val dependent = summon[Mirror.Of[x.type]] | ||
| summon[dependent.MirroredElemTypes =:= (A, x.a.B)] | ||
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| assert(Enum.EC(aa, 1) == generic.fromProduct((aa, 1))) | ||
| assert(Enum.EC(aa, 1) == dependent.fromProduct((aa, 1))) | ||
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| x match | ||
| case Enum.EC(a, b) => | ||
| val a1: A = a | ||
| // Dependent pattern matching is not currently supported | ||
| // val b1: a1.B = b | ||
| val b1 = b // Type is Enum.EC#a.B | ||
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| end test3 | ||
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| def main(args: Array[String]): Unit = | ||
| test1() | ||
| test2() | ||
| test3() |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| import scala.deriving.Mirror | ||
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| trait A: | ||
| type B | ||
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| // Test local mirrors | ||
| @main def Test = | ||
| case class CC(a: A, b: a.B) | ||
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| def test1(): Unit = | ||
| val generic = summon[Mirror.Of[CC]] | ||
| // No language syntax for type projection of a singleton type | ||
| // summon[generic.MirroredElemTypes =:= (A, CC#a.B)] | ||
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| val aa: A { type B = Int } = new A { type B = Int } | ||
| val x: CC { val a: aa.type } = CC(aa, 1).asInstanceOf[CC { val a: aa.type }] // manual `tracked` | ||
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| val dependent = summon[Mirror.Of[x.type]] | ||
| summon[dependent.MirroredElemTypes =:= (A, x.a.B)] | ||
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| assert(CC(aa, 1) == generic.fromProduct((aa, 1))) | ||
| assert(CC(aa, 1) == dependent.fromProduct((aa, 1))) | ||
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| x match | ||
| case CC(a, b) => | ||
| val a1: A = a | ||
| // Dependent pattern matching is not currently supported | ||
| // val b1: a1.B = b | ||
| val b1 = b // Type is CC#a.B | ||
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| end test1 | ||
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| case class CCPoly[T <: A](a: T, b: a.B) | ||
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| def test2(): Unit = | ||
| val generic = summon[Mirror.Of[CCPoly[A]]] | ||
| // No language syntax for type projection of a singleton type | ||
| // summon[generic.MirroredElemTypes =:= (A, CCPoly[A]#a.B)] | ||
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| val aa: A { type B = Int } = new A { type B = Int } | ||
| val x: CCPoly[aa.type] = CCPoly(aa, 1) | ||
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| val dependent = summon[Mirror.Of[x.type]] | ||
| summon[dependent.MirroredElemTypes =:= (aa.type, x.a.B)] | ||
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| assert(CCPoly[A](aa, 1) == generic.fromProduct((aa, 1))) | ||
| assert(CCPoly[A](aa, 1) == dependent.fromProduct((aa, 1))) | ||
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| x match | ||
| case CCPoly(a, b) => | ||
| val a1: A = a | ||
| // Dependent pattern matching is not currently supported | ||
| // val b1: a1.B = b | ||
| val b1 = b // Type is CC#a.B | ||
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| end test2 | ||
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| enum Enum: | ||
| case EC(a: A, b: a.B) | ||
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| def test3(): Unit = | ||
| val generic = summon[Mirror.Of[Enum.EC]] | ||
| // No language syntax for type projection of a singleton type | ||
| // summon[generic.MirroredElemTypes =:= (A, Enum.EC#a.B)] | ||
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| val aa: A { type B = Int } = new A { type B = Int } | ||
| val x: Enum.EC { val a: aa.type } = Enum.EC(aa, 1).asInstanceOf[Enum.EC { val a: aa.type }] // manual `tracked` | ||
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| val dependent = summon[Mirror.Of[x.type]] | ||
| summon[dependent.MirroredElemTypes =:= (A, x.a.B)] | ||
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| assert(Enum.EC(aa, 1) == generic.fromProduct((aa, 1))) | ||
| assert(Enum.EC(aa, 1) == dependent.fromProduct((aa, 1))) | ||
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| x match | ||
| case Enum.EC(a, b) => | ||
| val a1: A = a | ||
| // Dependent pattern matching is not currently supported | ||
| // val b1: a1.B = b | ||
| val b1 = b // Type is Enum.EC#a.B | ||
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| end test3 | ||
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| test1() | ||
| test2() | ||
| test3() |