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Refine the bounds of the Tuple.Filter type lambda predicate .. #21286

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Merged
merged 1 commit into from
Nov 11, 2024
Merged

Refine the bounds of the Tuple.Filter type lambda predicate .. #21286

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2 changes: 1 addition & 1 deletion library/src/scala/Tuple.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ object Tuple {
* ```
* @syntax markdown
*/
type Filter[Tup <: Tuple, P[_] <: Boolean] <: Tuple = Tup match {
type Filter[Tup <: Tuple, P[_ <: Union[Tup]] <: Boolean] <: Tuple = Tup match {
case EmptyTuple => EmptyTuple
case h *: t => P[h] match {
case true => h *: Filter[t, P]
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12 changes: 12 additions & 0 deletions tests/neg/tuple-filter-compat.scala
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@@ -0,0 +1,12 @@

type OldFilter[Tup <: Tuple, P[_] <: Boolean] = Nothing
type NewFilter[Tup <: Tuple, P[_ <: Tuple.Union[Tup]] <: Boolean] = Nothing

trait A:
type X >: OldFilter <: OldFilter

trait B1 extends A:
type X = OldFilter // ok

trait B2 extends A:
type X = NewFilter // error: breaking change
6 changes: 6 additions & 0 deletions tests/pos/tuple-filter.scala
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@@ -1,10 +1,16 @@
import scala.compiletime.ops.int.<

type P[x] <: Boolean = x match {
case 3 => false
case _ => true
}

type RejectAll[x] = false

type Pos[X <: Int] = 0 < X

def Test =
summon[Tuple.Filter[(1, 2, 3, 4), P] =:= (1, 2, 4)]
summon[Tuple.Filter[(1, 2, 3, 4), RejectAll] =:= EmptyTuple]
summon[Tuple.Filter[EmptyTuple, P] =:= EmptyTuple]
summon[Tuple.Filter[(1, -2, 3, -4), Pos] =:= (1, 3)]
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