Merge pull request #8494 from dotty-staging/fix-7872

Fix #7872: Add regression test

Author: nicolasstucki

compiler/test/dotc/pos-test-pickling.blacklist

@@ -25,6 +25,7 @@ matchtype.scala
 6322.scala
 i7087.scala
 i7868.scala
+i7872.scala
 
 # Opaque type
 i5720.scala
@@ -37,4 +38,4 @@ i7580.scala
 nullable.scala
 
 # parameter untupling with overloaded functions (see comment in Applications.normArg)
-i7757.scala
+i7757.scala

tests/pos/i7872.scala

@@ -0,0 +1,23 @@
+object Test {
+  def flip: (x: 0 | 1) => x.type match { case 0 => 1 case 1 => 0 } = ???
+  flip(0): 1
+  flip(1): 0
+  flip(if ??? then 0 else 1)
+  val n: 0 | 1 = if ??? then 0 else 1
+  flip(n)
+  val m: n.type match { case 0 => 1 case 1 => 0 } = flip(n)
+}
+
+object Test2 {
+  type Flip[N <: 0 | 1] <: 0 | 1 = N match { case 0 => 1 case 1 => 0 }
+  def flip: (x: 0 | 1) => Flip[x.type] = ???
+  flip(0): 1
+  flip(1): 0
+}
+
+object Test3 {
+  type Flip[N <: 0 | 1] <: 0 | 1 = N match { case 0 => 1 case 1 => 0 }
+  def flip(x: 0 | 1): Flip[x.type] = ???
+  flip(0): 1
+  flip(1): 0
+}