Test case for #12950

Author: odersky

tests/pos/i12950/repro_1.scala

@@ -0,0 +1,27 @@
+package repro
+object repro:
+    object opq:
+        opaque type Lift[T] = Int
+        extension(v: Int)
+            def lift[T]: Lift[T] = v
+        extension[T](l: Lift[T])
+            def value: Int = l
+
+    export opq.Lift as Lift
+    export opq.lift as lift
+
+    final type Two
+
+    extension[TL](l: Lift[TL])
+        def repro[TR](using m: Mul[TL, TR]): Int = l.value + m.value
+
+    abstract class Mul[TL, TR]:
+        val value: Int
+
+    transparent inline given mulGivenInt[TL <: Int & Singleton, TR <: Int & Singleton]: Mul[TL, TR] =
+        val m: Int = scala.compiletime.constValue[TL] * scala.compiletime.constValue[TR]
+        new Mul[TL, TR] { val value: Int = m }
+
+    transparent inline given mulGivenTwo[TR <: Int & Singleton]: Mul[Two, TR] =
+        val m: Int = 2 * scala.compiletime.constValue[TR]
+        new Mul[Two, TR] { val value: Int = m }

tests/pos/i12950/test_2.scala

@@ -0,0 +1,6 @@
+import repro.repro.{*, given}
+
+val x = 1.lift[Two]
+val _ = x.repro[2]
+val y = 1.lift[2]
+val _ = y.repro[2]