Fix #5455: Fix computation of companion object of opaque type

Author: odersky

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -985,7 +985,7 @@ object SymDenotations {
       if (is(Module)) sourceModule
       else if (isOpaqueAlias)
         info match {
-          case TypeAlias(TypeRef(TermRef(prefix, _), _)) => prefix.termSymbol
+          case TypeAlias(TypeRef(prefix: TermRef, _)) => prefix.termSymbol
         }
       else registeredCompanion.sourceModule
 

tests/pos/i5455.scala

@@ -0,0 +1,42 @@
+object Library {
+
+  opaque type Nat = Int
+
+  object Nat {
+    def apply(n: Int): Nat = {
+      require(n >= 0)
+      n
+    }
+    def times(x: Nat, y: Nat): Nat = x * y
+    def toInt(n: Nat): Int = n
+
+    implicit class NatOps(val self: Nat) extends AnyVal {
+      def *(other: Nat): Nat = self * other
+      def toInt: Int = self.asInstanceOf
+    }
+  }
+}
+
+object User extends App {
+  import Library._
+
+  val x = Nat(3)
+  val y = Nat(4)
+
+  val a = x * y               // inferred type is Library.Nat.Nat
+  val b = double1(x)          // inferred type is Library.Nat
+  val c = double2(x)          // inferred type is Library.Nat.Nat
+
+  assert(a.toInt == 12)       // works
+  //assert(b.toInt == 6)      // error: toInt is not a member of Library.Nat
+  assert(c.toInt == 6)        // works
+
+  def double0(n: Nat): Nat = n * Nat(2) // ok
+
+  def double3(n: Nat): Nat = Nat.NatOps(n) * Nat(2) // ok
+
+
+  def double1(n: Nat.Nat): Nat = n * Nat(2)     // output type is incorrect
+
+  def double2(n: Nat.Nat): Nat.Nat =n * Nat(2)  // works
+}