From 6985b5dd9eebdc150ac1063ba7c4de2ca6991efb Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 3 Feb 2021 14:23:14 +0100
Subject: [PATCH] Let the info of opaque types always depends on the prefix

Fixes #11277
---
 compiler/src/dotty/tools/dotc/core/Types.scala | 1 +
 tests/pos/i11277.scala                         | 8 ++++++++
 2 files changed, 9 insertions(+)
 create mode 100644 tests/pos/i11277.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 59f8c37cbf55..e5b826e4f2b1 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -2299,6 +2299,7 @@ object Types {
      */
     private def infoDependsOnPrefix(symd: SymDenotation, prefix: Type)(using Context): Boolean =
       symd.maybeOwner.membersNeedAsSeenFrom(prefix) && !symd.is(NonMember)
+      || prefix.isInstanceOf[Types.ThisType] && symd.is(Opaque) // see pos/i11277.scala for a test where this matters
 
     /** Is this a reference to a class or object member? */
     def isMemberRef(using Context): Boolean = designator match {
diff --git a/tests/pos/i11277.scala b/tests/pos/i11277.scala
new file mode 100644
index 000000000000..b1dd6a2a119f
--- /dev/null
+++ b/tests/pos/i11277.scala
@@ -0,0 +1,8 @@
+class Foo {
+  opaque type Num = Int
+
+  val z = Test.id(this)(1)
+}
+object Test {
+  def id(f: Foo)(x: f.Num): f.Num = x
+}
\ No newline at end of file