From 2a7296e6a605d57bee827842314687c726f5db54 Mon Sep 17 00:00:00 2001
From: Olivier Blanvillain <olivier.blanvillain@gmail.com>
Date: Thu, 9 Apr 2020 20:26:37 +0200
Subject: [PATCH] Fix #8647: Remove TypeParamRef from instantiated test

---
 .../dotty/tools/dotc/core/TypeComparer.scala  |  2 +-
 tests/pos/8647.scala                          | 53 +++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/8647.scala

diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index e2ba1745c1d3..5744461c1ca0 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -2359,7 +2359,7 @@ class TypeComparer(initctx: Context) extends ConstraintHandling[AbsentContext] w
                     x && {
                       t match {
                         case tp: TypeRef if tp.symbol.isAbstractOrParamType => false
-                        case _: SkolemType | _: TypeVar | _: TypeParamRef => false
+                        case _: SkolemType | _: TypeVar => false
                         case _ => foldOver(x, t)
                       }
                     }
diff --git a/tests/pos/8647.scala b/tests/pos/8647.scala
new file mode 100644
index 000000000000..5e8f839b27ca
--- /dev/null
+++ b/tests/pos/8647.scala
@@ -0,0 +1,53 @@
+final class Two[A, B]()
+
+final class Blaaa
+
+final class Bla[X]
+
+object Test1 {
+
+  type Foo[X] = X match
+    case Two[Blaaa, _] =>
+      String
+    case Two[String, _] =>
+      Int
+
+  def test: Foo[Two[String, String]] = 1
+}
+
+object Test2 {
+  type Foo[X] = X match
+    case Two[Bla[_], _] =>
+      String
+    case Two[String, _] =>
+      Int
+
+  def test: Foo[Two[String, String]] = 1
+}
+
+
+object Test3 {
+  type Id[W] = W
+
+  type M[X, Y] = X match {
+    case Int   => String
+    case Id[x] => Y match {
+      case Two[Bla[a], _] => Int
+      case _ => String
+    }
+  }
+  val x: M[Boolean, Two[Boolean, Boolean]] = ""
+}
+
+object Test4 {
+  type Id[W] = W
+
+  type M[X, Y] = X match {
+    case Int   => String
+    case Id[x] => Y match {
+      case Two[Bla[`x`], _] => Int
+      case _ => String
+    }
+  }
+  val x: M[Boolean, Two[Bla[Boolean], Boolean]] = 1
+}