From 03a8f644c2b99073c2cca79e4d2c01539fa3391a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Pa=C5=82ka?= <prolativus@gmail.com>
Date: Wed, 22 Mar 2023 13:09:33 +0100
Subject: [PATCH] Improve subtyping check for not yet eta-expanded higher
 kinded types

---
 .../src/dotty/tools/dotc/core/TypeComparer.scala   |  2 +-
 tests/pos/i16183/Lib_1.scala                       | 14 ++++++++++++++
 tests/pos/i16183/Test_2.scala                      |  6 ++++++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i16183/Lib_1.scala
 create mode 100644 tests/pos/i16183/Test_2.scala

diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 9dda18c72f26..ac6a6b9481d8 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -580,7 +580,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
             val base = nonExprBaseType(tp1, cls2)
             if (base.typeSymbol == cls2) return true
           }
-          else if tp1.isLambdaSub && !tp1.isAnyKind then
+          else if tp1.typeParams.nonEmpty && !tp1.isAnyKind then
             return recur(tp1, EtaExpansion(tp2))
         fourthTry
     }
diff --git a/tests/pos/i16183/Lib_1.scala b/tests/pos/i16183/Lib_1.scala
new file mode 100644
index 000000000000..824af18e1d40
--- /dev/null
+++ b/tests/pos/i16183/Lib_1.scala
@@ -0,0 +1,14 @@
+package pkg
+
+trait Foo1[A]
+trait Foo2[A] extends Foo1[A]
+
+trait Bar[F[_]]
+object Bar {
+  implicit val bar: Bar[pkg.Foo2] = ???
+}
+
+trait Qux
+object Qux {
+  implicit def qux[F[_]](implicit bar: Bar[F]): F[Qux] = ???
+}
\ No newline at end of file
diff --git a/tests/pos/i16183/Test_2.scala b/tests/pos/i16183/Test_2.scala
new file mode 100644
index 000000000000..c8c5cbed838c
--- /dev/null
+++ b/tests/pos/i16183/Test_2.scala
@@ -0,0 +1,6 @@
+import pkg._
+
+object Test {
+  implicitly[Foo2[Qux]]
+  implicitly[Foo1[Qux]]
+}
\ No newline at end of file