Improve subtyping check for not yet eta-expanded higher kinded types

Author: prolativ

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
     }

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] = ???
+}

tests/pos/i16183/Test_2.scala

@@ -0,0 +1,6 @@
+import pkg._
+
+object Test {
+  implicitly[Foo2[Qux]]
+  implicitly[Foo1[Qux]]
+}