Fix #17997: Handle intersection type as this type of super type (#18069)

Fix #17997: Handle intersection type as this type of super type

Author: olhotak

compiler/src/dotty/tools/dotc/transform/init/Semantic.scala

@@ -1229,7 +1229,20 @@ object Semantic:
         ref match
         case Select(supert: Super, _) =>
           val SuperType(thisTp, superTp) = supert.tpe: @unchecked
-          val thisValue2 = extendTrace(ref) { resolveThis(thisTp.classSymbol.asClass, thisV, klass) }
+          val thisValue2 = extendTrace(ref) {
+            thisTp match
+            case thisTp: ThisType             =>
+              cases(thisTp, thisV, klass)
+
+            case AndType(thisTp: ThisType, _) =>
+              // Self-type annotation will generate an intersection type for `this`.
+              // See examples/i17997.scala
+              cases(thisTp, thisV, klass)
+
+            case _ =>
+              report.warning("[Internal error] Unexpected type " + thisTp.show + ", trace:\n" + Trace.show, ref)
+              Hot
+          }
           withTrace(trace2) { thisValue2.call(ref.symbol, args, thisTp, superTp) }
 
         case Select(qual, _) =>

tests/init/pos/i17997.scala

@@ -0,0 +1,20 @@
+abstract class FunSuite:
+  def foo(): Unit = println("FunSuite")
+
+  foo()
+
+trait MySelfType
+
+trait MyTrait extends FunSuite { this: MySelfType =>
+}
+
+abstract class MyAbstractClass extends FunSuite { this: MySelfType =>
+
+  override def foo() = {
+    println("MyAbstractClass")
+    super.foo()
+  }
+}
+
+final class MyFinalClass extends MyAbstractClass with MyTrait with MySelfType:
+  val n: Int = 100