Fix exception

Author: liufengyun

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

@@ -230,7 +230,7 @@ object Summarization {
         Summary.empty
 
       case thisTp: ThisType =>
-        val cls = thisTp.widen.classSymbol.asClass
+        val cls = thisTp.tref.classSymbol.asClass
         Summary.empty + ThisRef(cls)(source)
 
       case SuperType(thisTp, superTp) =>

tests/init/crash/i7821.scala

@@ -0,0 +1,24 @@
+object XObject {
+  opaque type X = Int
+
+  def anX: X = 5
+
+  given ops as Object {
+    def (x: X) + (y: X): X = x + y
+  }
+}
+
+object MyXObject {
+  opaque type MyX = XObject.X
+
+  def anX: MyX = XObject.anX
+
+  given ops as Object {
+    def (x: MyX) + (y: MyX): MyX = x + y // error: warring: Infinite recursive call
+  }
+}
+
+object Main extends App {
+  println(XObject.anX + XObject.anX) // prints 10
+  println(MyXObject.anX + MyXObject.anX) // infinite loop
+}