Waiting for named fields

One would like to write
```
case tp @ ClassInfo(cls = cls) =>
```

Author: som-snytt

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -6048,7 +6048,8 @@ object Types extends TypeUtils {
     end samParent
 
     def samClass(tp: Type)(using Context): Symbol = tp match
-      case tp @ ClassInfo(_, cls, _, _, _) =>
+      case tp: ClassInfo =>
+        val cls = tp.cls
         def takesNoArgs(tp: Type) =
           !tp.classSymbol.primaryConstructor.exists
               // e.g. `ContextFunctionN` does not have constructors