Add debug code

Author: odersky

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

@@ -5944,6 +5944,16 @@ object Types extends TypeUtils {
 
     def samClass(tp: Type)(using Context): Symbol = tp match
       case tp: ClassInfo =>
+        val cls = tp.cls
+        def zeroParamsOLD(tp: Type): Boolean = tp.stripPoly match
+          case mt: MethodType => mt.paramInfos.isEmpty && !mt.resultType.isInstanceOf[MethodType]
+          case et: ExprType => true
+          case _ => false
+        val validCtorOLD =
+          val ctor = cls.primaryConstructor
+          // `ContextFunctionN` does not have constructors
+          !ctor.exists || zeroParamsOLD(ctor.info)
+
         def zeroParams(tp: Type): Boolean = tp.stripPoly match
           case mt: MethodType =>
             val noArgsNeeded = mt.paramInfos match
@@ -5957,9 +5967,14 @@ object Types extends TypeUtils {
           val ctor = cls.primaryConstructor
           (!ctor.exists || zeroParams(ctor.info)) // `ContextFunctionN` does not have constructors
           && (!cls.is(Trait) || validCtor(cls.info.parents.head.classSymbol))
+        val validCtorNEW = validCtor(tp.cls)
+
+        if validCtorNEW != validCtorOLD then
+          println(i"SAM change for $tp with parent ${cls.info.parents.head.classSymbol.fullName}, now $validCtorNEW")
+
         def isInstantiable =
           !tp.cls.isOneOf(FinalOrSealed) && (tp.appliedRef <:< tp.selfType)
-        if validCtor(tp.cls) && isInstantiable then tp.cls
+        if validCtorNEW && isInstantiable then tp.cls
         else NoSymbol
       case tp: AppliedType =>
         samClass(tp.superType)