Improved type constraint checks constrained by other generic params

IDEHelper/Compiler/BfExprEvaluator.cpp

@@ -11877,21 +11877,28 @@ void BfExprEvaluator::Visit(BfDynamicCastExpression* dynCastExpr)
 	if (targetType->IsGenericParam())
 	{
 		wasGenericParamType = true;
-		//wasGenericParamType = false; // "was", not "is"
+		BfGenericParamInstance* origGenericParam = NULL;
-		auto genericParamType = (BfGenericParamType*) targetType;
+		int pass = 0;
+		while ((targetType != NULL) && (targetType->IsGenericParam()))
+		{
+			auto genericParamType = (BfGenericParamType*)targetType;
 			auto genericParam = mModule->GetGenericParamInstance(genericParamType);
+			if (pass == 0)
+				origGenericParam = genericParam;
 			auto typeConstraint = genericParam->mTypeConstraint;
 			if ((typeConstraint == NULL) && (genericParam->mGenericParamFlags & (BfGenericParamFlag_Class | BfGenericParamFlag_Interface)))
 				typeConstraint = mModule->mContext->mBfObjectType;
-
+			targetType = typeConstraint;
-		if ((typeConstraint == NULL) || (!typeConstraint->IsObject()))
+			if (++pass >= 100) // Sanity - but we should have caught circular error before
-		{
+				break;
-			mModule->Fail(StrFormat("The type parameter '%s' cannot be used with the 'as' operator because it does not have a class type constraint nor a 'class' or 'interface' constraint",
-				genericParam->GetGenericParamDef()->mName.c_str()), dynCastExpr->mTypeRef);
-			return;
 		}
 
-		targetType = typeConstraint;		
+		if ((targetType == NULL) || (!targetType->IsObjectOrInterface()))
+		{
+			mModule->Fail(StrFormat("The type parameter '%s' cannot be used with the 'as' operator because it does not have a class type constraint nor a 'class' or 'interface' constraint",
+				origGenericParam->GetGenericParamDef()->mName.c_str()), dynCastExpr->mTypeRef);
+			return;
+		}
 	}
 
 	if (targetType->IsVar())
@@ -11930,7 +11937,7 @@ void BfExprEvaluator::Visit(BfDynamicCastExpression* dynCastExpr)
 	auto _CheckResult = [&]()
 	{
 		if ((mResult) && (origTargetType->IsGenericParam()))
-			mResult = mModule->GetDefaultTypedValue(origTargetType);		
+			mResult = mModule->GetDefaultTypedValue(origTargetType, false, BfDefaultValueKind_Undef);
 	};
 
 	if ((targetValue.mType->IsNullable()) && (targetType->IsInterface()))

IDEHelper/Compiler/BfStmtEvaluator.cpp

@@ -1198,14 +1198,23 @@ void BfModule::TryInitVar(BfAstNode* checkNode, BfLocalVariable* localVar, BfTyp
 
 	if (varType->IsGenericParam())
 	{	
-		auto genericParamType = (BfGenericParamType*) varType;
+		int pass = 0;
+		while (varType->IsGenericParam())
+		{
+			auto genericParamType = (BfGenericParamType*)varType;
+
 			auto genericParam = GetGenericParamInstance(genericParamType);
 			auto typeConstraint = genericParam->mTypeConstraint;
-		if ((typeConstraint == NULL) && (genericParam->mGenericParamFlags & BfGenericParamFlag_Class))
+			if ((typeConstraint == NULL) && (genericParam->mGenericParamFlags & (BfGenericParamFlag_Class | BfGenericParamFlag_Interface)))
 				typeConstraint = mContext->mBfObjectType;
 			if (typeConstraint != NULL)
 				varType = typeConstraint;
-		initValue = GetDefaultTypedValue(varType);
+			else
+				break;
+			if (++pass >= 100) // Sanity - but we should have caught circular error before
+				break;
+		}
+		initValue = GetDefaultTypedValue(varType, false, BfDefaultValueKind_Undef);
 	}
 
 	BfTypeInstance* srcTypeInstance = initValue.mType->ToTypeInstance();

IDEHelper/Tests/src/Generics2.bf

@@ -165,6 +165,19 @@ namespace Tests
 		public static int GenClassMethodB(GenClass<int> a) { return a.test++; }
 		public static int GenClassMethodC<A>(A a) where A : GenClass<int> { return a.test += 1; }
 
+		public static TDerived AssertSubtype<TBase, TDerived>(TBase instance)
+			where TDerived : TBase
+			where TBase : class
+		{
+			if (instance == null)
+				Runtime.FatalError();
+			if (TDerived derived = instance as TDerived)
+			{
+				return derived;
+			}
+			Runtime.FatalError();
+		}
+
 		[Test]
 		public static void TestBasics()
 		{