Merge pull request #3580 from RZhang05/unwrap-optionals-with-dynamic-…

…cast

Unwrap optionals with dynamic cast

runtime/interpreter/interpreter_expression.go

@@ -1335,6 +1335,13 @@ func (interpreter *Interpreter) VisitCastingExpression(expression *ast.CastingEx
 		// thus this is the only place where it becomes necessary to "instantiate" the result of a map to its
 		// concrete outputs. In other places (e.g. interface conformance checks) we want to leave maps generic,
 		// so we don't substitute them.
+
+		// if the target is anystruct or anyresource we want to preserve optionals
+		unboxedExpectedType := sema.UnwrapOptionalType(expectedType)
+		if !(unboxedExpectedType == sema.AnyStructType || unboxedExpectedType == sema.AnyResourceType) {
+			// otherwise dynamic cast now always unboxes optionals
+			value = interpreter.Unbox(locationRange, value)
+		}
 		valueSemaType := interpreter.SubstituteMappedEntitlements(interpreter.MustSemaTypeOfValue(value))
 		valueStaticType := ConvertSemaToStaticType(interpreter, valueSemaType)
 		isSubType := interpreter.IsSubTypeOfSemaType(valueStaticType, expectedType)