anchor.diff:        if (returnType is InterfaceType) {
           if (returnType.classNode == handleClass) {
             diagnosticReporter.report(messageFfiLeafCallMustNotReturnHandle,
  -              node.fileOffset, 1, node.location.file);
  +              node.fileOffset, 1, node.location?.file);
           }
         }
         // Check if any of the argument types are Handle.
         for (InterfaceType param in functionType.positionalParameters) {
           if (param.classNode == handleClass) {
             diagnosticReporter.report(messageFfiLeafCallMustNotTakeHandle,
  -              node.fileOffset, 1, node.location.file);
  +              node.fileOffset, 1, node.location?.file);
           }
         }
       }
  
positive.code:         templateFfiNotStatic.withArguments(fromFunctionMethod.name.text),
          node.fileOffset,
          1,
          node.location.file);
      throw _FfiStaticTypeError();
    }
  
  
negative.code:               nativeType, currentLibrary.isNonNullableByDefault),
            node.fileOffset,
            1,
            node.location?.file);
        throw _FfiStaticTypeError();
      }
    }
  