Signal manager: Add a tooltip about mismatching types

Author: janezd

orangecanvas/canvas/items/linkitem.py

@@ -670,6 +670,13 @@ def setDynamicEnabled(self, enabled):
             self.__dynamicEnabled = enabled
             if self.__dynamic:
                 self.__updatePen()
+        self.__update_tooltip()
+
+    def __update_tooltip(self):
+        if self.__dynamicEnabled:
+            self.curveItem.setToolTip(None)
+        else:
+            self.curveItem.setToolTip(f"{self.sourceItem.title()} is not providing the proper data type required by {self.sinkItem.title()}")
 
     def isDynamicEnabled(self):
         # type: () -> bool