Merging lines with certain relations should be warned/forbidden

[afmenez]

When merging lines (roads, rivers) with differing relations of some types (borders!), the user should be at least warned of the change.

[bhousel]

When merging lines (roads, rivers) with differing relations of some types (borders!), the user should be at least warned of the change.

Can you give an example? I thought that iD already prevents merging lines in some cases because they belong to relations.

[afmenez]

Sure. Let's say a have a city limit that coincides with a river (like this one: http://www.openstreetmap.org/way/472662123). In this case, only the river is shown on the editor interface (even when the line is selected you have to scroll way down to see that there's a relation attached to the river). You can then shift select an adjacent section of the river (like this one http://www.openstreetmap.org/way/472662128) and merge them. This should't be possible, or at least a warning should be given before the merge.