Fence gates, daylight sensors, observers, and leaves cut redstone wire as if they were solid opaque

Note: leaves are only affected by this when using fast graphics/fast leaves and after turning the wire on and off after changing the setting.

In the screenshot shown below, you can see a line of redstone dust being "functionally" cut by a hopper but "visually" not.

The reason why the lamp behind the hopper is lit would be that the redstone "line" next to it is treated internally as a directionless redstone dot.

Edit:
Hoppers now works as intended but there are other blocks which still exhibit similar behaviour, see picture and comments:

UPDATE: Fixed completely for piston heads as of 0.15.90.8 and for leaves as of 0.17.0.2.