Misleading test of value presence in WeakSet/WeakMap

[Oldřich Jedlička]

After this assignment:

es6-features/features.txt

Line 1322 in 75bf0b4

 6| foo |=| null  /* remove only reference to foo */ 

See the following lines:

es6-features/features.txt

Lines 1323 to 1324 in 75bf0b4

 6| attachedData.has(foo) === |false| 
 6| isMarked.has(foo)     === |false| 

Those basically test if value null is in the map/set, not if foo is still in the map/set. There exists no way to check whether the value is in the map/set when the last reference is lost, so those tests actually do not test what they are trying to show.