The unification process should throw an exception in a situation where infinite substitutions are possible #29
Description
When encountering a condition like "[x] > 10" the process will terminate without success if there is not a valid substitution for [x] already specified in the context. The reason is that there is infinite possibilities for the value of [x] so infinite substitutions sets would have to be generated. The same is true for conditions like [x] != A.
The problem is that it is hard to know for the author that a given rule is not being activated due to to this problem. Intuitively, one expects that the condition [x] > 10 will simply be propagated to the following conditions.
To solve this issue, we will generate an InvalidOperationException that will explain the problem.