occam revisited

The ST [10] compiler (and therefore also KRoC [11]) has implemented the following:

1. name is not used

2. Parameter name not used

3. Routine name not used

4. Name name descopes previous declaration

PC lint actually helps us enforce 1-4 above, since SPoC checks none of them.  It should.

Suggestion for more occam rules:

5. Name name assigned, but not subsequently used

6. Array name index index not used

Compiling the program below goes fine with SPoC, but PC-lint warns:

o: PROC Wish ()
     INT a, b, c:
     b := a
   :
p: Warning 530: a_3824 not initialized
   Warning 550: b_3825 not accessed
   Warning 529: c_3826 not subsequently referenced

How about this:

7. TIMER descopes TIMER (??)

INT time:
TIMER clock:
SEQ
  clock ? time
  TIMER clock: -- Meaningless
  clock ? time

Errata: The paper says 1-3, this is wrong. It should be 1-4.