throw error when locking / unlocking is not symmetric, add a test

base/lock.jl

@@ -28,12 +28,12 @@ unlock(o::Any) = unlock(o.lock)
 
 function unlock(rl::ReentrantLock)
  rl.reentrancy_cnt = rl.reentrancy_cnt - 1
+ if rl.reentrancy_cnt < 0
+ error("unlock count must match lock count")
+ end
  if rl.reentrancy_cnt == 0
  rl.locked_by = nothing
  notify(rl.cond_wait)
- elseif rl.reentrancy_cnt < 0
- AssertionError("unlock count must match lock count")
  end
- rl
+ return rl
 end
-

test/misc.jl

@@ -135,3 +135,10 @@ immutable NoMethodHasThisType end
  warning_str = readall(`$exename -f -e $script`)
  @test contains(warning_str, "f()")
 end
+
+# lock / unlock
+let l = ReentrantLock()
+ lock(l)
+ unlock(l)
+ @test_throws ErrorException unlock(l)
+end