Add tests from vibe-d:core.

tests/vibe.core.core.1590.d

@@ -0,0 +1,59 @@
+/+ dub.sdl:
+    name "tests"
+    description "Semaphore hang"
+    dependency "vibe-core" path="../"
++/
+module test;
+import std.stdio;
+import std.socket;
+import std.datetime;
+import std.functional;
+import core.time;
+import vibe.core.core;
+import vibe.core.log;
+import vibe.core.concurrency;
+import vibe.core.connectionpool;
+
+class Conn {}
+
+void main()
+{
+    runTask({
+        // create pool with 2 max connections
+        bool[int] results;
+        auto pool = new ConnectionPool!Conn({ return new Conn; }, 2);
+        auto task = Task.getThis(); // main task
+        void worker(int id) {
+            {
+                auto conn = pool.lockConnection(); // <-- worker(4) hangs here
+                sleep(1.msecs); // <-- important, without sleep everything works fine
+            }
+            task.send(id); // send signal to the main task
+        }
+        // run 4 tasks (2 * pool max connections)
+        runTask(&worker, 1);
+        runTask(&worker, 2);
+        runTask(&worker, 3);
+        runTask(&worker, 4);
+
+        // wait for first signal and run one more task
+        results[receiveOnly!int] = true;
+        runTask(&worker, 5);
+
+        // wait for other signals
+        results[receiveOnly!int] = true;
+        results[receiveOnly!int] = true;
+        results[receiveOnly!int] = true;
+        results[receiveOnly!int] = true;
+
+        foreach (r; results.byKey)
+            assert(r >= 1 && r <= 5);
+
+        exitEventLoop();
+    });
+
+    setTimer(1.seconds, { assert(false, "Test has hung."); });
+
+    runEventLoop();
+}
+