Remove deprecated ContinuationWaitHandle::start()

ContinuationWaitHandle::start() was deprecated in favor of Awaitable
interface's getWaitHandle().

Remove ContinuationWaitHandle::start() from public API and rename it
internally to c_ContinuationWaitHandle::Create() that is called only from
Continuation's getWaitHandle(). Since it is guaranteed that the
Continuation does not have associated any wait handle, we can remove the
code that handles that case.

hphp/idl/asio.idl.json

@@ -449,25 +449,6 @@
                     "args": [
                     ]
                 },
-                {
-                    "name": "start",
-                    "desc": "Start asynchronous execution of a given Continuation",
-                    "flags": [
-                        "IsStatic",
-                        "HasDocComment"
-                    ],
-                    "return": {
-                        "type": "Object",
-                        "desc": "A WaitHandle representing started Continuation"
-                    },
-                    "args": [
-                        {
-                            "name": "continuation",
-                            "type": "Object",
-                            "desc": "A Continuation to be started"
-                        }
-                    ]
-                },
                 {
                     "name": "getPrivData",
                     "desc": "Get user's private data",

hphp/runtime/ext/asio/continuation_wait_handle.cpp

@@ -43,18 +43,15 @@ c_ContinuationWaitHandle::~c_ContinuationWaitHandle() {
 
 void c_ContinuationWaitHandle::t___construct() {
   Object e(SystemLib::AllocInvalidOperationExceptionObject(
-        "Use ContinuationWaitHandle::start() instead of constructor"));
+        "Use $continuation->getWaitHandle() instead of constructor"));
   throw e;
 }
 
-Object c_ContinuationWaitHandle::ti_start(const char* cls, CObjRef continuation) {
-  AsioSession* session = AsioSession::Get();
-  if (UNLIKELY(!continuation.instanceof(SystemLib::s_ContinuationClass))) {
-    Object e(SystemLib::AllocInvalidArgumentExceptionObject(
-        "Expected continuation to be an instance of Continuation"));
-    throw e;
-  }
+void c_ContinuationWaitHandle::Create(c_Continuation* continuation) {
+  assert(continuation);
+  assert(continuation->m_waitHandle.isNull());
 
+  AsioSession* session = AsioSession::Get();
   uint16_t depth = session->getCurrentWaitHandleDepth();
   if (UNLIKELY(depth >= MAX_DEPTH)) {
     Object e(SystemLib::AllocInvalidOperationExceptionObject(
@@ -62,29 +59,21 @@ Object c_ContinuationWaitHandle::ti_start(const char* cls, CObjRef continuation)
     throw e;
   }
 
-  c_Continuation* cont = static_cast<c_Continuation*>(continuation.get());
-  if (!cont->m_waitHandle.isNull()) {
-    if (session->isInContext()) {
-      // throws if cross-context cycle found
-      cont->m_waitHandle->enterContext(session->getCurrentContextIdx());
-    }
-    return cont->m_waitHandle;
-  }
-
-  if (UNLIKELY(cont->m_index != -1)) {
+  if (UNLIKELY(continuation->m_index != -1)) {
     Object e(SystemLib::AllocInvalidOperationExceptionObject(
-      cont->m_running
+      continuation->m_running
       ? "Encountered an attempt to start currently running continuation"
       : "Encountered an attempt to start tainted continuation"));
     throw e;
   }
 
-  p_ContinuationWaitHandle wh = NEWOBJ(c_ContinuationWaitHandle)();
-  wh->start(cont, depth + 1);
+  continuation->m_waitHandle = NEWOBJ(c_ContinuationWaitHandle)();
+  continuation->m_waitHandle->initialize(continuation, depth + 1);
+
+  // needs to be called after continuation->m_waitHandle is set
   if (UNLIKELY(session->hasOnStartedCallback())) {
-    session->onStarted(wh);
+    session->onStarted(continuation->m_waitHandle);
   }
-  return wh;
 }
 
 Object c_ContinuationWaitHandle::t_getprivdata() {
@@ -95,12 +84,11 @@ void c_ContinuationWaitHandle::t_setprivdata(CObjRef data) {
   m_privData = data;
 }
 
-void c_ContinuationWaitHandle::start(c_Continuation* continuation, uint16_t depth) {
+void c_ContinuationWaitHandle::initialize(c_Continuation* continuation, uint16_t depth) {
   m_continuation = continuation;
   m_child = nullptr;
   m_privData = nullptr;
   m_depth = depth;
-  continuation->m_waitHandle = this;
 
   setState(STATE_SCHEDULED);
   if (isInContext()) {

hphp/runtime/ext/ext_asio.h

@@ -280,15 +280,12 @@ class c_ContinuationWaitHandle : public c_BlockableWaitHandle {
   public: c_ContinuationWaitHandle(VM::Class* cls = c_ContinuationWaitHandle::s_cls);
   public: ~c_ContinuationWaitHandle();
   public: void t___construct();
-  public: static Object ti_start(const char* cls , CObjRef continuation);
-  public: static Object t_start(CObjRef continuation) {
-    return ti_start("continuationwaithandle", continuation);
-  }
   public: Object t_getprivdata();
   public: void t_setprivdata(CObjRef data);
 
 
  public:
+  static void Create(c_Continuation* continuation);
   void run();
   uint16_t getDepth() { return m_depth; }
   String getName();
@@ -300,7 +297,7 @@ class c_ContinuationWaitHandle : public c_BlockableWaitHandle {
   c_WaitableWaitHandle* getChild();
 
  private:
-  void start(c_Continuation* continuation, uint16_t depth);
+  void initialize(c_Continuation* continuation, uint16_t depth);
   void markAsSucceeded(const TypedValue* result);
   void markAsFailed(CObjRef exception);
 

hphp/runtime/ext/ext_continuation.cpp

@@ -77,7 +77,11 @@ void c_Continuation::t_update(int64_t label, CVarRef value) {
 }
 
 Object c_Continuation::t_getwaithandle() {
-  return m_waitHandle.isNull() ? c_ContinuationWaitHandle::t_start(this) : m_waitHandle;
+  if (m_waitHandle.isNull()) {
+    c_ContinuationWaitHandle::Create(this);
+    assert(!m_waitHandle.isNull());
+  }
+  return m_waitHandle;
 }
 
 int64_t c_Continuation::t_getlabel() {

hphp/system/class_map.cpp

@@ -24852,12 +24852,6 @@ const char *g_class_map[] = {
   (const char *)0x8 /* KindOfNull */, NULL,
   NULL,
   NULL,
-  (const char *)0x10006240, "start", "", (const char*)0, (const char*)0,
-  "/**\n * ( excerpt from http://php.net/manual/en/continuationwaithandle.start.php\n * )\n *\n * Start asynchronous execution of a given Continuation\n *\n * @continuation\n *             object  A Continuation to be started\n *\n * @return     object  A WaitHandle representing started Continuation\n */",
-  (const char *)0x40 /* KindOfObject */, (const char *)0x2000, "continuation", "", (const char *)0x40 /* KindOfObject */, "", (const char *)0, "", (const char *)0, NULL,
-  NULL,
-  NULL,
-  NULL,
   (const char *)0x10006040, "getPrivData", "", (const char*)0, (const char*)0,
   "/**\n * ( excerpt from\n * http://php.net/manual/en/continuationwaithandle.getprivdata.php )\n *\n * Get user's private data\n *\n * @return     object  An Object with user's private data\n */",
   (const char *)0x40 /* KindOfObject */, NULL,