Update for Continuation

lib/Internal/EmitSource.php

@@ -35,7 +35,7 @@ final class EmitSource
     /** @var Deferred[] */
     private array $backPressure = [];
 
-    /** @var \Fiber[] */
+    /** @var \Continuation[] */
     private array $waiting = [];
 
     private int $consumePosition = 0;
@@ -116,7 +116,10 @@ final class EmitSource
             return null;
         }
 
-        return \Fiber::suspend(fn(\Fiber $fiber) => $this->waiting[$position] = $fiber, Loop::get());
+        return \Fiber::suspend(
+            fn(\Continuation $continuation) => $this->waiting[$position] = $continuation,
+            Loop::get()
+        );
     }
 
     public function pipe(): Pipeline
@@ -210,9 +213,9 @@ final class EmitSource
         $position = $this->emitPosition++;
 
         if (isset($this->waiting[$position])) {
-            $fiber = $this->waiting[$position];
+            $continuation = $this->waiting[$position];
             unset($this->waiting[$position]);
-            Loop::defer(fn() => $fiber->resume($value));
+            Loop::defer(static fn() => $continuation->resume($value));
 
             // Send-values are indexed as $this->consumePosition - 1, so use $position for the next value.
             if (isset($this->sendValues[$position])) {
@@ -356,11 +359,11 @@ final class EmitSource
             }
         }
 
-        foreach ($waiting as $fiber) {
+        foreach ($waiting as $continuation) {
             if (isset($this->exception)) {
-                $fiber->throw($this->exception);
+                $continuation->throw($this->exception);
             } else {
-                $fiber->resume();
+                $continuation->resume();
             }
         }
     }

lib/functions.php

@@ -25,10 +25,10 @@ namespace Amp
             $promise = Promise\all($promise);
         }
 
-        return \Fiber::suspend(static fn(\Fiber $fiber) => $promise->onResolve(
+        return \Fiber::suspend(static fn(\Continuation $continuation) => $promise->onResolve(
             static fn(?\Throwable $exception, mixed $value) => $exception
-                ? $fiber->throw($exception)
+                ? $continuation->throw($exception)
-                : $fiber->resume($value)
+                : $continuation->resume($value)
         ), Loop::get());
     }
 

stubs/Continuation.php

@@ -0,0 +1,32 @@
+<?php
+
+final class Continuation
+{
+    /**
+     * @return bool True if either {@see resume()} or {@see throw()} has been called previously.
+     */
+    public function continued(): bool { }
+
+    /**
+     * Resumes the fiber, returning the given value from {@see Fiber::suspend()}.
+     *
+     * @param mixed $value
+     *
+     * @throw FiberError If the continuation has already been used.
+     */
+    public function resume(mixed $value = null): void { }
+
+    /**
+     * Throws the given exception into the fiber from {@see Fiber::suspend()}.
+     *
+     * @param Throwable $exception
+     *
+     * @throw FiberError If the continuation has already been used.
+     */
+    public function throw(Throwable $exception): void { }
+
+    /**
+     * Cannot be constructed by user code.
+     */
+    private function __construct() { }
+}

stubs/Fiber.php

@@ -11,50 +11,21 @@ final class Fiber
     public static function run(callable $callback, mixed ...$args): void { }
 
     /**
-     * Private constructor to force use of {@see run()}.
+     * Suspend execution of the fiber. A Continuation object is provided as the first argument to the given callback.
-     */
+     * The fiber may be resumed with {@see Continuation::resume()} or {@see Continuation::throw()}.
-    private function __construct() { }
-
-    /**
-     * @return bool True if the fiber is suspended.
-     */
-    public function isSuspended(): bool { }
-
-    /**
-     * @return bool True if the fiber is currently running.
-     */
-    public function isRunning(): bool { }
-
-    /**
-     * @return bool True if the fiber has completed execution.
-     */
-    public function isTerminated(): bool { }
-
-    /**
-     * Resumes the fiber, returning the given value from {@see Fiber::suspend()}.
-     *
-     * @param mixed $value
-     */
-    public function resume(mixed $value = null): void { }
-
-    /**
-     * Throws the given exception into the fiber from {@see Fiber::suspend()}.
-     *
-     * @param Throwable $exception
-     */
-    public function throw(Throwable $exception): void { }
-
-    /**
-     * Suspend execution of the fiber. The Fiber object is provided as the first argument to the given callback.
-     * The fiber may be resumed with {@see Fiber::resume()} or {@see Fiber::throw()}.
      *
      * @param callable(Fiber):void $enqueue
      * @param FiberScheduler $scheduler
      *
-     * @return mixed Value provided to {@see Fiber::resume()}.
+     * @return mixed Value provided to {@see Continuation::resume()}.
      *
      * @throws FiberError Thrown if within {@see FiberScheduler::run()}.
-     * @throws Throwable Exception provided to {@see Fiber::throw()}.
+     * @throws Throwable Exception provided to {@see Continuation::throw()}.
      */
     public static function suspend(callable $enqueue, FiberScheduler $scheduler): mixed { }
+
+    /**
+     * Private constructor to force use of {@see run()}.
+     */
+    private function __construct() { }
 }