Install psalm as dev, sync scripts updates

vendor/amphp/byte-stream/lib/InputStreamChain.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace Amp\ByteStream;
+
+use Amp\Promise;
+use Amp\Success;
+use function Amp\call;
+
+final class InputStreamChain implements InputStream
+{
+    /** @var InputStream[] */
+    private $streams;
+    /** @var bool */
+    private $reading = false;
+
+    public function __construct(InputStream ...$streams)
+    {
+        $this->streams = $streams;
+    }
+
+    /** @inheritDoc */
+    public function read(): Promise
+    {
+        if ($this->reading) {
+            throw new PendingReadError;
+        }
+
+        if (!$this->streams) {
+            return new Success(null);
+        }
+
+        return call(function () {
+            $this->reading = true;
+
+            try {
+                while ($this->streams) {
+                    $chunk = yield $this->streams[0]->read();
+                    if ($chunk === null) {
+                        \array_shift($this->streams);
+                        continue;
+                    }
+
+                    return $chunk;
+                }
+
+                return null;
+            } finally {
+                $this->reading = false;
+            }
+        });
+    }
+}