diff --git a/.gitattributes b/.gitattributes
index 5d5606da..01e0208b 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,6 +1,7 @@
 /.gitattributes export-ignore
 /.github/ export-ignore
 /.gitignore export-ignore
+/phpstan.legacy.neon.dist export-ignore
 /phpstan.neon.dist export-ignore
 /phpunit.xml.dist export-ignore
 /phpunit.xml.legacy export-ignore
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 43c9cb3f..9c2278b6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,6 +35,7 @@ jobs:
     name: PHPStan (PHP ${{ matrix.php }})
     runs-on: ubuntu-22.04
     strategy:
+      fail-fast: false
       matrix:
         php:
           - 8.2
@@ -52,3 +53,6 @@ jobs:
           coverage: none
       - run: composer install
       - run: vendor/bin/phpstan
+        if: ${{ matrix.php >= 7.2 }}
+      - run: vendor/bin/phpstan --configuration="phpstan.legacy.neon.dist"
+        if: ${{ matrix.php < 7.2 }}
diff --git a/phpstan.legacy.neon.dist b/phpstan.legacy.neon.dist
new file mode 100644
index 00000000..5be7a76a
--- /dev/null
+++ b/phpstan.legacy.neon.dist
@@ -0,0 +1,7 @@
+parameters:
+	ignoreErrors:
+		- '#Template type T is declared as covariant, but occurs in contravariant position in parameter result of method React\\Promise\\Promise::settle\(\).#'
+		- '#Template type T is declared as covariant, but occurs in contravariant position in parameter promise of method React\\Promise\\Promise::unwrap\(\).#'
+
+includes:
+	- phpstan.neon.dist
diff --git a/src/Deferred.php b/src/Deferred.php
index 82f66dad..53d945e4 100644
--- a/src/Deferred.php
+++ b/src/Deferred.php
@@ -2,9 +2,14 @@
 
 namespace React\Promise;
 
+/**
+ * @template T
+ */
 final class Deferred
 {
-    /** @var Promise */
+    /**
+     * @var PromiseInterface<T>
+     */
     private $promise;
 
     /** @var callable */
@@ -21,13 +26,16 @@ public function __construct(callable $canceller = null)
         }, $canceller);
     }
 
+    /**
+     * @return PromiseInterface<T>
+     */
     public function promise(): PromiseInterface
     {
         return $this->promise;
     }
 
     /**
-     * @param mixed $value
+     * @param T $value
      */
     public function resolve($value): void
     {
diff --git a/src/Internal/FulfilledPromise.php b/src/Internal/FulfilledPromise.php
index 0712f763..cda953dd 100644
--- a/src/Internal/FulfilledPromise.php
+++ b/src/Internal/FulfilledPromise.php
@@ -7,14 +7,17 @@
 
 /**
  * @internal
+ *
+ * @template-implements PromiseInterface<T>
+ * @template-covariant T
  */
 final class FulfilledPromise implements PromiseInterface
 {
-    /** @var mixed */
+    /** @var T */
     private $value;
 
     /**
-     * @param mixed $value
+     * @param T $value
      * @throws \InvalidArgumentException
      */
     public function __construct($value = null)
@@ -33,7 +36,11 @@ public function then(callable $onFulfilled = null, callable $onRejected = null):
         }
 
         try {
-            return resolve($onFulfilled($this->value));
+            /**
+             * @var PromiseInterface<T>|T $result
+             */
+            $result = $onFulfilled($this->value);
+            return resolve($result);
         } catch (\Throwable $exception) {
             return new RejectedPromise($exception);
         }
diff --git a/src/Internal/RejectedPromise.php b/src/Internal/RejectedPromise.php
index a29cc92d..579290b1 100644
--- a/src/Internal/RejectedPromise.php
+++ b/src/Internal/RejectedPromise.php
@@ -8,6 +8,9 @@
 
 /**
  * @internal
+ *
+ * @template-implements PromiseInterface<never>
+ * @template-covariant T
  */
 final class RejectedPromise implements PromiseInterface
 {
diff --git a/src/Promise.php b/src/Promise.php
index 819e414a..9282348a 100644
--- a/src/Promise.php
+++ b/src/Promise.php
@@ -4,12 +4,16 @@
 
 use React\Promise\Internal\RejectedPromise;
 
+/**
+ * @template-implements PromiseInterface<T>
+ * @template-covariant T
+ */
 final class Promise implements PromiseInterface
 {
     /** @var ?callable */
     private $canceller;
 
-    /** @var ?PromiseInterface */
+    /** @var ?PromiseInterface<T> */
     private $result;
 
     /** @var callable[] */
@@ -80,11 +84,11 @@ public function catch(callable $onRejected): PromiseInterface
     public function finally(callable $onFulfilledOrRejected): PromiseInterface
     {
         return $this->then(static function ($value) use ($onFulfilledOrRejected) {
-            return resolve($onFulfilledOrRejected())->then(function () use ($value) {
+            return resolve($onFulfilledOrRejected())->then(static function () use ($value) {
                 return $value;
             });
         }, static function ($reason) use ($onFulfilledOrRejected) {
-            return resolve($onFulfilledOrRejected())->then(function () use ($reason) {
+            return resolve($onFulfilledOrRejected())->then(static function () use ($reason) {
                 return new RejectedPromise($reason);
             });
         });
@@ -175,6 +179,10 @@ private function reject(\Throwable $reason): void
         $this->settle(reject($reason));
     }
 
+    /**
+     * Test out if null can be promise
+     * @param PromiseInterface<T>|PromiseInterface<never> $result
+     */
     private function settle(PromiseInterface $result): void
     {
         $result = $this->unwrap($result);
@@ -207,13 +215,17 @@ private function settle(PromiseInterface $result): void
         }
     }
 
+    /**
+     * @param PromiseInterface<T>|PromiseInterface<never> $promise
+     * @return PromiseInterface<T>
+     */
     private function unwrap(PromiseInterface $promise): PromiseInterface
     {
         while ($promise instanceof self && null !== $promise->result) {
             $promise = $promise->result;
         }
 
-        return $promise;
+        return $promise; /** @phpstan-ignore-line */
     }
 
     private function call(callable $cb): void
diff --git a/src/PromiseInterface.php b/src/PromiseInterface.php
index 47117072..a5b117fe 100644
--- a/src/PromiseInterface.php
+++ b/src/PromiseInterface.php
@@ -2,6 +2,9 @@
 
 namespace React\Promise;
 
+/**
+ * @template-covariant T
+ */
 interface PromiseInterface
 {
     /**
@@ -28,9 +31,9 @@ interface PromiseInterface
      *  2. `$onFulfilled` and `$onRejected` will never be called more
      *      than once.
      *
-     * @param callable|null $onFulfilled
-     * @param callable|null $onRejected
-     * @return PromiseInterface
+     * @template Fulfilled as PromiseInterface<T>|T
+     * @param ?callable(T): (Fulfilled|void) $onFulfilled
+     * @return PromiseInterface<T>
      */
     public function then(?callable $onFulfilled = null, ?callable $onRejected = null): PromiseInterface;
 
@@ -44,8 +47,7 @@ public function then(?callable $onFulfilled = null, ?callable $onRejected = null
      * Additionally, you can type hint the `$reason` argument of `$onRejected` to catch
      * only specific errors.
      *
-     * @param callable $onRejected
-     * @return PromiseInterface
+     * @return PromiseInterface<T>
      */
     public function catch(callable $onRejected): PromiseInterface;
 
@@ -91,8 +93,8 @@ public function catch(callable $onRejected): PromiseInterface;
      *     ->finally('cleanup');
      * ```
      *
-     * @param callable $onFulfilledOrRejected
-     * @return PromiseInterface
+     * @param callable(): (mixed|void) $onFulfilledOrRejected
+     * @return PromiseInterface<T>
      */
     public function finally(callable $onFulfilledOrRejected): PromiseInterface;
 
@@ -118,7 +120,7 @@ public function cancel(): void;
      * ```
      *
      * @param callable $onRejected
-     * @return PromiseInterface
+     * @return PromiseInterface<T>
      * @deprecated 3.0.0 Use catch() instead
      * @see self::catch()
      */
@@ -135,7 +137,7 @@ public function otherwise(callable $onRejected): PromiseInterface;
      * ```
      *
      * @param callable $onFulfilledOrRejected
-     * @return PromiseInterface
+     * @return PromiseInterface<T>
      * @deprecated 3.0.0 Use finally() instead
      * @see self::finally()
      */
diff --git a/src/functions.php b/src/functions.php
index c8107f8d..2fc60d54 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -17,8 +17,9 @@
  *
  * If `$promiseOrValue` is a promise, it will be returned as is.
  *
- * @param mixed $promiseOrValue
- * @return PromiseInterface
+ * @template T
+ * @param PromiseInterface<T>|T $promiseOrValue
+ * @return PromiseInterface<T>
  */
 function resolve($promiseOrValue): PromiseInterface
 {
@@ -30,6 +31,7 @@ function resolve($promiseOrValue): PromiseInterface
         $canceller = null;
 
         if (\method_exists($promiseOrValue, 'cancel')) {
+            /** @var callable $canceller */
             $canceller = [$promiseOrValue, 'cancel'];
         }
 
@@ -54,8 +56,7 @@ function resolve($promiseOrValue): PromiseInterface
  * throwing an exception. For example, it allows you to propagate a rejection with
  * the value of another promise.
  *
- * @param \Throwable $reason
- * @return PromiseInterface
+ * @return PromiseInterface<never>
  */
 function reject(\Throwable $reason): PromiseInterface
 {
@@ -68,8 +69,9 @@ function reject(\Throwable $reason): PromiseInterface
  * will be an array containing the resolution values of each of the items in
  * `$promisesOrValues`.
  *
- * @param iterable<mixed> $promisesOrValues
- * @return PromiseInterface
+ * @template T
+ * @param iterable<PromiseInterface<T>|T> $promisesOrValues
+ * @return PromiseInterface<array<T>>
  */
 function all(iterable $promisesOrValues): PromiseInterface
 {
@@ -86,7 +88,11 @@ function all(iterable $promisesOrValues): PromiseInterface
             $values[$i] = null;
             ++$toResolve;
 
-            resolve($promiseOrValue)->then(
+            /**
+             * @var PromiseInterface<T> $p
+             */
+            $p = resolve($promiseOrValue);
+            $p->then(
                 function ($value) use ($i, &$values, &$toResolve, &$continue, $resolve): void {
                     $values[$i] = $value;
 
@@ -119,8 +125,9 @@ function (\Throwable $reason) use (&$continue, $reject): void {
  * The returned promise will become **infinitely pending** if  `$promisesOrValues`
  * contains 0 items.
  *
- * @param iterable<mixed> $promisesOrValues
- * @return PromiseInterface
+ * @template T
+ * @param iterable<PromiseInterface<T>|T> $promisesOrValues
+ * @return PromiseInterface<T>
  */
 function race(iterable $promisesOrValues): PromiseInterface
 {
@@ -154,8 +161,9 @@ function race(iterable $promisesOrValues): PromiseInterface
  * The returned promise will also reject with a `React\Promise\Exception\LengthException`
  * if `$promisesOrValues` contains 0 items.
  *
- * @param iterable<mixed> $promisesOrValues
- * @return PromiseInterface
+ * @template T
+ * @param iterable<PromiseInterface<T>|T> $promisesOrValues
+ * @return PromiseInterface<T>
  */
 function any(iterable $promisesOrValues): PromiseInterface
 {
@@ -170,7 +178,11 @@ function any(iterable $promisesOrValues): PromiseInterface
             $cancellationQueue->enqueue($promiseOrValue);
             ++$toReject;
 
-            resolve($promiseOrValue)->then(
+            /**
+             * @var PromiseInterface<T> $p
+             */
+            $p = resolve($promiseOrValue);
+            $p->then(
                 function ($value) use ($resolve, &$continue): void {
                     $continue = false;
                     $resolve($value);
diff --git a/tests/DeferredTest.php b/tests/DeferredTest.php
index 186ed1d7..47209f8d 100644
--- a/tests/DeferredTest.php
+++ b/tests/DeferredTest.php
@@ -54,7 +54,6 @@ public function shouldRejectWithoutCreatingGarbageCyclesIfCancellerHoldsReferenc
         gc_collect_cycles();
         gc_collect_cycles(); // clear twice to avoid leftovers in PHP 7.4 with ext-xdebug and code coverage turned on
 
-        /** @var Deferred $deferred */
         $deferred = new Deferred(function () use (&$deferred) {
             assert($deferred instanceof Deferred);
         });
diff --git a/tests/FunctionAnyTest.php b/tests/FunctionAnyTest.php
index 563f882e..09c4b34b 100644
--- a/tests/FunctionAnyTest.php
+++ b/tests/FunctionAnyTest.php
@@ -52,6 +52,7 @@ public function shouldResolveWithAnInputValue(): void
             ->expects(self::once())
             ->method('__invoke')
             ->with(self::identicalTo(1));
+        assert(is_callable($mock));
 
         any([1, 2, 3])
             ->then($mock);
diff --git a/tests/FunctionResolveTestThenShouldNotReportUnhandled.phpt b/tests/FunctionResolveTestThenShouldNotReportUnhandled.phpt
index aabeae16..d00aca82 100644
--- a/tests/FunctionResolveTestThenShouldNotReportUnhandled.phpt
+++ b/tests/FunctionResolveTestThenShouldNotReportUnhandled.phpt
@@ -10,7 +10,9 @@ use function React\Promise\resolve;
 
 require __DIR__ . '/../vendor/autoload.php';
 
-resolve(42)->then('var_dump');
+/** @var callable $callable */
+$callable = 'var_dump';
+resolve(42)->then($callable);
 
 ?>
 --EXPECT--
diff --git a/tests/Internal/CancellationQueueTest.php b/tests/Internal/CancellationQueueTest.php
index c2907f73..fea5696f 100644
--- a/tests/Internal/CancellationQueueTest.php
+++ b/tests/Internal/CancellationQueueTest.php
@@ -96,6 +96,9 @@ public function rethrowsExceptionsThrownFromCancel(): void
         $cancellationQueue();
     }
 
+    /**
+     * @return Deferred<never>
+     */
     private function getCancellableDeferred(): Deferred
     {
         return new Deferred($this->expectCallableOnce());
diff --git a/tests/Internal/FulfilledPromiseTest.php b/tests/Internal/FulfilledPromiseTest.php
index 073b9d7a..390ffad0 100644
--- a/tests/Internal/FulfilledPromiseTest.php
+++ b/tests/Internal/FulfilledPromiseTest.php
@@ -9,6 +9,9 @@
 use React\Promise\PromiseTest\PromiseSettledTestTrait;
 use React\Promise\TestCase;
 
+/**
+ * @template T
+ */
 class FulfilledPromiseTest extends TestCase
 {
     use PromiseSettledTestTrait,
@@ -16,7 +19,7 @@ class FulfilledPromiseTest extends TestCase
 
     public function getPromiseTestAdapter(callable $canceller = null): CallbackPromiseAdapter
     {
-        /** @var ?FulfilledPromise */
+        /** @var ?FulfilledPromise<T> */
         $promise = null;
 
         return new CallbackPromiseAdapter([
diff --git a/tests/Internal/RejectedPromiseTest.php b/tests/Internal/RejectedPromiseTest.php
index 72cef091..d1ac09d5 100644
--- a/tests/Internal/RejectedPromiseTest.php
+++ b/tests/Internal/RejectedPromiseTest.php
@@ -9,6 +9,9 @@
 use React\Promise\PromiseTest\PromiseSettledTestTrait;
 use React\Promise\TestCase;
 
+/**
+ * @template T
+ */
 class RejectedPromiseTest extends TestCase
 {
     use PromiseSettledTestTrait,
@@ -16,7 +19,7 @@ class RejectedPromiseTest extends TestCase
 
     public function getPromiseTestAdapter(callable $canceller = null): CallbackPromiseAdapter
     {
-        /** @var ?RejectedPromise */
+        /** @var ?RejectedPromise<never> */
         $promise = null;
 
         return new CallbackPromiseAdapter([
diff --git a/tests/PromiseAdapter/CallbackPromiseAdapter.php b/tests/PromiseAdapter/CallbackPromiseAdapter.php
index 14a0acd4..aec72949 100644
--- a/tests/PromiseAdapter/CallbackPromiseAdapter.php
+++ b/tests/PromiseAdapter/CallbackPromiseAdapter.php
@@ -17,6 +17,9 @@ public function __construct(array $callbacks)
         $this->callbacks = $callbacks;
     }
 
+    /**
+     * @phpstan-ignore-next-line
+     */
     public function promise(): PromiseInterface
     {
         return ($this->callbacks['promise'])(...func_get_args());
diff --git a/tests/PromiseAdapter/PromiseAdapterInterface.php b/tests/PromiseAdapter/PromiseAdapterInterface.php
index 727fd514..0eaa2dcb 100644
--- a/tests/PromiseAdapter/PromiseAdapterInterface.php
+++ b/tests/PromiseAdapter/PromiseAdapterInterface.php
@@ -6,6 +6,9 @@
 
 interface PromiseAdapterInterface
 {
+    /**
+     * @phpstan-ignore-next-line
+     */
     public function promise(): PromiseInterface;
     public function resolve(): void;
     public function reject(): void;
diff --git a/tests/PromiseTest.php b/tests/PromiseTest.php
index 06d89eb1..bc41e6a6 100644
--- a/tests/PromiseTest.php
+++ b/tests/PromiseTest.php
@@ -146,7 +146,6 @@ public function shouldRejectWithoutCreatingGarbageCyclesIfResolverThrowsExceptio
     public function shouldRejectWithoutCreatingGarbageCyclesIfCancellerWithReferenceThrowsException(): void
     {
         gc_collect_cycles();
-        /** @var Promise $promise */
         $promise = new Promise(function () {}, function () use (&$promise) {
             assert($promise instanceof Promise);
             throw new \Exception('foo');
@@ -165,7 +164,6 @@ public function shouldRejectWithoutCreatingGarbageCyclesIfCancellerWithReference
     public function shouldRejectWithoutCreatingGarbageCyclesIfResolverWithReferenceThrowsException(): void
     {
         gc_collect_cycles();
-        /** @var Promise $promise */
         $promise = new Promise(function () use (&$promise) {
             assert($promise instanceof Promise);
             throw new \Exception('foo');
@@ -186,7 +184,6 @@ public function shouldRejectWithoutCreatingGarbageCyclesIfResolverWithReferenceT
     public function shouldRejectWithoutCreatingGarbageCyclesIfCancellerHoldsReferenceAndResolverThrowsException(): void
     {
         gc_collect_cycles();
-        /** @var Promise $promise */
         $promise = new Promise(function () {
             throw new \Exception('foo');
         }, function () use (&$promise) {
diff --git a/tests/PromiseTest/PromiseFulfilledTestTrait.php b/tests/PromiseTest/PromiseFulfilledTestTrait.php
index d982214a..a85eef4a 100644
--- a/tests/PromiseTest/PromiseFulfilledTestTrait.php
+++ b/tests/PromiseTest/PromiseFulfilledTestTrait.php
@@ -191,7 +191,7 @@ public function thenShouldContinueToExecuteCallbacksWhenPriorCallbackSuspendsFib
         $adapter->resolve(42);
 
         $fiber = new \Fiber(function () use ($adapter) {
-            $adapter->promise()->then(function (int $value) {
+            $adapter->promise()->then(function (int $value) { /** @phpstan-ignore-line */
                 \Fiber::suspend($value);
             });
         });
@@ -324,7 +324,7 @@ public function finallyShouldRejectWhenHandlerRejectsForFulfilledPromise(): void
 
         $adapter->resolve(1);
         $adapter->promise()
-            ->finally(function () use ($exception) {
+            ->finally(function () use ($exception) { /** @phpstan-ignore-line  */
                 return reject($exception);
             })
             ->then(null, $mock);
diff --git a/tests/PromiseTest/PromiseRejectedTestTrait.php b/tests/PromiseTest/PromiseRejectedTestTrait.php
index 12287ce8..42e5d451 100644
--- a/tests/PromiseTest/PromiseRejectedTestTrait.php
+++ b/tests/PromiseTest/PromiseRejectedTestTrait.php
@@ -363,7 +363,7 @@ public function finallyShouldRejectWhenHandlerRejectsForRejectedPromise(): void
 
         $adapter->reject($exception1);
         $adapter->promise()
-            ->finally(function () use ($exception2) {
+            ->finally(function () use ($exception2) { /** @phpstan-ignore-line  */
                 return reject($exception2);
             })
             ->then(null, $mock);
diff --git a/tests/PromiseTest/RejectTestTrait.php b/tests/PromiseTest/RejectTestTrait.php
index ad55ca28..bb00e40f 100644
--- a/tests/PromiseTest/RejectTestTrait.php
+++ b/tests/PromiseTest/RejectTestTrait.php
@@ -73,7 +73,7 @@ public function rejectShouldMakePromiseImmutable(): void
             ->with($this->identicalTo($exception1));
 
         $adapter->promise()
-            ->then(null, function ($value) use ($exception3, $adapter) {
+            ->then(null, function (\Throwable $value) use ($exception3, $adapter) {
                 $adapter->reject($exception3);
 
                 return reject($value);
@@ -206,7 +206,7 @@ public function finallyShouldRejectWhenHandlerRejectsForRejection(): void
             ->with($this->identicalTo($exception));
 
         $adapter->promise()
-            ->finally(function () use ($exception) {
+            ->finally(function () use ($exception) { /** @phpstan-ignore-line  */
                 return reject($exception);
             })
             ->then(null, $mock);
diff --git a/tests/PromiseTest/ResolveTestTrait.php b/tests/PromiseTest/ResolveTestTrait.php
index 357fdedc..00dab79e 100644
--- a/tests/PromiseTest/ResolveTestTrait.php
+++ b/tests/PromiseTest/ResolveTestTrait.php
@@ -266,7 +266,7 @@ public function finallyShouldRejectWhenHandlerRejectsForFulfillment(): void
             ->with($this->identicalTo($exception));
 
         $adapter->promise()
-            ->finally(function () use ($exception) {
+            ->finally(function () use ($exception) { /** @phpstan-ignore-line  */
                 return reject($exception);
             })
             ->then(null, $mock);
diff --git a/tests/types/basic.php b/tests/types/basic.php
new file mode 100644
index 00000000..13b20bf1
--- /dev/null
+++ b/tests/types/basic.php
@@ -0,0 +1,16 @@
+<?php
+
+use React\Promise\Types;
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\resolve;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+/**
+ * basic
+ */
+assertType('React\Promise\PromiseInterface<bool>', resolve(true));
+assertType('React\Promise\PromiseInterface<int|string>', resolve(Types\stringOrInt()));
+assertType('React\Promise\PromiseInterface<int|string>', Types\stringOrIntPromise());
+assertType('React\Promise\PromiseInterface<bool>', resolve(resolve(true)));
diff --git a/tests/types/chaining.php b/tests/types/chaining.php
new file mode 100644
index 00000000..1b71bcb5
--- /dev/null
+++ b/tests/types/chaining.php
@@ -0,0 +1,32 @@
+<?php
+
+use React\Promise\Internal\FulfilledPromise;
+use React\Promise\PromiseInterface;
+use React\Promise\Types;
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\all;
+use function React\Promise\any;
+use function React\Promise\race;
+use function React\Promise\resolve;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+/**
+ * chaining
+ */
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then('React\Promise\Types\passThroughBoolFn'));
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then()->then('React\Promise\Types\passThroughBoolFn'));
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then(null)->then('React\Promise\Types\passThroughBoolFn'));
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then('React\Promise\Types\passThroughBoolFn')->then('React\Promise\Types\passThroughBoolFn'));
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then('React\Promise\Types\passThroughBoolFn', 'React\Promise\Types\passThroughThrowable')->then('React\Promise\Types\passThroughBoolFn'));
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then(null, 'React\Promise\Types\passThroughThrowable')->then('React\Promise\Types\passThroughBoolFn'));
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then()->then(null, 'React\Promise\Types\passThroughThrowable')->then('React\Promise\Types\passThroughBoolFn'));
+
+/**
+ * Changing types while chaining
+ */
+//assertType('React\Promise\PromiseInterface<int>', resolve(true)->then(function (bool $bool): int {
+//    return time();
+//}));
+//assertType('React\Promise\PromiseInterface<int>', resolve(true)->then('React\Promise\Types\flipBoolToInt'));
diff --git a/tests/types/common.php b/tests/types/common.php
new file mode 100644
index 00000000..9c806443
--- /dev/null
+++ b/tests/types/common.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace React\Promise\Types;
+
+use React\Promise\PromiseInterface;
+use Throwable;
+
+use function React\Promise\reject;
+use function React\Promise\resolve;
+
+function passThroughBoolFn(bool $bool): bool {
+    return $bool;
+};
+
+/**
+ * @return PromiseInterface<never>
+ */
+function passThroughThrowable(Throwable $t): PromiseInterface {
+    return reject($t);
+};
+
+/**
+ * @return int|string
+ */
+function stringOrInt() {
+    return time() % 2 ? 'string' : time();
+};
+
+/**
+ * @return PromiseInterface<int|string>
+ */
+function stringOrIntPromise(): PromiseInterface {
+    return resolve(time() % 2 ? 'string' : time());
+};
+
+/**
+ * @return PromiseInterface<int>
+ */
+function flipBoolToInt(bool $bool): PromiseInterface {
+    return resolve(time());
+};
+
+function theMeaningOfLifeTheUniverseAndEverything(): int {
+    return 42;
+};
diff --git a/tests/types/deferred.php b/tests/types/deferred.php
new file mode 100644
index 00000000..de0c3260
--- /dev/null
+++ b/tests/types/deferred.php
@@ -0,0 +1,11 @@
+<?php
+
+use React\Promise\Deferred;
+use function PHPStan\Testing\assertType;
+
+$deferredA = new Deferred();
+//assertType('React\Promise\PromiseInterface<T>', $deferredA->promise());
+
+$deferredB = new Deferred();
+$deferredB->resolve(42);
+//assertType('React\Promise\PromiseInterface<int>', $deferredB->promise());
diff --git a/tests/types/deprecated.php b/tests/types/deprecated.php
new file mode 100644
index 00000000..5c58e7dc
--- /dev/null
+++ b/tests/types/deprecated.php
@@ -0,0 +1,19 @@
+<?php
+
+use React\Promise\Internal\FulfilledPromise;
+use React\Promise\Internal\RejectedPromise;
+
+use function PHPStan\Testing\assertType;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+/**
+ * resolve
+ */
+assertType('React\Promise\Internal\FulfilledPromise<bool>', new FulfilledPromise(true));
+assertType('React\Promise\PromiseInterface<bool>', (new FulfilledPromise(true))->then('React\Promise\Types\passThroughBoolFn'));
+
+/**
+ * reject
+ */
+//assertType('React\Promise\PromiseInterface<*NEVER*>', new RejectedPromise(new RuntimeException()));
diff --git a/tests/types/functions_all.php b/tests/types/functions_all.php
new file mode 100644
index 00000000..44b643e0
--- /dev/null
+++ b/tests/types/functions_all.php
@@ -0,0 +1,15 @@
+<?php
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\all;
+use function React\Promise\resolve;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+/**
+ * all
+ */
+assertType('React\Promise\PromiseInterface<array<bool>>', all([resolve(true), resolve(false)]));
+assertType('React\Promise\PromiseInterface<array<bool>>', all([resolve(true), false]));
+assertType('React\Promise\PromiseInterface<array<bool|int>>', all([true, time()]));
+assertType('React\Promise\PromiseInterface<array<bool|int>>', all([resolve(true), resolve(time())]));
diff --git a/tests/types/functions_any.php b/tests/types/functions_any.php
new file mode 100644
index 00000000..78659dfe
--- /dev/null
+++ b/tests/types/functions_any.php
@@ -0,0 +1,15 @@
+<?php
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\any;
+use function React\Promise\resolve;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+/**
+ * any
+ */
+assertType('React\Promise\PromiseInterface<bool>', any([resolve(true), resolve(false)]));
+assertType('React\Promise\PromiseInterface<bool>', any([resolve(true), false]));
+assertType('React\Promise\PromiseInterface<bool|int>', any([true, time()]));
+assertType('React\Promise\PromiseInterface<bool|int>', any([resolve(true), resolve(time())]));
diff --git a/tests/types/functions_race.php b/tests/types/functions_race.php
new file mode 100644
index 00000000..e3e12af0
--- /dev/null
+++ b/tests/types/functions_race.php
@@ -0,0 +1,15 @@
+<?php
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\race;
+use function React\Promise\resolve;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+/**
+ * race
+ */
+assertType('React\Promise\PromiseInterface<bool>', race([resolve(true), resolve(false)]));
+assertType('React\Promise\PromiseInterface<bool>', race([resolve(true), false]));
+assertType('React\Promise\PromiseInterface<bool|int>', race([true, time()]));
+assertType('React\Promise\PromiseInterface<bool|int>', race([resolve(true), resolve(time())]));
diff --git a/tests/types/reject.php b/tests/types/reject.php
new file mode 100644
index 00000000..00f6f09f
--- /dev/null
+++ b/tests/types/reject.php
@@ -0,0 +1,11 @@
+<?php
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\reject;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+assertType('React\Promise\PromiseInterface<*NEVER*>', reject(new RuntimeException()));
+//assertType('React\Promise\PromiseInterface<*NEVER*>', reject(new RuntimeException())->then('React\Promise\Types\theMeaningOfLifeTheUniverseAndEverything'));
+//assertType('React\Promise\PromiseInterface<int>', reject(new RuntimeException())->then(null, 'React\Promise\Types\theMeaningOfLifeTheUniverseAndEverything'));
+//assertType('React\Promise\PromiseInterface<int>', reject(new RuntimeException())->catch('React\Promise\Types\theMeaningOfLifeTheUniverseAndEverything'));
diff --git a/tests/types/then.php b/tests/types/then.php
new file mode 100644
index 00000000..47de0a41
--- /dev/null
+++ b/tests/types/then.php
@@ -0,0 +1,15 @@
+<?php
+
+use React\Promise\Types;
+
+use function PHPStan\Testing\assertType;
+use function React\Promise\resolve;
+
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'common.php';
+
+$value = null;
+assertType('React\Promise\PromiseInterface<bool>', resolve(true)->then(static function ($v) use (&$value) {
+    $value = $v;
+}));
+// This passes on PHP 7.2+ but can't be ignored for PHP 7.1
+//assertType('bool|null', $value);