get rid of call_user_func (#32)

`call_user_func_array` is deprecated in the latest nightly builds, changing to `$callable()`.

I added a test to confirm this still works with all *reasonable* ways of providing callables (lambda, fun, class_meth, inst_meth). This likely breaks `'func_name'` and `varray['ClassName', 'methodName']` but those would be broken soon anyway by the HHVM migration to use native function pointers.

src/ExpectObj.hack

@@ -525,9 +525,12 @@ class ExpectObj<T> extends Assert {
    *
    *   expect( () ==> invariant_violation('...') )->notToThrow(); // would fail
    */
-  public function notToThrow(?string $msg = null, mixed ...$args): void {
+  public function notToThrow(
+    ?string $msg = null,
+    mixed ...$args
+  ): void where T as (function(): mixed) {
     $msg = \vsprintf($msg, $args);
-    $e = $this->tryCallWithArgsReturnException(varray[], \Exception::class);
+    $e = $this->tryCallReturnException(\Exception::class);
     if ($e !== null) {
       $msg = Str\format(
         "%s was thrown: %s\n%s",
@@ -572,7 +575,7 @@ class ExpectObj<T> extends Assert {
     mixed ...$args
   ): TException where T = (function(): TRet) {
     $msg = \vsprintf($msg ?? '', $args);
-    $exception = $this->tryCallWithArgsReturnException(vec[], $exception_class);
+    $exception = $this->tryCallReturnException($exception_class);
 
     if (!$exception) {
       throw new \Exception(
@@ -652,13 +655,12 @@ class ExpectObj<T> extends Assert {
    **** Private implementation details ***
    ***************************************
    ***************************************/
-  private function tryCallWithArgsReturnException<Tclass as \Throwable>(
-    Container<mixed> $args,
+  private function tryCallReturnException<Tclass as \Throwable>(
     classname<Tclass> $expected_exception_type,
-  ): ?Tclass {
+  ): ?Tclass where T as (function(): mixed) {
     try {
       $callable = $this->var;
-      $returned = \call_user_func_array($callable, $args);
+      $returned = $callable();
 
       if ($returned is Awaitable<_>) {
         /* HHAST_IGNORE_ERROR[DontUseAsioJoin] */

tests/ExpectObjTest.hack

@@ -536,4 +536,25 @@ final class ExpectObjTest extends HackTest {
     \restore_error_handler();
     expect($previous)->toEqual('not_a_function', 'Error handler contaminated');
   }
+
+  /**
+   * Test that all reasonable ways of providing a (function(): mixed) work.
+   */
+  public function testCallables(): void {
+    expect(() ==> self::exampleStaticCallable())
+      ->toThrow(\Exception::class, 'Static method called!');
+    expect(class_meth(self::class, 'exampleStaticCallable'))
+      ->toThrow(\Exception::class, 'Static method called!');
+    expect(inst_meth($this, 'exampleInstanceCallable'))
+      ->toThrow(\Exception::class, 'Instance method called!');
+    expect(fun('time'))->notToThrow();
+  }
+
+  public static function exampleStaticCallable(): void {
+    throw new \Exception('Static method called!');
+  }
+
+  public function exampleInstanceCallable(): void {
+    throw new \Exception('Instance method called!');
+  }
 }