Add first-class callables

Support acquiring a Closure to a callable using the syntax
func(...), $obj->method(...), etc. This is essentially a
shortcut for Closure::fromCallable().

RFC: https://wiki.php.net/rfc/first_class_callable_syntax

Closes GH-7019.

Co-Authored-By: Nikita Popov <nikita.ppv@gmail.com>

Author: krakjoe

UPGRADING

@@ -197,6 +197,10 @@ PHP 8.1 UPGRADE NOTES
     default values, static variable and global constant initializers, as well
     as attribute arguments.
     RFC: https://wiki.php.net/rfc/new_in_initializers
+  . Closures for callables can now be created using the syntax `myFunc(...)`,
+    which is the same as `Closure::fromCallable('myFunc')`. Yes, the `...` is
+    part of the syntax, not an omission.
+    RFC: https://wiki.php.net/rfc/first_class_callable_syntax
   . File uploads now provide an additional full_path key, which contains the
     full path (rather than just the basename) of the uploaded file. This is
     intended for use in conjunction with "upload webkitdirectory".

Zend/Optimizer/optimize_func_calls.c

@@ -188,6 +188,7 @@ void zend_optimize_func_calls(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 			case ZEND_DO_ICALL:
 			case ZEND_DO_UCALL:
 			case ZEND_DO_FCALL_BY_NAME:
+			case ZEND_CALLABLE_CONVERT:
 				call--;
 				if (call_stack[call].func && call_stack[call].opline) {
 					zend_op *fcall = call_stack[call].opline;
@@ -216,7 +217,8 @@ void zend_optimize_func_calls(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 					}
 
 					if ((ZEND_OPTIMIZER_PASS_16 & ctx->optimization_level)
-					 && call_stack[call].try_inline) {
+							&& call_stack[call].try_inline
+							&& opline->opcode != ZEND_CALLABLE_CONVERT) {
 						zend_try_inline_call(op_array, fcall, opline, call_stack[call].func);
 					}
 				}

Zend/Optimizer/zend_call_graph.c

@@ -106,6 +106,7 @@ ZEND_API int zend_analyze_calls(zend_arena **arena, zend_script *script, uint32_
 			case ZEND_DO_ICALL:
 			case ZEND_DO_UCALL:
 			case ZEND_DO_FCALL_BY_NAME:
+			case ZEND_CALLABLE_CONVERT:
 				func_info->flags |= ZEND_FUNC_HAS_CALLS;
 				if (call_info) {
 					call_info->caller_call_opline = opline;

Zend/Optimizer/zend_inference.c

@@ -21,6 +21,7 @@
 #include "zend_inference.h"
 #include "zend_func_info.h"
 #include "zend_call_graph.h"
+#include "zend_closures.h"
 #include "zend_worklist.h"
 #include "zend_optimizer_internal.h"
 
@@ -3504,6 +3505,10 @@ static zend_always_inline int _zend_update_type_info(
 				}
 			}
 			break;
+		case ZEND_CALLABLE_CONVERT:
+			UPDATE_SSA_TYPE(MAY_BE_OBJECT | MAY_BE_RC1 | MAY_BE_RCN, ssa_op->result_def);
+			UPDATE_SSA_OBJ_TYPE(zend_ce_closure, /* is_instanceof */ false, ssa_op->result_def);
+			break;
 		case ZEND_FETCH_CONSTANT:
 		case ZEND_FETCH_CLASS_CONSTANT:
 			UPDATE_SSA_TYPE(MAY_BE_RC1|MAY_BE_RCN|MAY_BE_ANY|MAY_BE_ARRAY_KEY_ANY|MAY_BE_ARRAY_OF_ANY, ssa_op->result_def);

Zend/tests/first_class_callable_001.phpt

@@ -0,0 +1,10 @@
+--TEST--
+First Class Callable from Internal
+--FILE--
+<?php
+$sprintf = sprintf(...);
+
+echo $sprintf("Hello %s", "World");
+?>
+--EXPECT--
+Hello World

Zend/tests/first_class_callable_002.phpt

@@ -0,0 +1,14 @@
+--TEST--
+First Class Callable from User
+--FILE--
+<?php
+function foo() {
+    return "OK";
+}
+
+$foo = foo(...);
+
+echo $foo();
+?>
+--EXPECT--
+OK

Zend/tests/first_class_callable_003.phpt

@@ -0,0 +1,17 @@
+--TEST--
+First Class Callable from Method
+--FILE--
+<?php
+class Foo {
+    public function bar()  {
+        echo "OK";
+    }
+}
+
+$foo = new Foo;
+$bar = $foo->bar(...);
+
+echo $bar();
+?>
+--EXPECT--
+OK

Zend/tests/first_class_callable_004.phpt

@@ -0,0 +1,21 @@
+--TEST--
+First Class Callable from Private Scope
+--FILE--
+<?php
+class Foo {
+    private function method() {
+        return __METHOD__;
+    }
+
+    public function bar()  {
+        return $this->method(...);
+    }
+}
+
+$foo = new Foo;
+$bar = $foo->bar(...);
+
+echo ($bar())();
+?>
+--EXPECT--
+Foo::method

Zend/tests/first_class_callable_005.phpt

@@ -0,0 +1,26 @@
+--TEST--
+First Class Callable from Magic
+--FILE--
+<?php
+class Foo {
+    public function __call($method, $args) {
+        return $method;
+    }
+
+    public static function __callStatic($method, $args) {
+        return $method;
+    }
+}
+
+$foo = new Foo;
+$bar = $foo->anythingInstance(...);
+
+echo $bar() . PHP_EOL;
+
+$qux = Foo::anythingStatic(...);
+
+echo $qux();
+?>
+--EXPECT--
+anythingInstance
+anythingStatic

Zend/tests/first_class_callable_006.phpt

@@ -0,0 +1,13 @@
+--TEST--
+First Class Callable from Closure
+--FILE--
+<?php
+$foo = function(){};
+$bar = $foo(...);
+
+if ($foo === $bar) {
+    echo "OK";
+}
+?>
+--EXPECT--
+OK