[RFC] Closure self-reference

Zend/Optimizer/dce.c

@@ -125,6 +125,7 @@ static inline bool may_have_side_effects(
 		case ZEND_FUNC_NUM_ARGS:
 		case ZEND_FUNC_GET_ARGS:
 		case ZEND_ARRAY_KEY_EXISTS:
+		case ZEND_BIND_SELF_REFERENCE:
 			/* No side effects */
 			return 0;
 		case ZEND_ADD_ARRAY_ELEMENT:

Zend/Optimizer/zend_inference.c

@@ -4363,6 +4363,7 @@ static void zend_mark_cv_references(const zend_op_array *op_array, const zend_sc
 					case ZEND_SEND_REF:
 					case ZEND_SEND_VAR_EX:
 					case ZEND_SEND_FUNC_ARG:
+					case ZEND_BIND_SELF_REFERENCE:
 						break;
 					case ZEND_INIT_ARRAY:
 					case ZEND_ADD_ARRAY_ELEMENT:

Zend/Optimizer/zend_ssa.c

@@ -698,6 +698,7 @@ static zend_always_inline int _zend_ssa_rename_op(const zend_op_array *op_array,
 		case ZEND_FETCH_DIM_FUNC_ARG:
 		case ZEND_FETCH_DIM_UNSET:
 		case ZEND_FETCH_LIST_W:
+		case ZEND_BIND_SELF_REFERENCE:
 			if (opline->op1_type == IS_CV) {
 				goto add_op1_def;
 			}

Zend/tests/closures/closure_self_reference_arrow.phpt

@@ -0,0 +1,25 @@
+--TEST--
+Testing Closure self-reference functionality: Arrow functions
+--FILE--
+<?php
+
+$factorial = fn(int $num) as $fn : int => $num > 1 ? $num * $fn($num - 1) : $num;
+
+echo "5! = ", $factorial(5), PHP_EOL;
+
+
+$fn = fn() as $a => fn(int $b) as $a => $a;
+
+echo new ReflectionParameter($fn()(1), 'b'), PHP_EOL;
+
+
+$c = 123;
+$fn = fn() as $c => fn() => $c;
+
+echo get_class($fn()()), PHP_EOL;
+
+?>
+--EXPECTF--
+5! = 120
+Parameter #0 [ <required> int $b ]
+Closure

Zend/tests/closures/closure_self_reference_basic.phpt

@@ -0,0 +1,40 @@
+--TEST--
+Testing Closure self-reference functionality: Basic
+--FILE--
+<?php
+
+$factorial = function(int $num) as $factorial {
+    if($num > 1) {
+        return $num * $factorial($num - 1);
+    }
+    return $num;
+};
+
+echo "4! = ", $factorial(4), PHP_EOL;
+
+$dynamic = function(bool $root = false) as $test use(&$dynamic) {
+    if ($root) {
+        $dynamic = function() {
+            return "Hello";
+        };
+        return $test();
+    } else {
+        return "Hi";
+    }
+};
+
+echo $dynamic(true), PHP_EOL;
+echo $dynamic(true), PHP_EOL;
+
+echo (function() as $fn : string {
+    echo get_class($fn), PHP_EOL;
+    return "Bye";
+})(), PHP_EOL;
+
+?>
+--EXPECTF--
+4! = 24
+Hi
+Hello
+Closure
+Bye

Zend/tests/closures/closure_self_reference_error_arrow_param.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Closure self-reference can't reuse parameter variable name (arrow function)
+--FILE--
+<?php
+
+fn(int $a) as $a => 1;
+
+?>
+--EXPECTF--
+Fatal error: Cannot use lexical variable $a as self reference in %s on line %d

Zend/tests/closures/closure_self_reference_error_arrow_this.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Closure self-reference can't use this as a variable name (arrow function)
+--FILE--
+<?php
+
+fn() as $this => 1;
+
+?>
+--EXPECTF--
+Fatal error: Cannot use $this as self reference in %s on line %d

Zend/tests/closures/closure_self_reference_error_bind.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Closure self-reference can't reuse static variable name
+--FILE--
+<?php
+
+function() as $a use($a) {};
+
+?>
+--EXPECTF--
+Fatal error: Cannot use lexical variable $a as self reference in %s on line %d

Zend/tests/closures/closure_self_reference_error_param.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Closure self-reference can't reuse parameter variable name
+--FILE--
+<?php
+
+function(int $a) as $a {};
+
+?>
+--EXPECTF--
+Fatal error: Cannot use lexical variable $a as self reference in %s on line %d

Zend/tests/closures/closure_self_reference_error_this.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Closure self-reference can't use this as a variable name
+--FILE--
+<?php
+
+function() as $this {};
+
+?>
+--EXPECTF--
+Fatal error: Cannot use $this as self reference in %s on line %d

Zend/tests/closures/closure_self_reference_generator.phpt

@@ -0,0 +1,23 @@
+--TEST--
+Testing Closure self-reference functionality: Generator
+--FILE--
+<?php
+
+$fn = function(int $max) as $fn {
+    yield from range($max, 0, -1);
+    if ($max > 1) {
+        yield from $fn($max - 1);
+    }
+};
+print_r(iterator_to_array($fn(2), false));
+
+?>
+--EXPECT--
+Array
+(
+    [0] => 2
+    [1] => 1
+    [2] => 0
+    [3] => 1
+    [4] => 0
+)

Zend/tests/closures/closure_self_reference_instances.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Testing Closure self-reference functionality: Closure instances
+--FILE--
+<?php
+
+$map = new WeakMap();
+
+$fn = function() as $fn use ($map) {
+    var_dump(isset($map[$fn]));
+};
+$map[$fn] = 1;
+$fn();
+$fn->call(new class {});
+$fn();
+
+var_dump(count($map));
+unset($fn);
+var_dump(count($map));
+
+?>
+--EXPECT--
+bool(true)
+bool(false)
+bool(true)
+int(1)
+int(0)

Zend/tests/closures/closure_self_reference_this.phpt

@@ -0,0 +1,32 @@
+--TEST--
+Testing Closure self-reference functionality: This binding
+--FILE--
+<?php
+
+$closure = null;
+$fn = function(bool $root = false, bool $set = false) as $fn use(&$closure) : void {
+    echo $this::A, PHP_EOL;
+    if ($set) {
+        $closure = $fn;
+    }
+    if ($root) {
+        $fn();
+    }
+    return;
+};
+$fn = $fn->bindTo(new class{const A="bind";});
+$fn(true, true);
+$fn->call(new class{const A="call";}, true, true);
+$fn(true, false);
+$closure(true, false);
+
+?>
+--EXPECTF--
+bind
+bind
+call
+call
+bind
+bind
+call
+call

Zend/zend_ast.c

@@ -111,7 +111,7 @@ ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_class_const_or_name(zend_ast *
 
 ZEND_API zend_ast *zend_ast_create_decl(
 	zend_ast_kind kind, uint32_t flags, uint32_t start_lineno, zend_string *doc_comment,
-	zend_string *name, zend_ast *child0, zend_ast *child1, zend_ast *child2, zend_ast *child3, zend_ast *child4
+	zend_string *name, zend_ast *child0, zend_ast *child1, zend_ast *child2, zend_ast *child3, zend_ast *child4, zend_ast *child5
 ) {
 	zend_ast_decl *ast;
 
@@ -128,6 +128,7 @@ ZEND_API zend_ast *zend_ast_create_decl(
 	ast->child[2] = child2;
 	ast->child[3] = child3;
 	ast->child[4] = child4;
+	ast->child[5] = child5;
 
 	return (zend_ast *) ast;
 }
@@ -1165,7 +1166,8 @@ ZEND_API void ZEND_FASTCALL zend_ast_destroy(zend_ast *ast)
 		zend_ast_destroy(decl->child[1]);
 		zend_ast_destroy(decl->child[2]);
 		zend_ast_destroy(decl->child[3]);
-		ast = decl->child[4];
+		zend_ast_destroy(decl->child[4]);
+		ast = decl->child[5];
 		goto tail_call;
 	}
 }

Zend/zend_ast.h

@@ -210,7 +210,7 @@ typedef struct _zend_ast_decl {
 	uint32_t flags;
 	zend_string *doc_comment;
 	zend_string *name;
-	zend_ast *child[5];
+	zend_ast *child[6];
 } zend_ast_decl;
 
 typedef void (*zend_ast_process_t)(zend_ast *ast);
@@ -294,7 +294,7 @@ ZEND_API zend_ast * ZEND_FASTCALL zend_ast_list_add(zend_ast *list, zend_ast *op
 
 ZEND_API zend_ast *zend_ast_create_decl(
 	zend_ast_kind kind, uint32_t flags, uint32_t start_lineno, zend_string *doc_comment,
-	zend_string *name, zend_ast *child0, zend_ast *child1, zend_ast *child2, zend_ast *child3, zend_ast *child4
+	zend_string *name, zend_ast *child0, zend_ast *child1, zend_ast *child2, zend_ast *child3, zend_ast *child4, zend_ast *child5
 );
 
 typedef struct {

Zend/zend_closures.c

@@ -149,7 +149,7 @@ ZEND_METHOD(Closure, call)
 	ZVAL_UNDEF(&closure_result);
 	fci.retval = &closure_result;
 
-	if (closure->func.common.fn_flags & ZEND_ACC_GENERATOR) {
+	if (closure->func.common.fn_flags & (ZEND_ACC_GENERATOR | ZEND_ACC_SELF_REFERENCE)) {
 		zval new_closure;
 		zend_create_closure(&new_closure, &closure->func, newclass, closure->called_scope, newthis);
 		closure = (zend_closure *) Z_OBJ(new_closure);

Zend/zend_compile.c

@@ -7195,7 +7195,7 @@ static void find_implicit_binds_recursively(closure_info *info, zend_ast *ast) {
 	}
 }
 
-static void find_implicit_binds(closure_info *info, zend_ast *params_ast, zend_ast *stmt_ast)
+static void find_implicit_binds(closure_info *info, zend_ast *params_ast, zend_ast *stmt_ast, zend_ast *as_ast)
 {
 	zend_ast_list *param_list = zend_ast_get_list(params_ast);
 	uint32_t i;
@@ -7209,6 +7209,9 @@ static void find_implicit_binds(closure_info *info, zend_ast *params_ast, zend_a
 		zend_ast *param_ast = param_list->child[i];
 		zend_hash_del(&info->uses, zend_ast_get_str(param_ast->child[1]));
 	}
+	if (as_ast) {
+		zend_hash_del(&info->uses, zend_ast_get_str(as_ast));
+	}
 }
 
 static void compile_implicit_lexical_binds(
@@ -7272,6 +7275,36 @@ static void zend_compile_closure_uses(zend_ast *ast) /* {{{ */
 }
 /* }}} */
 
+static void zend_compile_closure_self_reference(zend_ast *ast) /* {{{ */
+{
+	zend_op_array* op_array = CG(active_op_array);
+
+	zend_string *var_name = zend_ast_get_str(ast);
+
+	CG(zend_lineno) = zend_ast_get_lineno(ast);
+
+	{
+		int i;
+		for (i = 0; i < op_array->last_var; i++) {
+			if (zend_string_equals(op_array->vars[i], var_name)) {
+				zend_error_noreturn(E_COMPILE_ERROR,
+					"Cannot use lexical variable $%s as self reference", ZSTR_VAL(var_name));
+			}
+		}
+	}
+
+	if (zend_string_equals_literal(var_name, "this")) {
+		zend_error_noreturn(E_COMPILE_ERROR, "Cannot use $this as self reference");
+	}
+
+	zend_op *opline;
+
+	opline = zend_emit_op(NULL, ZEND_BIND_SELF_REFERENCE, NULL, NULL);
+	opline->op1_type = IS_CV;
+	opline->op1.var = lookup_cv(var_name);
+}
+/* }}} */
+
 static void zend_compile_implicit_closure_uses(closure_info *info)
 {
 	zend_string *var_name;
@@ -7433,6 +7466,7 @@ static void zend_compile_func_decl(znode *result, zend_ast *ast, bool toplevel)
 	zend_ast *uses_ast = decl->child[1];
 	zend_ast *stmt_ast = decl->child[2];
 	zend_ast *return_type_ast = decl->child[3];
+	zend_ast *as_ast = decl->child[5];
 	bool is_method = decl->kind == ZEND_AST_METHOD;
 	zend_string *lcname;
 
@@ -7467,7 +7501,7 @@ static void zend_compile_func_decl(znode *result, zend_ast *ast, bool toplevel)
 	} else {
 		lcname = zend_begin_func_decl(result, op_array, decl, toplevel);
 		if (decl->kind == ZEND_AST_ARROW_FUNC) {
-			find_implicit_binds(&info, params_ast, stmt_ast);
+			find_implicit_binds(&info, params_ast, stmt_ast, as_ast);
 			compile_implicit_lexical_binds(&info, result, op_array);
 		} else if (uses_ast) {
 			zend_compile_closure_binding(result, op_array, uses_ast);
@@ -7520,6 +7554,11 @@ static void zend_compile_func_decl(znode *result, zend_ast *ast, bool toplevel)
 		zend_compile_closure_uses(uses_ast);
 	}
 
+	if (as_ast) {
+		zend_compile_closure_self_reference(as_ast);
+		op_array->fn_flags |= ZEND_ACC_SELF_REFERENCE;
+	}
+
 	if (ast->kind == ZEND_AST_ARROW_FUNC) {
 		bool needs_return = true;
 		if (op_array->fn_flags & ZEND_ACC_HAS_RETURN_TYPE) {

Zend/zend_compile.h

@@ -304,7 +304,7 @@ typedef struct _zend_oparray_context {
 /* Class cannot be serialized or unserialized             |     |     |     */
 #define ZEND_ACC_NOT_SERIALIZABLE        (1 << 29) /*  X  |     |     |     */
 /*                                                        |     |     |     */
-/* Function Flags (unused: 28-30)                         |     |     |     */
+/* Function Flags (unused: 29-30)                         |     |     |     */
 /* ==============                                         |     |     |     */
 /*                                                        |     |     |     */
 /* deprecation flag                                       |     |     |     */
@@ -364,6 +364,9 @@ typedef struct _zend_oparray_context {
 #define ZEND_ACC_COMPILE_TIME_EVAL       (1 << 27) /*     |  X  |     |     */
 /*                                                        |     |     |     */
 /* op_array uses strict mode types                        |     |     |     */
+#define ZEND_ACC_SELF_REFERENCE          (1 << 28) /*     |  X  |     |     */
+/*                                                        |     |     |     */
+/* op_array uses strict mode types                        |     |     |     */
 #define ZEND_ACC_STRICT_TYPES            (1U << 31) /*    |  X  |     |     */