Fix compiler assumptions about self/etc wrt closures

* Don't throw an error if self/parent/static are used in a closure
  (outside a class).
* Don't propagate self:: constants into closures
* Use runtime fetch for self::class in closures

Fixes bug #66811.

Zend/tests/bug66811.phpt

@@ -0,0 +1,37 @@
+--TEST--
+Bug #66811: Cannot access static::class in lambda, writen outside of a class
+--FILE--
+<?php
+class A {
+    public static function f() {
+        return function () {
+            var_dump(self::class);
+            var_dump(static::class);
+        };
+    }
+}
+
+class B extends A {}
+
+$f = B::f();
+$f();
+
+$g = $f->bindTo(null, A::class);
+$g();
+
+$foo = function () {
+    var_dump(self::class);
+    var_dump(static::class);
+};
+
+$bar = $foo->bindTo(null, A::class);
+$bar();
+
+?>
+--EXPECT--
+string(1) "A"
+string(1) "B"
+string(1) "A"
+string(1) "A"
+string(1) "A"
+string(1) "A"

Zend/tests/no_class_const_propagation_in_closures.phpt

@@ -0,0 +1,25 @@
+--TEST--
+self:: class constants should not be propagated into closures, due to scope rebinding
+--FILE--
+<?php
+
+class A {
+    const C = 'A::C';
+
+    public function f() {
+        return function() {
+            return self::C;
+        };
+    }
+}
+
+class B {
+    const C = 'B::C';
+}
+
+$f = (new A)->f();
+var_dump($f->bindTo(null, 'B')());
+
+?>
+--EXPECT--
+string(4) "B::C"

Zend/tests/return_types/025.phpt

@@ -1,10 +1,12 @@
 --TEST--
-Return type of self is not allowed in closure
+Return type of self is allowed in closure
 
 --FILE--
 <?php
 
-$c = function(): self {};
+$c = function(): self { return $this; };
+var_dump($c->call(new stdClass));
 
---EXPECTF--
-Fatal error: Cannot use "self" when no class scope is active in %s on line 3
+--EXPECT--
+object(stdClass)#2 (0) {
+}

Zend/tests/return_types/027.phpt

@@ -1,9 +1,14 @@
 --TEST--
-Return type of parent is not allowed in closure
+Return type of parent is allowed in closure
 --FILE--
 <?php
 
-$c = function(): parent {};
+class A {}
+class B extends A {}
+
+$c = function(parent $x): parent { return $x; };
+var_dump($c->bindTo(null, 'B')(new A));
 
 --EXPECTF--
-Fatal error: Cannot use "parent" when no class scope is active in %s on line 3
+object(A)#%d (0) {
+}

Zend/zend_compile.c

@@ -1318,12 +1318,42 @@ static zend_bool zend_try_ct_eval_const(zval *zv, zend_string *name, zend_bool i
 }
 /* }}} */
 
+static inline zend_bool zend_is_scope_known() /* {{{ */
+{
+	if (CG(active_op_array)->fn_flags & ZEND_ACC_CLOSURE) {
+		/* Closures can be rebound to a different scope */
+		return 0;
+	}
+
+	if (!CG(active_class_entry)) {
+		/* Not being in a scope is a known scope */
+		return 1;
+	}
+
+	/* For traits self etc refers to the using class, not the trait itself */
+	return (CG(active_class_entry)->ce_flags & ZEND_ACC_TRAIT) == 0;
+}
+/* }}} */
+
+static inline zend_bool class_name_refers_to_active_ce(zend_string *class_name, uint32_t fetch_type) /* {{{ */
+{
+	if (!CG(active_class_entry)) {
+		return 0;
+	}
+	if (fetch_type == ZEND_FETCH_CLASS_SELF && zend_is_scope_known()) {
+		return 1;
+	}
+	return fetch_type == ZEND_FETCH_CLASS_DEFAULT
+		&& zend_string_equals_ci(class_name, CG(active_class_entry)->name);
+}
+/* }}} */
+
 static zend_bool zend_try_ct_eval_class_const(zval *zv, zend_string *class_name, zend_string *name) /* {{{ */
 {
 	uint32_t fetch_type = zend_get_class_fetch_type(class_name);
 	zval *c;
 
-	if (CG(active_class_entry) && (fetch_type == ZEND_FETCH_CLASS_SELF || (fetch_type == ZEND_FETCH_CLASS_DEFAULT && zend_string_equals_ci(class_name, CG(active_class_entry)->name)))) {
+	if (class_name_refers_to_active_ce(class_name, fetch_type)) {
 		c = zend_hash_find(&CG(active_class_entry)->constants_table, name);
 	} else if (fetch_type == ZEND_FETCH_CLASS_DEFAULT && !(CG(compiler_options) & ZEND_COMPILE_NO_CONSTANT_SUBSTITUTION)) {
 		zend_class_entry *ce = zend_hash_find_ptr_lc(CG(class_table), class_name->val, class_name->len);
@@ -1623,9 +1653,9 @@ static uint32_t zend_get_class_fetch_type_ast(zend_ast *name_ast) /* {{{ */
 }
 /* }}} */
 
-void zend_ensure_valid_class_fetch_type(uint32_t fetch_type) /* {{{ */
+static void zend_ensure_valid_class_fetch_type(uint32_t fetch_type) /* {{{ */
 {
-	if (fetch_type != ZEND_FETCH_CLASS_DEFAULT && !CG(active_class_entry)) {
+	if (fetch_type != ZEND_FETCH_CLASS_DEFAULT && !CG(active_class_entry) && zend_is_scope_known()) {
 		zend_error_noreturn(E_COMPILE_ERROR, "Cannot use \"%s\" when no class scope is active",
 			fetch_type == ZEND_FETCH_CLASS_SELF ? "self" :
 			fetch_type == ZEND_FETCH_CLASS_PARENT ? "parent" : "static");
@@ -6348,12 +6378,12 @@ void zend_compile_resolve_class_name(znode *result, zend_ast *ast) /* {{{ */
 
 	switch (fetch_type) {
 		case ZEND_FETCH_CLASS_SELF:
-			if (CG(active_class_entry)->ce_flags & ZEND_ACC_TRAIT) {
-				zend_op *opline = zend_emit_op_tmp(result, ZEND_FETCH_CLASS_NAME, NULL, NULL);
-				opline->extended_value = fetch_type;
-			} else {
+			if (CG(active_class_entry) && zend_is_scope_known()) {
 				result->op_type = IS_CONST;
 				ZVAL_STR_COPY(&result->u.constant, CG(active_class_entry)->name);
+			} else {
+				zend_op *opline = zend_emit_op_tmp(result, ZEND_FETCH_CLASS_NAME, NULL, NULL);
+				opline->extended_value = fetch_type;
 			}
 			break;
 		case ZEND_FETCH_CLASS_STATIC: