Add support for $obj::class

This allows $obj::class, which gives the same result as get_class($obj).
Anything other than an object results in TypeError.

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

Closes GH-5065.

Author: nikic

UPGRADING

@@ -367,6 +367,9 @@ PHP 8.0 UPGRADE NOTES
         class B extends A {
             public function method(...$everything) {}
         }
+  . It is now possible to fetch the class name of an object using
+    `$object::class`. The result is the same as `get_class($object)`.
+    RFC: https://wiki.php.net/rfc/class_name_literal_on_object
 
 
 - Date:

Zend/tests/class_name_of_var.phpt

@@ -0,0 +1,10 @@
+--TEST--
+An error should be generated when using ::class on a constant evaluated expression
+--FILE--
+<?php
+
+(1+1)::class;
+
+?>
+--EXPECTF--
+Fatal error: Cannot use ::class on value of type int in %s on line %d

Zend/tests/class_on_constant_evaluated_expression.phpt

@@ -0,0 +1,10 @@
+--TEST--
+::class on an expression cannot be used inside constant expressions
+--FILE--
+<?php
+
+const A = [0]::class;
+
+?>
+--EXPECTF--
+Fatal error: (expression)::class cannot be used in constant expressions in %s on line %d

Zend/tests/class_on_expression_in_constant_expression.phpt

@@ -0,0 +1,28 @@
+--TEST--
+Using ::class on an object
+--FILE--
+<?php
+
+$obj = new stdClass;
+var_dump($obj::class);
+$ref =& $obj;
+var_dump($ref::class);
+var_dump((new stdClass)::class);
+
+// Placed in a function to check that opcache doesn't perform incorrect constprop.
+function test() {
+    $other = null;
+    var_dump($other::class);
+}
+try {
+    test();
+} catch (TypeError $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+string(8) "stdClass"
+string(8) "stdClass"
+string(8) "stdClass"
+Cannot use ::class on value of type null

Zend/tests/class_on_object.phpt

@@ -1551,7 +1551,7 @@ static zend_bool zend_try_compile_const_expr_resolve_class_name(zval *zv, zend_a
 	zval *class_name;
 
 	if (class_ast->kind != ZEND_AST_ZVAL) {
-		zend_error_noreturn(E_COMPILE_ERROR, "Cannot use ::class with dynamic class name");
+		return 0;
 	}
 
 	class_name = zend_ast_get_zval(class_ast);
@@ -8246,15 +8246,27 @@ void zend_compile_class_const(znode *result, zend_ast *ast) /* {{{ */
 void zend_compile_class_name(znode *result, zend_ast *ast) /* {{{ */
 {
 	zend_ast *class_ast = ast->child[0];
-	zend_op *opline;
 
 	if (zend_try_compile_const_expr_resolve_class_name(&result->u.constant, class_ast)) {
 		result->op_type = IS_CONST;
 		return;
 	}
 
-	opline = zend_emit_op_tmp(result, ZEND_FETCH_CLASS_NAME, NULL, NULL);
-	opline->op1.num = zend_get_class_fetch_type(zend_ast_get_str(class_ast));
+	if (class_ast->kind == ZEND_AST_ZVAL) {
+		zend_op *opline = zend_emit_op_tmp(result, ZEND_FETCH_CLASS_NAME, NULL, NULL);
+		opline->op1.num = zend_get_class_fetch_type(zend_ast_get_str(class_ast));
+	} else {
+		znode expr_node;
+		zend_compile_expr(&expr_node, class_ast);
+		if (expr_node.op_type == IS_CONST) {
+			/* Unlikely case that happen if class_ast is constant folded.
+			 * Handle it here, to avoid needing a CONST specialization in the VM. */
+			zend_error_noreturn(E_COMPILE_ERROR, "Cannot use ::class on value of type %s",
+				zend_get_type_by_const(Z_TYPE(expr_node.u.constant)));
+		}
+
+		zend_emit_op_tmp(result, ZEND_FETCH_CLASS_NAME, &expr_node, NULL);
+	}
 }
 /* }}} */
 
@@ -8491,6 +8503,11 @@ void zend_compile_const_expr_class_name(zend_ast **ast_ptr) /* {{{ */
 {
 	zend_ast *ast = *ast_ptr;
 	zend_ast *class_ast = ast->child[0];
+	if (class_ast->kind != ZEND_AST_ZVAL) {
+		zend_error_noreturn(E_COMPILE_ERROR,
+			"(expression)::class cannot be used in constant expressions");
+	}
+
 	zend_string *class_name = zend_ast_get_str(class_ast);
 	uint32_t fetch_type = zend_get_class_fetch_type(class_name);
 

Zend/zend_compile.c

@@ -7992,14 +7992,32 @@ ZEND_VM_HANDLER(151, ZEND_ASSERT_CHECK, ANY, JMP_ADDR)
 	}
 }
 
-ZEND_VM_HANDLER(157, ZEND_FETCH_CLASS_NAME, UNUSED|CLASS_FETCH, ANY)
+ZEND_VM_HANDLER(157, ZEND_FETCH_CLASS_NAME, CV|TMPVAR|UNUSED|CLASS_FETCH, ANY)
 {
 	uint32_t fetch_type;
 	zend_class_entry *called_scope, *scope;
 	USE_OPLINE
 
-	fetch_type = opline->op1.num;
+	if (OP1_TYPE != IS_UNUSED) {
+		zval *op = GET_OP1_ZVAL_PTR(BP_VAR_R);
+		SAVE_OPLINE();
+		if (UNEXPECTED(Z_TYPE_P(op) != IS_OBJECT)) {
+			ZVAL_DEREF(op);
+			if (Z_TYPE_P(op) != IS_OBJECT) {
+				zend_type_error("Cannot use ::class on value of type %s",
+					zend_get_type_by_const(Z_TYPE_P(op)));
+				ZVAL_UNDEF(EX_VAR(opline->result.var));
+				FREE_OP1();
+				HANDLE_EXCEPTION();
+			}
+		}
 
+		ZVAL_STR_COPY(EX_VAR(opline->result.var), Z_OBJCE_P(op)->name);
+		FREE_OP1();
+		ZEND_VM_NEXT_OPCODE_CHECK_EXCEPTION();
+	}
+
+	fetch_type = opline->op1.num;
 	scope = EX(func)->op_array.scope;
 	if (UNEXPECTED(scope == NULL)) {
 		SAVE_OPLINE();