Allow empty statements before declare(strict_types)

Fixes GH-19719
Closes GH-19859

Author: ndossche

NEWS

@@ -13,6 +13,8 @@ PHP                                                                        NEWS
     using OPcache). (timwolla)
   . Fixed bug GH-19480 (error_log php.ini cannot be unset when open_basedir is
     configured). (nielsdos)
+  . Fixed bug GH-19719 (Allow empty statements before declare(strict_types)).
+    (nielsdos)
 
 - Curl:
   . Fix cloning of CURLOPT_POSTFIELDS when using the clone operator instead

Zend/tests/gh19719.phpt

@@ -0,0 +1,21 @@
+--TEST--
+GH-19719: Allow empty expressions before declare(strict_types)
+--FILE--
+<?php
+// e.g some comments
+?>
+<?php
+
+declare(strict_types=1);
+
+function takesInt(int $x) {}
+
+try {
+    takesInt('42');
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECTF--
+takesInt(): Argument #1 ($x) must be of type int, string given, called in %s on line %d

Zend/zend_compile.c

@@ -7008,7 +7008,7 @@ static void zend_compile_declare(zend_ast *ast) /* {{{ */
 		} else if (zend_string_equals_literal_ci(name, "strict_types")) {
 			zval value_zv;
 
-			if (FAILURE == zend_is_first_statement(ast, /* allow_nop */ 0)) {
+			if (FAILURE == zend_is_first_statement(ast, /* allow_nop */ true)) {
 				zend_error_noreturn(E_COMPILE_ERROR, "strict_types declaration must be "
 					"the very first statement in the script");
 			}