Mark backslashit and untrailingslashit as pure

functionMap.php

@@ -55,6 +55,7 @@
     'add_users_page' => [null, 'callback' => "''|callable"],
     'addslashes_gpc' => ['($gpc is string ? string : array)', '@phpstan-pure' => ''],
     'antispambot' => [null, 'hex_encoding' => '0|1'],
+    'backslashit' => [null, '@phpstan-pure' => ''],
     'block_version' => ["(\$content is '' ? 0 : 0|1)", '@phpstan-pure' => ''],
     'bool_from_yn' => ["(\$yn is 'y' ? true : false)", '@phpstan-pure' => ''],
     'build_dropdown_script_block_core_categories' => ['non-falsy-string'],
@@ -156,6 +157,7 @@
     'the_modified_date' => ['($display is true ? void : string)'],
     'the_title' => ['($display is true ? void : string|void)'],
     'trailingslashit' => ['non-falsy-string', '@phpstan-pure' => ''],
+    'untrailingslashit' => [null, '@phpstan-pure' => ''],
     'urldecode_deep' => ['T', '@phpstan-template' => 'T', 'value' => 'T'],
     'urlencode_deep' => ['T', '@phpstan-template' => 'T', 'value' => 'T'],
     'validate_file' => ["(\$file is '' ? 0 : (\$allowed_files is empty ? 0|1|2 : 0|1|2|3))"],

tests/data/pure/backslashit.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function backslashit;
+use function PHPStan\Testing\assertType;
+
+$value = Faker::string();
+
+if (backslashit($value) === 'foo') {
+    assertType("'foo'", backslashit($value));
+}
+
+if (backslashit($value) !== 'foo') {
+    assertType('string', backslashit($value));
+}

tests/data/pure/untrailingslashit.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function untrailingslashit;
+use function PHPStan\Testing\assertType;
+
+$value = Faker::string();
+
+if (untrailingslashit($value) === 'foo') {
+    assertType("'foo'", untrailingslashit($value));
+}
+
+if (untrailingslashit($value) !== 'foo') {
+    assertType('string', untrailingslashit($value));
+}

wordpress-stubs.php

@@ -109576,6 +109576,7 @@ function zeroise($number, $threshold)
      *
      * @param string $value Value to which backslashes will be added.
      * @return string String with backslashes inserted.
+     * @phpstan-pure
      */
     function backslashit($value)
     {
@@ -109609,6 +109610,7 @@ function trailingslashit($value)
      *
      * @param string $value Value from which trailing slashes will be removed.
      * @return string String without the trailing slashes.
+     * @phpstan-pure
      */
     function untrailingslashit($value)
     {