fallback slug separator to '-' in case of alphanumeric separator

Author: faissaloux

src/Illuminate/Support/Str.php

@@ -1464,6 +1464,7 @@ public static function singular($value)
     public static function slug($title, $separator = '-', $language = 'en', $dictionary = ['@' => 'at'])
     {
         $title = $language ? static::ascii($title, $language) : $title;
+        $separator = ctype_alnum($separator) ? '-' : $separator;
 
         // Convert all dashes/underscores into separator
         $flip = $separator === '-' ? '_' : '-';

tests/Support/SupportStringableTest.php

@@ -739,6 +739,10 @@ public function testSlug()
         $this->assertSame('sometext', (string) $this->stringable('some text')->slug(''));
         $this->assertSame('', (string) $this->stringable('')->slug(''));
         $this->assertSame('', (string) $this->stringable('')->slug());
+        $this->assertSame('hello-world', (string) $this->stringable('hello world')->slug('eb'));
+        $this->assertSame('hello-world', (string) $this->stringable('hello world')->slug('e'));
+        $this->assertSame('hello-world', (string) $this->stringable('hello world')->slug('2'));
+        $this->assertSame('hello-world', (string) $this->stringable('hello world')->slug('2'));
     }
 
     public function testSquish()