Do not prefix scalar strings with known internal class names

specs/string-literal/array-var.php

@@ -70,6 +70,31 @@
 
         PHP,
 
+    'String argument referencing a namespaced internal class' => <<<'PHP'
+        <?php
+
+        $subclasses['PDO\\Mysql'] = 'PDO\\Mysql';
+        $subclasses['Random\\Randomizer'] = 'Random\\Randomizer';
+        $subclasses['Filter\\FilterFailedException'] = 'Filter\\FilterFailedException';
+
+        $x = [
+            'Random\\Randomizer' => 'Random\\Randomizer',
+            'PDO\\Mysql' => 'PDO\\Mysql',
+            'Filter\\FilterFailedException' => 'Filter\\FilterFailedException',
+        ];
+
+        ----
+        <?php
+
+        namespace Humbug;
+
+        $subclasses['PDO\Mysql'] = 'PDO\Mysql';
+        $subclasses['Random\Randomizer'] = 'Random\Randomizer';
+        $subclasses['Filter\FilterFailedException'] = 'Filter\FilterFailedException';
+        $x = ['Random\Randomizer' => 'Random\Randomizer', 'PDO\Mysql' => 'PDO\Mysql', 'Filter\FilterFailedException' => 'Filter\FilterFailedException'];
+
+        PHP,
+
     'Array item of a list with class-like symbols' => <<<'PHP'
         <?php
 

specs/string-literal/new.php

@@ -48,6 +48,39 @@
 
         PHP,
 
+    'FQCN string argument referencing a namespaced internal class' => <<<'PHP'
+        <?php
+
+        new X('Random\\Randomizer');
+        new X('\\Random\\Randomizer');
+        new X('PDO\\Mysql');
+        new X('\\PDO\\Mysql');
+        new X('Pdo\\Sqlite');
+        new X('Filter\\FilterFailedException');
+        new X('\\Filter\\FilterFailedException');
+
+        new X('Symfony\\Component\\Yaml\\Ya_1');
+        new X('Yaml');
+        new DateTime('now');
+
+        ----
+        <?php
+
+        namespace Humbug;
+
+        new X('Random\Randomizer');
+        new X('\Random\Randomizer');
+        new X('PDO\Mysql');
+        new X('\PDO\Mysql');
+        new X('Pdo\Sqlite');
+        new X('Filter\FilterFailedException');
+        new X('\Filter\FilterFailedException');
+        new X('Humbug\Symfony\Component\Yaml\Ya_1');
+        new X('Yaml');
+        new \DateTime('now');
+
+        PHP,
+
     'FQCN string argument on exposed class' => SpecWithConfig::create(
         exposeClasses: ['Symfony\Component\Yaml\Yaml'],
         spec: <<<'PHP'

specs/string-literal/var.php

@@ -50,6 +50,28 @@
 
         PHP,
 
+    'FQCN string argument referencing a namespaced internal class' => <<<'PHP'
+        <?php
+
+        $x = 'Random\\Randomizer';
+        $x = '\\Random\\Randomizer';
+        $x = 'PDO\\Mysql';
+        $x = '\\PDO\\Mysql';
+        $x = 'Filter\\FilterFailedException';
+
+        ----
+        <?php
+
+        namespace Humbug;
+
+        $x = 'Random\Randomizer';
+        $x = '\Random\Randomizer';
+        $x = 'PDO\Mysql';
+        $x = '\PDO\Mysql';
+        $x = 'Filter\FilterFailedException';
+
+        PHP,
+
     'Invalid FQCN strings' => <<<'PHP'
         <?php
 

src/PhpParser/NodeVisitor/StringScalarPrefixer.php

@@ -182,9 +182,7 @@ private function prefixStringScalar(String_ $string): String_
 
         // If belongs to the global namespace then we cannot differentiate the
         // value from a symbol and a regular string hence we leave it alone
-        return $this->belongsToTheGlobalNamespace($string)
-            ? $string
-            : $this->createPrefixedString($string);
+        return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
     }
 
     private function prefixStringArg(String_ $string, Arg $parentNode, string $normalizedValue): String_
@@ -379,9 +377,15 @@ private static function isConstantNode(String_ $node): bool
     private function createPrefixedStringIfDoesNotBelongToGlobalNamespace(String_ $string): String_
     {
         // If belongs to the global namespace then we cannot differentiate the value from a symbol and a regular string
-        return $this->belongsToTheGlobalNamespace($string)
-            ? $string
-            : $this->createPrefixedString($string);
+        if ($this->belongsToTheGlobalNamespace($string)) {
+            return $string;
+        }
+
+        if ($this->enrichedReflector->isClassExcluded(ltrim($string->value, '\\'))) {
+            return $string;
+        }
+
+        return $this->createPrefixedString($string);
     }
 
     private function belongsToTheGlobalNamespace(String_ $string): bool