Make docblocks sligtly more phpdoc-compatible

src/Psalm/Checker/FileChecker.php

@@ -63,7 +63,7 @@ class FileChecker extends SourceChecker implements StatementsSource
     protected $function_checkers = [];
 
     /**
-     * @var ?Context
+     * @var null|Context
      */
     public $context;
 

src/Psalm/Checker/Statements/Expression/CallChecker.php

@@ -2325,7 +2325,7 @@ class CallChecker
             $array_arg_types[] = $array_arg_type;
         }
 
-        /** @var ?PhpParser\Node\Arg */
+        /** @var null|PhpParser\Node\Arg */
         $closure_arg = isset($args[$closure_index]) ? $args[$closure_index] : null;
 
         /** @var Type\Union|null */

src/Psalm/CodeLocation.php

@@ -41,7 +41,7 @@ class CodeLocation
     /** @var string */
     private $snippet = '';
 
-    /** @var ?string */
+    /** @var null|string */
     private $text;
 
     /** @var int|null */
@@ -50,13 +50,13 @@ class CodeLocation
     /** @var int|null */
     private $docblock_line_number;
 
-    /** @var ?int */
+    /** @var null|int */
     private $regex_type;
 
     /** @var bool */
     private $have_recalculated = false;
 
-    /** @var ?CodeLocation */
+    /** @var null|CodeLocation */
     public $previous_location;
 
     const VAR_TYPE = 0;

src/Psalm/Codebase.php

@@ -169,7 +169,7 @@ class Codebase
     public $collect_references = false;
 
     /**
-     * @var ?array<string, string>
+     * @var null|array<string, string>
      */
     private $composer_classmap;
 

src/Psalm/Context.php

@@ -45,7 +45,7 @@ class Context
     public $inside_isset = false;
 
     /**
-     * @var ?CodeLocation
+     * @var null|CodeLocation
      */
     public $include_location = null;
 

src/Psalm/FileManipulation/FunctionDocblockManipulator.php

@@ -32,25 +32,25 @@ class FunctionDocblockManipulator
     /** @var int */
     private $return_typehint_area_start;
 
-    /** @var ?int */
+    /** @var null|int */
     private $return_typehint_colon_start;
 
-    /** @var ?int */
+    /** @var null|int */
     private $return_typehint_start;
 
-    /** @var ?int */
+    /** @var null|int */
     private $return_typehint_end;
 
-    /** @var ?string */
+    /** @var null|string */
     private $new_php_return_type;
 
     /** @var bool */
     private $return_type_is_php_compatible = false;
 
-    /** @var ?string */
+    /** @var null|string */
     private $new_phpdoc_return_type;
 
-    /** @var ?string */
+    /** @var null|string */
     private $new_psalm_return_type;
 
     /** @var array<string, int> */

src/Psalm/Type/Union.php

@@ -60,7 +60,7 @@ class Union
      */
     public $by_ref = false;
 
-    /** @var ?string */
+    /** @var null|string */
     private $id;
 
     /**