Variable sniffs: minor performance tweak

The `AbstractVariableSniff` by default listens to all `T_VARIABLE`, `T_DOUBLE_QUOTED_STRING` and `T_HEREDOC` tokens.

The majority of the sniffs extending the `AbstractVariableSniff`, however, only handle `T_VARIABLE` tokens and in particular, only handle `T_VARIABLE` tokens when in an OO scope and nothing more.

This small tweak means these sniffs will no longer "listen" to `T_DOUBLE_QUOTED_STRING` and `T_HEREDOC` tokens, which should make them marginally faster, in particular for code bases containing lots of `T_DOUBLE_QUOTED_STRING` and `T_HEREDOC` tokens.

It also means that these sniff will no longer be triggered for `T_VARIABLE` tokens outside of an OO context.

src/Standards/PEAR/Sniffs/NamingConventions/ValidVariableNameSniff.php

@@ -10,12 +10,27 @@
 namespace PHP_CodeSniffer\Standards\PEAR\Sniffs\NamingConventions;
 
 use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\AbstractScopeSniff;
 use PHP_CodeSniffer\Sniffs\AbstractVariableSniff;
+use PHP_CodeSniffer\Util\Tokens;
 
 class ValidVariableNameSniff extends AbstractVariableSniff
 {
 
 
+    /**
+     * Only listen to variables within OO scopes.
+     */
+    public function __construct()
+    {
+        $scopes = Tokens::$ooScopeTokens;
+        $listen = [T_VARIABLE];
+
+        AbstractScopeSniff::__construct($scopes, $listen, false);
+
+    }//end __construct()
+
+
     /**
      * Processes class member variables.
      *

src/Standards/PSR2/Sniffs/Classes/PropertyDeclarationSniff.php

@@ -11,13 +11,27 @@
 
 use Exception;
 use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\AbstractScopeSniff;
 use PHP_CodeSniffer\Sniffs\AbstractVariableSniff;
 use PHP_CodeSniffer\Util\Tokens;
 
 class PropertyDeclarationSniff extends AbstractVariableSniff
 {
 
 
+    /**
+     * Only listen to variables within OO scopes.
+     */
+    public function __construct()
+    {
+        $scopes = Tokens::$ooScopeTokens;
+        $listen = [T_VARIABLE];
+
+        AbstractScopeSniff::__construct($scopes, $listen, false);
+
+    }//end __construct()
+
+
     /**
      * Processes the function tokens within the class.
      *

src/Standards/Squiz/Sniffs/Commenting/VariableCommentSniff.php

@@ -10,13 +10,28 @@
 namespace PHP_CodeSniffer\Standards\Squiz\Sniffs\Commenting;
 
 use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\AbstractScopeSniff;
 use PHP_CodeSniffer\Sniffs\AbstractVariableSniff;
 use PHP_CodeSniffer\Util\Common;
+use PHP_CodeSniffer\Util\Tokens;
 
 class VariableCommentSniff extends AbstractVariableSniff
 {
 
 
+    /**
+     * Only listen to variables within OO scopes.
+     */
+    public function __construct()
+    {
+        $scopes = Tokens::$ooScopeTokens;
+        $listen = [T_VARIABLE];
+
+        AbstractScopeSniff::__construct($scopes, $listen, false);
+
+    }//end __construct()
+
+
     /**
      * Called to process class member vars.
      *

src/Standards/Squiz/Sniffs/Scope/MemberVarScopeSniff.php

@@ -10,12 +10,27 @@
 namespace PHP_CodeSniffer\Standards\Squiz\Sniffs\Scope;
 
 use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\AbstractScopeSniff;
 use PHP_CodeSniffer\Sniffs\AbstractVariableSniff;
+use PHP_CodeSniffer\Util\Tokens;
 
 class MemberVarScopeSniff extends AbstractVariableSniff
 {
 
 
+    /**
+     * Only listen to variables within OO scopes.
+     */
+    public function __construct()
+    {
+        $scopes = Tokens::$ooScopeTokens;
+        $listen = [T_VARIABLE];
+
+        AbstractScopeSniff::__construct($scopes, $listen, false);
+
+    }//end __construct()
+
+
     /**
      * Processes the function tokens within the class.
      *

src/Standards/Squiz/Sniffs/WhiteSpace/MemberVarSpacingSniff.php

@@ -10,6 +10,7 @@
 namespace PHP_CodeSniffer\Standards\Squiz\Sniffs\WhiteSpace;
 
 use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\AbstractScopeSniff;
 use PHP_CodeSniffer\Sniffs\AbstractVariableSniff;
 use PHP_CodeSniffer\Util\Tokens;
 
@@ -31,6 +32,19 @@ class MemberVarSpacingSniff extends AbstractVariableSniff
     public $spacingBeforeFirst = 1;
 
 
+    /**
+     * Only listen to variables within OO scopes.
+     */
+    public function __construct()
+    {
+        $scopes = Tokens::$ooScopeTokens;
+        $listen = [T_VARIABLE];
+
+        AbstractScopeSniff::__construct($scopes, $listen, false);
+
+    }//end __construct()
+
+
     /**
      * Processes the function tokens within the class.
      *