PHP 8.0: NewNestedStaticAccess: add support for class constant dereferencing

Matt Turland · Matt Turland · commit 2a0925d26009 · 2020-12-27T15:24:53.000-06:00
> ... class constant accesses are only array and object dereferencable. This > means that while `Foo::$bar::$baz` is legal, `Foo::BAR::$baz` is not. > > This RFC proposes to make class constant accesses static derefencable as > well, so that `Foo::BAR::$baz` and `Foo::BAR::BAZ` become legal. Ref: * https://wiki.php.net/rfc/variable_syntax_tweaks#class_constant_dereferencability * php/php-src#5061 * php/php-src@ab154b7 Includes unit tests. Relates to PHPCompatibility#809.
diff --git a/PHPCompatibility/Sniffs/Syntax/NewNestedStaticAccessSniff.php b/PHPCompatibility/Sniffs/Syntax/NewNestedStaticAccessSniff.php
@@ -18,9 +18,13 @@
  * (Nested) Static property and constant fetches as well as method calls can be applied to
  * any dereferencable expression since PHP 7.0.
  *
+ * Class constants can be dereferenced since PHP 8.0.
+ *
  * PHP version 7.0
+ * PHP version 8.0
  *
  * @link https://wiki.php.net/rfc/uniform_variable_syntax
+ * @link https://wiki.php.net/rfc/variable_syntax_tweaks#class_constant_dereferencability
  *
  * @since 10.0.0
  */
@@ -64,7 +68,8 @@ public function register()
      */
     public function process(File $phpcsFile, $stackPtr)
     {
-        if ($this->supportsBelow('5.6') === false) {
+        // PHP 8.0 supports both nested static access and class constant dereferencing
+        if ($this->supportsBelow('7.4') === false) {
             return;
         }
 
@@ -122,19 +127,27 @@ public function process(File $phpcsFile, $stackPtr)
             return;
         }
 
-        // Ignore the one form of nested static access which is still not supported: ?::CONST::?.
+        // Class constants cannot be dereferenced before PHP 8.0.
         if ($seenBrackets === false
             && $tokens[$prev]['code'] === \T_STRING
             && $tokens[$prevOperator]['code'] === \T_DOUBLE_COLON
+            && $this->supportsBelow('7.4') === true
         ) {
+            $phpcsFile->addError(
+                'Class constants cannot be dereferenced in PHP 7.4 or earlier.',
+                $stackPtr,
+                'Found'
+            );
             return;
         }
 
         // This is nested static access.
-        $phpcsFile->addError(
-            'Nested access to static properties, constants and methods was not supported in PHP 5.6 or earlier.',
-            $stackPtr,
-            'Found'
-        );
+        if ($this->supportsBelow('5.6') === true) {
+            $phpcsFile->addError(
+                'Nested access to static properties, constants and methods was not supported in PHP 5.6 or earlier.',
+                $stackPtr,
+                'Found'
+            );
+        }
     }
 }
diff --git a/PHPCompatibility/Tests/Syntax/NewNestedStaticAccessUnitTest.inc b/PHPCompatibility/Tests/Syntax/NewNestedStaticAccessUnitTest.inc
@@ -30,7 +30,7 @@ echo ($foo->bar())::baz();
 // Parse error in any PHP version. Outside the scope of this sniff.
 echo $bar::($foo['bar'])::$baz;
 
-// Still not supported.
+// PHP 8.0: class constant dereferencing
 self::MY_CONSTANT::$baz;
 Foo::MY_CONSTANT::$baz;
 
diff --git a/PHPCompatibility/Tests/Syntax/NewNestedStaticAccessUnitTest.php b/PHPCompatibility/Tests/Syntax/NewNestedStaticAccessUnitTest.php
@@ -69,6 +69,37 @@ public function dataNestedStaticAccess()
     }
 
 
+    /**
+     * testClassConstantDereferencing
+     *
+     * @dataProvider dataClassConstantDereferencing
+     *
+     * @param int $line The line number.
+     *
+     * @return void
+     */
+    public function testClassConstantDereferencing($line)
+    {
+        $file = $this->sniffFile(__FILE__, '7.4');
+        $this->assertError($file, $line, 'Class constants cannot be dereferenced in PHP 7.4 or earlier.');
+    }
+
+    /**
+     * Data provider.
+     *
+     * @see testClassConstantDereferencing()
+     *
+     * @return array
+     */
+    public function dataClassConstantDereferencing()
+    {
+        return [
+            [34],
+            [35],
+        ];
+    }
+
+
     /**
      * Verify the sniff doesn't throw false positives.
      *
@@ -98,8 +129,6 @@ public function dataNoFalsePositives()
             [27],
             [28],
             [31],
-            [34],
-            [35],
         ];
     }
 
@@ -111,7 +140,7 @@ public function dataNoFalsePositives()
      */
     public function testNoViolationsInFileOnValidVersion()
     {
-        $file = $this->sniffFile(__FILE__, '7.0');
+        $file = $this->sniffFile(__FILE__, '8.0');
         $this->assertNoViolation($file);
     }
 }
