Generic/DuplicateClassName: bug fix - ignore namespace operator

The `namespace` keyword can also be used as an operator, in which case, the sniff as it were would throw false positives.

The fix now applies for this incidentally also fixes a nasty bug which could throw the sniff into an eternal loop when an unfinished namespace statement was encountered during live coding.

Includes unit tests.

**Note**: the unit test for the live coding situation has to be the last unit test file for this sniff so as to not influence the other tests. To that end, it has been numbered `99`.

Author: jrfnl

src/Standards/Generic/Sniffs/Classes/DuplicateClassNameSniff.php

@@ -11,6 +11,7 @@
 
 use PHP_CodeSniffer\Files\File;
 use PHP_CodeSniffer\Sniffs\Sniff;
+use PHP_CodeSniffer\Util\Tokens;
 
 class DuplicateClassNameSniff implements Sniff
 {
@@ -68,19 +69,25 @@ public function process(File $phpcsFile, $stackPtr)
 
             // Keep track of what namespace we are in.
             if ($tokens[$stackPtr]['code'] === T_NAMESPACE) {
-                $nsEnd = $phpcsFile->findNext(
-                    [
-                        T_NS_SEPARATOR,
-                        T_STRING,
-                        T_WHITESPACE,
-                    ],
-                    ($stackPtr + 1),
-                    null,
-                    true
-                );
-
-                $namespace = trim($phpcsFile->getTokensAsString(($stackPtr + 1), ($nsEnd - $stackPtr - 1)));
-                $stackPtr  = $nsEnd;
+                $nextNonEmpty = $phpcsFile->findNext(Tokens::$emptyTokens, ($stackPtr + 1), null, true);
+                if ($nextNonEmpty !== false
+                    // Ignore namespace keyword used as operator.
+                    && $tokens[$nextNonEmpty]['code'] !== T_NS_SEPARATOR
+                ) {
+                    $nsEnd = $phpcsFile->findNext(
+                        [
+                            T_NS_SEPARATOR,
+                            T_STRING,
+                            T_WHITESPACE,
+                        ],
+                        ($stackPtr + 1),
+                        null,
+                        true
+                    );
+
+                    $namespace = trim($phpcsFile->getTokensAsString(($stackPtr + 1), ($nsEnd - $stackPtr - 1)));
+                    $stackPtr  = $nsEnd;
+                }
             } else {
                 $nameToken = $phpcsFile->findNext(T_STRING, $stackPtr);
                 $name      = $tokens[$nameToken]['content'];

src/Standards/Generic/Tests/Classes/DuplicateClassNameUnitTest.7.inc

@@ -0,0 +1,9 @@
+<?php
+namespace E;
+namespace\functionCall();
+class MyClass {}
+interface YourInterface {}
+
+namespace F;
+namespace\functionCall();
+class MyClass {}

src/Standards/Generic/Tests/Classes/DuplicateClassNameUnitTest.99.inc

@@ -0,0 +1,7 @@
+<?php
+
+// Intentional parse error/live coding.
+// This should be the only test in this file.
+// Testing that the sniff is *not* triggered.
+
+namespace