C++: Initial cpp/comma-before-misleading-indentation

MRVA top 1000 run at: https://github.com/github/semmle-code/actions/runs/3106828111

Author: d10c

cpp/ql/src/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation.ql

@@ -1 +1,19 @@
-select 1
+/**
+ * @name Comma before misleading indentation
+ * @description The expressions before and after the comma operator can be misread because of an unusual difference in start columns.
+ * @kind problem
+ * @id cpp/comma-before-misleading-indentation
+ * @problem.severity recommendation
+ * @tags maintainability
+ *       readability
+ */
+
+import cpp
+
+from CommaExpr ce
+where
+  ce.fromSource() and
+  not exists(MacroInvocation me | ce = me.getAnAffectedElement()) and
+  ce.getLeftOperand().getLocation().getStartColumn() >
+    ce.getRightOperand().getLocation().getStartColumn()
+select ce, "Comma before misleading indentation."

cpp/ql/test/query-tests/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation/CommaBeforeMisleadingIndentation.expected

@@ -1 +1,2 @@
-| 1 |
+| test.cpp:9:3:10:8 | ... , ... | Comma before misleading indentation. |
+| test.cpp:17:7:18:4 | ... , ... | Comma before misleading indentation. |