Do not report "Declaration hides variable" for unnamed variables

Author: jketema

cpp/ql/src/Best Practices/Hiding/DeclarationHidesVariable.ql

@@ -18,6 +18,7 @@ where
   not lv1.isCompilerGenerated() and
   not lv2.isCompilerGenerated() and
   not lv1.getParentScope().(BlockStmt).isInMacroExpansion() and
-  not lv2.getParentScope().(BlockStmt).isInMacroExpansion()
+  not lv2.getParentScope().(BlockStmt).isInMacroExpansion() and
+  not lv1.getName() = "(unnamed local variable)"
 select lv1, "Variable " + lv1.getName() + " hides another variable of the same name (on $@).", lv2,
   "line " + lv2.getLocation().getStartLine().toString()

cpp/ql/test/query-tests/Best Practices/Hiding/DeclarationHidesVariable/DeclarationHidesVariable.expected

@@ -1,4 +1,2 @@
 | hiding.cpp:6:17:6:17 | i | Variable i hides another variable of the same name (on $@). | hiding.cpp:4:13:4:13 | i | line 4 |
 | hiding.cpp:18:15:18:15 | k | Variable k hides another variable of the same name (on $@). | hiding.cpp:15:11:15:11 | k | line 15 |
-| hiding.cpp:38:10:38:10 | (unnamed local variable) | Variable (unnamed local variable) hides another variable of the same name (on $@). | hiding.cpp:36:8:36:8 | (unnamed local variable) | line 36 |
-| hiding.cpp:39:10:39:10 | (unnamed local variable) | Variable (unnamed local variable) hides another variable of the same name (on $@). | hiding.cpp:36:8:36:8 | (unnamed local variable) | line 36 |

cpp/ql/test/query-tests/Best Practices/Hiding/DeclarationHidesVariable/hiding.cpp

@@ -35,7 +35,7 @@ void structuredBinding() {
   int xs[1] = {1};
   auto [x] = xs;
   {
-    auto [x] = xs; // BAD
-    auto [y] = xs; // GOOD [FALSE POSITIVE]
+    auto [x] = xs; // BAD [NOT DETECTED]
+    auto [y] = xs; // GOOD
   }
 }