[clang] [LifetimeSafety] Add support for iterator arithmetic (PR #195442)

[Utkarsh Saxena via cfe-commits]

================
@@ -139,8 +140,10 @@ bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee,
   if (RunningUnderLifetimeSafety &&
       isGslPointerType(Callee->getFunctionObjectParameterType()) &&
       isReferenceOrPointerLikeType(Callee->getReturnType())) {
-    if (Callee->getOverloadedOperator() == OverloadedOperatorKind::OO_Star ||
-        Callee->getOverloadedOperator() == OverloadedOperatorKind::OO_Arrow)
+    auto Op = Callee->getOverloadedOperator();
+    llvm::SmallDenseSet<OverloadedOperatorKind> PropagatingOps = {
+        OO_Star, OO_Arrow, OO_PlusPlus, OO_MinusMinus, OO_Plus, OO_Minus};
+    if (PropagatingOps.contains(Op))
----------------
usx95 wrote:

Consider using a `switch` block for `enum` instead of a `set`.

```cpp
switch (Callee->getOverloadedOperator()) {
case OO_Star: case OO_Arrow: case OO_PlusPlus:
case OO_MinusMinus: case OO_Plus: case OO_Minus:
  return true;
default:
  break;
}
```

Consider adding a line documenting this part.

`// Propagate origins through GSL pointer arithmetic and dereference operators.
`

https://github.com/llvm/llvm-project/pull/195442