[clang] [LifetimeSafety] Implement multi-level origins (PR #168344)

[Utkarsh Saxena via cfe-commits]

================
@@ -237,13 +357,24 @@ void FactsGenerator::handleGSLPointerConstruction(const CXXConstructExpr *CCE) {
   assert(isGslPointerType(CCE->getType()));
   if (CCE->getNumArgs() != 1)
     return;
-  if (hasOrigin(CCE->getArg(0)))
-    killAndFlowOrigin(*CCE, *CCE->getArg(0));
-  else
+
+  if (isGslPointerType(CCE->getArg(0)->getType())) {
+    OriginTree *ArgTree = getTree(*CCE->getArg(0));
+    assert(ArgTree && "GSL pointer argument should have an origin tree");
+    // GSL pointer is constructed from another gsl pointer.
+    // Example:
+    //  View(View v);
+    //  View(const View &v);
+    if (ArgTree->getDepth() == 2)
----------------
usx95 wrote:

Makes sense. Changed to 

```
if (Arg->isGLValue())

```

https://github.com/llvm/llvm-project/pull/168344