[clang] [LifetimeSafety] Detect iterator invalidation through container aliases (PR #195231)

[Zeyi Xu via cfe-commits]

================
@@ -254,6 +253,46 @@ void IteratorUsedAfterPushBack(std::vector<int> v) {
 }
 }  // namespace SimpleInvalidIterators
 
+namespace InvalidatingThroughContainerAliases {
+void IteratorInvalidatedThroughLocalReferenceAlias() {
+  std::vector<int> vv;
+  std::vector<int> &v = vv;
+  auto it = vv.begin(); // expected-warning {{object whose reference is captured is later invalidated}}
+  v.push_back(42);      // expected-note {{invalidated here}}
+  (void)it;             // expected-note {{later used here}}
+}
+
+void IteratorInvalidatedThroughPointerParameter(std::vector<int> *v) { // expected-warning {{parameter is later invalidated}}
+  auto it = v->begin();
+  v->push_back(42); // expected-note {{invalidated here}}
+  (void)it;         // expected-note {{later used here}}
+}
+} // namespace InvalidatingThroughContainerAliases
+
+namespace ContainerObjectAliases {
+// FIXME: Distinguish owner-borrow from content-borrow.
----------------
zeyi2 wrote:

Thanks for the feedback :)

In earlier discussion in https://github.com/llvm/llvm-project/issues/193044#issuecomment-4333628748

> Invalidations already has quite a few false-positives atm and all of them are because of this limitation. So additional FP should be fine for now. We can fix them in precise path modelling in a separate PR.

Given that these diagnostics are not broadly recommended yet, I was assuming this tradeoff is acceptable for this PR, so I kept these as FIXME tests.

https://github.com/llvm/llvm-project/pull/195231