[clang] [analyzer] Support interestingness in ArrayBoundV2 (PR #78315)

[Balazs Benics via cfe-commits]

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@@ -381,66 +542,98 @@ void ArrayBoundCheckerV2::performCheck(const Expr *E, CheckerContext &C) const {
         compareValueToThreshold(State, ByteOffset, *KnownSize, SVB);
 
     if (ExceedsUpperBound) {
+      // The offset may be invalid (>= Size)...
       if (!WithinUpperBound) {
-        // We know that the index definitely exceeds the upper bound.
-        if (isa<ArraySubscriptExpr>(E) && isInAddressOf(E, C.getASTContext())) {
-          // ...but this is within an addressof expression, so we need to check
-          // for the exceptional case that `&array[size]` is valid.
-          auto [EqualsToThreshold, NotEqualToThreshold] =
-              compareValueToThreshold(ExceedsUpperBound, ByteOffset, *KnownSize,
-                                      SVB, /*CheckEquality=*/true);
-          if (EqualsToThreshold && !NotEqualToThreshold) {
-            // We are definitely in the exceptional case, so return early
-            // instead of reporting a bug.
-            C.addTransition(EqualsToThreshold);
-            return;
-          }
+        // ...and it cannot be within bounds, so report an error, unless we can
+        // definitely determine that this is an idiomatic `&array[size]`
+        // expression that calculates the past-the-end pointer.
+        if (isIdiomaticPastTheEndPtr(E, ExceedsUpperBound, ByteOffset,
+                                     *KnownSize, C)) {
+          // FIXME: this duplicates the `addTransition` at the end of the
+          // function, but `goto` is taboo nowdays.
+          C.addTransition(ExceedsUpperBound, SUR.createNoteTag(C));
+          return;
----------------
steakhal wrote:

I think it's fine. `goto` would be worse. I also thought about `scope_exit`, but no.
This way it's local, and easy to reason about. With any other approach the scope of which we would need to reason about would be significantly bigger. Feel free to remove this FIXME.

https://github.com/llvm/llvm-project/pull/78315