[clang] [analyzer] Mention possibility of underflow in array overflow errors (PR #84201)

[Balázs Kéri via cfe-commits]

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@@ -603,6 +611,8 @@ void ArrayBoundCheckerV2::performCheck(const Expr *E, CheckerContext &C) const {
     auto [WithinUpperBound, ExceedsUpperBound] =
         compareValueToThreshold(State, ByteOffset, *KnownSize, SVB);
 
+    bool AssumedNonNegative = SUR.assumedNonNegative();
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balazske wrote:

The name `AssumedNonNegative` looks misleading (in variable and function arguments too). This has meaning like `CanBeNegative` which is a better name for this.

https://github.com/llvm/llvm-project/pull/84201