[clang] [analyzer] Support pack indexing expressions (PR #173186)

[via cfe-commits]

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@@ -3296,6 +3302,14 @@ void ExprEngine::VisitCommonDeclRefExpr(const Expr *Ex, const NamedDecl *D,
 
     SVal V = UnknownVal();
 
+    // For pack indexing expressions. Binding is not available here but through
+    // the expanded expressions in the PackIndexingExpr node.
+    if (BD->isParameterPack()) {
+      Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V), nullptr,
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isuckatcs wrote:

We should probably add a FIXME here instead of just binding `UnknownVal` to the bind expression. This should eventually be handled.

In this case the binding is a sub-region of the pack (e.g.: only the first/last N elements), right? Can't we model this somehow?

https://github.com/llvm/llvm-project/pull/173186