[clang] [clang][analyzer] Stable order for SymbolRef-keyed containers (PR #121551)

[Balazs Benics via cfe-commits]

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@@ -56,6 +68,8 @@ class SymExpr : public llvm::FoldingSetNode {
 
   Kind getKind() const { return K; }
 
+  SymbolID getSymbolID() const { return Sym; }
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steakhal wrote:

This is expected to be a fairly infrequently used API. I think this deserves to be highlighted on this getter. Especially because modern IDEs will only display these notes and not the notes at the `Sym` declaration.

In other words, why would / where would anyone use this API?
In this patch I could only see a single caller, `ImutContainerInfo`.

https://github.com/llvm/llvm-project/pull/121551