[PATCH] D151557: [ADT] Fix DenseMapInfo<variant>::isEqual to delegate to DenseMapInfo, not ==

[Elliot Goodrich via Phabricator via llvm-commits]

IncludeGuardian requested changes to this revision.
IncludeGuardian added inline comments.
This revision now requires changes to proceed.


================
Comment at: llvm/include/llvm/ADT/DenseMapInfo.h:354-356
+    return std::visit(detail::EqVisitor{detail::variantGetDynamic(
+                          RHS, std::make_index_sequence<sizeof...(Ts)>{})},
+                      LHS);
----------------
I think we may be able to use `std::visit` twice and rely on the type of the parameter in the second visit matching the original type of the value we cast to `const void *`.

```
    const void *ErasedLHSValue = std::visit([](const auto& LHSValue){
        return static_cast<const void *>(&LHSValue);
    }, l);

    return std::visit([=](const auto& RHSValue){
        using T = std::remove_reference_t<decltype(RHSValue)>;
        return DenseMapInfo<T>::isEqual(*static_cast<T *>(ErasedLHSValue), RHSValue);
    }, r);
```


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D151557