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The reason for having it in libcore is that specialization is unstable, and that `type_name` is part of `core_instrinsics` which is forever unstable. In addition, the macros in question can reuse this type and so we get some code reuse.\r\n\r\n## Does this expose specialization?\r\n\r\n**Yes** in the sense that you have to fall back to `type_name` and `impl<T> BEDInternal for BestEffortDebug<T>` if we decide to remove specialization entirely. The output thus becomes effectively useless, but no code will break as a result of removing specialization. The guarantees section in the documentation also explicitly states that the output format is not guaranteed.\r\n\r\n**No** in the sense that specialization is not effectively stabilized as a result of this. The \"inner helper trait\" hack is used in other places such as: 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