No `unused field` warnings are produced on enums deriving thiserror::Error

see this playground example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=ef85fe807b9e27cb5ffbf6e3a11a1b0c

The warnings generated with a regular enum are not created for a `thiserror` enum, making it quite hard to catch unused fields in errors. Is this expected ?

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From what I can see, if it helps for debugging:
`thiserror` version 1.0.59 did produce these warnings. However there were no way to disable them (adding #[allow(unused)] to the whole enum, or to the variant did not make the warning go away)

Thanks for the work !

Start with the linked Rust playground example and compare its warnings for a regular enum with those for an enum deriving thiserror::Error. Check the reported behavior against thiserror version 1.0.59, including whether #[allow(unused)] affects the warning; done means the intended unused-field warnings are produced with sensible allow behavior.

Written by the indexing model from the issue text.