Deserializing untagged enum variants broke/changed between v1.0.38 and v1.0.39

[tecywiz121]

Still working out the details, but something changed between 1.0.38 and 1.0.39 that's broken my untagged enum.

I'm doing a bisect right now to figure out the commit that introduced the change.

[dtolnay]

Can you share the enum that broke? Is there a custom Deserialize impl involved?

[tecywiz121]

Sure! Sorry, got a little lost in trying to get cargo to use my local serde.

I wanted a way to reference another file from inside of a TOML file, so I made this. As an aside, if there's a more idiomatic way to do this with serde, I'm all ears.

Playground

Gist

[dtolnay]

I think the trouble is because TOML represents bytes as an array of integers (playground) rather than a string -- so when the Deserialize impl calls deserializer.deserialize_bytes(DataVisitor) the format is allowed to assume you are looking for its representation of bytes. In this case deserialize_str would work instead, or deserialize_any since TOML is self-describing and can figure out the type based on the input data.

Some unrelated suggestions:

• You can remove with = "expect_equal_to" because that is the default behavior of a newtype variant containing T.

• You can remove the bound attribute because that bound can be inferred -- just as derive(Debug) is inferring T: Debug, derive(Hash) is inferring T: Hash, etc.

[tecywiz121]

Thanks for the feedback, very much appreciated! The bound attribute was required when I first wrote this, but I guess that requirement is gone? Weird.

I'd still say this is a bug, since the behavior changed pretty dramatically for a patch version, no?

[dtolnay]

Absolutely. Thanks! This is fixed in 3c4961c and released in Serde 1.0.40 so the code in the gist is back to working as before. Really sorry about the breakage.