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Allow using a generic for construction via From #537

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Allow using a generic for construction via From #537

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@shepmaster shepmaster commented Dec 8, 2025

TL;DR, SNAFU learns this:

#[derive(Debug, Snafu)]
#[snafu(source(from(generic)))]
struct OuterError(MiddleError);

which effectively generates this implementation:

impl<Source> From<Source> for OuterError
where
    Source: Into<MiddleError>,
{
    fn from(error: Source) -> Self {
        OuterError(error.into())
    }
}

This applies to

  • opaque errors
  • context(false)
  • transparent

Resolves #481, resolves #518

@shepmaster shepmaster added the enhancement New feature or request label Dec 8, 2025
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This was referenced Dec 8, 2025
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Allow using a generic for construction via From
e174405 
Adds `from(generic)` and `from(exact)` to the existing `from(type,
transform)`.

This impacts
- opaque errors
- `context(false)`
- `transparent`

Gotchas:

- Transforming a type called `exact` or `generic` will not work
  anymore. You'll need to call it `r#exact` or `r#generic`.
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Add support for impl From<T> for ErrorEnum where T: Into<OneVariantsSource> Generate From<source> implementations for opaque error

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