Derive Macro StackError

#[derive(StackError)]
{
    // Attributes available to this derive:
    #[error]
}

Derive macro that implements StackError, Display, Debug and std::error::Error and generates From<T> impls for fields/variants configured via #[error(..)]. Derive macro for stack errors.

This derive macro can be applied to structs and enums. Unit, tuple and named-field variants are supported equally.

The macro will expand to implementations of StackError, Display, Debug and Error. It will also add [From] impls for fields configured via the error attribute.

Items with the derive macro applied accept an #[error(args)] attribute, where args is a comma-separated list of arguments. The supported arguments vary by on the kind of item:

• on enums:
  • #[error(from_sources)]: Creates From impls for the source types of all variants. Will fail to compile if multiple sources have the same type.
  • #[error(std_sources)]: Defaults all sources to be std errors instead of stack errors.
• on structs and enum variants:
  • #[error("format {field}: {}", a + b)]: Sets the display formatting. You can refer to named fields by their names, and to tuple fields by _0, _1 etc.
  • #[error(transparent)]: Directly forwards the display implementation to the error source, and omits the outer error in the source chain when reporting errors.
• on fields:
  • #[error(from)]: Creates a From impl for the field’s type to the error type.
  • #[error(source)]: The error’s source method returns a reference to whatever field is named source, or has the source attribute set.
  • #[error(std_err)]: Only on on source fields. Marks the error as a std error. Source fields not marked as std_err need to implement StackError.
  • #[error(stack_error)]: Only on source fields. Marks the error as a StackError. This is the default unless std_sources is set on the top-level item.
  • #[error(meta)]: Sets a field as the meta field for this error or variant. Must have type [::n0_error::Error`]