result-transformer-flow 0.0.2

Traits, macros and utilities for transforming Result values.
Documentation 
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use std::marker::PhantomData;

/// Step that maps the error value using a provided function.
#[derive(Debug, Clone, Copy)]
pub struct ErrMapStep<InputErr, OutputErr, MapperFn>
where
    MapperFn: Fn(InputErr) -> OutputErr,
{
    mapper: MapperFn,
    _phantom: PhantomData<(InputErr, OutputErr)>,
}

impl<InputErr, OutputErr, MapperFn> ErrMapStep<InputErr, OutputErr, MapperFn>
where
    MapperFn: Fn(InputErr) -> OutputErr,
{
    /// Creates a new [`ErrMapStep`].
    ///
    /// * `mapper` - function converting the error value to another type
    pub const fn new(mapper: MapperFn) -> Self {
        Self {
            mapper,
            _phantom: PhantomData,
        }
    }

    pub(crate) fn apply(&self, input_err: InputErr) -> OutputErr {
        (self.mapper)(input_err)
    }
}