thiserror/tests/test_generics.rs

#![allow(clippy::needless_late_init, clippy::uninlined_format_args)]

use core::fmt::{self, Debug, Display};
use thiserror::Error;

pub struct NoFormat;

#[derive(Debug)]
pub struct DebugOnly;

pub struct DisplayOnly;

impl Display for DisplayOnly {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("display only")
    }
}

#[derive(Debug)]
pub struct DebugAndDisplay;

impl Display for DebugAndDisplay {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("debug and display")
    }
}

// Should expand to:
//
//     impl<E> Display for EnumDebugField<E>
//     where
//         E: Debug;
//
//     impl<E> Error for EnumDebugField<E>
//     where
//         Self: Debug + Display;
//
#[derive(Error, Debug)]
pub enum EnumDebugGeneric<E> {
    #[error("{0:?}")]
    FatalError(E),
}

// Should expand to:
//
//     impl<E> Display for EnumFromGeneric<E>;
//
//     impl<E> Error for EnumFromGeneric<E>
//     where
//         EnumDebugGeneric<E>: Error + 'static,
//         Self: Debug + Display;
//
#[derive(Error, Debug)]
pub enum EnumFromGeneric<E> {
    #[error("enum from generic")]
    Source(#[from] EnumDebugGeneric<E>),
}

// Should expand to:
//
//     impl<HasDisplay, HasDebug, HasNeither> Display
//         for EnumCompound<HasDisplay, HasDebug, HasNeither>
//     where
//         HasDisplay: Display,
//         HasDebug: Debug;
//
//     impl<HasDisplay, HasDebug, HasNeither> Error
//         for EnumCompound<HasDisplay, HasDebug, HasNeither>
//     where
//         Self: Debug + Display;
//
#[derive(Error)]
pub enum EnumCompound<HasDisplay, HasDebug, HasNeither> {
    #[error("{0} {1:?}")]
    DisplayDebug(HasDisplay, HasDebug),
    #[error("{0}")]
    Display(HasDisplay, HasNeither),
    #[error("{1:?}")]
    Debug(HasNeither, HasDebug),
}

impl<HasDisplay, HasDebug, HasNeither> Debug for EnumCompound<HasDisplay, HasDebug, HasNeither> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("EnumCompound")
    }
}

#[test]
fn test_display_enum_compound() {
    let mut instance: EnumCompound<DisplayOnly, DebugOnly, NoFormat>;

    instance = EnumCompound::DisplayDebug(DisplayOnly, DebugOnly);
    assert_eq!(format!("{}", instance), "display only DebugOnly");

    instance = EnumCompound::Display(DisplayOnly, NoFormat);
    assert_eq!(format!("{}", instance), "display only");

    instance = EnumCompound::Debug(NoFormat, DebugOnly);
    assert_eq!(format!("{}", instance), "DebugOnly");
}

// Should expand to:
//
//     impl<E> Display for EnumTransparentGeneric<E>
//     where
//         E: Display;
//
//     impl<E> Error for EnumTransparentGeneric<E>
//     where
//         E: Error,
//         Self: Debug + Display;
//
#[derive(Error, Debug)]
pub enum EnumTransparentGeneric<E> {
    #[error(transparent)]
    Other(E),
}

// Should expand to:
//
//     impl<E> Display for StructDebugGeneric<E>
//     where
//         E: Debug;
//
//     impl<E> Error for StructDebugGeneric<E>
//     where
//         Self: Debug + Display;
//
#[derive(Error, Debug)]
#[error("{underlying:?}")]
pub struct StructDebugGeneric<E> {
    pub underlying: E,
}

// Should expand to:
//
//     impl<E> Error for StructFromGeneric<E>
//     where
//         StructDebugGeneric<E>: Error + 'static,
//         Self: Debug + Display;
//
#[derive(Error, Debug)]
pub struct StructFromGeneric<E> {
    #[from]
    pub source: StructDebugGeneric<E>,
}

// Should expand to:
//
//     impl<E> Display for StructTransparentGeneric<E>
//     where
//         E: Display;
//
//     impl<E> Error for StructTransparentGeneric<E>
//     where
//         E: Error,
//         Self: Debug + Display;
//
#[derive(Error, Debug)]
#[error(transparent)]
pub struct StructTransparentGeneric<E>(pub E);

// Regression test for https://github.com/dtolnay/thiserror/issues/345
#[test]
fn test_no_bound_on_named_fmt() {
    #[derive(Error, Debug)]
    #[error("{thing}", thing = "...")]
    struct Error<T> {
        thing: T,
    }

    let error = Error { thing: DebugOnly };
    assert_eq!(error.to_string(), "...");
}