Struct const_format::fmt::DebugTuple

source ·

pub struct DebugTuple<'f, 'w> { /* private fields */ }

Available on crate feature fmt only.

Expand description

For debug formatting a tuple struct, or tuple variant.

Example

This example demonstrates how you can debug format a tuple struct, and an enum of tuple variants.

#![feature(const_mut_refs)]

use const_format::{Error, Formatter};
use const_format::{call_debug_fmt, coerce_to_fmt, formatc, impl_fmt, try_};

fn main() {
    const STRUC: &str = formatc!("{:?}", Foo(5, [8, 13, 21], "34"));
    const ENUM_: &str = formatc!("{:?}", Bar::Baz(false, None));
     
    assert_eq!(STRUC, "Foo(5, [8, 13, 21], \"34\")");
    assert_eq!(ENUM_, "Baz(false, None)");
}

struct Foo(u32, [u32; 3], &'static str);

enum Bar {
    Baz(bool, Option<bool>),
}

impl_fmt!{
    impl Foo;
     
    const fn const_debug_fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
        let mut f = f.debug_tuple("Foo");
        try_!(coerce_to_fmt!(&self.0).const_debug_fmt(f.field()));
        try_!(coerce_to_fmt!(&self.1).const_debug_fmt(f.field()));
        try_!(coerce_to_fmt!(&self.2).const_debug_fmt(f.field()));
        f.finish()
    }
}

impl_fmt!{
    impl Bar;
     
    const fn const_debug_fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
        match self {
            Bar::Baz(f0, f1) => {
                let mut f = f.debug_tuple("Baz");
                 
                // This macro allows debug formatting some generic types that
                // don't have a const_debug_fmt fn, like Options which wrap non-std types.
                call_debug_fmt!(std, f0, f.field());
                call_debug_fmt!(Option, f1, f.field());
                 
                f.finish()
            }
        }
    }
}