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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Implementation of the `{:?}` format qualifier
//!
//! This module contains the `Poly` trait which is used to implement the `{:?}`
//! format expression in formatting macros. This trait is defined for all types
//! automatically, so it is likely not necessary to use this module manually
use std::fmt;
use repr;
/// Format trait for the `?` character
pub trait Poly {
/// Formats the value using the given formatter.
#[experimental]
fn fmt(&self, &mut fmt::Formatter) -> fmt::Result;
}
#[doc(hidden)]
pub fn secret_poly<T: Poly>(x: &T, fmt: &mut fmt::Formatter) -> fmt::Result {
// FIXME #11938 - UFCS would make us able call the this method
// directly Poly::fmt(x, fmt).
x.fmt(fmt)
}
impl<T> Poly for T {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match (f.width, f.precision) {
(None, None) => {
match repr::write_repr(f, self) {
Ok(()) => Ok(()),
Err(..) => Err(fmt::WriteError),
}
}
// If we have a specified width for formatting, then we have to make
// this allocation of a new string
_ => {
let s = repr::repr_to_string(self);
f.pad(s.as_slice())
}
}
}
}
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