b53454e2e4
This commit moves reflection (as well as the {:?} format modifier) to a new
libdebug crate, all of which is marked experimental.
This is a breaking change because it now requires the debug crate to be
explicitly linked if the :? format qualifier is used. This means that any code
using this feature will have to add `extern crate debug;` to the top of the
crate. Any code relying on reflection will also need to do this.
Closes #12019
[breaking-change]
54 lines
1.7 KiB
Rust
54 lines
1.7 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Implementation of the `{:?}` format qualifier
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//!
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//! This module contains the `Poly` trait which is used to implement the `{:?}`
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//! format expression in formatting macros. This trait is defined for all types
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//! automatically, so it is likely not necessary to use this module manually
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use std::fmt;
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use repr;
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/// Format trait for the `?` character
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pub trait Poly {
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/// Formats the value using the given formatter.
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#[experimental]
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fn fmt(&self, &mut fmt::Formatter) -> fmt::Result;
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}
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#[doc(hidden)]
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pub fn secret_poly<T: Poly>(x: &T, fmt: &mut fmt::Formatter) -> fmt::Result {
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// FIXME #11938 - UFCS would make us able call the this method
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// directly Poly::fmt(x, fmt).
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x.fmt(fmt)
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}
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impl<T> Poly for T {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match (f.width, f.precision) {
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(None, None) => {
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match repr::write_repr(f, self) {
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Ok(()) => Ok(()),
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Err(..) => Err(fmt::WriteError),
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}
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}
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// If we have a specified width for formatting, then we have to make
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// this allocation of a new string
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_ => {
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let s = repr::repr_to_str(self);
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f.pad(s.as_slice())
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}
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}
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}
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}
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