Make std::fmt a simple re-export from collections

1 files changed, 401 insertions, 9 deletions

diff --git a/src/libcollections/fmt.rs b/src/libcollections/fmt.rs
index b3f31f33a3a..5f337528d78 100644
--- a/src/libcollections/fmt.rs
+++ b/src/libcollections/fmt.rs
@@ -1,4 +1,4 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2013-2015 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -7,15 +7,409 @@
 // <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.
+//
+// ignore-lexer-test FIXME #15679
 
-//! Formatting support for `String`.
+//! Utilities for formatting and printing strings
+//!
+//! This module contains the runtime support for the `format!` syntax extension.
+//! This macro is implemented in the compiler to emit calls to this module in
+//! order to format arguments at runtime into strings and streams.
+//!
+//! ## Usage
+//!
+//! The `format!` macro is intended to be familiar to those coming from C's
+//! printf/fprintf functions or Python's `str.format` function. In its current
+//! revision, the `format!` macro returns a `String` type which is the result of
+//! the formatting. In the future it will also be able to pass in a stream to
+//! format arguments directly while performing minimal allocations.
+//!
+//! Some examples of the `format!` extension are:
+//!
+//! ```
+//! format!("Hello");                  // => "Hello"
+//! format!("Hello, {}!", "world");    // => "Hello, world!"
+//! format!("The number is {}", 1);   // => "The number is 1"
+//! format!("{:?}", (3, 4));         // => "(3, 4)"
+//! format!("{value}", value=4);      // => "4"
+//! format!("{} {}", 1, 2u);          // => "1 2"
+//! ```
+//!
+//! From these, you can see that the first argument is a format string. It is
+//! required by the compiler for this to be a string literal; it cannot be a
+//! variable passed in (in order to perform validity checking). The compiler
+//! will then parse the format string and determine if the list of arguments
+//! provided is suitable to pass to this format string.
+//!
+//! ### Positional parameters
+//!
+//! Each formatting argument is allowed to specify which value argument it's
+//! referencing, and if omitted it is assumed to be "the next argument". For
+//! example, the format string `{} {} {}` would take three parameters, and they
+//! would be formatted in the same order as they're given. The format string
+//! `{2} {1} {0}`, however, would format arguments in reverse order.
+//!
+//! Things can get a little tricky once you start intermingling the two types of
+//! positional specifiers. The "next argument" specifier can be thought of as an
+//! iterator over the argument. Each time a "next argument" specifier is seen,
+//! the iterator advances. This leads to behavior like this:
+//!
+//! ```rust
+//! format!("{1} {} {0} {}", 1, 2); // => "2 1 1 2"
+//! ```
+//!
+//! The internal iterator over the argument has not been advanced by the time
+//! the first `{}` is seen, so it prints the first argument. Then upon reaching
+//! the second `{}`, the iterator has advanced forward to the second argument.
+//! Essentially, parameters which explicitly name their argument do not affect
+//! parameters which do not name an argument in terms of positional specifiers.
+//!
+//! A format string is required to use all of its arguments, otherwise it is a
+//! compile-time error. You may refer to the same argument more than once in the
+//! format string, although it must always be referred to with the same type.
+//!
+//! ### Named parameters
+//!
+//! Rust itself does not have a Python-like equivalent of named parameters to a
+//! function, but the `format!` macro is a syntax extension which allows it to
+//! leverage named parameters. Named parameters are listed at the end of the
+//! argument list and have the syntax:
+//!
+//! ```text
+//! identifier '=' expression
+//! ```
+//!
+//! For example, the following `format!` expressions all use named argument:
+//!
+//! ```
+//! format!("{argument}", argument = "test");   // => "test"
+//! format!("{name} {}", 1, name = 2);        // => "2 1"
+//! format!("{a} {c} {b}", a="a", b='b', c=3);  // => "a 3 b"
+//! ```
+//!
+//! It is illegal to put positional parameters (those without names) after
+//! arguments which have names. Like with positional parameters, it is illegal
+//! to provide named parameters that are unused by the format string.
+//!
+//! ### Argument types
+//!
+//! Each argument's type is dictated by the format string. It is a requirement
+//! that every argument is only ever referred to by one type. For example, this
+//! is an invalid format string:
+//!
+//! ```text
+//! {0:x} {0:o}
+//! ```
+//!
+//! This is invalid because the first argument is both referred to as a
+//! hexadecimal as well as an
+//! octal.
+//!
+//! There are various parameters which do require a particular type, however.
+//! Namely if the syntax `{:.*}` is used, then the number of characters to print
+//! precedes the actual object being formatted, and the number of characters
+//! must have the type `uint`. Although a `uint` can be printed with `{}`, it is
+//! illegal to reference an argument as such. For example this is another
+//! invalid format string:
+//!
+//! ```text
+//! {:.*} {0}
+//! ```
+//!
+//! ### Formatting traits
+//!
+//! When requesting that an argument be formatted with a particular type, you
+//! are actually requesting that an argument ascribes to a particular trait.
+//! This allows multiple actual types to be formatted via `{:x}` (like `i8` as
+//! well as `int`).  The current mapping of types to traits is:
+//!
+//! * *nothing* ⇒ `Display`
+//! * `?` ⇒ `Debug`
+//! * `o` ⇒ `Octal`
+//! * `x` ⇒ `LowerHex`
+//! * `X` ⇒ `UpperHex`
+//! * `p` ⇒ `Pointer`
+//! * `b` ⇒ `Binary`
+//! * `e` ⇒ `LowerExp`
+//! * `E` ⇒ `UpperExp`
+//!
+//! What this means is that any type of argument which implements the
+//! `fmt::Binary` trait can then be formatted with `{:b}`. Implementations
+//! are provided for these traits for a number of primitive types by the
+//! standard library as well. If no format is specified (as in `{}` or `{:6}`),
+//! then the format trait used is the `Display` trait.
+//!
+//! When implementing a format trait for your own type, you will have to
+//! implement a method of the signature:
+//!
+//! ```rust
+//! # use std::fmt;
+//! # struct Foo; // our custom type
+//! # impl fmt::Display for Foo {
+//! fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//! # write!(f, "testing, testing")
+//! # } }
+//! ```
+//!
+//! Your type will be passed as `self` by-reference, and then the function
+//! should emit output into the `f.buf` stream. It is up to each format trait
+//! implementation to correctly adhere to the requested formatting parameters.
+//! The values of these parameters will be listed in the fields of the
+//! `Formatter` struct. In order to help with this, the `Formatter` struct also
+//! provides some helper methods.
+//!
+//! Additionally, the return value of this function is `fmt::Result` which is a
+//! typedef to `Result<(), IoError>` (also known as `IoResult<()>`). Formatting
+//! implementations should ensure that they return errors from `write!`
+//! correctly (propagating errors upward).
+//!
+//! An example of implementing the formatting traits would look
+//! like:
+//!
+//! ```rust
+//! use std::fmt;
+//! use std::f64;
+//! use std::num::Float;
+//!
+//! #[derive(Debug)]
+//! struct Vector2D {
+//!     x: int,
+//!     y: int,
+//! }
+//!
+//! impl fmt::Display for Vector2D {
+//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!         // The `f` value implements the `Writer` trait, which is what the
+//!         // write! macro is expecting. Note that this formatting ignores the
+//!         // various flags provided to format strings.
+//!         write!(f, "({}, {})", self.x, self.y)
+//!     }
+//! }
+//!
+//! // Different traits allow different forms of output of a type. The meaning
+//! // of this format is to print the magnitude of a vector.
+//! impl fmt::Binary for Vector2D {
+//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!         let magnitude = (self.x * self.x + self.y * self.y) as f64;
+//!         let magnitude = magnitude.sqrt();
+//!
+//!         // Respect the formatting flags by using the helper method
+//!         // `pad_integral` on the Formatter object. See the method documentation
+//!         // for details, and the function `pad` can be used to pad strings.
+//!         let decimals = f.precision().unwrap_or(3);
+//!         let string = f64::to_str_exact(magnitude, decimals);
+//!         f.pad_integral(true, "", string.as_slice())
+//!     }
+//! }
+//!
+//! fn main() {
+//!     let myvector = Vector2D { x: 3, y: 4 };
+//!
+//!     println!("{}", myvector);       // => "(3, 4)"
+//!     println!("{:?}", myvector);     // => "Vector2D {x: 3, y:4}"
+//!     println!("{:10.3b}", myvector); // => "     5.000"
+//! }
+//! ```
+//!
+//! #### fmt::Display vs fmt::Debug
+//!
+//! These two formatting traits have distinct purposes:
+//!
+//! - `fmt::Display` implementations assert that the type can be faithfully
+//!   represented as a UTF-8 string at all times. It is **not** expected that
+//!   all types implement the `Display` trait.
+//! - `fmt::Debug` implementations should be implemented for **all** public types.
+//!   Output will typically represent the internal state as faithfully as possible.
+//!   The purpose of the `Debug` trait is to facilitate debugging Rust code. In
+//!   most cases, using `#[derive(Debug)]` is sufficient and recommended.
+//!
+//! Some examples of the output from both traits:
+//!
+//! ```
+//! assert_eq!(format!("{} {:?}", 3i32, 4i32), "3 4");
+//! assert_eq!(format!("{} {:?}", 'a', 'b'), "a 'b'");
+//! assert_eq!(format!("{} {:?}", "foo\n", "bar\n"), "foo\n \"bar\\n\"");
+//! ```
+//!
+//! ### Related macros
+//!
+//! There are a number of related macros in the `format!` family. The ones that
+//! are currently implemented are:
+//!
+//! ```ignore
+//! format!      // described above
+//! write!       // first argument is a &mut old_io::Writer, the destination
+//! writeln!     // same as write but appends a newline
+//! print!       // the format string is printed to the standard output
+//! println!     // same as print but appends a newline
+//! format_args! // described below.
+//! ```
+//!
+//! #### `write!`
+//!
+//! This and `writeln` are two macros which are used to emit the format string
+//! to a specified stream. This is used to prevent intermediate allocations of
+//! format strings and instead directly write the output. Under the hood, this
+//! function is actually invoking the `write` function defined in this module.
+//! Example usage is:
+//!
+//! ```rust
+//! # #![allow(unused_must_use)]
+//! let mut w = Vec::new();
+//! write!(&mut w, "Hello {}!", "world");
+//! ```
+//!
+//! #### `print!`
+//!
+//! This and `println` emit their output to stdout. Similarly to the `write!`
+//! macro, the goal of these macros is to avoid intermediate allocations when
+//! printing output. Example usage is:
+//!
+//! ```rust
+//! print!("Hello {}!", "world");
+//! println!("I have a newline {}", "character at the end");
+//! ```
+//!
+//! #### `format_args!`
+//! This is a curious macro which is used to safely pass around
+//! an opaque object describing the format string. This object
+//! does not require any heap allocations to create, and it only
+//! references information on the stack. Under the hood, all of
+//! the related macros are implemented in terms of this. First
+//! off, some example usage is:
+//!
+//! ```
+//! use std::fmt;
+//! use std::old_io;
+//!
+//! fmt::format(format_args!("this returns {}", "String"));
+//!
+//! let mut some_writer = old_io::stdout();
+//! write!(&mut some_writer, "{}", format_args!("print with a {}", "macro"));
+//!
+//! fn my_fmt_fn(args: fmt::Arguments) {
+//!     write!(&mut old_io::stdout(), "{}", args);
+//! }
+//! my_fmt_fn(format_args!("or a {} too", "function"));
+//! ```
+//!
+//! The result of the `format_args!` macro is a value of type `fmt::Arguments`.
+//! This structure can then be passed to the `write` and `format` functions
+//! inside this module in order to process the format string.
+//! The goal of this macro is to even further prevent intermediate allocations
+//! when dealing formatting strings.
+//!
+//! For example, a logging library could use the standard formatting syntax, but
+//! it would internally pass around this structure until it has been determined
+//! where output should go to.
+//!
+//! ## Syntax
+//!
+//! The syntax for the formatting language used is drawn from other languages,
+//! so it should not be too alien. Arguments are formatted with python-like
+//! syntax, meaning that arguments are surrounded by `{}` instead of the C-like
+//! `%`. The actual grammar for the formatting syntax is:
+//!
+//! ```text
+//! format_string := <text> [ format <text> ] *
+//! format := '{' [ argument ] [ ':' format_spec ] '}'
+//! argument := integer | identifier
+//!
+//! format_spec := [[fill]align][sign]['#'][0][width]['.' precision][type]
+//! fill := character
+//! align := '<' | '^' | '>'
+//! sign := '+' | '-'
+//! width := count
+//! precision := count | '*'
+//! type := identifier | ''
+//! count := parameter | integer
+//! parameter := integer '$'
+//! ```
+//!
+//! ## Formatting Parameters
+//!
+//! Each argument being formatted can be transformed by a number of formatting
+//! parameters (corresponding to `format_spec` in the syntax above). These
+//! parameters affect the string representation of what's being formatted. This
+//! syntax draws heavily from Python's, so it may seem a bit familiar.
+//!
+//! ### Fill/Alignment
+//!
+//! The fill character is provided normally in conjunction with the `width`
+//! parameter. This indicates that if the value being formatted is smaller than
+//! `width` some extra characters will be printed around it. The extra
+//! characters are specified by `fill`, and the alignment can be one of two
+//! options:
+//!
+//! * `<` - the argument is left-aligned in `width` columns
+//! * `^` - the argument is center-aligned in `width` columns
+//! * `>` - the argument is right-aligned in `width` columns
+//!
+//! ### Sign/#/0
+//!
+//! These can all be interpreted as flags for a particular formatter.
+//!
+//! * '+' - This is intended for numeric types and indicates that the sign
+//!         should always be printed. Positive signs are never printed by
+//!         default, and the negative sign is only printed by default for the
+//!         `Signed` trait. This flag indicates that the correct sign (+ or -)
+//!         should always be printed.
+//! * '-' - Currently not used
+//! * '#' - This flag is indicates that the "alternate" form of printing should
+//!         be used. By default, this only applies to the integer formatting
+//!         traits and performs like:
+//!     * `x` - precedes the argument with a "0x"
+//!     * `X` - precedes the argument with a "0x"
+//!     * `t` - precedes the argument with a "0b"
+//!     * `o` - precedes the argument with a "0o"
+//! * '0' - This is used to indicate for integer formats that the padding should
+//!         both be done with a `0` character as well as be sign-aware. A format
+//!         like `{:08d}` would yield `00000001` for the integer `1`, while the
+//!         same format would yield `-0000001` for the integer `-1`. Notice that
+//!         the negative version has one fewer zero than the positive version.
+//!
+//! ### Width
+//!
+//! This is a parameter for the "minimum width" that the format should take up.
+//! If the value's string does not fill up this many characters, then the
+//! padding specified by fill/alignment will be used to take up the required
+//! space.
+//!
+//! The default fill/alignment for non-numerics is a space and left-aligned. The
+//! defaults for numeric formatters is also a space but with right-alignment. If
+//! the '0' flag is specified for numerics, then the implicit fill character is
+//! '0'.
+//!
+//! The value for the width can also be provided as a `uint` in the list of
+//! parameters by using the `2$` syntax indicating that the second argument is a
+//! `uint` specifying the width.
+//!
+//! ### Precision
+//!
+//! For non-numeric types, this can be considered a "maximum width". If the
+//! resulting string is longer than this width, then it is truncated down to
+//! this many characters and only those are emitted.
+//!
+//! For integral types, this has no meaning currently.
+//!
+//! For floating-point types, this indicates how many digits after the decimal
+//! point should be printed.
+//!
+//! ## Escaping
 //!
-//! See `core::fmt` and `std::fmt` for full documentation on string
-//! formatting.
+//! The literal characters `{` and `}` may be included in a string by preceding
+//! them with the same character. For example, the `{` character is escaped with
+//! `{{` and the `}` character is escaped with `}}`.
 
-#![stable(feature = "rust1", since = "1.0.0")]
+#![unstable(feature = "std_misc")]
 
-use core::fmt;
+pub use core::fmt::{Formatter, Result, Writer, rt};
+pub use core::fmt::{Show, String, Octal, Binary};
+pub use core::fmt::{Display, Debug};
+pub use core::fmt::{LowerHex, UpperHex, Pointer};
+pub use core::fmt::{LowerExp, UpperExp};
+pub use core::fmt::Error;
+pub use core::fmt::{ArgumentV1, Arguments, write, radix, Radix, RadixFmt};
 
 use string;
 
@@ -35,9 +429,7 @@ use string;
 /// assert_eq!(s, "Hello, world!".to_string());
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn format(args: fmt::Arguments) -> string::String {
-    // FIXME #21826
-    use core::fmt::Writer;
+pub fn format(args: Arguments) -> string::String {
     let mut output = string::String::new();
     let _ = write!(&mut output, "{}", args);
     output