Add initial support for a new formatting syntax

src/libstd/either.rs

@@ -24,7 +24,7 @@ use vec;
 use vec::{OwnedVector, ImmutableVector};
 
 /// `Either` is a type that represents one of two alternatives
-#[deriving(Clone, Eq)]
+#[deriving(Clone, Eq, IterBytes)]
 pub enum Either<L, R> {
     Left(L),
     Right(R)

src/libstd/fmt/mod.rs

@@ -0,0 +1,368 @@
+// Copyright 2013 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.
+
+use prelude::*;
+
+use cast;
+use int;
+use rt::io::Decorator;
+use rt::io::mem::MemWriter;
+use rt::io;
+use str;
+use sys;
+use uint;
+use util;
+use vec;
+
+pub mod parse;
+pub mod rt;
+
+/// A struct to represent both where to emit formatting strings to and how they
+/// should be formatted. A mutable version of this is passed to all formatting
+/// traits.
+pub struct Formatter<'self> {
+    /// Flags for formatting (packed version of rt::Flag)
+    flags: uint,
+    /// Character used as 'fill' whenever there is alignment
+    fill: char,
+    /// Boolean indication of whether the output should be left-aligned
+    alignleft: bool,
+    /// Optionally specified integer width that the output should be
+    width: Option<uint>,
+    /// Optionally specified precision for numeric types
+    precision: Option<uint>,
+
+    /// Output buffer.
+    buf: &'self mut io::Writer,
+
+    priv curarg: vec::VecIterator<'self, Argument<'self>>,
+    priv args: &'self [Argument<'self>],
+}
+
+/// This struct represents the generic "argument" which is taken by the Xprintf
+/// family of functions. It contains a function to format the given value. At
+/// compile time it is ensured that the function and the value have the correct
+/// types, and then this struct is used to canonicalize arguments to one type.
+pub struct Argument<'self> {
+    priv formatter: extern "Rust" fn(&util::Void, &mut Formatter),
+    priv value: &'self util::Void,
+}
+
+#[allow(missing_doc)]
+pub trait Bool { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Char { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Signed { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Unsigned { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Octal { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Binary { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait LowerHex { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait UpperHex { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait String { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Poly { fn fmt(&Self, &mut Formatter); }
+#[allow(missing_doc)]
+pub trait Pointer { fn fmt(&Self, &mut Formatter); }
+
+/// The sprintf function takes a precompiled format string and a list of
+/// arguments, to return the resulting formatted string.
+///
+/// This is currently an unsafe function because the types of all arguments
+/// aren't verified by immediate callers of this function. This currently does
+/// not validate that the correct types of arguments are specified for each
+/// format specifier, nor that each argument itself contains the right function
+/// for formatting the right type value. Because of this, the function is marked
+/// as `unsafe` if this is being called manually.
+///
+/// Thankfully the rust compiler provides the macro `ifmt!` which will perform
+/// all of this validation at compile-time and provides a safe interface for
+/// invoking this function.
+///
+/// # Arguments
+///
+///   * fmts - the precompiled format string to emit.
+///   * args - the list of arguments to the format string. These are only the
+///            positional arguments (not named)
+///
+/// Note that this function assumes that there are enough arguments for the
+/// format string.
+pub unsafe fn sprintf(fmt: &[rt::Piece], args: &[Argument]) -> ~str {
+    let output = MemWriter::new();
+    {
+        let mut formatter = Formatter {
+            flags: 0,
+            width: None,
+            precision: None,
+            // FIXME(#8248): shouldn't need a transmute
+            buf: cast::transmute(&output as &io::Writer),
+            alignleft: false,
+            fill: ' ',
+            args: args,
+            curarg: args.iter(),
+        };
+        for piece in fmt.iter() {
+            formatter.run(piece, None);
+        }
+    }
+    return str::from_bytes_owned(output.inner());
+}
+
+impl<'self> Formatter<'self> {
+    fn run(&mut self, piece: &rt::Piece, cur: Option<&str>) {
+        let setcount = |slot: &mut Option<uint>, cnt: &parse::Count| {
+            match *cnt {
+                parse::CountIs(n) => { *slot = Some(n); }
+                parse::CountImplied => { *slot = None; }
+                parse::CountIsParam(i) => {
+                    let v = self.args[i].value;
+                    unsafe { *slot = Some(*(v as *util::Void as *uint)); }
+                }
+                parse::CountIsNextParam => {
+                    let v = self.curarg.next().unwrap().value;
+                    unsafe { *slot = Some(*(v as *util::Void as *uint)); }
+                }
+            }
+        };
+
+        match *piece {
+            rt::String(s) => { self.buf.write(s.as_bytes()); }
+            rt::CurrentArgument(()) => { self.buf.write(cur.unwrap().as_bytes()); }
+            rt::Argument(ref arg) => {
+                // Fill in the format parameters into the formatter
+                self.fill = arg.format.fill;
+                self.alignleft = arg.format.alignleft;
+                self.flags = arg.format.flags;
+                setcount(&mut self.width, &arg.format.width);
+                setcount(&mut self.precision, &arg.format.precision);
+
+                // Extract the correct argument
+                let value = match arg.position {
+                    rt::ArgumentNext => { *self.curarg.next().unwrap() }
+                    rt::ArgumentIs(i) => self.args[i],
+                };
+
+                // Then actually do some printing
+                match arg.method {
+                    None => { (value.formatter)(value.value, self); }
+                    Some(ref method) => { self.execute(*method, value); }
+                }
+            }
+        }
+    }
+
+    fn execute(&mut self, method: &rt::Method, arg: Argument) {
+        match *method {
+            // Pluralization is selection upon a numeric value specified as the
+            // parameter.
+            rt::Plural(offset, ref selectors, ref default) => {
+                // This is validated at compile-time to be a pointer to a
+                // '&uint' value.
+                let value: &uint = unsafe { cast::transmute(arg.value) };
+                let value = *value;
+
+                // First, attempt to match against explicit values without the
+                // offsetted value
+                for s in selectors.iter() {
+                    match s.selector {
+                        Right(val) if value == val => {
+                            return self.runplural(value, s.result);
+                        }
+                        _ => {}
+                    }
+                }
+
+                // Next, offset the value and attempt to match against the
+                // keyword selectors.
+                let value = value - match offset { Some(i) => i, None => 0 };
+                for s in selectors.iter() {
+                    let run = match s.selector {
+                        Left(parse::Zero) => value == 0,
+                        Left(parse::One) => value == 1,
+                        Left(parse::Two) => value == 2,
+
+                        // XXX: Few/Many should have a user-specified boundary
+                        //      One possible option would be in the function
+                        //      pointer of the 'arg: Argument' struct.
+                        Left(parse::Few) => value < 8,
+                        Left(parse::Many) => value >= 8,
+
+                        Right(*) => false
+                    };
+                    if run {
+                        return self.runplural(value, s.result);
+                    }
+                }
+
+                self.runplural(value, *default);
+            }
+
+            // Select is just a matching against the string specified.
+            rt::Select(ref selectors, ref default) => {
+                // This is validated at compile-time to be a pointer to a
+                // string slice,
+                let value: & &str = unsafe { cast::transmute(arg.value) };
+                let value = *value;
+
+                for s in selectors.iter() {
+                    if s.selector == value {
+                        for piece in s.result.iter() {
+                            self.run(piece, Some(value));
+                        }
+                        return;
+                    }
+                }
+                for piece in default.iter() {
+                    self.run(piece, Some(value));
+                }
+            }
+        }
+    }
+
+    fn runplural(&mut self, value: uint, pieces: &[rt::Piece]) {
+        do uint::to_str_bytes(value, 10) |buf| {
+            let valuestr = str::from_bytes_slice(buf);
+            for piece in pieces.iter() {
+                self.run(piece, Some(valuestr));
+            }
+        }
+    }
+}
+
+/// This is a function which calls are emitted to by the compiler itself to
+/// create the Argument structures that are passed into the `sprintf` function.
+#[doc(hidden)]
+pub fn argument<'a, T>(f: extern "Rust" fn(&T, &mut Formatter),
+                       t: &'a T) -> Argument<'a> {
+    unsafe {
+        Argument {
+            formatter: cast::transmute(f),
+            value: cast::transmute(t)
+        }
+    }
+}
+
+/// When the compiler determines that the type of an argument *must* be a string
+/// (such as for select), then it invokes this method.
+#[doc(hidden)]
+pub fn argumentstr<'a>(s: &'a &str) -> Argument<'a> {
+    argument(String::fmt, s)
+}
+
+/// When the compiler determines that the type of an argument *must* be a uint
+/// (such as for plural), then it invokes this method.
+#[doc(hidden)]
+pub fn argumentuint<'a>(s: &'a uint) -> Argument<'a> {
+    argument(Unsigned::fmt, s)
+}
+
+// Implementations of the core formatting traits
+
+impl Bool for bool {
+    fn fmt(b: &bool, f: &mut Formatter) {
+        String::fmt(&(if *b {"true"} else {"false"}), f);
+    }
+}
+
+impl<'self> String for &'self str {
+    fn fmt(s: & &'self str, f: &mut Formatter) {
+        // XXX: formatting args
+        f.buf.write(s.as_bytes())
+    }
+}
+
+impl Char for char {
+    fn fmt(c: &char, f: &mut Formatter) {
+        // XXX: formatting args
+        // XXX: shouldn't require an allocation
+        let mut s = ~"";
+        s.push_char(*c);
+        f.buf.write(s.as_bytes());
+    }
+}
+
+impl Signed for int {
+    fn fmt(c: &int, f: &mut Formatter) {
+        // XXX: formatting args
+        do int::to_str_bytes(*c, 10) |buf| {
+            f.buf.write(buf);
+        }
+    }
+}
+
+impl Unsigned for uint {
+    fn fmt(c: &uint, f: &mut Formatter) {
+        // XXX: formatting args
+        do uint::to_str_bytes(*c, 10) |buf| {
+            f.buf.write(buf);
+        }
+    }
+}
+
+impl Octal for uint {
+    fn fmt(c: &uint, f: &mut Formatter) {
+        // XXX: formatting args
+        do uint::to_str_bytes(*c, 8) |buf| {
+            f.buf.write(buf);
+        }
+    }
+}
+
+impl LowerHex for uint {
+    fn fmt(c: &uint, f: &mut Formatter) {
+        // XXX: formatting args
+        do uint::to_str_bytes(*c, 16) |buf| {
+            f.buf.write(buf);
+        }
+    }
+}
+
+impl UpperHex for uint {
+    fn fmt(c: &uint, f: &mut Formatter) {
+        // XXX: formatting args
+        do uint::to_str_bytes(*c, 16) |buf| {
+            let mut local = [0u8, ..16];
+            for (l, &b) in local.mut_iter().zip(buf.iter()) {
+                *l = match b as char {
+                    'a' .. 'f' => (b - 'a' as u8) + 'A' as u8,
+                    _ => b,
+                };
+            }
+            f.buf.write(local.slice_to(buf.len()));
+        }
+    }
+}
+
+impl<T> Poly for T {
+    fn fmt(t: &T, f: &mut Formatter) {
+        // XXX: formatting args
+        let s = sys::log_str(t);
+        f.buf.write(s.as_bytes());
+    }
+}
+
+// n.b. use 'const' to get an implementation for both '*mut' and '*' at the same
+//      time.
+impl<T> Pointer for *const T {
+    fn fmt(t: &*const T, f: &mut Formatter) {
+        // XXX: formatting args
+        f.buf.write("0x".as_bytes());
+        LowerHex::fmt(&(*t as uint), f);
+    }
+}
+
+// If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
+// it's a lot easier than creating all of the rt::Piece structures here.

src/libstd/fmt/rt.rs

@@ -0,0 +1,62 @@
+// Copyright 2013 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.
+
+//! This is an internal module used by the ifmt! runtime. These structures are
+//! emitted to static arrays to precompile format strings ahead of time.
+//!
+//! These definitions are similar to their `ct` equivalents, but differ in that
+//! these can be statically allocated and are slightly optimized for the runtime
+
+#[allow(missing_doc)];
+#[doc(hidden)];
+
+use either::Either;
+use fmt::parse;
+use option::Option;
+
+pub enum Piece<'self> {
+    String(&'self str),
+    // FIXME(#8259): this shouldn't require the unit-value here
+    CurrentArgument(()),
+    Argument(Argument<'self>),
+}
+
+pub struct Argument<'self> {
+    position: Position,
+    format: FormatSpec,
+    method: Option<&'self Method<'self>>
+}
+
+pub struct FormatSpec {
+    fill: char,
+    alignleft: bool,
+    flags: uint,
+    precision: parse::Count,
+    width: parse::Count,
+}
+
+pub enum Position {
+    ArgumentNext, ArgumentIs(uint)
+}
+
+pub enum Method<'self> {
+    Plural(Option<uint>, &'self [PluralArm<'self>], &'self [Piece<'self>]),
+    Select(&'self [SelectArm<'self>], &'self [Piece<'self>]),
+}
+
+pub struct PluralArm<'self> {
+    selector: Either<parse::PluralKeyword, uint>,
+    result: &'self [Piece<'self>],
+}
+
+pub struct SelectArm<'self> {
+    selector: &'self str,
+    result: &'self [Piece<'self>],
+}

src/libstd/rt/io/mem.rs

@@ -26,7 +26,7 @@ pub struct MemWriter {
 }
 
 impl MemWriter {
-    pub fn new() -> MemWriter { MemWriter { buf: ~[] } }
+    pub fn new() -> MemWriter { MemWriter { buf: vec::with_capacity(128) } }
 }
 
 impl Writer for MemWriter {

src/libstd/std.rs

@@ -177,6 +177,7 @@ pub mod rand;
 pub mod run;
 pub mod sys;
 pub mod cast;
+pub mod fmt;
 pub mod repr;
 pub mod cleanup;
 pub mod reflect;
@@ -216,4 +217,6 @@ mod std {
     pub use unstable;
     pub use str;
     pub use os;
+    pub use fmt;
+    pub use to_bytes;
 }

src/libsyntax/ext/base.rs

@@ -139,6 +139,8 @@ pub fn syntax_expander_table() -> SyntaxEnv {
                                 ext::tt::macro_rules::add_new_extension));
     syntax_expanders.insert(intern(&"fmt"),
                             builtin_normal_tt(ext::fmt::expand_syntax_ext));
+    syntax_expanders.insert(intern(&"ifmt"),
+                            builtin_normal_tt(ext::ifmt::expand_syntax_ext));
     syntax_expanders.insert(
         intern(&"auto_encode"),
         @SE(ItemDecorator(ext::auto_encode::expand_auto_encode)));

src/libsyntax/ext/expand.rs

@@ -1014,7 +1014,9 @@ pub fn expand_crate(parse_sess: @mut parse::ParseSess,
         .. *afp};
     let f = make_fold(f_pre);
 
-    @f.fold_crate(c)
+    let ret = @f.fold_crate(c);
+    parse_sess.span_diagnostic.handler().abort_if_errors();
+    return ret;
 }
 
 // given a function from idents to idents, produce

src/libsyntax/syntax.rs

@@ -73,6 +73,7 @@ pub mod ext {
 
     pub mod cfg;
     pub mod fmt;
+    pub mod ifmt;
     pub mod env;
     pub mod bytes;
     pub mod concat_idents;

src/test/compile-fail/ifmt-bad-arg.rs

@@ -0,0 +1,74 @@
+// Copyright 2013 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.
+
+fn main() {
+    // bad arguments to the ifmt! call
+
+    ifmt!();                //~ ERROR: expects at least one
+    ifmt!("{}");            //~ ERROR: invalid reference to argument
+
+    ifmt!("{1}", 1);        //~ ERROR: invalid reference to argument `1`
+                            //~^ ERROR: argument never used
+    ifmt!("{foo}");         //~ ERROR: no argument named `foo`
+
+    ifmt!("{}", 1, 2);               //~ ERROR: argument never used
+    ifmt!("{1}", 1, 2);              //~ ERROR: argument never used
+    ifmt!("{}", 1, foo=2);           //~ ERROR: named argument never used
+    ifmt!("{foo}", 1, foo=2);        //~ ERROR: argument never used
+    ifmt!("", foo=2);                //~ ERROR: named argument never used
+
+    ifmt!("{0:d} {0:s}", 1);         //~ ERROR: redeclared with type `s`
+    ifmt!("{foo:d} {foo:s}", foo=1); //~ ERROR: redeclared with type `s`
+
+    ifmt!("{foo}", foo=1, foo=2);    //~ ERROR: duplicate argument
+    ifmt!("#");                      //~ ERROR: `#` reference used
+    ifmt!("", foo=1, 2);             //~ ERROR: positional arguments cannot follow
+    ifmt!("" 1);                     //~ ERROR: expected token: `,`
+    ifmt!("", 1 1);                  //~ ERROR: expected token: `,`
+
+    ifmt!("{0, select, a{} a{} other{}}", "a");    //~ ERROR: duplicate selector
+    ifmt!("{0, plural, =1{} =1{} other{}}", 1u);   //~ ERROR: duplicate selector
+    ifmt!("{0, plural, one{} one{} other{}}", 1u); //~ ERROR: duplicate selector
+
+    // bad syntax of the format string
+
+    ifmt!("{"); //~ ERROR: unterminated format string
+    ifmt!("\\ "); //~ ERROR: invalid escape
+    ifmt!("\\"); //~ ERROR: expected an escape
+
+    ifmt!("{0, }", 1); //~ ERROR: expected method
+    ifmt!("{0, foo}", 1); //~ ERROR: unknown method
+    ifmt!("{0, select}", "a"); //~ ERROR: must be followed by
+    ifmt!("{0, plural}", 1); //~ ERROR: must be followed by
+
+    ifmt!("{0, select, a{{}", 1); //~ ERROR: must be terminated
+    ifmt!("{0, select, {} other{}}", "a"); //~ ERROR: empty selector
+    ifmt!("{0, select, other{} other{}}", "a"); //~ ERROR: multiple `other`
+    ifmt!("{0, plural, offset: other{}}", "a"); //~ ERROR: must be an integer
+    ifmt!("{0, plural, offset 1 other{}}", "a"); //~ ERROR: be followed by `:`
+    ifmt!("{0, plural, =a{} other{}}", "a"); //~ ERROR: followed by an integer
+    ifmt!("{0, plural, a{} other{}}", "a"); //~ ERROR: unexpected plural
+    ifmt!("{0, select, a{}}", "a"); //~ ERROR: must provide an `other`
+    ifmt!("{0, plural, =1{}}", "a"); //~ ERROR: must provide an `other`
+
+    ifmt!("{0, plural, other{{0:s}}}", "a"); //~ ERROR: previously used as
+    ifmt!("{:s} {0, plural, other{}}", "a"); //~ ERROR: argument used to
+    ifmt!("{0, select, other{}} \
+           {0, plural, other{}}", "a");
+    //~^ ERROR: declared with multiple formats
+
+    // It should be illegal to use implicit placement arguments nested inside of
+    // format strings because otherwise the "internal pointer of which argument
+    // is next" would be invalidated if different cases had different numbers of
+    // arguments.
+    ifmt!("{0, select, other{{}}}", "a"); //~ ERROR: cannot use implicit
+    ifmt!("{0, plural, other{{}}}", 1); //~ ERROR: cannot use implicit
+    ifmt!("{0, plural, other{{1:.*d}}}", 1, 2); //~ ERROR: cannot use implicit
+}

src/test/compile-fail/ifmt-bad-plural.rs

@@ -0,0 +1,14 @@
+// Copyright 2013 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.
+
+fn main() {
+    ifmt!("{0, plural, other{}}", "a");
+    //~^ ERROR: expected uint but found
+}

src/test/compile-fail/ifmt-bad-select.rs

@@ -0,0 +1,14 @@
+// Copyright 2013 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.
+
+fn main() {
+    ifmt!("{0, select, other{}}", 2);
+    //~^ ERROR: expected &str but found integral
+}

src/test/compile-fail/ifmt-unimpl.rs

@@ -0,0 +1,14 @@
+// Copyright 2013 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.
+
+fn main() {
+    ifmt!("{:d}", "3");
+    //~^ ERROR: failed to find an implementation of trait std::fmt::Signed
+}

src/test/compile-fail/ifmt-unknown-trait.rs

@@ -0,0 +1,14 @@
+// Copyright 2013 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.
+
+fn main() {
+    ifmt!("{:notimplemented}", "3");
+    //~^ ERROR: unknown format trait `notimplemented`
+}

src/test/run-pass/ifmt.rs

@@ -0,0 +1,71 @@
+// Copyright 2013 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.
+
+use std::fmt;
+
+struct A;
+struct B;
+
+#[fmt="foo"]
+impl fmt::Signed for A {
+    fn fmt(_: &A, f: &mut fmt::Formatter) { f.buf.write("aloha".as_bytes()); }
+}
+impl fmt::Signed for B {
+    fn fmt(_: &B, f: &mut fmt::Formatter) { f.buf.write("adios".as_bytes()); }
+}
+
+pub fn main() {
+    fn t(a: ~str, b: &str) { assert_eq!(a, b.to_owned()); }
+
+    // Make sure there's a poly formatter that takes anything
+    t(ifmt!("{}", 1), "1");
+    t(ifmt!("{}", A), "{}");
+    t(ifmt!("{}", ()), "()");
+    t(ifmt!("{}", @(~1, "foo")), "@(~1, \"foo\")");
+
+    // Various edge cases without formats
+    t(ifmt!(""), "");
+    t(ifmt!("hello"), "hello");
+    t(ifmt!("hello \\{"), "hello {");
+
+    // At least exercise all the formats
+    t(ifmt!("{:b}", true), "true");
+    t(ifmt!("{:c}", '☃'), "☃");
+    t(ifmt!("{:d}", 10), "10");
+    t(ifmt!("{:i}", 10), "10");
+    t(ifmt!("{:u}", 10u), "10");
+    t(ifmt!("{:o}", 10u), "12");
+    t(ifmt!("{:x}", 10u), "a");
+    t(ifmt!("{:X}", 10u), "A");
+    t(ifmt!("{:s}", "foo"), "foo");
+    t(ifmt!("{:p}", 0x1234 as *int), "0x1234");
+    t(ifmt!("{:p}", 0x1234 as *mut int), "0x1234");
+    t(ifmt!("{:d}", A), "aloha");
+    t(ifmt!("{:d}", B), "adios");
+    t(ifmt!("foo {:s} ☃☃☃☃☃☃", "bar"), "foo bar ☃☃☃☃☃☃");
+    t(ifmt!("{1} {0}", 0, 1), "1 0");
+    t(ifmt!("{foo} {bar}", foo=0, bar=1), "0 1");
+    t(ifmt!("{foo} {1} {bar} {0}", 0, 1, foo=2, bar=3), "2 1 3 0");
+    t(ifmt!("{} {0:s}", "a"), "a a");
+    t(ifmt!("{} {0}", "a"), "\"a\" \"a\"");
+
+    // Methods should probably work
+    t(ifmt!("{0, plural, =1{a#} =2{b#} zero{c#} other{d#}}", 0u), "c0");
+    t(ifmt!("{0, plural, =1{a#} =2{b#} zero{c#} other{d#}}", 1u), "a1");
+    t(ifmt!("{0, plural, =1{a#} =2{b#} zero{c#} other{d#}}", 2u), "b2");
+    t(ifmt!("{0, plural, =1{a#} =2{b#} zero{c#} other{d#}}", 3u), "d3");
+    t(ifmt!("{0, select, a{a#} b{b#} c{c#} other{d#}}", "a"), "aa");
+    t(ifmt!("{0, select, a{a#} b{b#} c{c#} other{d#}}", "b"), "bb");
+    t(ifmt!("{0, select, a{a#} b{b#} c{c#} other{d#}}", "c"), "cc");
+    t(ifmt!("{0, select, a{a#} b{b#} c{c#} other{d#}}", "d"), "dd");
+    t(ifmt!("{1, select, a{#{0:s}} other{#{1}}}", "b", "a"), "ab");
+    t(ifmt!("{1, select, a{#{0}} other{#{1}}}", "c", "b"), "bb");
+}
+