macros.rs.html -- source
Description: Source to the Rust file `/usr/obj/ports/rust-1.16.0/rustc-1.16.0-src/src/libcore/macros.rs`.
Keywords: rust, rustlang, rust-lang

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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.

    /// Entry point of thread panic, for details, see std::macros
    #[macro_export]
    #[allow_internal_unstable]
    #[stable(feature = "core", since = "1.6.0")]
    macro_rules! panic {
        () => (
            panic!("explicit panic")
        );
        ($msg:expr) => ({
            static _MSG_FILE_LINE: (&'static str, &'static str, u32) = ($msg, file!(), line!());
            $crate::panicking::panic(&_MSG_FILE_LINE)
        });
        ($fmt:expr, $($arg:tt)*) => ({
            // The leading _'s are to avoid dead code warnings if this is
            // used inside a dead function. Just `#[allow(dead_code)]` is
            // insufficient, since the user may have
            // `#[forbid(dead_code)]` and which cannot be overridden.
            static _FILE_LINE: (&'static str, u32) = (file!(), line!());
            $crate::panicking::panic_fmt(format_args!($fmt, $($arg)*), &_FILE_LINE)
        });
    }

    /// Ensure that a boolean expression is `true` at runtime.
    ///
    /// This will invoke the `panic!` macro if the provided expression cannot be
    /// evaluated to `true` at runtime.
    ///
    /// Assertions are always checked in both debug and release builds, and cannot
    /// be disabled. See `debug_assert!` for assertions that are not enabled in
    /// release builds by default.
    ///
    /// Unsafe code relies on `assert!` to enforce run-time invariants that, if
    /// violated could lead to unsafety.
    ///
    /// Other use-cases of `assert!` include [testing] and enforcing run-time
    /// invariants in safe code (whose violation cannot result in unsafety).
    ///
    /// This macro has a second version, where a custom panic message can
    /// be provided with or without arguments for formatting.
    ///
    /// [testing]: ../book/testing.html
    ///
    /// # Examples
    ///
    /// ```
    /// // the panic message for these assertions is the stringified value of the
    /// // expression given.
    /// assert!(true);
    ///
    /// fn some_computation() -> bool { true } // a very simple function
    ///
    /// assert!(some_computation());
    ///
    /// // assert with a custom message
    /// let x = true;
    /// assert!(x, "x wasn't true!");
    ///
    /// let a = 3; let b = 27;
    /// assert!(a + b == 30, "a = {}, b = {}", a, b);
    /// ```
    #[macro_export]
    #[stable(feature = "rust1", since = "1.0.0")]
    macro_rules! assert {
        ($cond:expr) => (
            if !$cond {
                panic!(concat!("assertion failed: ", stringify!($cond)))
            }
        );
        ($cond:expr, $($arg:tt)+) => (
            if !$cond {
                panic!($($arg)+)
            }
        );
    }

    /// Asserts that two expressions are equal to each other.
    ///
    /// On panic, this macro will print the values of the expressions with their
    /// debug representations.
    ///
    /// Like `assert!()`, this macro has a second version, where a custom
    /// panic message can be provided.
    ///
    /// # Examples
    ///
    /// ```
    /// let a = 3;
    /// let b = 1 + 2;
    /// assert_eq!(a, b);
    ///
    /// assert_eq!(a, b, "we are testing addition with {} and {}", a, b);
    /// ```
    #[macro_export]
    #[stable(feature = "rust1", since = "1.0.0")]
    macro_rules! assert_eq {
        ($left:expr , $right:expr) => ({
            match (&$left, &$right) {
                (left_val, right_val) => {
                    if !(*left_val == *right_val) {
                        panic!("assertion failed: `(left == right)` \
                               (left: `{:?}`, right: `{:?}`)", left_val, right_val)
                    }
                }
            }
        });
        ($left:expr , $right:expr, $($arg:tt)*) => ({
            match (&($left), &($right)) {
                (left_val, right_val) => {
                    if !(*left_val == *right_val) {
                        panic!("assertion failed: `(left == right)` \
                               (left: `{:?}`, right: `{:?}`): {}", left_val, right_val,
                               format_args!($($arg)*))
                    }
                }
            }
        });
    }

    /// Asserts that two expressions are not equal to each other.
    ///
    /// On panic, this macro will print the values of the expressions with their
    /// debug representations.
    ///
    /// Like `assert!()`, this macro has a second version, where a custom
    /// panic message can be provided.
    ///
    /// # Examples
    ///
    /// ```
    /// let a = 3;
    /// let b = 2;
    /// assert_ne!(a, b);
    ///
    /// assert_ne!(a, b, "we are testing that the values are not equal");
    /// ```
    #[macro_export]
    #[stable(feature = "assert_ne", since = "1.12.0")]
    macro_rules! assert_ne {
        ($left:expr , $right:expr) => ({
            match (&$left, &$right) {
                (left_val, right_val) => {
                    if *left_val == *right_val {
                        panic!("assertion failed: `(left != right)` \
                               (left: `{:?}`, right: `{:?}`)", left_val, right_val)
                    }
                }
            }
        });
        ($left:expr , $right:expr, $($arg:tt)*) => ({
            match (&($left), &($right)) {
                (left_val, right_val) => {
                    if *left_val == *right_val {
                        panic!("assertion failed: `(left != right)` \
                               (left: `{:?}`, right: `{:?}`): {}", left_val, right_val,
                               format_args!($($arg)*))
                    }
                }
            }
        });
    }

    /// Ensure that a boolean expression is `true` at runtime.
    ///
    /// This will invoke the `panic!` macro if the provided expression cannot be
    /// evaluated to `true` at runtime.
    ///
    /// Like `assert!`, this macro also has a second version, where a custom panic
    /// message can be provided.
    ///
    /// Unlike `assert!`, `debug_assert!` statements are only enabled in non
    /// optimized builds by default. An optimized build will omit all
    /// `debug_assert!` statements unless `-C debug-assertions` is passed to the
    /// compiler. This makes `debug_assert!` useful for checks that are too
    /// expensive to be present in a release build but may be helpful during
    /// development.
    ///
    /// An unchecked assertion allows a program in an inconsistent state to keep
    /// running, which might have unexpected consequences but does not introduce
    /// unsafety as long as this only happens in safe code. The performance cost
    /// of assertions, is however, not measurable in general. Replacing `assert!`
    /// with `debug_assert!` is thus only encouraged after thorough profiling, and
    /// more importantly, only in safe code!
    ///
    /// # Examples
    ///
    /// ```
    /// // the panic message for these assertions is the stringified value of the
    /// // expression given.
    /// debug_assert!(true);
    ///
    /// fn some_expensive_computation() -> bool { true } // a very simple function
    /// debug_assert!(some_expensive_computation());
    ///
    /// // assert with a custom message
    /// let x = true;
    /// debug_assert!(x, "x wasn't true!");
    ///
    /// let a = 3; let b = 27;
    /// debug_assert!(a + b == 30, "a = {}, b = {}", a, b);
    /// ```
    #[macro_export]
    #[stable(feature = "rust1", since = "1.0.0")]
    macro_rules! debug_assert {
        ($($arg:tt)*) => (if cfg!(debug_assertions) { assert!($($arg)*); })
    }

    /// Asserts that two expressions are equal to each other.
    ///
    /// On panic, this macro will print the values of the expressions with their
    /// debug representations.
    ///
    /// Unlike `assert_eq!`, `debug_assert_eq!` statements are only enabled in non
    /// optimized builds by default. An optimized build will omit all
    /// `debug_assert_eq!` statements unless `-C debug-assertions` is passed to the
    /// compiler. This makes `debug_assert_eq!` useful for checks that are too
    /// expensive to be present in a release build but may be helpful during
    /// development.
    ///
    /// # Examples
    ///
    /// ```
    /// let a = 3;
    /// let b = 1 + 2;
    /// debug_assert_eq!(a, b);
    /// ```
    #[macro_export]
    #[stable(feature = "rust1", since = "1.0.0")]
    macro_rules! debug_assert_eq {
        ($($arg:tt)*) => (if cfg!(debug_assertions) { assert_eq!($($arg)*); })
    }

    /// Asserts that two expressions are not equal to each other.
    ///
    /// On panic, this macro will print the values of the expressions with their
    /// debug representations.
    ///
    /// Unlike `assert_ne!`, `debug_assert_ne!` statements are only enabled in non
    /// optimized builds by default. An optimized build will omit all
    /// `debug_assert_ne!` statements unless `-C debug-assertions` is passed to the
    /// compiler. This makes `debug_assert_ne!` useful for checks that are too
    /// expensive to be present in a release build but may be helpful during
    /// development.
    ///
    /// # Examples
    ///
    /// ```
    /// let a = 3;
    /// let b = 2;
    /// debug_assert_ne!(a, b);
    /// ```
    #[macro_export]
    #[stable(feature = "assert_ne", since = "1.12.0")]
    macro_rules! debug_assert_ne {
        ($($arg:tt)*) => (if cfg!(debug_assertions) { assert_ne!($($arg)*); })
    }

    /// Helper macro for reducing boilerplate code for matching `Result` together
    /// with converting downstream errors.
    ///
    /// Prefer using `?` syntax to `try!`. `?` is built in to the language and is
    /// more succinct than `try!`. It is the standard method for error propagation.
    ///
    /// `try!` matches the given `Result`. In case of the `Ok` variant, the
    /// expression has the value of the wrapped value.
    ///
    /// In case of the `Err` variant, it retrieves the inner error. `try!` then
    /// performs conversion using `From`. This provides automatic conversion
    /// between specialized errors and more general ones. The resulting
    /// error is then immediately returned.
    ///
    /// Because of the early return, `try!` can only be used in functions that
    /// return `Result`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::io;
    /// use std::fs::File;
    /// use std::io::prelude::*;
    ///
    /// enum MyError {
    ///     FileWriteError
    /// }
    ///
    /// impl From<io::Error> for MyError {
    ///     fn from(e: io::Error) -> MyError {
    ///         MyError::FileWriteError
    ///     }
    /// }
    ///
    /// fn write_to_file_using_try() -> Result<(), MyError> {
    ///     let mut file = try!(File::create("my_best_friends.txt"));
    ///     try!(file.write_all(b"This is a list of my best friends."));
    ///     println!("I wrote to the file");
    ///     Ok(())
    /// }
    /// // This is equivalent to:
    /// fn write_to_file_using_match() -> Result<(), MyError> {
    ///     let mut file = try!(File::create("my_best_friends.txt"));
    ///     match file.write_all(b"This is a list of my best friends.") {
    ///         Ok(v) => v,
    ///         Err(e) => return Err(From::from(e)),
    ///     }
    ///     println!("I wrote to the file");
    ///     Ok(())
    /// }
    /// ```
    #[macro_export]
    #[stable(feature = "rust1", since = "1.0.0")]
    macro_rules! try {
        ($expr:expr) => (match $expr {
            $crate::result::Result::Ok(val) => val,
            $crate::result::Result::Err(err) => {
                return $crate::result::Result::Err($crate::convert::From::from(err))
            }
        })
    }

    /// Write formatted data into a buffer
    ///
    /// This macro accepts a 'writer' (any value with a `write_fmt` method), a format string, and a
    /// list of arguments to format.
    ///
    /// The `write_fmt` method usually comes from an implementation of [`std::fmt::Write`][fmt_write]
    /// or [`std::io::Write`][io_write] traits. The term 'writer' refers to an implementation of one of
    /// these two traits.
    ///
    /// Passed arguments will be formatted according to the specified format string and the resulting
    /// string will be passed to the writer.
    ///
    /// See [`std::fmt`][fmt] for more information on format syntax.
    ///
    /// `write!` returns whatever the 'write_fmt' method returns.
    ///
    /// Common return values include: [`fmt::Result`][fmt_result], [`io::Result`][io_result]
    ///
    /// [fmt]: ../std/fmt/index.html
    /// [fmt_write]: ../std/fmt/trait.Write.html
    /// [io_write]: ../std/io/trait.Write.html
    /// [fmt_result]: ../std/fmt/type.Result.html
    /// [io_result]: ../std/io/type.Result.html
    ///
    /// # Examples
    ///
    /// ```
    /// use std::io::Write;
    ///
    /// let mut w = Vec::new();
    /// write!(&mut w, "test").unwrap();
    /// write!(&mut w, "formatted {}", "arguments").unwrap();
    ///
    /// assert_eq!(w, b"testformatted arguments");
    /// ```
    ///
    /// A module can import both `std::fmt::Write` and `std::io::Write` and call `write!` on objects
    /// implementing either, as objects do not typically implement both. However, the module must
    /// import the traits qualified so their names do not conflict:
    ///
    /// ```
    /// use std::fmt::Write as FmtWrite;
    /// use std::io::Write as IoWrite;
    ///
    /// let mut s = String::new();
    /// let mut v = Vec::new();
    /// write!(&mut s, "{} {}", "abc", 123).unwrap(); // uses fmt::Write::write_fmt
    /// write!(&mut v, "s = {:?}", s).unwrap(); // uses io::Write::write_fmt
    /// assert_eq!(v, b"s = \"abc 123\"");
    /// ```
    #[macro_export]
    #[stable(feature = "core", since = "1.6.0")]
    macro_rules! write {
        ($dst:expr, $($arg:tt)*) => ($dst.write_fmt(format_args!($($arg)*)))
    }

    /// Write formatted data into a buffer, with a newline appended.
    ///
    /// On all platforms, the newline is the LINE FEED character (`\n`/`U+000A`) alone
    /// (no additional CARRIAGE RETURN (`\r`/`U+000D`).
    ///
    /// This macro accepts a 'writer' (any value with a `write_fmt` method), a format string, and a
    /// list of arguments to format.
    ///
    /// The `write_fmt` method usually comes from an implementation of [`std::fmt::Write`][fmt_write]
    /// or [`std::io::Write`][io_write] traits. The term 'writer' refers to an implementation of one of
    /// these two traits.
    ///
    /// Passed arguments will be formatted according to the specified format string and the resulting
    /// string will be passed to the writer, along with the appended newline.
    ///
    /// See [`std::fmt`][fmt] for more information on format syntax.
    ///
    /// `write!` returns whatever the 'write_fmt' method returns.
    ///
    /// Common return values include: [`fmt::Result`][fmt_result], [`io::Result`][io_result]
    ///
    /// [fmt]: ../std/fmt/index.html
    /// [fmt_write]: ../std/fmt/trait.Write.html
    /// [io_write]: ../std/io/trait.Write.html
    /// [fmt_result]: ../std/fmt/type.Result.html
    /// [io_result]: ../std/io/type.Result.html
    ///
    /// # Examples
    ///
    /// ```
    /// use std::io::Write;
    ///
    /// let mut w = Vec::new();
    /// writeln!(&mut w).unwrap();
    /// writeln!(&mut w, "test").unwrap();
    /// writeln!(&mut w, "formatted {}", "arguments").unwrap();
    ///
    /// assert_eq!(&w[..], "\ntest\nformatted arguments\n".as_bytes());
    /// ```
    ///
    /// A module can import both `std::fmt::Write` and `std::io::Write` and call `write!` on objects
    /// implementing either, as objects do not typically implement both. However, the module must
    /// import the traits qualified so their names do not conflict:
    ///
    /// ```
    /// use std::fmt::Write as FmtWrite;
    /// use std::io::Write as IoWrite;
    ///
    /// let mut s = String::new();
    /// let mut v = Vec::new();
    /// writeln!(&mut s, "{} {}", "abc", 123).unwrap(); // uses fmt::Write::write_fmt
    /// writeln!(&mut v, "s = {:?}", s).unwrap(); // uses io::Write::write_fmt
    /// assert_eq!(v, b"s = \"abc 123\\n\"\n");
    /// ```
    #[macro_export]
    #[stable(feature = "rust1", since = "1.0.0")]
    macro_rules! writeln {
        ($dst:expr) => (
            write!($dst, "\n")
        );
        ($dst:expr, $fmt:expr) => (
            write!($dst, concat!($fmt, "\n"))
        );
        ($dst:expr, $fmt:expr, $($arg:tt)*) => (
            write!($dst, concat!($fmt, "\n"), $($arg)*)
        );
    }

    /// A utility macro for indicating unreachable code.
    ///
    /// This is useful any time that the compiler can't determine that some code is unreachable. For
    /// example:
    ///
    /// * Match arms with guard conditions.
    /// * Loops that dynamically terminate.
    /// * Iterators that dynamically terminate.
    ///
    /// # Panics
    ///
    /// This will always panic.
    ///
    /// # Examples
    ///
    /// Match arms:
    ///
    /// ```
    /// # #[allow(dead_code)]
    /// fn foo(x: Option<i32>) {
    ///     match x {
    ///         Some(n) if n >= 0 => println!("Some(Non-negative)"),
    ///         Some(n) if n <  0 => println!("Some(Negative)"),
    ///         Some(_)           => unreachable!(), // compile error if commented out
    ///         None              => println!("None")
    ///     }
    /// }
    /// ```
    ///
    /// Iterators:
    ///
    /// ```
    /// # #[allow(dead_code)]
    /// fn divide_by_three(x: u32) -> u32 { // one of the poorest implementations of x/3
    ///     for i in 0.. {
    ///         if 3*i < i { panic!("u32 overflow"); }
    ///         if x < 3*i { return i-1; }
    ///     }
    ///     unreachable!();
    /// }
    /// ```
    #[macro_export]
    #[stable(feature = "core", since = "1.6.0")]
    macro_rules! unreachable {
        () => ({
            panic!("internal error: entered unreachable code")
        });
        ($msg:expr) => ({
            unreachable!("{}", $msg)
        });
        ($fmt:expr, $($arg:tt)*) => ({
            panic!(concat!("internal error: entered unreachable code: ", $fmt), $($arg)*)
        });
    }

    /// A standardized placeholder for marking unfinished code. It panics with the
    /// message `"not yet implemented"` when executed.
    ///
    /// This can be useful if you are prototyping and are just looking to have your
    /// code typecheck, or if you're implementing a trait that requires multiple
    /// methods, and you're only planning on using one of them.
    ///
    /// # Examples
    ///
    /// Here's an example of some in-progress code. We have a trait `Foo`:
    ///
    /// ```
    /// trait Foo {
    ///     fn bar(&self);
    ///     fn baz(&self);
    /// }
    /// ```
    ///
    /// We want to implement `Foo` on one of our types, but we also want to work on
    /// just `bar()` first. In order for our code to compile, we need to implement
    /// `baz()`, so we can use `unimplemented!`:
    ///
    /// ```
    /// # trait Foo {
    /// #     fn bar(&self);
    /// #     fn baz(&self);
    /// # }
    /// struct MyStruct;
    ///
    /// impl Foo for MyStruct {
    ///     fn bar(&self) {
    ///         // implementation goes here
    ///     }
    ///
    ///     fn baz(&self) {
    ///         // let's not worry about implementing baz() for now
    ///         unimplemented!();
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let s = MyStruct;
    ///     s.bar();
    ///
    ///     // we aren't even using baz() yet, so this is fine.
    /// }
    /// ```
    #[macro_export]
    #[stable(feature = "core", since = "1.6.0")]
    macro_rules! unimplemented {
        () => (panic!("not yet implemented"))
    }

    /// Built-in macros to the compiler itself.
    ///
    /// These macros do not have any corresponding definition with a `macro_rules!`
    /// macro, but are documented here. Their implementations can be found hardcoded
    /// into libsyntax itself.
    ///
    /// For more information, see documentation for `std`'s macros.
    mod builtin {
        /// The core macro for formatted string creation & output.
        ///
        /// For more information, see the documentation for [`std::format_args!`].
        ///
        /// [`std::format_args!`]: ../std/macro.format_args.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! format_args { ($fmt:expr, $($args:tt)*) => ({
            /* compiler built-in */
        }) }

        /// Inspect an environment variable at compile time.
        ///
        /// For more information, see the documentation for [`std::env!`].
        ///
        /// [`std::env!`]: ../std/macro.env.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! env { ($name:expr) => ({ /* compiler built-in */ }) }

        /// Optionally inspect an environment variable at compile time.
        ///
        /// For more information, see the documentation for [`std::option_env!`].
        ///
        /// [`std::option_env!`]: ../std/macro.option_env.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! option_env { ($name:expr) => ({ /* compiler built-in */ }) }

        /// Concatenate identifiers into one identifier.
        ///
        /// For more information, see the documentation for [`std::concat_idents!`].
        ///
        /// [`std::concat_idents!`]: ../std/macro.concat_idents.html
        #[unstable(feature = "concat_idents_macro", issue = "29599")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! concat_idents {
            ($($e:ident),*) => ({ /* compiler built-in */ })
        }

        /// Concatenates literals into a static string slice.
        ///
        /// For more information, see the documentation for [`std::concat!`].
        ///
        /// [`std::concat!`]: ../std/macro.concat.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! concat { ($($e:expr),*) => ({ /* compiler built-in */ }) }

        /// A macro which expands to the line number on which it was invoked.
        ///
        /// For more information, see the documentation for [`std::line!`].
        ///
        /// [`std::line!`]: ../std/macro.line.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! line { () => ({ /* compiler built-in */ }) }

        /// A macro which expands to the column number on which it was invoked.
        ///
        /// For more information, see the documentation for [`std::column!`].
        ///
        /// [`std::column!`]: ../std/macro.column.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! column { () => ({ /* compiler built-in */ }) }

        /// A macro which expands to the file name from which it was invoked.
        ///
        /// For more information, see the documentation for [`std::file!`].
        ///
        /// [`std::file!`]: ../std/macro.file.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! file { () => ({ /* compiler built-in */ }) }

        /// A macro which stringifies its argument.
        ///
        /// For more information, see the documentation for [`std::stringify!`].
        ///
        /// [`std::stringify!`]: ../std/macro.stringify.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! stringify { ($t:tt) => ({ /* compiler built-in */ }) }

        /// Includes a utf8-encoded file as a string.
        ///
        /// For more information, see the documentation for [`std::include_str!`].
        ///
        /// [`std::include_str!`]: ../std/macro.include_str.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! include_str { ($file:expr) => ({ /* compiler built-in */ }) }

        /// Includes a file as a reference to a byte array.
        ///
        /// For more information, see the documentation for [`std::include_bytes!`].
        ///
        /// [`std::include_bytes!`]: ../std/macro.include_bytes.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! include_bytes { ($file:expr) => ({ /* compiler built-in */ }) }

        /// Expands to a string that represents the current module path.
        ///
        /// For more information, see the documentation for [`std::module_path!`].
        ///
        /// [`std::module_path!`]: ../std/macro.module_path.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! module_path { () => ({ /* compiler built-in */ }) }

        /// Boolean evaluation of configuration flags.
        ///
        /// For more information, see the documentation for [`std::cfg!`].
        ///
        /// [`std::cfg!`]: ../std/macro.cfg.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! cfg { ($($cfg:tt)*) => ({ /* compiler built-in */ }) }

        /// Parse a file as an expression or an item according to the context.
        ///
        /// For more information, see the documentation for [`std::include!`].
        ///
        /// [`std::include!`]: ../std/macro.include.html
        #[stable(feature = "rust1", since = "1.0.0")]
        #[macro_export]
        #[cfg(dox)]
        macro_rules! include { ($file:expr) => ({ /* compiler built-in */ }) }
    }

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