1595 lines
54 KiB
Rust
1595 lines
54 KiB
Rust
#[doc = include_str!("panic.md")]
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#[macro_export]
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#[rustc_builtin_macro(core_panic)]
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#[allow_internal_unstable(edition_panic)]
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#[stable(feature = "core", since = "1.6.0")]
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#[rustc_diagnostic_item = "core_panic_macro"]
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macro_rules! panic {
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// Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021`
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// depending on the edition of the caller.
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($($arg:tt)*) => {
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/* compiler built-in */
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};
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}
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/// Asserts that two expressions are equal to each other (using [`PartialEq`]).
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///
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/// On panic, this macro will print the values of the expressions with their
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/// debug representations.
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///
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/// Like [`assert!`], this macro has a second form, where a custom
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/// panic message can be provided.
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///
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/// # Examples
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///
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/// ```
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/// let a = 3;
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/// let b = 1 + 2;
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/// assert_eq!(a, b);
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///
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/// assert_eq!(a, b, "we are testing addition with {} and {}", a, b);
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/// ```
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#[macro_export]
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#[stable(feature = "rust1", since = "1.0.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "assert_eq_macro")]
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#[allow_internal_unstable(core_panic)]
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macro_rules! assert_eq {
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($left:expr, $right:expr $(,)?) => {
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match (&$left, &$right) {
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(left_val, right_val) => {
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if !(*left_val == *right_val) {
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let kind = $crate::panicking::AssertKind::Eq;
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// The reborrows below are intentional. Without them, the stack slot for the
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// borrow is initialized even before the values are compared, leading to a
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// noticeable slow down.
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$crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::None);
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}
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}
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}
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};
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($left:expr, $right:expr, $($arg:tt)+) => {
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match (&$left, &$right) {
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(left_val, right_val) => {
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if !(*left_val == *right_val) {
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let kind = $crate::panicking::AssertKind::Eq;
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// The reborrows below are intentional. Without them, the stack slot for the
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// borrow is initialized even before the values are compared, leading to a
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// noticeable slow down.
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$crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($arg)+)));
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}
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}
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}
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};
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}
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/// Asserts that two expressions are not equal to each other (using [`PartialEq`]).
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///
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/// On panic, this macro will print the values of the expressions with their
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/// debug representations.
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///
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/// Like [`assert!`], this macro has a second form, where a custom
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/// panic message can be provided.
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///
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/// # Examples
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///
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/// ```
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/// let a = 3;
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/// let b = 2;
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/// assert_ne!(a, b);
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///
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/// assert_ne!(a, b, "we are testing that the values are not equal");
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/// ```
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#[macro_export]
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#[stable(feature = "assert_ne", since = "1.13.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "assert_ne_macro")]
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#[allow_internal_unstable(core_panic)]
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macro_rules! assert_ne {
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($left:expr, $right:expr $(,)?) => {
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match (&$left, &$right) {
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(left_val, right_val) => {
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if *left_val == *right_val {
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let kind = $crate::panicking::AssertKind::Ne;
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// The reborrows below are intentional. Without them, the stack slot for the
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// borrow is initialized even before the values are compared, leading to a
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// noticeable slow down.
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$crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::None);
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}
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}
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}
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};
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($left:expr, $right:expr, $($arg:tt)+) => {
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match (&($left), &($right)) {
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(left_val, right_val) => {
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if *left_val == *right_val {
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let kind = $crate::panicking::AssertKind::Ne;
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// The reborrows below are intentional. Without them, the stack slot for the
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// borrow is initialized even before the values are compared, leading to a
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// noticeable slow down.
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$crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($arg)+)));
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}
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}
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}
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};
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}
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/// Asserts that an expression matches any of the given patterns.
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///
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/// Like in a `match` expression, the pattern can be optionally followed by `if`
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/// and a guard expression that has access to names bound by the pattern.
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///
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/// On panic, this macro will print the value of the expression with its
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/// debug representation.
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///
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/// Like [`assert!`], this macro has a second form, where a custom
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/// panic message can be provided.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(assert_matches)]
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///
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/// use std::assert_matches::assert_matches;
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///
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/// let a = 1u32.checked_add(2);
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/// let b = 1u32.checked_sub(2);
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/// assert_matches!(a, Some(_));
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/// assert_matches!(b, None);
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///
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/// let c = Ok("abc".to_string());
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/// assert_matches!(c, Ok(x) | Err(x) if x.len() < 100);
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/// ```
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#[unstable(feature = "assert_matches", issue = "82775")]
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#[allow_internal_unstable(core_panic)]
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#[rustc_macro_transparency = "semitransparent"]
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pub macro assert_matches {
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($left:expr, $(|)? $( $pattern:pat_param )|+ $( if $guard: expr )? $(,)?) => {
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match $left {
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$( $pattern )|+ $( if $guard )? => {}
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ref left_val => {
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$crate::panicking::assert_matches_failed(
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left_val,
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$crate::stringify!($($pattern)|+ $(if $guard)?),
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$crate::option::Option::None
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);
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}
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}
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},
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($left:expr, $(|)? $( $pattern:pat_param )|+ $( if $guard: expr )?, $($arg:tt)+) => {
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match $left {
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$( $pattern )|+ $( if $guard )? => {}
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ref left_val => {
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$crate::panicking::assert_matches_failed(
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left_val,
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$crate::stringify!($($pattern)|+ $(if $guard)?),
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$crate::option::Option::Some($crate::format_args!($($arg)+))
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);
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}
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}
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},
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}
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/// Asserts that a boolean expression is `true` at runtime.
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///
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/// This will invoke the [`panic!`] macro if the provided expression cannot be
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/// evaluated to `true` at runtime.
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///
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/// Like [`assert!`], this macro also has a second version, where a custom panic
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/// message can be provided.
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///
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/// # Uses
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///
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/// Unlike [`assert!`], `debug_assert!` statements are only enabled in non
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/// optimized builds by default. An optimized build will not execute
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/// `debug_assert!` statements unless `-C debug-assertions` is passed to the
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/// compiler. This makes `debug_assert!` useful for checks that are too
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/// expensive to be present in a release build but may be helpful during
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/// development. The result of expanding `debug_assert!` is always type checked.
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///
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/// An unchecked assertion allows a program in an inconsistent state to keep
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/// running, which might have unexpected consequences but does not introduce
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/// unsafety as long as this only happens in safe code. The performance cost
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/// of assertions, however, is not measurable in general. Replacing [`assert!`]
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/// with `debug_assert!` is thus only encouraged after thorough profiling, and
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/// more importantly, only in safe code!
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///
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/// # Examples
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///
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/// ```
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/// // the panic message for these assertions is the stringified value of the
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/// // expression given.
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/// debug_assert!(true);
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///
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/// fn some_expensive_computation() -> bool { true } // a very simple function
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/// debug_assert!(some_expensive_computation());
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///
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/// // assert with a custom message
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/// let x = true;
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/// debug_assert!(x, "x wasn't true!");
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///
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/// let a = 3; let b = 27;
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/// debug_assert!(a + b == 30, "a = {}, b = {}", a, b);
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/// ```
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#[macro_export]
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#[stable(feature = "rust1", since = "1.0.0")]
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#[rustc_diagnostic_item = "debug_assert_macro"]
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#[allow_internal_unstable(edition_panic)]
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macro_rules! debug_assert {
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($($arg:tt)*) => {
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if $crate::cfg!(debug_assertions) {
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$crate::assert!($($arg)*);
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}
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};
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}
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/// Asserts that two expressions are equal to each other.
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///
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/// On panic, this macro will print the values of the expressions with their
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/// debug representations.
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///
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/// Unlike [`assert_eq!`], `debug_assert_eq!` statements are only enabled in non
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/// optimized builds by default. An optimized build will not execute
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/// `debug_assert_eq!` statements unless `-C debug-assertions` is passed to the
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/// compiler. This makes `debug_assert_eq!` useful for checks that are too
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/// expensive to be present in a release build but may be helpful during
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/// development. The result of expanding `debug_assert_eq!` is always type checked.
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///
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/// # Examples
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///
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/// ```
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/// let a = 3;
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/// let b = 1 + 2;
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/// debug_assert_eq!(a, b);
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/// ```
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#[macro_export]
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#[stable(feature = "rust1", since = "1.0.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "debug_assert_eq_macro")]
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macro_rules! debug_assert_eq {
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($($arg:tt)*) => {
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if $crate::cfg!(debug_assertions) {
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$crate::assert_eq!($($arg)*);
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}
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};
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}
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/// Asserts that two expressions are not equal to each other.
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///
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/// On panic, this macro will print the values of the expressions with their
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/// debug representations.
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///
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/// Unlike [`assert_ne!`], `debug_assert_ne!` statements are only enabled in non
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/// optimized builds by default. An optimized build will not execute
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/// `debug_assert_ne!` statements unless `-C debug-assertions` is passed to the
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/// compiler. This makes `debug_assert_ne!` useful for checks that are too
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/// expensive to be present in a release build but may be helpful during
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/// development. The result of expanding `debug_assert_ne!` is always type checked.
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///
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/// # Examples
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///
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/// ```
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/// let a = 3;
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/// let b = 2;
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/// debug_assert_ne!(a, b);
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/// ```
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#[macro_export]
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#[stable(feature = "assert_ne", since = "1.13.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "debug_assert_ne_macro")]
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macro_rules! debug_assert_ne {
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($($arg:tt)*) => {
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if $crate::cfg!(debug_assertions) {
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$crate::assert_ne!($($arg)*);
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}
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};
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}
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/// Asserts that an expression matches any of the given patterns.
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///
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/// Like in a `match` expression, the pattern can be optionally followed by `if`
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/// and a guard expression that has access to names bound by the pattern.
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///
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/// On panic, this macro will print the value of the expression with its
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/// debug representation.
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///
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/// Unlike [`assert_matches!`], `debug_assert_matches!` statements are only
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/// enabled in non optimized builds by default. An optimized build will not
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/// execute `debug_assert_matches!` statements unless `-C debug-assertions` is
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/// passed to the compiler. This makes `debug_assert_matches!` useful for
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/// checks that are too expensive to be present in a release build but may be
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/// helpful during development. The result of expanding `debug_assert_matches!`
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/// is always type checked.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(assert_matches)]
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///
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/// use std::assert_matches::debug_assert_matches;
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///
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/// let a = 1u32.checked_add(2);
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/// let b = 1u32.checked_sub(2);
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/// debug_assert_matches!(a, Some(_));
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/// debug_assert_matches!(b, None);
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///
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/// let c = Ok("abc".to_string());
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/// debug_assert_matches!(c, Ok(x) | Err(x) if x.len() < 100);
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/// ```
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#[macro_export]
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#[unstable(feature = "assert_matches", issue = "82775")]
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#[allow_internal_unstable(assert_matches)]
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#[rustc_macro_transparency = "semitransparent"]
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pub macro debug_assert_matches($($arg:tt)*) {
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if $crate::cfg!(debug_assertions) {
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$crate::assert_matches::assert_matches!($($arg)*);
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}
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}
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|
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/// Returns whether the given expression matches any of the given patterns.
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///
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/// Like in a `match` expression, the pattern can be optionally followed by `if`
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/// and a guard expression that has access to names bound by the pattern.
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///
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/// # Examples
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///
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/// ```
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/// let foo = 'f';
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/// assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
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///
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/// let bar = Some(4);
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/// assert!(matches!(bar, Some(x) if x > 2));
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/// ```
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#[macro_export]
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#[stable(feature = "matches_macro", since = "1.42.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "matches_macro")]
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macro_rules! matches {
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($expression:expr, $pattern:pat $(if $guard:expr)? $(,)?) => {
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match $expression {
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$pattern $(if $guard)? => true,
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_ => false
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}
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};
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}
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/// Unwraps a result or propagates its error.
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///
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/// The [`?` operator][propagating-errors] was added to replace `try!`
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/// and should be used instead. Furthermore, `try` is a reserved word
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/// in Rust 2018, so if you must use it, you will need to use the
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/// [raw-identifier syntax][ris]: `r#try`.
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///
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/// [propagating-errors]: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
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/// [ris]: https://doc.rust-lang.org/nightly/rust-by-example/compatibility/raw_identifiers.html
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///
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/// `try!` matches the given [`Result`]. In case of the `Ok` variant, the
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/// expression has the value of the wrapped value.
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///
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/// In case of the `Err` variant, it retrieves the inner error. `try!` then
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/// performs conversion using `From`. This provides automatic conversion
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/// between specialized errors and more general ones. The resulting
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/// error is then immediately returned.
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///
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/// Because of the early return, `try!` can only be used in functions that
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/// return [`Result`].
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///
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/// # Examples
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///
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/// ```
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/// use std::io;
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/// use std::fs::File;
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/// use std::io::prelude::*;
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///
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/// enum MyError {
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/// FileWriteError
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/// }
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///
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/// impl From<io::Error> for MyError {
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/// fn from(e: io::Error) -> MyError {
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/// MyError::FileWriteError
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/// }
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/// }
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///
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/// // The preferred method of quick returning Errors
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/// fn write_to_file_question() -> Result<(), MyError> {
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/// let mut file = File::create("my_best_friends.txt")?;
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/// file.write_all(b"This is a list of my best friends.")?;
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/// Ok(())
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/// }
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///
|
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/// // The previous method of quick returning Errors
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/// fn write_to_file_using_try() -> Result<(), MyError> {
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/// let mut file = r#try!(File::create("my_best_friends.txt"));
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/// r#try!(file.write_all(b"This is a list of my best friends."));
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/// Ok(())
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/// }
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///
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/// // This is equivalent to:
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/// fn write_to_file_using_match() -> Result<(), MyError> {
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/// let mut file = r#try!(File::create("my_best_friends.txt"));
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/// match file.write_all(b"This is a list of my best friends.") {
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/// Ok(v) => v,
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/// Err(e) => return Err(From::from(e)),
|
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/// }
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/// Ok(())
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/// }
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/// ```
|
|
#[macro_export]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
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#[deprecated(since = "1.39.0", note = "use the `?` operator instead")]
|
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#[doc(alias = "?")]
|
|
macro_rules! r#try {
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|
($expr:expr $(,)?) => {
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match $expr {
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$crate::result::Result::Ok(val) => val,
|
|
$crate::result::Result::Err(err) => {
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|
return $crate::result::Result::Err($crate::convert::From::from(err));
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|
}
|
|
}
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};
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}
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|
|
|
/// Writes formatted data into a buffer.
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|
///
|
|
/// This macro accepts a 'writer', a format string, and a list of arguments. Arguments will be
|
|
/// formatted according to the specified format string and the result will be passed to the writer.
|
|
/// The writer may be any value with a `write_fmt` method; generally this comes from an
|
|
/// implementation of either the [`fmt::Write`] or the [`io::Write`] trait. The macro
|
|
/// returns whatever the `write_fmt` method returns; commonly a [`fmt::Result`], or an
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/// [`io::Result`].
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///
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|
/// See [`std::fmt`] for more information on the format string syntax.
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///
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/// [`std::fmt`]: ../std/fmt/index.html
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/// [`fmt::Write`]: crate::fmt::Write
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/// [`io::Write`]: ../std/io/trait.Write.html
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/// [`fmt::Result`]: crate::fmt::Result
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|
/// [`io::Result`]: ../std/io/type.Result.html
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///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::io::Write;
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///
|
|
/// fn main() -> std::io::Result<()> {
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|
/// let mut w = Vec::new();
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|
/// write!(&mut w, "test")?;
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|
/// write!(&mut w, "formatted {}", "arguments")?;
|
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///
|
|
/// assert_eq!(w, b"testformatted arguments");
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/// Ok(())
|
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/// }
|
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/// ```
|
|
///
|
|
/// 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
|
|
/// avoid conflict between the trait names, such as by importing them as `_` or otherwise renaming
|
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/// them:
|
|
///
|
|
/// ```
|
|
/// use std::fmt::Write as _;
|
|
/// use std::io::Write as _;
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///
|
|
/// fn main() -> Result<(), Box<dyn std::error::Error>> {
|
|
/// let mut s = String::new();
|
|
/// let mut v = Vec::new();
|
|
///
|
|
/// write!(&mut s, "{} {}", "abc", 123)?; // uses fmt::Write::write_fmt
|
|
/// write!(&mut v, "s = {:?}", s)?; // uses io::Write::write_fmt
|
|
/// assert_eq!(v, b"s = \"abc 123\"");
|
|
/// Ok(())
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// If you also need the trait names themselves, such as to implement one or both on your types,
|
|
/// import the containing module and then name them with a prefix:
|
|
///
|
|
/// ```
|
|
/// # #![allow(unused_imports)]
|
|
/// use std::fmt::{self, Write as _};
|
|
/// use std::io::{self, Write as _};
|
|
///
|
|
/// struct Example;
|
|
///
|
|
/// impl fmt::Write for Example {
|
|
/// fn write_str(&mut self, _s: &str) -> core::fmt::Result {
|
|
/// unimplemented!();
|
|
/// }
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// Note: This macro can be used in `no_std` setups as well.
|
|
/// In a `no_std` setup you are responsible for the implementation details of the components.
|
|
///
|
|
/// ```no_run
|
|
/// use core::fmt::Write;
|
|
///
|
|
/// struct Example;
|
|
///
|
|
/// impl Write for Example {
|
|
/// fn write_str(&mut self, _s: &str) -> core::fmt::Result {
|
|
/// unimplemented!();
|
|
/// }
|
|
/// }
|
|
///
|
|
/// let mut m = Example{};
|
|
/// write!(&mut m, "Hello World").expect("Not written");
|
|
/// ```
|
|
#[macro_export]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "write_macro")]
|
|
macro_rules! write {
|
|
($dst:expr, $($arg:tt)*) => {
|
|
$dst.write_fmt($crate::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`).
|
|
///
|
|
/// For more information, see [`write!`]. For information on the format string syntax, see
|
|
/// [`std::fmt`].
|
|
///
|
|
/// [`std::fmt`]: ../std/fmt/index.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::io::{Write, Result};
|
|
///
|
|
/// fn main() -> Result<()> {
|
|
/// let mut w = Vec::new();
|
|
/// writeln!(&mut w)?;
|
|
/// writeln!(&mut w, "test")?;
|
|
/// writeln!(&mut w, "formatted {}", "arguments")?;
|
|
///
|
|
/// assert_eq!(&w[..], "\ntest\nformatted arguments\n".as_bytes());
|
|
/// Ok(())
|
|
/// }
|
|
/// ```
|
|
#[macro_export]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "writeln_macro")]
|
|
#[allow_internal_unstable(format_args_nl)]
|
|
macro_rules! writeln {
|
|
($dst:expr $(,)?) => {
|
|
$crate::write!($dst, "\n")
|
|
};
|
|
($dst:expr, $($arg:tt)*) => {
|
|
$dst.write_fmt($crate::format_args_nl!($($arg)*))
|
|
};
|
|
}
|
|
|
|
/// Indicates 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.
|
|
///
|
|
/// If the determination that the code is unreachable proves incorrect, the
|
|
/// program immediately terminates with a [`panic!`].
|
|
///
|
|
/// The unsafe counterpart of this macro is the [`unreachable_unchecked`] function, which
|
|
/// will cause undefined behavior if the code is reached.
|
|
///
|
|
/// [`unreachable_unchecked`]: crate::hint::unreachable_unchecked
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This will always [`panic!`] because `unreachable!` is just a shorthand for `panic!` with a
|
|
/// fixed, specific message.
|
|
///
|
|
/// Like `panic!`, this macro has a second form for displaying custom values.
|
|
///
|
|
/// # 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!("The loop should always return");
|
|
/// }
|
|
/// ```
|
|
#[macro_export]
|
|
#[rustc_builtin_macro(unreachable)]
|
|
#[allow_internal_unstable(edition_panic)]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "unreachable_macro")]
|
|
macro_rules! unreachable {
|
|
// Expands to either `$crate::panic::unreachable_2015` or `$crate::panic::unreachable_2021`
|
|
// depending on the edition of the caller.
|
|
($($arg:tt)*) => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Indicates unimplemented code by panicking with a message of "not implemented".
|
|
///
|
|
/// This allows your code to type-check, which is useful if you are prototyping or
|
|
/// implementing a trait that requires multiple methods which you don't plan to use all of.
|
|
///
|
|
/// The difference between `unimplemented!` and [`todo!`] is that while `todo!`
|
|
/// conveys an intent of implementing the functionality later and the message is "not yet
|
|
/// implemented", `unimplemented!` makes no such claims. Its message is "not implemented".
|
|
/// Also some IDEs will mark `todo!`s.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This will always [`panic!`] because `unimplemented!` is just a shorthand for `panic!` with a
|
|
/// fixed, specific message.
|
|
///
|
|
/// Like `panic!`, this macro has a second form for displaying custom values.
|
|
///
|
|
/// [`todo!`]: crate::todo
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Say we have a trait `Foo`:
|
|
///
|
|
/// ```
|
|
/// trait Foo {
|
|
/// fn bar(&self) -> u8;
|
|
/// fn baz(&self);
|
|
/// fn qux(&self) -> Result<u64, ()>;
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// We want to implement `Foo` for 'MyStruct', but for some reason it only makes sense
|
|
/// to implement the `bar()` function. `baz()` and `qux()` will still need to be defined
|
|
/// in our implementation of `Foo`, but we can use `unimplemented!` in their definitions
|
|
/// to allow our code to compile.
|
|
///
|
|
/// We still want to have our program stop running if the unimplemented methods are
|
|
/// reached.
|
|
///
|
|
/// ```
|
|
/// # trait Foo {
|
|
/// # fn bar(&self) -> u8;
|
|
/// # fn baz(&self);
|
|
/// # fn qux(&self) -> Result<u64, ()>;
|
|
/// # }
|
|
/// struct MyStruct;
|
|
///
|
|
/// impl Foo for MyStruct {
|
|
/// fn bar(&self) -> u8 {
|
|
/// 1 + 1
|
|
/// }
|
|
///
|
|
/// fn baz(&self) {
|
|
/// // It makes no sense to `baz` a `MyStruct`, so we have no logic here
|
|
/// // at all.
|
|
/// // This will display "thread 'main' panicked at 'not implemented'".
|
|
/// unimplemented!();
|
|
/// }
|
|
///
|
|
/// fn qux(&self) -> Result<u64, ()> {
|
|
/// // We have some logic here,
|
|
/// // We can add a message to unimplemented! to display our omission.
|
|
/// // This will display:
|
|
/// // "thread 'main' panicked at 'not implemented: MyStruct isn't quxable'".
|
|
/// unimplemented!("MyStruct isn't quxable");
|
|
/// }
|
|
/// }
|
|
///
|
|
/// fn main() {
|
|
/// let s = MyStruct;
|
|
/// s.bar();
|
|
/// }
|
|
/// ```
|
|
#[macro_export]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "unimplemented_macro")]
|
|
#[allow_internal_unstable(core_panic)]
|
|
macro_rules! unimplemented {
|
|
() => {
|
|
$crate::panicking::panic("not implemented")
|
|
};
|
|
($($arg:tt)+) => {
|
|
$crate::panic!("not implemented: {}", $crate::format_args!($($arg)+))
|
|
};
|
|
}
|
|
|
|
/// Indicates unfinished code.
|
|
///
|
|
/// This can be useful if you are prototyping and just
|
|
/// want a placeholder to let your code pass type analysis.
|
|
///
|
|
/// The difference between [`unimplemented!`] and `todo!` is that while `todo!` conveys
|
|
/// an intent of implementing the functionality later and the message is "not yet
|
|
/// implemented", `unimplemented!` makes no such claims. Its message is "not implemented".
|
|
/// Also some IDEs will mark `todo!`s.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This will always [`panic!`].
|
|
///
|
|
/// # 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 `todo!`:
|
|
///
|
|
/// ```
|
|
/// # 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
|
|
/// todo!();
|
|
/// }
|
|
/// }
|
|
///
|
|
/// fn main() {
|
|
/// let s = MyStruct;
|
|
/// s.bar();
|
|
///
|
|
/// // we aren't even using baz(), so this is fine.
|
|
/// }
|
|
/// ```
|
|
#[macro_export]
|
|
#[stable(feature = "todo_macro", since = "1.40.0")]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "todo_macro")]
|
|
#[allow_internal_unstable(core_panic)]
|
|
macro_rules! todo {
|
|
() => {
|
|
$crate::panicking::panic("not yet implemented")
|
|
};
|
|
($($arg:tt)+) => {
|
|
$crate::panic!("not yet implemented: {}", $crate::format_args!($($arg)+))
|
|
};
|
|
}
|
|
|
|
/// Definitions of built-in macros.
|
|
///
|
|
/// Most of the macro properties (stability, visibility, etc.) are taken from the source code here,
|
|
/// with exception of expansion functions transforming macro inputs into outputs,
|
|
/// those functions are provided by the compiler.
|
|
pub(crate) mod builtin {
|
|
|
|
/// Causes compilation to fail with the given error message when encountered.
|
|
///
|
|
/// This macro should be used when a crate uses a conditional compilation strategy to provide
|
|
/// better error messages for erroneous conditions. It's the compiler-level form of [`panic!`],
|
|
/// but emits an error during *compilation* rather than at *runtime*.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Two such examples are macros and `#[cfg]` environments.
|
|
///
|
|
/// Emit a better compiler error if a macro is passed invalid values. Without the final branch,
|
|
/// the compiler would still emit an error, but the error's message would not mention the two
|
|
/// valid values.
|
|
///
|
|
/// ```compile_fail
|
|
/// macro_rules! give_me_foo_or_bar {
|
|
/// (foo) => {};
|
|
/// (bar) => {};
|
|
/// ($x:ident) => {
|
|
/// compile_error!("This macro only accepts `foo` or `bar`");
|
|
/// }
|
|
/// }
|
|
///
|
|
/// give_me_foo_or_bar!(neither);
|
|
/// // ^ will fail at compile time with message "This macro only accepts `foo` or `bar`"
|
|
/// ```
|
|
///
|
|
/// Emit a compiler error if one of a number of features isn't available.
|
|
///
|
|
/// ```compile_fail
|
|
/// #[cfg(not(any(feature = "foo", feature = "bar")))]
|
|
/// compile_error!("Either feature \"foo\" or \"bar\" must be enabled for this crate.");
|
|
/// ```
|
|
#[stable(feature = "compile_error_macro", since = "1.20.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! compile_error {
|
|
($msg:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Constructs parameters for the other string-formatting macros.
|
|
///
|
|
/// This macro functions by taking a formatting string literal containing
|
|
/// `{}` for each additional argument passed. `format_args!` prepares the
|
|
/// additional parameters to ensure the output can be interpreted as a string
|
|
/// and canonicalizes the arguments into a single type. Any value that implements
|
|
/// the [`Display`] trait can be passed to `format_args!`, as can any
|
|
/// [`Debug`] implementation be passed to a `{:?}` within the formatting string.
|
|
///
|
|
/// This macro produces a value of type [`fmt::Arguments`]. This value can be
|
|
/// passed to the macros within [`std::fmt`] for performing useful redirection.
|
|
/// All other formatting macros ([`format!`], [`write!`], [`println!`], etc) are
|
|
/// proxied through this one. `format_args!`, unlike its derived macros, avoids
|
|
/// heap allocations.
|
|
///
|
|
/// You can use the [`fmt::Arguments`] value that `format_args!` returns
|
|
/// in `Debug` and `Display` contexts as seen below. The example also shows
|
|
/// that `Debug` and `Display` format to the same thing: the interpolated
|
|
/// format string in `format_args!`.
|
|
///
|
|
/// ```rust
|
|
/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
|
|
/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
|
|
/// assert_eq!("1 foo 2", display);
|
|
/// assert_eq!(display, debug);
|
|
/// ```
|
|
///
|
|
/// For more information, see the documentation in [`std::fmt`].
|
|
///
|
|
/// [`Display`]: crate::fmt::Display
|
|
/// [`Debug`]: crate::fmt::Debug
|
|
/// [`fmt::Arguments`]: crate::fmt::Arguments
|
|
/// [`std::fmt`]: ../std/fmt/index.html
|
|
/// [`format!`]: ../std/macro.format.html
|
|
/// [`println!`]: ../std/macro.println.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::fmt;
|
|
///
|
|
/// let s = fmt::format(format_args!("hello {}", "world"));
|
|
/// assert_eq!(s, format!("hello {}", "world"));
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "format_args_macro")]
|
|
#[allow_internal_unsafe]
|
|
#[allow_internal_unstable(fmt_internals)]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! format_args {
|
|
($fmt:expr) => {{ /* compiler built-in */ }};
|
|
($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Same as [`format_args`], but can be used in some const contexts.
|
|
///
|
|
/// This macro is used by the panic macros for the `const_panic` feature.
|
|
///
|
|
/// This macro will be removed once `format_args` is allowed in const contexts.
|
|
#[unstable(feature = "const_format_args", issue = "none")]
|
|
#[allow_internal_unstable(fmt_internals, const_fmt_arguments_new)]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! const_format_args {
|
|
($fmt:expr) => {{ /* compiler built-in */ }};
|
|
($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Same as [`format_args`], but adds a newline in the end.
|
|
#[unstable(
|
|
feature = "format_args_nl",
|
|
issue = "none",
|
|
reason = "`format_args_nl` is only for internal \
|
|
language use and is subject to change"
|
|
)]
|
|
#[allow_internal_unstable(fmt_internals)]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! format_args_nl {
|
|
($fmt:expr) => {{ /* compiler built-in */ }};
|
|
($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Inspects an environment variable at compile time.
|
|
///
|
|
/// This macro will expand to the value of the named environment variable at
|
|
/// compile time, yielding an expression of type `&'static str`. Use
|
|
/// [`std::env::var`] instead if you want to read the value at runtime.
|
|
///
|
|
/// [`std::env::var`]: ../std/env/fn.var.html
|
|
///
|
|
/// If the environment variable is not defined, then a compilation error
|
|
/// will be emitted. To not emit a compile error, use the [`option_env!`]
|
|
/// macro instead.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let path: &'static str = env!("PATH");
|
|
/// println!("the $PATH variable at the time of compiling was: {path}");
|
|
/// ```
|
|
///
|
|
/// You can customize the error message by passing a string as the second
|
|
/// parameter:
|
|
///
|
|
/// ```compile_fail
|
|
/// let doc: &'static str = env!("documentation", "what's that?!");
|
|
/// ```
|
|
///
|
|
/// If the `documentation` environment variable is not defined, you'll get
|
|
/// the following error:
|
|
///
|
|
/// ```text
|
|
/// error: what's that?!
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! env {
|
|
($name:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
($name:expr, $error_msg:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Optionally inspects an environment variable at compile time.
|
|
///
|
|
/// If the named environment variable is present at compile time, this will
|
|
/// expand into an expression of type `Option<&'static str>` whose value is
|
|
/// `Some` of the value of the environment variable. If the environment
|
|
/// variable is not present, then this will expand to `None`. See
|
|
/// [`Option<T>`][Option] for more information on this type. Use
|
|
/// [`std::env::var`] instead if you want to read the value at runtime.
|
|
///
|
|
/// [`std::env::var`]: ../std/env/fn.var.html
|
|
///
|
|
/// A compile time error is never emitted when using this macro regardless
|
|
/// of whether the environment variable is present or not.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let key: Option<&'static str> = option_env!("SECRET_KEY");
|
|
/// println!("the secret key might be: {key:?}");
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! option_env {
|
|
($name:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Concatenates identifiers into one identifier.
|
|
///
|
|
/// This macro takes any number of comma-separated identifiers, and
|
|
/// concatenates them all into one, yielding an expression which is a new
|
|
/// identifier. Note that hygiene makes it such that this macro cannot
|
|
/// capture local variables. Also, as a general rule, macros are only
|
|
/// allowed in item, statement or expression position. That means while
|
|
/// you may use this macro for referring to existing variables, functions or
|
|
/// modules etc, you cannot define a new one with it.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(concat_idents)]
|
|
///
|
|
/// # fn main() {
|
|
/// fn foobar() -> u32 { 23 }
|
|
///
|
|
/// let f = concat_idents!(foo, bar);
|
|
/// println!("{}", f());
|
|
///
|
|
/// // fn concat_idents!(new, fun, name) { } // not usable in this way!
|
|
/// # }
|
|
/// ```
|
|
#[unstable(
|
|
feature = "concat_idents",
|
|
issue = "29599",
|
|
reason = "`concat_idents` is not stable enough for use and is subject to change"
|
|
)]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! concat_idents {
|
|
($($e:ident),+ $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Concatenates literals into a byte slice.
|
|
///
|
|
/// This macro takes any number of comma-separated literals, and concatenates them all into
|
|
/// one, yielding an expression of type `&[u8; _]`, which represents all of the literals
|
|
/// concatenated left-to-right. The literals passed can be any combination of:
|
|
///
|
|
/// - byte literals (`b'r'`)
|
|
/// - byte strings (`b"Rust"`)
|
|
/// - arrays of bytes/numbers (`[b'A', 66, b'C']`)
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(concat_bytes)]
|
|
///
|
|
/// # fn main() {
|
|
/// let s: &[u8; 6] = concat_bytes!(b'A', b"BC", [68, b'E', 70]);
|
|
/// assert_eq!(s, b"ABCDEF");
|
|
/// # }
|
|
/// ```
|
|
#[unstable(feature = "concat_bytes", issue = "87555")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! concat_bytes {
|
|
($($e:literal),+ $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Concatenates literals into a static string slice.
|
|
///
|
|
/// This macro takes any number of comma-separated literals, yielding an
|
|
/// expression of type `&'static str` which represents all of the literals
|
|
/// concatenated left-to-right.
|
|
///
|
|
/// Integer and floating point literals are stringified in order to be
|
|
/// concatenated.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let s = concat!("test", 10, 'b', true);
|
|
/// assert_eq!(s, "test10btrue");
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! concat {
|
|
($($e:expr),* $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Expands to the line number on which it was invoked.
|
|
///
|
|
/// With [`column!`] and [`file!`], these macros provide debugging information for
|
|
/// developers about the location within the source.
|
|
///
|
|
/// The expanded expression has type `u32` and is 1-based, so the first line
|
|
/// in each file evaluates to 1, the second to 2, etc. This is consistent
|
|
/// with error messages by common compilers or popular editors.
|
|
/// The returned line is *not necessarily* the line of the `line!` invocation itself,
|
|
/// but rather the first macro invocation leading up to the invocation
|
|
/// of the `line!` macro.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let current_line = line!();
|
|
/// println!("defined on line: {current_line}");
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! line {
|
|
() => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Expands to the column number at which it was invoked.
|
|
///
|
|
/// With [`line!`] and [`file!`], these macros provide debugging information for
|
|
/// developers about the location within the source.
|
|
///
|
|
/// The expanded expression has type `u32` and is 1-based, so the first column
|
|
/// in each line evaluates to 1, the second to 2, etc. This is consistent
|
|
/// with error messages by common compilers or popular editors.
|
|
/// The returned column is *not necessarily* the line of the `column!` invocation itself,
|
|
/// but rather the first macro invocation leading up to the invocation
|
|
/// of the `column!` macro.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let current_col = column!();
|
|
/// println!("defined on column: {current_col}");
|
|
/// ```
|
|
///
|
|
/// `column!` counts Unicode code points, not bytes or graphemes. As a result, the first two
|
|
/// invocations return the same value, but the third does not.
|
|
///
|
|
/// ```
|
|
/// let a = ("foobar", column!()).1;
|
|
/// let b = ("人之初性本善", column!()).1;
|
|
/// let c = ("f̅o̅o̅b̅a̅r̅", column!()).1; // Uses combining overline (U+0305)
|
|
///
|
|
/// assert_eq!(a, b);
|
|
/// assert_ne!(b, c);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! column {
|
|
() => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Expands to the file name in which it was invoked.
|
|
///
|
|
/// With [`line!`] and [`column!`], these macros provide debugging information for
|
|
/// developers about the location within the source.
|
|
///
|
|
/// The expanded expression has type `&'static str`, and the returned file
|
|
/// is not the invocation of the `file!` macro itself, but rather the
|
|
/// first macro invocation leading up to the invocation of the `file!`
|
|
/// macro.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let this_file = file!();
|
|
/// println!("defined in file: {this_file}");
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! file {
|
|
() => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Stringifies its arguments.
|
|
///
|
|
/// This macro will yield an expression of type `&'static str` which is the
|
|
/// stringification of all the tokens passed to the macro. No restrictions
|
|
/// are placed on the syntax of the macro invocation itself.
|
|
///
|
|
/// Note that the expanded results of the input tokens may change in the
|
|
/// future. You should be careful if you rely on the output.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let one_plus_one = stringify!(1 + 1);
|
|
/// assert_eq!(one_plus_one, "1 + 1");
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! stringify {
|
|
($($t:tt)*) => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Includes a UTF-8 encoded file as a string.
|
|
///
|
|
/// The file is located relative to the current file (similarly to how
|
|
/// modules are found). The provided path is interpreted in a platform-specific
|
|
/// way at compile time. So, for instance, an invocation with a Windows path
|
|
/// containing backslashes `\` would not compile correctly on Unix.
|
|
///
|
|
/// This macro will yield an expression of type `&'static str` which is the
|
|
/// contents of the file.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Assume there are two files in the same directory with the following
|
|
/// contents:
|
|
///
|
|
/// File 'spanish.in':
|
|
///
|
|
/// ```text
|
|
/// adiós
|
|
/// ```
|
|
///
|
|
/// File 'main.rs':
|
|
///
|
|
/// ```ignore (cannot-doctest-external-file-dependency)
|
|
/// fn main() {
|
|
/// let my_str = include_str!("spanish.in");
|
|
/// assert_eq!(my_str, "adiós\n");
|
|
/// print!("{my_str}");
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// Compiling 'main.rs' and running the resulting binary will print "adiós".
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "include_str_macro")]
|
|
macro_rules! include_str {
|
|
($file:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Includes a file as a reference to a byte array.
|
|
///
|
|
/// The file is located relative to the current file (similarly to how
|
|
/// modules are found). The provided path is interpreted in a platform-specific
|
|
/// way at compile time. So, for instance, an invocation with a Windows path
|
|
/// containing backslashes `\` would not compile correctly on Unix.
|
|
///
|
|
/// This macro will yield an expression of type `&'static [u8; N]` which is
|
|
/// the contents of the file.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Assume there are two files in the same directory with the following
|
|
/// contents:
|
|
///
|
|
/// File 'spanish.in':
|
|
///
|
|
/// ```text
|
|
/// adiós
|
|
/// ```
|
|
///
|
|
/// File 'main.rs':
|
|
///
|
|
/// ```ignore (cannot-doctest-external-file-dependency)
|
|
/// fn main() {
|
|
/// let bytes = include_bytes!("spanish.in");
|
|
/// assert_eq!(bytes, b"adi\xc3\xb3s\n");
|
|
/// print!("{}", String::from_utf8_lossy(bytes));
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// Compiling 'main.rs' and running the resulting binary will print "adiós".
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
#[cfg_attr(not(test), rustc_diagnostic_item = "include_bytes_macro")]
|
|
macro_rules! include_bytes {
|
|
($file:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Expands to a string that represents the current module path.
|
|
///
|
|
/// The current module path can be thought of as the hierarchy of modules
|
|
/// leading back up to the crate root. The first component of the path
|
|
/// returned is the name of the crate currently being compiled.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// mod test {
|
|
/// pub fn foo() {
|
|
/// assert!(module_path!().ends_with("test"));
|
|
/// }
|
|
/// }
|
|
///
|
|
/// test::foo();
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! module_path {
|
|
() => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Evaluates boolean combinations of configuration flags at compile-time.
|
|
///
|
|
/// In addition to the `#[cfg]` attribute, this macro is provided to allow
|
|
/// boolean expression evaluation of configuration flags. This frequently
|
|
/// leads to less duplicated code.
|
|
///
|
|
/// The syntax given to this macro is the same syntax as the [`cfg`]
|
|
/// attribute.
|
|
///
|
|
/// `cfg!`, unlike `#[cfg]`, does not remove any code and only evaluates to true or false. For
|
|
/// example, all blocks in an if/else expression need to be valid when `cfg!` is used for
|
|
/// the condition, regardless of what `cfg!` is evaluating.
|
|
///
|
|
/// [`cfg`]: ../reference/conditional-compilation.html#the-cfg-attribute
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let my_directory = if cfg!(windows) {
|
|
/// "windows-specific-directory"
|
|
/// } else {
|
|
/// "unix-directory"
|
|
/// };
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! cfg {
|
|
($($cfg:tt)*) => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Parses a file as an expression or an item according to the context.
|
|
///
|
|
/// **Warning**: For multi-file Rust projects, the `include!` macro is probably not what you
|
|
/// are looking for. Usually, multi-file Rust projects use
|
|
/// [modules](https://doc.rust-lang.org/reference/items/modules.html). Multi-file projects and
|
|
/// modules are explained in the Rust-by-Example book
|
|
/// [here](https://doc.rust-lang.org/rust-by-example/mod/split.html) and the module system is
|
|
/// explained in the Rust Book
|
|
/// [here](https://doc.rust-lang.org/book/ch07-02-defining-modules-to-control-scope-and-privacy.html).
|
|
///
|
|
/// The included file is placed in the surrounding code
|
|
/// [unhygienically](https://doc.rust-lang.org/reference/macros-by-example.html#hygiene). If
|
|
/// the included file is parsed as an expression and variables or functions share names across
|
|
/// both files, it could result in variables or functions being different from what the
|
|
/// included file expected.
|
|
///
|
|
/// The included file is located relative to the current file (similarly to how modules are
|
|
/// found). The provided path is interpreted in a platform-specific way at compile time. So,
|
|
/// for instance, an invocation with a Windows path containing backslashes `\` would not
|
|
/// compile correctly on Unix.
|
|
///
|
|
/// # Uses
|
|
///
|
|
/// The `include!` macro is primarily used for two purposes. It is used to include
|
|
/// documentation that is written in a separate file and it is used to include [build artifacts
|
|
/// usually as a result from the `build.rs`
|
|
/// script](https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script).
|
|
///
|
|
/// When using the `include` macro to include stretches of documentation, remember that the
|
|
/// included file still needs to be a valid rust syntax. It is also possible to
|
|
/// use the [`include_str`] macro as `#![doc = include_str!("...")]` (at the module level) or
|
|
/// `#[doc = include_str!("...")]` (at the item level) to include documentation from a plain
|
|
/// text or markdown file.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Assume there are two files in the same directory with the following contents:
|
|
///
|
|
/// File 'monkeys.in':
|
|
///
|
|
/// ```ignore (only-for-syntax-highlight)
|
|
/// ['🙈', '🙊', '🙉']
|
|
/// .iter()
|
|
/// .cycle()
|
|
/// .take(6)
|
|
/// .collect::<String>()
|
|
/// ```
|
|
///
|
|
/// File 'main.rs':
|
|
///
|
|
/// ```ignore (cannot-doctest-external-file-dependency)
|
|
/// fn main() {
|
|
/// let my_string = include!("monkeys.in");
|
|
/// assert_eq!("🙈🙊🙉🙈🙊🙉", my_string);
|
|
/// println!("{my_string}");
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// Compiling 'main.rs' and running the resulting binary will print
|
|
/// "🙈🙊🙉🙈🙊🙉".
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! include {
|
|
($file:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Asserts that a boolean expression is `true` at runtime.
|
|
///
|
|
/// This will invoke the [`panic!`] macro if the provided expression cannot be
|
|
/// evaluated to `true` at runtime.
|
|
///
|
|
/// # Uses
|
|
///
|
|
/// Assertions are always checked in both debug and release builds, and cannot
|
|
/// be disabled. See [`debug_assert!`] for assertions that are not enabled in
|
|
/// release builds by default.
|
|
///
|
|
/// Unsafe code may rely on `assert!` to enforce run-time invariants that, if
|
|
/// violated could lead to unsafety.
|
|
///
|
|
/// Other use-cases of `assert!` include testing and enforcing run-time
|
|
/// invariants in safe code (whose violation cannot result in unsafety).
|
|
///
|
|
/// # Custom Messages
|
|
///
|
|
/// This macro has a second form, where a custom panic message can
|
|
/// be provided with or without arguments for formatting. See [`std::fmt`]
|
|
/// for syntax for this form. Expressions used as format arguments will only
|
|
/// be evaluated if the assertion fails.
|
|
///
|
|
/// [`std::fmt`]: ../std/fmt/index.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// // the panic message for these assertions is the stringified value of the
|
|
/// // expression given.
|
|
/// assert!(true);
|
|
///
|
|
/// fn some_computation() -> bool { true } // a very simple function
|
|
///
|
|
/// assert!(some_computation());
|
|
///
|
|
/// // assert with a custom message
|
|
/// let x = true;
|
|
/// assert!(x, "x wasn't true!");
|
|
///
|
|
/// let a = 3; let b = 27;
|
|
/// assert!(a + b == 30, "a = {}, b = {}", a, b);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
#[rustc_diagnostic_item = "assert_macro"]
|
|
#[allow_internal_unstable(core_panic, edition_panic, generic_assert_internals)]
|
|
macro_rules! assert {
|
|
($cond:expr $(,)?) => {{ /* compiler built-in */ }};
|
|
($cond:expr, $($arg:tt)+) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Prints passed tokens into the standard output.
|
|
#[unstable(
|
|
feature = "log_syntax",
|
|
issue = "29598",
|
|
reason = "`log_syntax!` is not stable enough for use and is subject to change"
|
|
)]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! log_syntax {
|
|
($($arg:tt)*) => {
|
|
/* compiler built-in */
|
|
};
|
|
}
|
|
|
|
/// Enables or disables tracing functionality used for debugging other macros.
|
|
#[unstable(
|
|
feature = "trace_macros",
|
|
issue = "29598",
|
|
reason = "`trace_macros` is not stable enough for use and is subject to change"
|
|
)]
|
|
#[rustc_builtin_macro]
|
|
#[macro_export]
|
|
macro_rules! trace_macros {
|
|
(true) => {{ /* compiler built-in */ }};
|
|
(false) => {{ /* compiler built-in */ }};
|
|
}
|
|
|
|
/// Attribute macro used to apply derive macros.
|
|
///
|
|
/// See [the reference] for more info.
|
|
///
|
|
/// [the reference]: ../../../reference/attributes/derive.html
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_builtin_macro]
|
|
pub macro derive($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Attribute macro used to apply derive macros for implementing traits
|
|
/// in a const context.
|
|
///
|
|
/// See [the reference] for more info.
|
|
///
|
|
/// [the reference]: ../../../reference/attributes/derive.html
|
|
#[unstable(feature = "derive_const", issue = "none")]
|
|
#[rustc_builtin_macro]
|
|
pub macro derive_const($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Attribute macro applied to a function to turn it into a unit test.
|
|
///
|
|
/// See [the reference] for more info.
|
|
///
|
|
/// [the reference]: ../../../reference/attributes/testing.html#the-test-attribute
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[allow_internal_unstable(test, rustc_attrs)]
|
|
#[rustc_builtin_macro]
|
|
pub macro test($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Attribute macro applied to a function to turn it into a benchmark test.
|
|
#[unstable(
|
|
feature = "test",
|
|
issue = "50297",
|
|
soft,
|
|
reason = "`bench` is a part of custom test frameworks which are unstable"
|
|
)]
|
|
#[allow_internal_unstable(test, rustc_attrs)]
|
|
#[rustc_builtin_macro]
|
|
pub macro bench($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// An implementation detail of the `#[test]` and `#[bench]` macros.
|
|
#[unstable(
|
|
feature = "custom_test_frameworks",
|
|
issue = "50297",
|
|
reason = "custom test frameworks are an unstable feature"
|
|
)]
|
|
#[allow_internal_unstable(test, rustc_attrs)]
|
|
#[rustc_builtin_macro]
|
|
pub macro test_case($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Attribute macro applied to a static to register it as a global allocator.
|
|
///
|
|
/// See also [`std::alloc::GlobalAlloc`](../../../std/alloc/trait.GlobalAlloc.html).
|
|
#[stable(feature = "global_allocator", since = "1.28.0")]
|
|
#[allow_internal_unstable(rustc_attrs)]
|
|
#[rustc_builtin_macro]
|
|
pub macro global_allocator($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Attribute macro applied to a function to register it as a handler for allocation failure.
|
|
///
|
|
/// See also [`std::alloc::handle_alloc_error`](../../../std/alloc/fn.handle_alloc_error.html).
|
|
#[unstable(feature = "alloc_error_handler", issue = "51540")]
|
|
#[allow_internal_unstable(rustc_attrs)]
|
|
#[rustc_builtin_macro]
|
|
pub macro alloc_error_handler($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Keeps the item it's applied to if the passed path is accessible, and removes it otherwise.
|
|
#[unstable(
|
|
feature = "cfg_accessible",
|
|
issue = "64797",
|
|
reason = "`cfg_accessible` is not fully implemented"
|
|
)]
|
|
#[rustc_builtin_macro]
|
|
pub macro cfg_accessible($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Expands all `#[cfg]` and `#[cfg_attr]` attributes in the code fragment it's applied to.
|
|
#[unstable(
|
|
feature = "cfg_eval",
|
|
issue = "82679",
|
|
reason = "`cfg_eval` is a recently implemented feature"
|
|
)]
|
|
#[rustc_builtin_macro]
|
|
pub macro cfg_eval($($tt:tt)*) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Unstable placeholder for type ascription.
|
|
#[rustc_builtin_macro]
|
|
#[unstable(
|
|
feature = "type_ascription",
|
|
issue = "23416",
|
|
reason = "placeholder syntax for type ascription"
|
|
)]
|
|
pub macro type_ascribe($expr:expr, $ty:ty) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Unstable implementation detail of the `rustc` compiler, do not use.
|
|
#[rustc_builtin_macro]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[allow_internal_unstable(core_intrinsics, libstd_sys_internals, rt)]
|
|
#[deprecated(since = "1.52.0", note = "rustc-serialize is deprecated and no longer supported")]
|
|
#[doc(hidden)] // While technically stable, using it is unstable, and deprecated. Hide it.
|
|
pub macro RustcDecodable($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
|
|
/// Unstable implementation detail of the `rustc` compiler, do not use.
|
|
#[rustc_builtin_macro]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[allow_internal_unstable(core_intrinsics, rt)]
|
|
#[deprecated(since = "1.52.0", note = "rustc-serialize is deprecated and no longer supported")]
|
|
#[doc(hidden)] // While technically stable, using it is unstable, and deprecated. Hide it.
|
|
pub macro RustcEncodable($item:item) {
|
|
/* compiler built-in */
|
|
}
|
|
}
|