}
/// Create a zero-size type similar to a closure type, but named.
-#[unstable(feature = "std_internals", issue = "0")]
+#[unstable(feature = "std_internals", issue = "none")]
macro_rules! impl_fn_for_zst {
($(
$( #[$attr: meta] )*
)+
}
}
-
-/// A macro for defining `#[cfg]` if-else statements.
-///
-/// The macro provided by this crate, `cfg_if`, is similar to the `if/elif` C
-/// preprocessor macro by allowing definition of a cascade of `#[cfg]` cases,
-/// emitting the implementation which matches first.
-///
-/// This allows you to conveniently provide a long list `#[cfg]`'d blocks of code
-/// without having to rewrite each clause multiple times.
-///
-/// # Example
-///
-/// ```
-/// #[macro_use]
-/// extern crate cfg_if;
-///
-/// cfg_if! {
-/// if #[cfg(unix)] {
-/// fn foo() { /* unix specific functionality */ }
-/// } else if #[cfg(target_pointer_width = "32")] {
-/// fn foo() { /* non-unix, 32-bit functionality */ }
-/// } else {
-/// fn foo() { /* fallback implementation */ }
-/// }
-/// }
-///
-/// # fn main() {}
-/// ```
-macro_rules! cfg_if {
- // match if/else chains with a final `else`
- ($(
- if #[cfg($($meta:meta),*)] { $($it:item)* }
- ) else * else {
- $($it2:item)*
- }) => {
- cfg_if! {
- @__items
- () ;
- $( ( ($($meta),*) ($($it)*) ), )*
- ( () ($($it2)*) ),
- }
- };
-
- // match if/else chains lacking a final `else`
- (
- if #[cfg($($i_met:meta),*)] { $($i_it:item)* }
- $(
- else if #[cfg($($e_met:meta),*)] { $($e_it:item)* }
- )*
- ) => {
- cfg_if! {
- @__items
- () ;
- ( ($($i_met),*) ($($i_it)*) ),
- $( ( ($($e_met),*) ($($e_it)*) ), )*
- ( () () ),
- }
- };
-
- // Internal and recursive macro to emit all the items
- //
- // Collects all the negated cfgs in a list at the beginning and after the
- // semicolon is all the remaining items
- (@__items ($($not:meta,)*) ; ) => {};
- (@__items ($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
- // Emit all items within one block, applying an approprate #[cfg]. The
- // #[cfg] will require all `$m` matchers specified and must also negate
- // all previous matchers.
- cfg_if! { @__apply cfg(all($($m,)* not(any($($not),*)))), $($it)* }
-
- // Recurse to emit all other items in `$rest`, and when we do so add all
- // our `$m` matchers to the list of `$not` matchers as future emissions
- // will have to negate everything we just matched as well.
- cfg_if! { @__items ($($not,)* $($m,)*) ; $($rest)* }
- };
-
- // Internal macro to Apply a cfg attribute to a list of items
- (@__apply $m:meta, $($it:item)*) => {
- $(#[$m] $it)*
- };
-}