Vendor things

third-party/vendor/static_assertions/src/assert_trait.rs

@@ -0,0 +1,105 @@
+/// Asserts that the trait is a child of all of the other traits.
+///
+/// Related:
+/// - [`assert_trait_super_all!`]
+///
+/// # Examples
+///
+/// All types that implement [`Copy`] must implement [`Clone`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_trait_sub_all!(Copy: Clone);
+/// ```
+///
+/// All types that implement [`Ord`] must implement [`PartialEq`], [`Eq`], and
+/// [`PartialOrd`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_trait_sub_all!(Ord: PartialEq, Eq, PartialOrd);
+/// ```
+///
+/// The following example fails to compile because [`Eq`] is not required for
+/// [`PartialOrd`]:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_trait_sub_all!(PartialOrd: Eq);
+/// ```
+///
+/// [`assert_trait_super_all!`]: macro.assert_trait_super_all.html
+///
+/// [`Copy`]:       https://doc.rust-lang.org/std/marker/trait.Copy.html
+/// [`Clone`]:      https://doc.rust-lang.org/std/clone/trait.Clone.html
+/// [`Ord`]:        https://doc.rust-lang.org/std/cmp/trait.Ord.html
+/// [`PartialOrd`]: https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html
+/// [`Eq`]:         https://doc.rust-lang.org/std/cmp/trait.Eq.html
+/// [`PartialEq`]:  https://doc.rust-lang.org/std/cmp/trait.PartialEq.html
+#[macro_export]
+macro_rules! assert_trait_sub_all {
+    ($sub:path: $($super:path),+ $(,)?) => {
+        const _: () = {
+            // One scope per super-trait.
+            $({
+                #[allow(non_camel_case_types)]
+                trait __Impl_Implication: $super {}
+
+                // Can only be implemented for `$sub` types if `$super` is
+                // also implemented.
+                impl<T: $sub> __Impl_Implication for T {}
+            })+
+        };
+    };
+}
+
+/// Asserts that the trait is a parent of all of the other traits.
+///
+/// Related:
+/// - [`assert_trait_sub_all!`]
+///
+/// # Examples
+///
+/// With this, traits `A` and `B` can both be tested to require [`Copy`] on a
+/// single line:
+///
+/// ```
+/// # use static_assertions::assert_trait_super_all;
+/// trait A: Copy {}
+/// trait B: Copy {}
+///
+/// assert_trait_super_all!(Copy: A, B);
+/// ```
+///
+/// Otherwise, each sub-trait would require its own call to
+/// [`assert_trait_sub_all!`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// # trait A: Copy {}
+/// # trait B: Copy {}
+/// assert_trait_sub_all!(A: Copy);
+/// assert_trait_sub_all!(B: Copy);
+/// ```
+///
+/// The following example fails to compile because trait `C` does not require
+/// [`Copy`]:
+///
+/// ```compile_fail
+/// # use static_assertions::assert_trait_super_all;
+/// # trait A: Copy {}
+/// # trait B: Copy {}
+/// trait C {}
+///
+/// assert_trait_super_all!(Copy: A, B, C);
+/// ```
+///
+/// [`assert_trait_sub_all!`]: macro.assert_trait_sub_all.html
+///
+/// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
+#[macro_export(local_inner_macros)]
+macro_rules! assert_trait_super_all {
+    ($super:path: $($sub:path),+ $(,)?) => {
+        $(assert_trait_sub_all!($sub: $super);)+
+    };
+}