Vendor things

third-party/vendor/zerocopy-derive/tests/union_from_bytes.rs

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+// Copyright 2019 The Fuchsia Authors
+//
+// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// This file may not be copied, modified, or distributed except according to
+// those terms.
+
+#![allow(warnings)]
+
+use std::{marker::PhantomData, option::IntoIter};
+
+use {
+    static_assertions::assert_impl_all,
+    zerocopy::{FromBytes, FromZeroes},
+};
+
+// A union is `FromBytes` if:
+// - all fields are `FromBytes`
+
+#[derive(Clone, Copy, FromZeroes, FromBytes)]
+union Zst {
+    a: (),
+}
+
+assert_impl_all!(Zst: FromBytes);
+
+#[derive(FromZeroes, FromBytes)]
+union One {
+    a: u8,
+}
+
+assert_impl_all!(One: FromBytes);
+
+#[derive(FromZeroes, FromBytes)]
+union Two {
+    a: u8,
+    b: Zst,
+}
+
+assert_impl_all!(Two: FromBytes);
+
+#[derive(FromZeroes, FromBytes)]
+union TypeParams<'a, T: Copy, I: Iterator>
+where
+    I::Item: Copy,
+{
+    a: T,
+    c: I::Item,
+    d: u8,
+    e: PhantomData<&'a [u8]>,
+    f: PhantomData<&'static str>,
+    g: PhantomData<String>,
+}
+
+assert_impl_all!(TypeParams<'static, (), IntoIter<()>>: FromBytes);
+
+// Deriving `FromBytes` should work if the union has bounded parameters.
+
+#[derive(FromZeroes, FromBytes)]
+#[repr(C)]
+union WithParams<'a: 'b, 'b: 'a, const N: usize, T: 'a + 'b + FromBytes>
+where
+    'a: 'b,
+    'b: 'a,
+    T: 'a + 'b + Copy + FromBytes,
+{
+    a: [T; N],
+    b: PhantomData<&'a &'b ()>,
+}
+
+assert_impl_all!(WithParams<'static, 'static, 42, u8>: FromBytes);