[derive] Test with trivial_bounds feature

The nightly `trivial_bounds` causes some derive-emitted code to compile
which is designed to fail compilation. This commit adds a test that
ensures that the emitted code still triggers some compiler errors.

Affects #61

Closes #500

Author: joshlf

zerocopy-derive/tests/ui-nightly/trivial_bounds.rs

@@ -0,0 +1,74 @@
+// Copyright 2019 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#![feature(trivial_bounds)]
+
+#[macro_use]
+extern crate zerocopy;
+
+#[path = "../util.rs"]
+mod util;
+
+use self::util::{NotZerocopy, AU16};
+
+fn main() {}
+
+// These tests are compiled with the `trivial_bounds` feature enabled. We emit
+// code which is designed to fail compilation for types we wish to reject.
+// `trivial_bounds` causes some of this code to succeed. These tests exist to
+// ensure that at least *some* emitted code still fails compilation even when
+// `trivial_bounds` is enabled.
+
+//
+// FromZeroes errors
+//
+
+#[derive(FromZeroes)]
+struct FromZeroes1 {
+    value: NotZerocopy,
+}
+
+//
+// FromBytes errors
+//
+
+#[derive(FromBytes)]
+struct FromBytes1 {
+    value: NotZerocopy,
+}
+
+//
+// AsBytes errors
+//
+
+#[derive(AsBytes)]
+#[repr(C)]
+struct AsBytes1 {
+    value: NotZerocopy,
+}
+
+//
+// Unaligned errors
+//
+
+#[derive(Unaligned)]
+#[repr(C)]
+struct Unaligned1 {
+    aligned: AU16,
+}
+
+// This specifically tests a bug we had in an old version of the code in which
+// the trait bound would only be enforced for the first field's type.
+#[derive(Unaligned)]
+#[repr(C)]
+struct Unaligned2 {
+    unaligned: u8,
+    aligned: AU16,
+}
+
+#[derive(Unaligned)]
+#[repr(transparent)]
+struct Unaligned3 {
+    aligned: AU16,
+}

zerocopy-derive/tests/ui-nightly/trivial_bounds.stderr

@@ -0,0 +1,22 @@
+error[E0277]: the trait bound `FromBytes1: FromZeroes` is not satisfied
+  --> tests/ui-nightly/trivial_bounds.rs:36:10
+   |
+36 | #[derive(FromBytes)]
+   |          ^^^^^^^^^ the trait `FromZeroes` is not implemented for `FromBytes1`
+   |
+   = help: the following other types implement trait `FromZeroes`:
+             bool
+             char
+             isize
+             i8
+             i16
+             i32
+             i64
+             i128
+           and $N others
+note: required by a bound in `FromBytes`
+  --> $WORKSPACE/src/lib.rs
+   |
+   | pub unsafe trait FromBytes: FromZeroes {
+   |                             ^^^^^^^^^^ required by this bound in `FromBytes`
+   = note: this error originates in the derive macro `FromBytes` (in Nightly builds, run with -Z macro-backtrace for more info)