tests: add expand and compile-fail tests for [Maybe]Zeroable

Signed-off-by: Benno Lossin <[email protected]>

Author: BennoLossin

tests/ui/compile-fail/zeroable/not_all_fields_zeroable.rs

@@ -0,0 +1,10 @@
+extern crate pin_init;
+use pin_init::*;
+
+#[derive(Zeroable)]
+struct Foo {
+    a: usize,
+    b: &'static Foo,
+}
+
+fn main() {}

tests/ui/compile-fail/zeroable/not_all_fields_zeroable.stderr

@@ -0,0 +1,17 @@
+error[E0277]: the trait bound `&'static Foo: pin_init::Zeroable` is not satisfied
+ --> tests/ui/compile-fail/zeroable/not_all_fields_zeroable.rs:7:8
+  |
+7 |     b: &'static Foo,
+  |        ^^^^^^^^^^^^ the trait `pin_init::Zeroable` is not implemented for `&'static Foo`
+  |
+note: required by a bound in `assert_zeroable`
+ --> tests/ui/compile-fail/zeroable/not_all_fields_zeroable.rs:4:10
+  |
+4 | #[derive(Zeroable)]
+  |          ^^^^^^^^ required by this bound in `assert_zeroable`
+  = note: this error originates in the macro `::pin_init::__derive_zeroable` which comes from the expansion of the derive macro `Zeroable` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider removing the leading `&`-reference
+  |
+7 -     b: &'static Foo,
+7 +     b: Foo,
+  |

tests/ui/expand/zeroable.expanded.rs

@@ -0,0 +1,42 @@
+use pin_init::*;
+struct Foo {
+    a: usize,
+    pub(crate) b: usize,
+}
+#[automatically_derived]
+unsafe impl ::pin_init::Zeroable for Foo {}
+const _: () = {
+    fn assert_zeroable<T: ?::core::marker::Sized + ::pin_init::Zeroable>() {}
+    fn ensure_zeroable() {
+        assert_zeroable::<usize>();
+        assert_zeroable::<usize>();
+    }
+};
+struct Bar {
+    a: usize,
+    b: &'static usize,
+}
+#[automatically_derived]
+unsafe impl ::pin_init::Zeroable for Bar
+where
+    usize: for<'__dummy> ::pin_init::Zeroable,
+    &'static usize: for<'__dummy> ::pin_init::Zeroable,
+{}
+trait Trait {}
+struct WithGenerics<'a, T, U: Trait> {
+    a: T,
+    u: &'a U,
+}
+#[automatically_derived]
+unsafe impl<
+    'a,
+    T: ::pin_init::Zeroable,
+    U: ::pin_init::Zeroable + Trait,
+> ::pin_init::Zeroable for WithGenerics<'a, T, U> {}
+const _: () = {
+    fn assert_zeroable<T: ?::core::marker::Sized + ::pin_init::Zeroable>() {}
+    fn ensure_zeroable<'a, T: ::pin_init::Zeroable, U: ::pin_init::Zeroable + Trait>() {
+        assert_zeroable::<T>();
+        assert_zeroable::<&'a U>();
+    }
+};

tests/ui/expand/zeroable.rs

@@ -0,0 +1,21 @@
+use pin_init::*;
+
+#[derive(Zeroable)]
+struct Foo {
+    a: usize,
+    pub(crate) b: usize,
+}
+
+#[derive(MaybeZeroable)]
+struct Bar {
+    a: usize,
+    b: &'static usize,
+}
+
+trait Trait {}
+
+#[derive(Zeroable)]
+struct WithGenerics<'a, T, U: Trait> {
+    a: T,
+    u: &'a U,
+}