[derive] Test exact output of derives (#1664)

Makes progress on #367, #1634

zerocopy-derive/Cargo.toml

@@ -37,6 +37,7 @@ syn = "2.0.46"
 once_cell = "=1.9"
 rustversion = "1.0"
 static_assertions = "1.1"
+synstructure = "0.13.1"
 testutil = { path = "../testutil" }
 # Pinned to a specific version so that the version used for local development
 # and the version used in CI are guaranteed to be the same. Future versions

zerocopy-derive/src/lib.rs

@@ -30,6 +30,8 @@
 
 mod r#enum;
 mod ext;
+#[cfg(test)]
+mod output_tests;
 mod repr;
 
 use proc_macro2::{TokenStream, TokenTree};
@@ -419,7 +421,7 @@ fn derive_try_from_bytes_struct(ast: &DeriveInput, strct: &DataStruct) -> proc_m
             // validity of a struct is just the composition of the bit
             // validities of its fields, so this is a sound implementation of
             // `is_bit_valid`.
-            fn is_bit_valid<A: ::zerocopy::pointer::invariant::Aliasing + ::zerocopy::pointer::invariant::AtLeast<::zerocopy::pointer::invariant::Shared>>(
+            fn is_bit_valid<A: ::zerocopy::pointer::invariant::Aliasing + ::zerocopy::pointer::invariant::AtLeast<::zerocopy::pointer::invariant::Shared> >(
                 mut candidate: ::zerocopy::Maybe<Self, A>
             ) -> bool {
                 true #(&& {

zerocopy-derive/src/output_tests.rs

@@ -0,0 +1,193 @@
+// Copyright 2024 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.
+
+use synstructure::test_derive;
+
+macro_rules! impl_synstructure_derive {
+    ($($outer:ident => $inner:ident),* $(,)?) => {
+        $(
+            #[allow(non_snake_case)]
+            fn $outer(s: synstructure::Structure) -> proc_macro2::TokenStream {
+                super::$inner(s.ast())
+            }
+        )*
+    };
+}
+
+impl_synstructure_derive!(
+    KnownLayout => derive_known_layout_inner,
+    Immutable => derive_no_cell_inner,
+    TryFromBytes => derive_try_from_bytes_inner,
+    FromZeros => derive_from_zeros_inner,
+    FromBytes => derive_from_bytes_inner,
+    IntoBytes => derive_into_bytes_inner,
+    Unaligned => derive_unaligned_inner,
+);
+
+#[test]
+fn test_known_layout() {
+    test_derive! {
+        KnownLayout {
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::KnownLayout for Foo<>
+            where
+                Self: ::zerocopy::util::macro_util::core_reexport::marker::Sized,
+            {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+
+                type PointerMetadata = ();
+
+                const LAYOUT: ::zerocopy::DstLayout = ::zerocopy::DstLayout::for_type::<Self>();
+
+                #[inline(always)]
+                fn raw_from_ptr_len(
+                    bytes: ::zerocopy::util::macro_util::core_reexport::ptr::NonNull<u8>,
+                    _meta: (),
+                ) -> ::zerocopy::util::macro_util::core_reexport::ptr::NonNull<Self> {
+                    bytes.cast::<Self>()
+                }
+
+                #[inline(always)]
+                fn pointer_to_metadata(
+                    _ptr: ::zerocopy::util::macro_util::core_reexport::ptr::NonNull<Self>,
+                ) -> () {
+                }
+            }
+        } no_build
+    }
+}
+
+#[test]
+fn test_immutable() {
+    test_derive! {
+        Immutable {
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::Immutable for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+            }
+        } no_build
+    }
+}
+
+#[test]
+fn test_try_from_bytes() {
+    test_derive! {
+        TryFromBytes {
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::TryFromBytes for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+
+                fn is_bit_valid<
+                    A: ::zerocopy::pointer::invariant::Aliasing
+                        + ::zerocopy::pointer::invariant::AtLeast<::zerocopy::pointer::invariant::Shared>
+                >(
+                    mut candidate: ::zerocopy::Maybe<Self, A>
+                ) -> bool {
+                    true
+                }
+            }
+        } no_build
+    }
+}
+
+#[test]
+fn test_from_zeros() {
+    test_derive! {
+        FromZeros {
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::TryFromBytes for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+
+                fn is_bit_valid<
+                    A: ::zerocopy::pointer::invariant::Aliasing
+                        + ::zerocopy::pointer::invariant::AtLeast<::zerocopy::pointer::invariant::Shared>
+                >(
+                    mut candidate: ::zerocopy::Maybe<Self, A>
+                ) -> bool {
+                    true
+                }
+            }
+
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::FromZeros for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+            }
+        } no_build
+    }
+}
+
+#[test]
+fn test_from_bytes() {
+    test_derive! {
+        FromBytes {
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::TryFromBytes for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+
+                fn is_bit_valid<
+                    A: ::zerocopy::pointer::invariant::Aliasing
+                        + ::zerocopy::pointer::invariant::AtLeast<::zerocopy::pointer::invariant::Shared>
+                >(
+                    mut candidate: ::zerocopy::Maybe<Self, A>
+                ) -> bool {
+                    true
+                }
+            }
+
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::FromZeros for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+            }
+
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::FromBytes for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+            }
+        } no_build
+    }
+}
+
+#[test]
+fn test_into_bytes() {
+    test_derive! {
+        IntoBytes {
+            #[repr(C)]
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::IntoBytes for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+            }
+        } no_build
+    }
+}
+
+#[test]
+fn test_unaligned() {
+    test_derive! {
+        Unaligned {
+            #[repr(C)]
+            struct Foo;
+        } expands to {
+            #[allow(deprecated)]
+            unsafe impl<> ::zerocopy::Unaligned for Foo<> where {
+                fn only_derive_is_allowed_to_implement_this_trait() {}
+            }
+        } no_build
+    }
+}