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Diffstat (limited to 'rust/qemu-api/src/assertions.rs')
-rw-r--r-- | rust/qemu-api/src/assertions.rs | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/rust/qemu-api/src/assertions.rs b/rust/qemu-api/src/assertions.rs new file mode 100644 index 0000000..a2d38c8 --- /dev/null +++ b/rust/qemu-api/src/assertions.rs @@ -0,0 +1,152 @@ +// Copyright 2024, Red Hat Inc. +// Author(s): Paolo Bonzini <pbonzini@redhat.com> +// SPDX-License-Identifier: GPL-2.0-or-later + +#![doc(hidden)] +//! This module provides macros to check the equality of types and +//! the type of `struct` fields. This can be useful to ensure that +//! types match the expectations of C code. +//! +//! Documentation is hidden because it only exposes macros, which +//! are exported directly from `qemu_api`. + +// Based on https://stackoverflow.com/questions/64251852/x/70978292#70978292 +// (stackoverflow answers are released under MIT license). + +#[doc(hidden)] +pub trait EqType { + type Itself; +} + +impl<T> EqType for T { + type Itself = T; +} + +/// Assert that two types are the same. +/// +/// # Examples +/// +/// ``` +/// # use qemu_api::assert_same_type; +/// # use std::ops::Deref; +/// assert_same_type!(u32, u32); +/// assert_same_type!(<Box<u32> as Deref>::Target, u32); +/// ``` +/// +/// Different types will cause a compile failure +/// +/// ```compile_fail +/// # use qemu_api::assert_same_type; +/// assert_same_type!(&Box<u32>, &u32); +/// ``` +#[macro_export] +macro_rules! assert_same_type { + ($t1:ty, $t2:ty) => { + const _: () = { + #[allow(unused)] + fn assert_same_type(v: $t1) { + fn types_must_be_equal<T, U>(_: T) + where + T: $crate::assertions::EqType<Itself = U>, + { + } + types_must_be_equal::<_, $t2>(v); + } + }; + }; +} + +/// Assert that a field of a struct has the given type. +/// +/// # Examples +/// +/// ``` +/// # use qemu_api::assert_field_type; +/// pub struct A { +/// field1: u32, +/// } +/// +/// assert_field_type!(A, field1, u32); +/// ``` +/// +/// Different types will cause a compile failure +/// +/// ```compile_fail +/// # use qemu_api::assert_field_type; +/// # pub struct A { field1: u32 } +/// assert_field_type!(A, field1, i32); +/// ``` +#[macro_export] +macro_rules! assert_field_type { + (@internal $param_name:ident, $ti:ty, $t:ty, $($field:tt)*) => { + const _: () = { + #[allow(unused)] + fn assert_field_type($param_name: &$t) { + fn types_must_be_equal<T, U>(_: &T) + where + T: $crate::assertions::EqType<Itself = U>, + { + } + types_must_be_equal::<_, $ti>(&$($field)*); + } + }; + }; + + ($t:ty, $i:tt, $ti:ty) => { + $crate::assert_field_type!(@internal v, $ti, $t, v.$i); + }; + + ($t:ty, $i:tt, $ti:ty, num = $num:ident) => { + $crate::assert_field_type!(@internal v, $ti, $t, v.$i[0]); + }; +} + +/// Assert that an expression matches a pattern. This can also be +/// useful to compare enums that do not implement `Eq`. +/// +/// # Examples +/// +/// ``` +/// # use qemu_api::assert_match; +/// // JoinHandle does not implement `Eq`, therefore the result +/// // does not either. +/// let result: Result<std::thread::JoinHandle<()>, u32> = Err(42); +/// assert_match!(result, Err(42)); +/// ``` +#[macro_export] +macro_rules! assert_match { + ($a:expr, $b:pat) => { + assert!( + match $a { + $b => true, + _ => false, + }, + "{} = {:?} does not match {}", + stringify!($a), + $a, + stringify!($b) + ); + }; +} + +/// Assert at compile time that an expression is true. This is similar +/// to `const { assert!(...); }` but it works outside functions, as well as +/// on versions of Rust before 1.79. +/// +/// # Examples +/// +/// ``` +/// # use qemu_api::static_assert; +/// static_assert!("abc".len() == 3); +/// ``` +/// +/// ```compile_fail +/// # use qemu_api::static_assert; +/// static_assert!("abc".len() == 2); // does not compile +/// ``` +#[macro_export] +macro_rules! static_assert { + ($x:expr) => { + const _: () = assert!($x); + }; +} |