| 1 | // Copyright 2024, Red Hat Inc. |
| 2 | // Author(s): Paolo Bonzini <pbonzini@redhat.com> |
| 3 | // SPDX-License-Identifier: GPL-2.0-or-later |
| 4 | |
| 5 | #![doc(hidden)] |
| 6 | //! This module provides macros to check the equality of types and |
| 7 | //! the type of `struct` fields. This can be useful to ensure that |
| 8 | //! types match the expectations of C code. |
| 9 | //! |
| 10 | //! Documentation is hidden because it only exposes macros, which |
| 11 | //! are exported directly from `common`. |
| 12 | |
| 13 | // Based on https://stackoverflow.com/questions/64251852/x/70978292#70978292 |
| 14 | // (stackoverflow answers are released under MIT license). |
| 15 | |
| 16 | #[doc(hidden)] |
| 17 | pub trait EqType { |
| 18 | type Itself; |
| 19 | } |
| 20 | |
| 21 | impl<T> EqType for T { |
| 22 | type Itself = T; |
| 23 | } |
| 24 | |
| 25 | /// Assert that two types are the same. |
| 26 | /// |
| 27 | /// # Examples |
| 28 | /// |
| 29 | /// ``` |
| 30 | /// # use common::assert_same_type; |
| 31 | /// # use std::ops::Deref; |
| 32 | /// assert_same_type!(u32, u32); |
| 33 | /// assert_same_type!(<Box<u32> as Deref>::Target, u32); |
| 34 | /// ``` |
| 35 | /// |
| 36 | /// Different types will cause a compile failure |
| 37 | /// |
| 38 | /// ```compile_fail |
| 39 | /// # use common::assert_same_type; |
| 40 | /// assert_same_type!(&Box<u32>, &u32); |
| 41 | /// ``` |
| 42 | #[macro_export] |
| 43 | macro_rules! assert_same_type { |
| 44 | ($t1:ty, $t2:ty) => { |
| 45 | const _: () = { |
| 46 | #[allow(unused)] |
| 47 | fn assert_same_type(v: $t1) { |
| 48 | fn types_must_be_equal<T, U>(_: T) |
| 49 | where |
| 50 | T: $crate::assertions::EqType<Itself = U>, |
| 51 | { |
| 52 | } |
| 53 | types_must_be_equal::<_, $t2>(v); |
| 54 | } |
| 55 | }; |
| 56 | }; |
| 57 | } |
| 58 | |
| 59 | /// Assert that a field of a struct has the given type. |
| 60 | /// |
| 61 | /// # Examples |
| 62 | /// |
| 63 | /// ``` |
| 64 | /// # use common::assert_field_type; |
| 65 | /// pub struct A { |
| 66 | /// field1: u32, |
| 67 | /// } |
| 68 | /// |
| 69 | /// assert_field_type!(A, field1, u32); |
| 70 | /// ``` |
| 71 | /// |
| 72 | /// Different types will cause a compile failure |
| 73 | /// |
| 74 | /// ```compile_fail |
| 75 | /// # use common::assert_field_type; |
| 76 | /// # pub struct A { field1: u32 } |
| 77 | /// assert_field_type!(A, field1, i32); |
| 78 | /// ``` |
| 79 | #[macro_export] |
| 80 | macro_rules! assert_field_type { |
| 81 | (@internal $param_name:ident, $ti:ty, $t:ty, $($field:tt)*) => { |
| 82 | const _: () = { |
| 83 | #[allow(unused)] |
| 84 | const fn assert_field_type($param_name: &$t) { |
| 85 | const fn types_must_be_equal<T, U>(_: &T) |
| 86 | where |
| 87 | T: $crate::assertions::EqType<Itself = U>, |
| 88 | { |
| 89 | } |
| 90 | types_must_be_equal::<_, $ti>(&$($field)*); |
| 91 | } |
| 92 | }; |
| 93 | }; |
| 94 | |
| 95 | ($t:ty, $i:tt, $ti:ty) => { |
| 96 | $crate::assert_field_type!(@internal v, $ti, $t, v.$i); |
| 97 | }; |
| 98 | } |
| 99 | |
| 100 | /// Assert that an expression matches a pattern. This can also be |
| 101 | /// useful to compare enums that do not implement `Eq`. |
| 102 | /// |
| 103 | /// # Examples |
| 104 | /// |
| 105 | /// ``` |
| 106 | /// # use common::assert_match; |
| 107 | /// // JoinHandle does not implement `Eq`, therefore the result |
| 108 | /// // does not either. |
| 109 | /// let result: Result<std::thread::JoinHandle<()>, u32> = Err(42); |
| 110 | /// assert_match!(result, Err(42)); |
| 111 | /// ``` |
| 112 | #[macro_export] |
| 113 | macro_rules! assert_match { |
| 114 | ($a:expr, $b:pat) => { |
| 115 | assert!( |
| 116 | match $a { |
| 117 | $b => true, |
| 118 | _ => false, |
| 119 | }, |
| 120 | "{} = {:?} does not match {}", |
| 121 | stringify!($a), |
| 122 | $a, |
| 123 | stringify!($b) |
| 124 | ); |
| 125 | }; |
| 126 | } |
| 127 | |
| 128 | /// Assert at compile time that an expression is true. This is similar |
| 129 | /// to `const { assert!(...); }` but it works outside functions, as well as |
| 130 | /// on versions of Rust before 1.79. |
| 131 | /// |
| 132 | /// # Examples |
| 133 | /// |
| 134 | /// ``` |
| 135 | /// # use common::static_assert; |
| 136 | /// static_assert!("abc".len() == 3); |
| 137 | /// ``` |
| 138 | /// |
| 139 | /// ```compile_fail |
| 140 | /// # use common::static_assert; |
| 141 | /// static_assert!("abc".len() == 2); // does not compile |
| 142 | /// ``` |
| 143 | #[macro_export] |
| 144 | macro_rules! static_assert { |
| 145 | ($x:expr) => { |
| 146 | const _: () = assert!($x); |
| 147 | }; |
| 148 | } |