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| </pre><pre class="rust"><code><span class="doccomment">/// Asserts that the type implements exactly one in a set of traits. |
| /// |
| /// Related: |
| /// - [`assert_impl_any!`] |
| /// - [`assert_impl_all!`] |
| /// - [`assert_not_impl_all!`] |
| /// - [`assert_not_impl_any!`] |
| /// |
| /// # Examples |
| /// |
| /// Given some type `Foo`, it is expected to implement either `Snap`, `Crackle`, |
| /// or `Pop`: |
| /// |
| /// ```compile_fail |
| /// # use static_assertions::assert_impl_one; fn main() {} |
| /// struct Foo; |
| /// |
| /// trait Snap {} |
| /// trait Crackle {} |
| /// trait Pop {} |
| /// |
| /// assert_impl_one!(Foo: Snap, Crackle, Pop); |
| /// ``` |
| /// |
| /// If _only_ `Crackle` is implemented, the assertion passes: |
| /// |
| /// ``` |
| /// # use static_assertions::assert_impl_one; fn main() {} |
| /// # struct Foo; |
| /// # trait Snap {} |
| /// # trait Crackle {} |
| /// # trait Pop {} |
| /// impl Crackle for Foo {} |
| /// |
| /// assert_impl_one!(Foo: Snap, Crackle, Pop); |
| /// ``` |
| /// |
| /// If `Snap` or `Pop` is _also_ implemented, the assertion fails: |
| /// |
| /// ```compile_fail |
| /// # use static_assertions::assert_impl_one; fn main() {} |
| /// # struct Foo; |
| /// # trait Snap {} |
| /// # trait Crackle {} |
| /// # trait Pop {} |
| /// # impl Crackle for Foo {} |
| /// impl Pop for Foo {} |
| /// |
| /// assert_impl_one!(Foo: Snap, Crackle, Pop); |
| /// ``` |
| /// |
| /// [`assert_impl_any!`]: macro.assert_impl_any.html |
| /// [`assert_impl_all!`]: macro.assert_impl_all.html |
| /// [`assert_not_impl_all!`]: macro.assert_not_impl_all.html |
| /// [`assert_not_impl_any!`]: macro.assert_not_impl_any.html |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>assert_impl_one { |
| (<span class="macro-nonterminal">$x</span>:ty: $(<span class="macro-nonterminal">$t</span>:path),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="kw">const _</span>: <span class="kw">fn</span>() = || { |
| <span class="comment">// Generic trait that must be implemented for `$x` exactly once. |
| </span><span class="kw">trait </span>AmbiguousIfMoreThanOne<A> { |
| <span class="comment">// Required for actually being able to reference the trait. |
| </span><span class="kw">fn </span>some_item() {} |
| } |
| |
| <span class="comment">// Creates multiple scoped `Token` types for each trait `$t`, over |
| // which a specialized `AmbiguousIfMoreThanOne<Token>` is |
| // implemented for every type that implements `$t`. |
| </span>$({ |
| <span class="attribute">#[allow(dead_code)] |
| </span><span class="kw">struct </span>Token; |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized + <span class="macro-nonterminal">$t</span>> AmbiguousIfMoreThanOne<Token> <span class="kw">for </span>T {} |
| })+ |
| |
| <span class="comment">// If there is only one specialized trait impl, type inference with |
| // `_` can be resolved and this can compile. Fails to compile if |
| // `$x` implements more than one `AmbiguousIfMoreThanOne<Token>` or |
| // does not implement any at all. |
| </span><span class="kw">let _ </span>= <<span class="macro-nonterminal">$x </span><span class="kw">as </span>AmbiguousIfMoreThanOne<<span class="kw">_</span>>>::some_item; |
| }; |
| }; |
| } |
| |
| <span class="doccomment">/// Asserts that the type implements _all_ of the given traits. |
| /// |
| /// See [`assert_not_impl_all!`] for achieving the opposite effect. |
| /// |
| /// # Examples |
| /// |
| /// This can be used to ensure types implement auto traits such as [`Send`] and |
| /// [`Sync`], as well as traits with [blanket `impl`s][blanket]. |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_impl_all!(u32: Copy, Send); |
| /// assert_impl_all!(&str: Into<String>); |
| /// ``` |
| /// |
| /// The following example fails to compile because raw pointers do not implement |
| /// [`Send`] since they cannot be moved between threads safely: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_impl_all!(*const u8: Send); |
| /// ``` |
| /// |
| /// [`assert_not_impl_all!`]: macro.assert_not_impl_all.html |
| /// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html |
| /// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html |
| /// [blanket]: https://doc.rust-lang.org/book/ch10-02-traits.html#using-trait-bounds-to-conditionally-implement-methods |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>assert_impl_all { |
| (<span class="macro-nonterminal">$</span><span class="kw">type</span>:<span class="macro-nonterminal">ty</span>: $(<span class="macro-nonterminal">$</span><span class="kw">trait</span>:<span class="macro-nonterminal">path</span>),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="kw">const _</span>: <span class="kw">fn</span>() = || { |
| <span class="comment">// Only callable when `$type` implements all traits in `$($trait)+`. |
| </span><span class="kw">fn </span>assert_impl_all<T: <span class="question-mark">?</span>Sized $(+ <span class="macro-nonterminal">$</span><span class="kw">trait</span>)+>() {} |
| <span class="macro-nonterminal">assert_impl_all</span>::<<span class="macro-nonterminal">$</span><span class="kw">type</span>>(); |
| }; |
| }; |
| } |
| |
| <span class="doccomment">/// Asserts that the type implements _any_ of the given traits. |
| /// |
| /// See [`assert_not_impl_any!`] for achieving the opposite effect. |
| /// |
| /// # Examples |
| /// |
| /// `u8` cannot be converted from `u16`, but it can be converted into `u16`: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_impl_any!(u8: From<u16>, Into<u16>); |
| /// ``` |
| /// |
| /// The unit type cannot be converted from `u8` or `u16`, but it does implement |
| /// [`Send`]: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_impl_any!((): From<u8>, From<u16>, Send); |
| /// ``` |
| /// |
| /// The following example fails to compile because raw pointers do not implement |
| /// [`Send`] or [`Sync`] since they cannot be moved or shared between threads |
| /// safely: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_impl_any!(*const u8: Send, Sync); |
| /// ``` |
| /// |
| /// [`assert_not_impl_any!`]: macro.assert_not_impl_any.html |
| /// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html |
| /// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html |
| </span><span class="attribute">#[<span class="macro-nonterminal">macro_export</span>] |
| </span><span class="macro">macro_rules! </span>assert_impl_any { |
| (<span class="macro-nonterminal">$x</span>:ty: $(<span class="macro-nonterminal">$t</span>:path),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="kw">const _</span>: <span class="kw">fn</span>() = || { |
| <span class="kw">use </span><span class="macro-nonterminal">$crate::_core::marker::PhantomData</span>; |
| <span class="kw">use </span><span class="macro-nonterminal">$crate::_core::ops::Deref</span>; |
| |
| <span class="comment">// Fallback to use as the first iterative assignment to `previous`. |
| </span><span class="kw">let </span>previous = AssertImplAnyFallback; |
| <span class="kw">struct </span>AssertImplAnyFallback; |
| |
| <span class="comment">// Ensures that blanket traits can't impersonate the method. This |
| // prevents a false positive attack where---if a blanket trait is in |
| // scope that has `_static_assertions_impl_any`---the macro will |
| // compile when it shouldn't. |
| // |
| // See https://github.com/nvzqz/static-assertions-rs/issues/19 for |
| // more info. |
| </span><span class="kw">struct </span>ActualAssertImplAnyToken; |
| <span class="kw">trait </span>AssertImplAnyToken {} |
| <span class="kw">impl </span>AssertImplAnyToken <span class="kw">for </span>ActualAssertImplAnyToken {} |
| <span class="kw">fn </span>assert_impl_any_token<T: AssertImplAnyToken>(<span class="kw">_</span>: T) {} |
| |
| $(<span class="kw">let </span>previous = { |
| <span class="kw">struct </span>Wrapper<T, N>(PhantomData<T>, N); |
| |
| <span class="comment">// If the method for this wrapper can't be called then the |
| // compiler will insert a deref and try again. This forwards the |
| // compiler's next attempt to the previous wrapper. |
| </span><span class="kw">impl</span><T, N> Deref <span class="kw">for </span>Wrapper<T, N> { |
| <span class="kw">type </span>Target = N; |
| |
| <span class="kw">fn </span>deref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span><span class="self">Self</span>::Target { |
| <span class="kw-2">&</span><span class="self">self</span>.<span class="number">1 |
| </span>} |
| } |
| |
| <span class="comment">// This impl is bounded on the `$t` trait, so the method can |
| // only be called if `$x` implements `$t`. This is why a new |
| // `Wrapper` is defined for each `previous`. |
| </span><span class="kw">impl</span><T: <span class="macro-nonterminal">$t</span>, N> Wrapper<T, N> { |
| <span class="kw">fn </span>_static_assertions_impl_any(<span class="kw-2">&</span><span class="self">self</span>) -> ActualAssertImplAnyToken { |
| ActualAssertImplAnyToken |
| } |
| } |
| |
| Wrapper::<<span class="macro-nonterminal">$x</span>, <span class="kw">_</span>>(PhantomData, previous) |
| };)+ |
| |
| <span class="comment">// Attempt to find the method that can actually be called. The found |
| // method must return a type that implements the sealed `Token` |
| // trait, this ensures that blanket trait methods can't cause this |
| // macro to compile. |
| </span>assert_impl_any_token(previous._static_assertions_impl_any()); |
| }; |
| }; |
| } |
| |
| <span class="doccomment">/// Asserts that the type does **not** implement _all_ of the given traits. |
| /// |
| /// This can be used to ensure types do not implement auto traits such as |
| /// [`Send`] and [`Sync`], as well as traits with [blanket `impl`s][blanket]. |
| /// |
| /// Note that the combination of all provided traits is required to not be |
| /// implemented. If you want to check that none of multiple traits are |
| /// implemented you should invoke [`assert_not_impl_any!`] instead. |
| /// |
| /// # Examples |
| /// |
| /// Although `u32` implements `From<u16>`, it does not implement `Into<usize>`: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_not_impl_all!(u32: From<u16>, Into<usize>); |
| /// ``` |
| /// |
| /// The following example fails to compile since `u32` can be converted into |
| /// `u64`. |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_not_impl_all!(u32: Into<u64>); |
| /// ``` |
| /// |
| /// The following compiles because [`Cell`] is not both [`Sync`] _and_ [`Send`]: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// use std::cell::Cell; |
| /// |
| /// assert_not_impl_all!(Cell<u32>: Sync, Send); |
| /// ``` |
| /// |
| /// But it is [`Send`], so this fails to compile: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// # std::cell::Cell; |
| /// assert_not_impl_all!(Cell<u32>: Send); |
| /// ``` |
| /// |
| /// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html |
| /// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html |
| /// [`assert_not_impl_any!`]: macro.assert_not_impl_any.html |
| /// [`Cell`]: https://doc.rust-lang.org/std/cell/struct.Cell.html |
| /// [blanket]: https://doc.rust-lang.org/book/ch10-02-traits.html#using-trait-bounds-to-conditionally-implement-methods |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>assert_not_impl_all { |
| (<span class="macro-nonterminal">$x</span>:ty: $(<span class="macro-nonterminal">$t</span>:path),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="kw">const _</span>: <span class="kw">fn</span>() = || { |
| <span class="comment">// Generic trait with a blanket impl over `()` for all types. |
| </span><span class="kw">trait </span>AmbiguousIfImpl<A> { |
| <span class="comment">// Required for actually being able to reference the trait. |
| </span><span class="kw">fn </span>some_item() {} |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized> AmbiguousIfImpl<()> <span class="kw">for </span>T {} |
| |
| <span class="comment">// Used for the specialized impl when *all* traits in |
| // `$($t)+` are implemented. |
| </span><span class="attribute">#[allow(dead_code)] |
| </span><span class="kw">struct </span>Invalid; |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized $(+ <span class="macro-nonterminal">$t</span>)+> AmbiguousIfImpl<Invalid> <span class="kw">for </span>T {} |
| |
| <span class="comment">// If there is only one specialized trait impl, type inference with |
| // `_` can be resolved and this can compile. Fails to compile if |
| // `$x` implements `AmbiguousIfImpl<Invalid>`. |
| </span><span class="kw">let _ </span>= <<span class="macro-nonterminal">$x </span><span class="kw">as </span>AmbiguousIfImpl<<span class="kw">_</span>>>::some_item; |
| }; |
| }; |
| } |
| |
| <span class="doccomment">/// Asserts that the type does **not** implement _any_ of the given traits. |
| /// |
| /// This can be used to ensure types do not implement auto traits such as |
| /// [`Send`] and [`Sync`], as well as traits with [blanket `impl`s][blanket]. |
| /// |
| /// This macro causes a compilation failure if any of the provided individual |
| /// traits are implemented for the type. If you want to check that a combination |
| /// of traits is not implemented you should invoke [`assert_not_impl_all!`] |
| /// instead. For single traits both macros behave the same. |
| /// |
| /// # Examples |
| /// |
| /// If `u32` were to implement `Into` conversions for `usize` _and_ for `u8`, |
| /// the following would fail to compile: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_not_impl_any!(u32: Into<usize>, Into<u8>); |
| /// ``` |
| /// |
| /// This is also good for simple one-off cases: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_not_impl_any!(&'static mut u8: Copy); |
| /// ``` |
| /// |
| /// The following example fails to compile since `u32` can be converted into |
| /// `u64` even though it can not be converted into a `u16`: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_not_impl_any!(u32: Into<u64>, Into<u16>); |
| /// ``` |
| /// |
| /// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html |
| /// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html |
| /// [`assert_not_impl_all!`]: macro.assert_not_impl_all.html |
| /// [blanket]: https://doc.rust-lang.org/book/ch10-02-traits.html#using-trait-bounds-to-conditionally-implement-methods |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>assert_not_impl_any { |
| (<span class="macro-nonterminal">$x</span>:ty: $(<span class="macro-nonterminal">$t</span>:path),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="kw">const _</span>: <span class="kw">fn</span>() = || { |
| <span class="comment">// Generic trait with a blanket impl over `()` for all types. |
| </span><span class="kw">trait </span>AmbiguousIfImpl<A> { |
| <span class="comment">// Required for actually being able to reference the trait. |
| </span><span class="kw">fn </span>some_item() {} |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized> AmbiguousIfImpl<()> <span class="kw">for </span>T {} |
| |
| <span class="comment">// Creates multiple scoped `Invalid` types for each trait `$t`, over |
| // which a specialized `AmbiguousIfImpl<Invalid>` is implemented for |
| // every type that implements `$t`. |
| </span>$({ |
| <span class="attribute">#[allow(dead_code)] |
| </span><span class="kw">struct </span>Invalid; |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized + <span class="macro-nonterminal">$t</span>> AmbiguousIfImpl<Invalid> <span class="kw">for </span>T {} |
| })+ |
| |
| <span class="comment">// If there is only one specialized trait impl, type inference with |
| // `_` can be resolved and this can compile. Fails to compile if |
| // `$x` implements any `AmbiguousIfImpl<Invalid>`. |
| </span><span class="kw">let _ </span>= <<span class="macro-nonterminal">$x </span><span class="kw">as </span>AmbiguousIfImpl<<span class="kw">_</span>>>::some_item; |
| }; |
| }; |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="static_assertions" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
