1 use core::fmt::{self, Debug};
2 use core::marker::PhantomData;
3
4 pub trait FnOnce1<A> {
5 type Output;
call_once(self, arg: A) -> Self::Output6 fn call_once(self, arg: A) -> Self::Output;
7 }
8
9 impl<T, A, R> FnOnce1<A> for T
10 where
11 T: FnOnce(A) -> R,
12 {
13 type Output = R;
call_once(self, arg: A) -> R14 fn call_once(self, arg: A) -> R {
15 self(arg)
16 }
17 }
18
19 pub trait FnMut1<A>: FnOnce1<A> {
call_mut(&mut self, arg: A) -> Self::Output20 fn call_mut(&mut self, arg: A) -> Self::Output;
21 }
22
23 impl<T, A, R> FnMut1<A> for T
24 where
25 T: FnMut(A) -> R,
26 {
call_mut(&mut self, arg: A) -> R27 fn call_mut(&mut self, arg: A) -> R {
28 self(arg)
29 }
30 }
31
32 // Not used, but present for completeness
33 #[allow(unreachable_pub)]
34 pub trait Fn1<A>: FnMut1<A> {
call(&self, arg: A) -> Self::Output35 fn call(&self, arg: A) -> Self::Output;
36 }
37
38 impl<T, A, R> Fn1<A> for T
39 where
40 T: Fn(A) -> R,
41 {
call(&self, arg: A) -> R42 fn call(&self, arg: A) -> R {
43 self(arg)
44 }
45 }
46
47 macro_rules! trivial_fn_impls {
48 ($name:ident <$($arg:ident),*> $t:ty = $debug:literal) => {
49 impl<$($arg),*> Copy for $t {}
50 impl<$($arg),*> Clone for $t {
51 fn clone(&self) -> Self { *self }
52 }
53 impl<$($arg),*> Debug for $t {
54 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
55 f.write_str($debug)
56 }
57 }
58 impl<$($arg,)* A> FnMut1<A> for $t where Self: FnOnce1<A> {
59 fn call_mut(&mut self, arg: A) -> Self::Output {
60 self.call_once(arg)
61 }
62 }
63 impl<$($arg,)* A> Fn1<A> for $t where Self: FnOnce1<A> {
64 fn call(&self, arg: A) -> Self::Output {
65 self.call_once(arg)
66 }
67 }
68 pub(crate) fn $name<$($arg),*>() -> $t {
69 Default::default()
70 }
71 }
72 }
73
74 pub struct OkFn<E>(PhantomData<fn(E)>);
75
76 impl<E> Default for OkFn<E> {
default() -> Self77 fn default() -> Self {
78 Self(PhantomData)
79 }
80 }
81
82 impl<A, E> FnOnce1<A> for OkFn<E> {
83 type Output = Result<A, E>;
call_once(self, arg: A) -> Self::Output84 fn call_once(self, arg: A) -> Self::Output {
85 Ok(arg)
86 }
87 }
88
89 trivial_fn_impls!(ok_fn <T> OkFn<T> = "Ok");
90
91 #[derive(Debug, Copy, Clone, Default)]
92 pub struct ChainFn<F, G>(F, G);
93
94 impl<F, G, A> FnOnce1<A> for ChainFn<F, G>
95 where
96 F: FnOnce1<A>,
97 G: FnOnce1<F::Output>,
98 {
99 type Output = G::Output;
call_once(self, arg: A) -> Self::Output100 fn call_once(self, arg: A) -> Self::Output {
101 self.1.call_once(self.0.call_once(arg))
102 }
103 }
104 impl<F, G, A> FnMut1<A> for ChainFn<F, G>
105 where
106 F: FnMut1<A>,
107 G: FnMut1<F::Output>,
108 {
call_mut(&mut self, arg: A) -> Self::Output109 fn call_mut(&mut self, arg: A) -> Self::Output {
110 self.1.call_mut(self.0.call_mut(arg))
111 }
112 }
113 impl<F, G, A> Fn1<A> for ChainFn<F, G>
114 where
115 F: Fn1<A>,
116 G: Fn1<F::Output>,
117 {
call(&self, arg: A) -> Self::Output118 fn call(&self, arg: A) -> Self::Output {
119 self.1.call(self.0.call(arg))
120 }
121 }
chain_fn<F, G>(f: F, g: G) -> ChainFn<F, G>122 pub(crate) fn chain_fn<F, G>(f: F, g: G) -> ChainFn<F, G> {
123 ChainFn(f, g)
124 }
125
126 #[derive(Default)]
127 pub struct MergeResultFn;
128
129 impl<T> FnOnce1<Result<T, T>> for MergeResultFn {
130 type Output = T;
call_once(self, arg: Result<T, T>) -> Self::Output131 fn call_once(self, arg: Result<T, T>) -> Self::Output {
132 match arg {
133 Ok(x) => x,
134 Err(x) => x,
135 }
136 }
137 }
138 trivial_fn_impls!(merge_result_fn <> MergeResultFn = "merge_result");
139
140 #[derive(Debug, Copy, Clone, Default)]
141 pub struct InspectFn<F>(F);
142
143 #[allow(single_use_lifetimes)] // https://github.com/rust-lang/rust/issues/55058
144 impl<F, A> FnOnce1<A> for InspectFn<F>
145 where
146 F: for<'a> FnOnce1<&'a A, Output = ()>,
147 {
148 type Output = A;
call_once(self, arg: A) -> Self::Output149 fn call_once(self, arg: A) -> Self::Output {
150 self.0.call_once(&arg);
151 arg
152 }
153 }
154 #[allow(single_use_lifetimes)] // https://github.com/rust-lang/rust/issues/55058
155 impl<F, A> FnMut1<A> for InspectFn<F>
156 where
157 F: for<'a> FnMut1<&'a A, Output = ()>,
158 {
call_mut(&mut self, arg: A) -> Self::Output159 fn call_mut(&mut self, arg: A) -> Self::Output {
160 self.0.call_mut(&arg);
161 arg
162 }
163 }
164 #[allow(single_use_lifetimes)] // https://github.com/rust-lang/rust/issues/55058
165 impl<F, A> Fn1<A> for InspectFn<F>
166 where
167 F: for<'a> Fn1<&'a A, Output = ()>,
168 {
call(&self, arg: A) -> Self::Output169 fn call(&self, arg: A) -> Self::Output {
170 self.0.call(&arg);
171 arg
172 }
173 }
inspect_fn<F>(f: F) -> InspectFn<F>174 pub(crate) fn inspect_fn<F>(f: F) -> InspectFn<F> {
175 InspectFn(f)
176 }
177
178 #[derive(Debug, Copy, Clone, Default)]
179 pub struct MapOkFn<F>(F);
180
181 impl<F, T, E> FnOnce1<Result<T, E>> for MapOkFn<F>
182 where
183 F: FnOnce1<T>,
184 {
185 type Output = Result<F::Output, E>;
call_once(self, arg: Result<T, E>) -> Self::Output186 fn call_once(self, arg: Result<T, E>) -> Self::Output {
187 arg.map(|x| self.0.call_once(x))
188 }
189 }
190 impl<F, T, E> FnMut1<Result<T, E>> for MapOkFn<F>
191 where
192 F: FnMut1<T>,
193 {
call_mut(&mut self, arg: Result<T, E>) -> Self::Output194 fn call_mut(&mut self, arg: Result<T, E>) -> Self::Output {
195 arg.map(|x| self.0.call_mut(x))
196 }
197 }
198 impl<F, T, E> Fn1<Result<T, E>> for MapOkFn<F>
199 where
200 F: Fn1<T>,
201 {
call(&self, arg: Result<T, E>) -> Self::Output202 fn call(&self, arg: Result<T, E>) -> Self::Output {
203 arg.map(|x| self.0.call(x))
204 }
205 }
map_ok_fn<F>(f: F) -> MapOkFn<F>206 pub(crate) fn map_ok_fn<F>(f: F) -> MapOkFn<F> {
207 MapOkFn(f)
208 }
209
210 #[derive(Debug, Copy, Clone, Default)]
211 pub struct MapErrFn<F>(F);
212
213 impl<F, T, E> FnOnce1<Result<T, E>> for MapErrFn<F>
214 where
215 F: FnOnce1<E>,
216 {
217 type Output = Result<T, F::Output>;
call_once(self, arg: Result<T, E>) -> Self::Output218 fn call_once(self, arg: Result<T, E>) -> Self::Output {
219 arg.map_err(|x| self.0.call_once(x))
220 }
221 }
222 impl<F, T, E> FnMut1<Result<T, E>> for MapErrFn<F>
223 where
224 F: FnMut1<E>,
225 {
call_mut(&mut self, arg: Result<T, E>) -> Self::Output226 fn call_mut(&mut self, arg: Result<T, E>) -> Self::Output {
227 arg.map_err(|x| self.0.call_mut(x))
228 }
229 }
230 impl<F, T, E> Fn1<Result<T, E>> for MapErrFn<F>
231 where
232 F: Fn1<E>,
233 {
call(&self, arg: Result<T, E>) -> Self::Output234 fn call(&self, arg: Result<T, E>) -> Self::Output {
235 arg.map_err(|x| self.0.call(x))
236 }
237 }
map_err_fn<F>(f: F) -> MapErrFn<F>238 pub(crate) fn map_err_fn<F>(f: F) -> MapErrFn<F> {
239 MapErrFn(f)
240 }
241
242 #[derive(Debug, Copy, Clone)]
243 pub struct InspectOkFn<F>(F);
244
245 impl<'a, F, T, E> FnOnce1<&'a Result<T, E>> for InspectOkFn<F>
246 where
247 F: FnOnce1<&'a T, Output = ()>,
248 {
249 type Output = ();
call_once(self, arg: &'a Result<T, E>) -> Self::Output250 fn call_once(self, arg: &'a Result<T, E>) -> Self::Output {
251 if let Ok(x) = arg {
252 self.0.call_once(x)
253 }
254 }
255 }
256 impl<'a, F, T, E> FnMut1<&'a Result<T, E>> for InspectOkFn<F>
257 where
258 F: FnMut1<&'a T, Output = ()>,
259 {
call_mut(&mut self, arg: &'a Result<T, E>) -> Self::Output260 fn call_mut(&mut self, arg: &'a Result<T, E>) -> Self::Output {
261 if let Ok(x) = arg {
262 self.0.call_mut(x)
263 }
264 }
265 }
266 impl<'a, F, T, E> Fn1<&'a Result<T, E>> for InspectOkFn<F>
267 where
268 F: Fn1<&'a T, Output = ()>,
269 {
call(&self, arg: &'a Result<T, E>) -> Self::Output270 fn call(&self, arg: &'a Result<T, E>) -> Self::Output {
271 if let Ok(x) = arg {
272 self.0.call(x)
273 }
274 }
275 }
inspect_ok_fn<F>(f: F) -> InspectOkFn<F>276 pub(crate) fn inspect_ok_fn<F>(f: F) -> InspectOkFn<F> {
277 InspectOkFn(f)
278 }
279
280 #[derive(Debug, Copy, Clone)]
281 pub struct InspectErrFn<F>(F);
282
283 impl<'a, F, T, E> FnOnce1<&'a Result<T, E>> for InspectErrFn<F>
284 where
285 F: FnOnce1<&'a E, Output = ()>,
286 {
287 type Output = ();
call_once(self, arg: &'a Result<T, E>) -> Self::Output288 fn call_once(self, arg: &'a Result<T, E>) -> Self::Output {
289 if let Err(x) = arg {
290 self.0.call_once(x)
291 }
292 }
293 }
294 impl<'a, F, T, E> FnMut1<&'a Result<T, E>> for InspectErrFn<F>
295 where
296 F: FnMut1<&'a E, Output = ()>,
297 {
call_mut(&mut self, arg: &'a Result<T, E>) -> Self::Output298 fn call_mut(&mut self, arg: &'a Result<T, E>) -> Self::Output {
299 if let Err(x) = arg {
300 self.0.call_mut(x)
301 }
302 }
303 }
304 impl<'a, F, T, E> Fn1<&'a Result<T, E>> for InspectErrFn<F>
305 where
306 F: Fn1<&'a E, Output = ()>,
307 {
call(&self, arg: &'a Result<T, E>) -> Self::Output308 fn call(&self, arg: &'a Result<T, E>) -> Self::Output {
309 if let Err(x) = arg {
310 self.0.call(x)
311 }
312 }
313 }
inspect_err_fn<F>(f: F) -> InspectErrFn<F>314 pub(crate) fn inspect_err_fn<F>(f: F) -> InspectErrFn<F> {
315 InspectErrFn(f)
316 }
317
318 pub(crate) type MapOkOrElseFn<F, G> = ChainFn<MapOkFn<F>, ChainFn<MapErrFn<G>, MergeResultFn>>;
map_ok_or_else_fn<F, G>(f: F, g: G) -> MapOkOrElseFn<F, G>319 pub(crate) fn map_ok_or_else_fn<F, G>(f: F, g: G) -> MapOkOrElseFn<F, G> {
320 chain_fn(map_ok_fn(f), chain_fn(map_err_fn(g), merge_result_fn()))
321 }
322
323 #[derive(Debug, Copy, Clone, Default)]
324 pub struct UnwrapOrElseFn<F>(F);
325
326 impl<F, T, E> FnOnce1<Result<T, E>> for UnwrapOrElseFn<F>
327 where
328 F: FnOnce1<E, Output = T>,
329 {
330 type Output = T;
call_once(self, arg: Result<T, E>) -> Self::Output331 fn call_once(self, arg: Result<T, E>) -> Self::Output {
332 arg.unwrap_or_else(|x| self.0.call_once(x))
333 }
334 }
335 impl<F, T, E> FnMut1<Result<T, E>> for UnwrapOrElseFn<F>
336 where
337 F: FnMut1<E, Output = T>,
338 {
call_mut(&mut self, arg: Result<T, E>) -> Self::Output339 fn call_mut(&mut self, arg: Result<T, E>) -> Self::Output {
340 arg.unwrap_or_else(|x| self.0.call_mut(x))
341 }
342 }
343 impl<F, T, E> Fn1<Result<T, E>> for UnwrapOrElseFn<F>
344 where
345 F: Fn1<E, Output = T>,
346 {
call(&self, arg: Result<T, E>) -> Self::Output347 fn call(&self, arg: Result<T, E>) -> Self::Output {
348 arg.unwrap_or_else(|x| self.0.call(x))
349 }
350 }
unwrap_or_else_fn<F>(f: F) -> UnwrapOrElseFn<F>351 pub(crate) fn unwrap_or_else_fn<F>(f: F) -> UnwrapOrElseFn<F> {
352 UnwrapOrElseFn(f)
353 }
354
355 pub struct IntoFn<T>(PhantomData<fn() -> T>);
356
357 impl<T> Default for IntoFn<T> {
default() -> Self358 fn default() -> Self {
359 Self(PhantomData)
360 }
361 }
362 impl<A, T> FnOnce1<A> for IntoFn<T>
363 where
364 A: Into<T>,
365 {
366 type Output = T;
call_once(self, arg: A) -> Self::Output367 fn call_once(self, arg: A) -> Self::Output {
368 arg.into()
369 }
370 }
371
372 trivial_fn_impls!(into_fn <T> IntoFn<T> = "Into::into");
373