proptest/strategy/
statics.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
//-
// Copyright 2017 Jason Lingle
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Modified versions of the normal strategy combinators which take specialised
//! traits instead of normal functions.
//!
//! This entire module is strictly a workaround until
//! <https://github.com/rust-lang/rfcs/pull/1522> and
//! <https://github.com/rust-lang/rfcs/pull/2071> are available in stable. It
//! allows naming types built on the combinators without resorting to dynamic
//! dispatch or causing `Arc` to allocate space for a function pointer.
//!
//! External code is discouraged from using this module directly. It is
//! deliberately not exposed in a convenient way (i.e., via the `Strategy`
//! trait itself), but is nonetheless exposed since external trait implementors
//! may face the same issues.
//!
//! **This module is subject to removal at some point after the language
//! features linked above become stable.**

use crate::std_facade::fmt;

use crate::strategy::traits::*;
use crate::test_runner::*;

//==============================================================================
// Filter
//==============================================================================

/// Essentially `Fn (&T) -> bool`.
pub trait FilterFn<T> {
    /// Test whether `t` passes the filter.
    fn apply(&self, t: &T) -> bool;
}

/// Static version of `strategy::Filter`.
#[derive(Clone)]
#[must_use = "strategies do nothing unless used"]
pub struct Filter<S, F> {
    source: S,
    whence: Reason,
    fun: F,
}

impl<S, F> Filter<S, F> {
    /// Adapt strategy `source` to reject values which do not pass `filter`,
    /// using `whence` as the reported reason/location.
    pub fn new(source: S, whence: Reason, filter: F) -> Self {
        // NOTE: We don't use universal quantification R: Into<Reason>
        // since the module is not conveniently exposed.
        Filter {
            source,
            whence,
            fun: filter,
        }
    }
}

impl<S: fmt::Debug, F> fmt::Debug for Filter<S, F> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Filter")
            .field("source", &self.source)
            .field("whence", &self.whence)
            .field("fun", &"<function>")
            .finish()
    }
}

impl<S: Strategy, F: FilterFn<S::Value> + Clone> Strategy for Filter<S, F> {
    type Tree = Filter<S::Tree, F>;
    type Value = S::Value;

    fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
        loop {
            let val = self.source.new_tree(runner)?;
            if !self.fun.apply(&val.current()) {
                runner.reject_local(self.whence.clone())?;
            } else {
                return Ok(Filter {
                    source: val,
                    whence: "unused".into(),
                    fun: self.fun.clone(),
                });
            }
        }
    }
}

impl<S: ValueTree, F: FilterFn<S::Value>> Filter<S, F> {
    fn ensure_acceptable(&mut self) {
        while !self.fun.apply(&self.source.current()) {
            if !self.source.complicate() {
                panic!(
                    "Unable to complicate filtered strategy \
                     back into acceptable value"
                );
            }
        }
    }
}

impl<S: ValueTree, F: FilterFn<S::Value>> ValueTree for Filter<S, F> {
    type Value = S::Value;

    fn current(&self) -> S::Value {
        self.source.current()
    }

    fn simplify(&mut self) -> bool {
        if self.source.simplify() {
            self.ensure_acceptable();
            true
        } else {
            false
        }
    }

    fn complicate(&mut self) -> bool {
        if self.source.complicate() {
            self.ensure_acceptable();
            true
        } else {
            false
        }
    }
}

//==============================================================================
// Map
//==============================================================================

/// Essentially `Fn (T) -> Output`.
pub trait MapFn<T> {
    #[allow(missing_docs)]
    type Output: fmt::Debug;

    /// Map `T` to `Output`.
    fn apply(&self, t: T) -> Self::Output;
}

/// Static version of `strategy::Map`.
#[derive(Clone)]
#[must_use = "strategies do nothing unless used"]
pub struct Map<S, F> {
    source: S,
    fun: F,
}

impl<S, F> Map<S, F> {
    /// Adapt strategy `source` by applying `fun` to values it produces.
    pub fn new(source: S, fun: F) -> Self {
        Map { source, fun }
    }
}

impl<S: fmt::Debug, F> fmt::Debug for Map<S, F> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Map")
            .field("source", &self.source)
            .field("fun", &"<function>")
            .finish()
    }
}

impl<S: Strategy, F: Clone + MapFn<S::Value>> Strategy for Map<S, F> {
    type Tree = Map<S::Tree, F>;
    type Value = F::Output;

    fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
        self.source.new_tree(runner).map(|v| Map {
            source: v,
            fun: self.fun.clone(),
        })
    }
}

impl<S: ValueTree, F: MapFn<S::Value>> ValueTree for Map<S, F> {
    type Value = F::Output;

    fn current(&self) -> F::Output {
        self.fun.apply(self.source.current())
    }

    fn simplify(&mut self) -> bool {
        self.source.simplify()
    }

    fn complicate(&mut self) -> bool {
        self.source.complicate()
    }
}

impl<I, O: fmt::Debug> MapFn<I> for fn(I) -> O {
    type Output = O;
    fn apply(&self, x: I) -> Self::Output {
        self(x)
    }
}

pub(crate) fn static_map<S: Strategy, O: fmt::Debug>(
    strat: S,
    fun: fn(S::Value) -> O,
) -> Map<S, fn(S::Value) -> O> {
    Map::new(strat, fun)
}

//==============================================================================
// Tests
//==============================================================================

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_static_filter() {
        #[derive(Clone, Copy, Debug)]
        struct MyFilter;
        impl FilterFn<i32> for MyFilter {
            fn apply(&self, &v: &i32) -> bool {
                0 == v % 3
            }
        }

        let input = Filter::new(0..256, "%3".into(), MyFilter);

        for _ in 0..256 {
            let mut runner = TestRunner::default();
            let mut case = input.new_tree(&mut runner).unwrap();

            assert!(0 == case.current() % 3);

            while case.simplify() {
                assert!(0 == case.current() % 3);
            }
            assert!(0 == case.current() % 3);
        }
    }

    #[test]
    fn test_static_map() {
        #[derive(Clone, Copy, Debug)]
        struct MyMap;
        impl MapFn<i32> for MyMap {
            type Output = i32;
            fn apply(&self, v: i32) -> i32 {
                v * 2
            }
        }

        let input = Map::new(0..10, MyMap);

        TestRunner::default()
            .run(&input, |v| {
                assert!(0 == v % 2);
                Ok(())
            })
            .unwrap();
    }
}