rukt 0.2.4

Simple Rust dialect for token-based compile-time scripting
Documentation 
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

//! Reusable macro utilities.

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape {
    ([($($G:tt)*) $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils::escape!([$($G)*] [] $E ($crate::utils_escape_collect_parens; [$($T)*] $R $E ($crate::utils::escape) $N));
    };
    ([[$($G:tt)*] $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils::escape!([$($G)*] [] $E ($crate::utils_escape_collect_brackets; [$($T)*] $R $E ($crate::utils::escape) $N));
    };
    ([{$($G:tt)*} $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils::escape!([$($G)*] [] $E ($crate::utils_escape_collect_braces; [$($T)*] $R $E ($crate::utils::escape) $N));
    };
    ([$H:tt $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils_escape_detect!([=$H=] [$($T)*] $R $E $N);
    };
    ([] [$($R:tt)*] $E:tt ($F:path; $($C:tt)*)) => {
        $F!([$($R)*] $($C)*);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape_detect {
    ([$(=)$+] $T:tt [$($R:tt)*] [$($E:tt)*] $N:tt) => {
        $crate::utils::escape!($T [$($R)* $($E)*] [$($E)*] $N);
    };
    ([=$H:tt=] $T:tt [$($R:tt)*] $E:tt $N:tt) => {
        $crate::utils::escape!($T [$($R)* $H] $E $N);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape_collect_parens {
    ([$($G:tt)*] $T:tt [$($R:tt)*] $E:tt ($F:path) $N:tt) => {
        $F!($T [$($R)* ($($G)*)] $E $N);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape_collect_brackets {
    ([$($G:tt)*] $T:tt [$($R:tt)*] $E:tt ($F:path) $N:tt) => {
        $F!($T [$($R)* [$($G)*]] $E $N);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape_collect_braces {
    ([$($G:tt)*] $T:tt [$($R:tt)*] $E:tt ($F:path) $N:tt) => {
        $F!($T [$($R)* {$($G)*}] $E $N);
    };
}

/// Replace dollar sign tokens `$` with the given tokens.
///
/// The macro accepts the source tokens, followed by the initial output tokens,
/// followed by the escape tokens, followed by a next continuation.
///
/// ```
/// # use rukt::utils::escape;
/// macro_rules! define {
///     ([$($T:tt)*] $I:ident) => {
///         const $I: &str = stringify!($($T)*);
///     }
/// }
/// escape!([$name:ident($($arg:expr),*)] [] [<dollar>] (define; CALL_PATTERN));
/// assert_eq!(CALL_PATTERN, "<dollar>name:ident(<dollar>(<dollar>arg:expr),*)");
/// ```
///
/// Notice how all dollar signs the input tokens got replaced with the escape
/// tokens.
///
/// This is useful when the input tokens are meant to be matched against
/// literally as a pattern in a generated macro.
#[doc(inline)]
pub use utils_escape as escape;

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape_repetitions {
    ([($($G:tt)*) $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils::escape_repetitions!([$($G)*] [] $E ($crate::utils_escape_collect_parens; [$($T)*] $R $E ($crate::utils::escape_repetitions) $N));
    };
    ([[$($G:tt)*] $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils::escape_repetitions!([$($G)*] [] $E ($crate::utils_escape_collect_brackets; [$($T)*] $R $E ($crate::utils::escape_repetitions) $N));
    };
    ([{$($G:tt)*} $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils::escape_repetitions!([$($G)*] [] $E ($crate::utils_escape_collect_braces; [$($T)*] $R $E ($crate::utils::escape_repetitions) $N));
    };
    ([$H:tt ($($G:tt)*) $($T:tt)*] $R:tt $E:tt $N:tt) => {
        $crate::utils_escape_repetitions_detect!([=$H=] ($($G)*) [$($T)*] $R $E $N);
    };
    ([$H:tt $($T:tt)*] [$($R:tt)*] $E:tt $N:tt) => {
        $crate::utils::escape_repetitions!([$($T)*] [$($R)* $H] $E $N);
    };
    ([] [$($R:tt)*] $E:tt ($F:path; $($C:tt)*)) => {
        $F!([$($R)*] $($C)*);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! utils_escape_repetitions_detect {
    ([$(=)$+] ($($G:tt)*) $T:tt [$($R:tt)*] [$($E:tt)*] $N:tt) => {
        $crate::utils::escape_repetitions!([$($G)*] [] [$($E)*] ($crate::utils_escape_collect_parens; $T [$($R)* $($E)*] [$($E)*] ($crate::utils::escape_repetitions) $N));
    };
    ([=$H:tt=] ($($G:tt)*) $T:tt [$($R:tt)*] $E:tt $N:tt) => {
        $crate::utils::escape_repetitions!([$($G)*] [] $E ($crate::utils_escape_collect_parens; $T [$($R)* $H] $E ($crate::utils::escape_repetitions) $N));
    };
}

/// Replace the dollar sign `$` prefixing `macro_rules` repetitions with the
/// given tokens.
///
/// The macro accepts the source tokens, followed by the initial output tokens,
/// followed by the escape tokens, followed by a next continuation.
///
/// ```
/// # use rukt::utils::escape_repetitions;
/// macro_rules! define {
///     ([$($T:tt)*] $I:ident) => {
///         const $I: &str = stringify!($($T)*);
///     }
/// }
/// escape_repetitions!([$name:ident($($arg:expr),*)] [] [<dollar>] (define; CALL_PATTERN));
/// assert_eq!(CALL_PATTERN.replace(" ", ""), "$name:ident(<dollar>($arg:expr),*)");
/// ```
///
/// Notice how the repetition `$($arg:expr),*` turned into
/// `<dollar>($arg:expr),*`. The dollar sign `$` that would normally cause
/// `macro_rules` to identify a potential [fragment
/// repetition](https://doc.rust-lang.org/reference/macros-by-example.html#repetitions)
/// in the input tokens got replaced with the escape tokens.
///
/// This is useful when tokens are meant to be pasted into a generated macro,
/// but the expanded result should not be interpreted by `macro_rules`. (See
/// [`rust/35853`](https://github.com/rust-lang/rust/issues/35853))
///
/// The following example won't compile because the repetition `$($arg:expr),*`
/// pasted in the generated macro will be interpreted by `macro_rules` upon
/// expansion.
///
/// ```compile_fail
/// macro_rules! define {
///     ([$($T:tt)*] $I:ident) => {
///         macro_rules! $I {
///             () => {
///                 stringify!($($T)*)
///             };
///         }
///     }
/// }
/// define!([$name:ident($($arg:expr),*)] call_pattern);
/// assert_eq!(call_pattern!().replace(" ", ""), "$name:ident($($arg:expr),*)");
/// ```
/// ```text
/// error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
/// ```
///
/// By using [`escape_repetitions`], you can replace all the dollar sign `$`
/// tokens that would normally cause `macro_rules` to identify a potential
/// [fragment
/// repetition](https://doc.rust-lang.org/reference/macros-by-example.html#repetitions)
/// with a metavariable you'll substitute back for a dollar sign `$` when
/// expanding the generated macro.
///
/// ```
/// # use rukt::utils::escape_repetitions;
/// macro_rules! define {
///     ([$($T:tt)*] $I:ident $($E:tt)+) => {
///         macro_rules! $I {
///             ($($E)*) => {
///                 stringify!($($T)*)
///             };
///         }
///     }
/// }
/// escape_repetitions!([$name:ident($($arg:expr),*)] [] [$D] (define; call_pattern $D:tt));
/// assert_eq!(call_pattern!($).replace(" ", ""), "$name:ident($($arg:expr),*)");
/// ```
///
/// Note that due to
/// [hygiene](https://doc.rust-lang.org/reference/macros-by-example.html#hygiene),
/// the final substitution to unescape the dollar sign tokens only works if the
/// metavariable used for escaping and its corresponding pattern appear in
/// compatible lexical scopes. Passing them both at the call site ensures that
/// they match.
#[doc(inline)]
pub use utils_escape_repetitions as escape_repetitions;

#[doc(hidden)]
#[macro_export]
macro_rules! utils_select {
    ([$($T:tt)*] [$([[$($R1:tt)*] [$($R2:tt)*]])+] $N:tt $D:tt) => {
        macro_rules! __rukt_dispatch {
            $(
                ([$($R1)*] ($FF:path; $D($CC:tt)*)) => {
                    $FF!([$($R2)*] $D($CC)*);
                };
            )*
        }
        __rukt_dispatch!([$($T)*] $N);
    };
}

/// Select tokens associated with the first matching pattern.
#[doc(inline)]
pub use utils_select as select;

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

    #[test]
    fn test_escape_repetitions() {
        macro_rules! check {
            ($T:tt $expected:expr) => {
                assert_eq!(stringify!($T), $expected);
            };
        }

        escape_repetitions!([] [] [$REP] (check; "[]"));
        escape_repetitions!([hello world] [] [$REP] (check; "[hello world]"));
        escape_repetitions!([hello(world)] [] [$REP] (check; "[hello(world)]"));
        escape_repetitions!([{ hello }(world)] [] [$REP] (check; "[{ hello }(world)]"));
        escape_repetitions!([$($hello)* world] [] [$REP] (check; "[$REP($hello)* world]"));
        escape_repetitions!([$($hello)*(world)] [] [$REP] (check; "[$REP($hello)*(world)]"));
        escape_repetitions!([{ $($hello)* }(world)] [] [$REP] (check; "[{ $REP($hello)* }(world)]"));
        escape_repetitions!([$($hello)* $($world:tt, 42)+] [] [$REP] (check; "[$REP($hello)* $REP($world:tt, 42)+]"));
        escape_repetitions!([$($hello)*($($world:tt, 42)+)] [] [$REP] (check; "[$REP($hello)*($REP($world:tt, 42)+)]"));
        escape_repetitions!([{ $($hello)* }($($world:tt, 42)+)] [] [$REP] (check; "[{ $REP($hello)* }($REP($world:tt, 42)+)]"));
        escape_repetitions!([$($hello $(;)?)* $($world:tt, 42)+] [] [$REP] (check; "[$REP($hello $REP(;)?)* $REP($world:tt, 42)+]"));
        escape_repetitions!([$($hello $(;)?)*($($world:tt, 42)+)] [] [$REP] (check; "[$REP($hello $REP(;)?)*($REP($world:tt, 42)+)]"));
        escape_repetitions!([{ $($hello $(;)?)* }($($world:tt, 42)+)] [] [$REP] (check; "[{ $REP($hello $REP(;)?)* }($REP($world:tt, 42)+)]"));
    }
}