aboutsummaryrefslogtreecommitdiff
path: root/src/macros.rs
blob: 0731afefd443e2cfee1554cc0ecde0013635474d (plain)
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
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
pub use serde::de::{Deserialize, IntoDeserializer};

use crate::value::{Array, Table, Value};

/// Construct a [`toml::Value`] from TOML syntax.
///
/// [`toml::Value`]: value/enum.Value.html
///
/// ```rust
/// fn main() {
///     let cargo_toml = toml::toml! {
///         [package]
///         name = "toml"
///         version = "0.4.5"
///         authors = ["Alex Crichton <alex@alexcrichton.com>"]
///
///         [badges]
///         travis-ci = { repository = "alexcrichton/toml-rs" }
///
///         [dependencies]
///         serde = "1.0"
///
///         [dev-dependencies]
///         serde_derive = "1.0"
///         serde_json = "1.0"
///     };
///
///     println!("{:#?}", cargo_toml);
/// }
/// ```
#[macro_export]
macro_rules! toml {
    ($($toml:tt)+) => {{
        let table = $crate::value::Table::new();
        let mut root = $crate::Value::Table(table);
        $crate::toml_internal!(@toplevel root [] $($toml)+);
        root
    }};
}

// TT-muncher to parse TOML syntax into a toml::Value.
//
//    @toplevel -- Parse tokens outside of an inline table or inline array. In
//                 this state, `[table headers]` and `[[array headers]]` are
//                 allowed and `key = value` pairs are not separated by commas.
//
//    @topleveldatetime -- Helper to parse a Datetime from string and insert it
//                 into a table, continuing in the @toplevel state.
//
//    @path -- Turn a path segment into a string. Segments that look like idents
//                 are stringified, while quoted segments like `"cfg(windows)"`
//                 are not.
//
//    @value -- Parse the value part of a `key = value` pair, which may be a
//                 primitive or inline table or inline array.
//
//    @table -- Parse the contents of an inline table, returning them as a
//                 toml::Value::Table.
//
//    @tabledatetime -- Helper to parse a Datetime from string and insert it
//                 into a table, continuing in the @table state.
//
//    @array -- Parse the contents of an inline array, returning them as a
//                 toml::Value::Array.
//
//    @arraydatetime -- Helper to parse a Datetime from string and push it into
//                 an array, continuing in the @array state.
//
//    @trailingcomma -- Helper to append a comma to a sequence of tokens if the
//                 sequence is non-empty and does not already end in a trailing
//                 comma.
//
#[macro_export]
#[doc(hidden)]
macro_rules! toml_internal {
    // Base case, no elements remaining.
    (@toplevel $root:ident [$($path:tt)*]) => {};

    // Parse negative number `key = -value`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = - $v:tt $($rest:tt)*) => {
        $crate::toml_internal!(@toplevel $root [$($path)*] $($($k)-+).+ = (-$v) $($rest)*);
    };

    // Parse positive number `key = +value`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = + $v:tt $($rest:tt)*) => {
        $crate::toml_internal!(@toplevel $root [$($path)*] $($($k)-+).+ = ($v) $($rest)*);
    };

    // Parse offset datetime `key = 1979-05-27T00:32:00.999999-07:00`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt . $frac:tt - $tzh:tt : $tzm:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec . $frac - $tzh : $tzm) $($rest)*);
    };
    // Space instead of T.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt . $frac:tt - $tzh:tt : $tzm:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec . $frac - $tzh : $tzm) $($rest)*);
    };

    // Parse offset datetime `key = 1979-05-27T00:32:00-07:00`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt - $tzh:tt : $tzm:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec - $tzh : $tzm) $($rest)*);
    };
    // Space instead of T.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt - $tzh:tt : $tzm:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec - $tzh : $tzm) $($rest)*);
    };

    // Parse local datetime `key = 1979-05-27T00:32:00.999999`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt . $frac:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec . $frac) $($rest)*);
    };
    // Space instead of T.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt . $frac:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec . $frac) $($rest)*);
    };

    // Parse offset datetime `key = 1979-05-27T07:32:00Z` and local datetime `key = 1979-05-27T07:32:00`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec) $($rest)*);
    };
    // Space instead of T.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec) $($rest)*);
    };

    // Parse local date `key = 1979-05-27`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($yr - $mo - $day) $($rest)*);
    };

    // Parse local time `key = 00:32:00.999999`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $hr:tt : $min:tt : $sec:tt . $frac:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($hr : $min : $sec . $frac) $($rest)*);
    };

    // Parse local time `key = 07:32:00`.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $hr:tt : $min:tt : $sec:tt $($rest:tt)*) => {
        $crate::toml_internal!(@topleveldatetime $root [$($path)*] $($($k)-+).+ = ($hr : $min : $sec) $($rest)*);
    };

    // Parse any other `key = value` including string, inline array, inline
    // table, number, and boolean.
    (@toplevel $root:ident [$($path:tt)*] $($($k:tt)-+).+ = $v:tt $($rest:tt)*) => {{
        $crate::macros::insert_toml(
            &mut $root,
            &[$($path)* $(&concat!($("-", $crate::toml_internal!(@path $k),)+)[1..], )+],
            $crate::toml_internal!(@value $v));
        $crate::toml_internal!(@toplevel $root [$($path)*] $($rest)*);
    }};

    // Parse array header `[[bin]]`.
    (@toplevel $root:ident $oldpath:tt [[$($($path:tt)-+).+]] $($rest:tt)*) => {
        $crate::macros::push_toml(
            &mut $root,
            &[$(&concat!($("-", $crate::toml_internal!(@path $path),)+)[1..],)+]);
        $crate::toml_internal!(@toplevel $root [$(&concat!($("-", $crate::toml_internal!(@path $path),)+)[1..],)+] $($rest)*);
    };

    // Parse table header `[patch.crates-io]`.
    (@toplevel $root:ident $oldpath:tt [$($($path:tt)-+).+] $($rest:tt)*) => {
        $crate::macros::insert_toml(
            &mut $root,
            &[$(&concat!($("-", $crate::toml_internal!(@path $path),)+)[1..],)+],
            $crate::Value::Table($crate::value::Table::new()));
        $crate::toml_internal!(@toplevel $root [$(&concat!($("-", $crate::toml_internal!(@path $path),)+)[1..],)+] $($rest)*);
    };

    // Parse datetime from string and insert into table.
    (@topleveldatetime $root:ident [$($path:tt)*] $($($k:tt)-+).+ = ($($datetime:tt)+) $($rest:tt)*) => {
        $crate::macros::insert_toml(
            &mut $root,
            &[$($path)* $(&concat!($("-", $crate::toml_internal!(@path $k),)+)[1..], )+],
            $crate::Value::Datetime(concat!($(stringify!($datetime)),+).parse().unwrap()));
        $crate::toml_internal!(@toplevel $root [$($path)*] $($rest)*);
    };

    // Turn a path segment into a string.
    (@path $ident:ident) => {
        stringify!($ident)
    };

    // For a path segment that is not an ident, expect that it is already a
    // quoted string, like in `[target."cfg(windows)".dependencies]`.
    (@path $quoted:tt) => {
        $quoted
    };

    // Construct a Value from an inline table.
    (@value { $($inline:tt)* }) => {{
        let mut table = $crate::Value::Table($crate::value::Table::new());
        $crate::toml_internal!(@trailingcomma (@table table) $($inline)*);
        table
    }};

    // Construct a Value from an inline array.
    (@value [ $($inline:tt)* ]) => {{
        let mut array = $crate::value::Array::new();
        $crate::toml_internal!(@trailingcomma (@array array) $($inline)*);
        $crate::Value::Array(array)
    }};

    (@value (-nan)) => {
        $crate::Value::Float(-::std::f64::NAN)
    };

    (@value (nan)) => {
        $crate::Value::Float(::std::f64::NAN)
    };

    (@value nan) => {
        $crate::Value::Float(::std::f64::NAN)
    };

    (@value (-inf)) => {
        $crate::Value::Float(::std::f64::NEG_INFINITY)
    };

    (@value (inf)) => {
        $crate::Value::Float(::std::f64::INFINITY)
    };

    (@value inf) => {
        $crate::Value::Float(::std::f64::INFINITY)
    };

    // Construct a Value from any other type, probably string or boolean or number.
    (@value $v:tt) => {{
        // TODO: Implement this with something like serde_json::to_value instead.
        let de = $crate::macros::IntoDeserializer::<$crate::de::Error>::into_deserializer($v);
        <$crate::Value as $crate::macros::Deserialize>::deserialize(de).unwrap()
    }};

    // Base case of inline table.
    (@table $root:ident) => {};

    // Parse negative number `key = -value`.
    (@table $root:ident $($($k:tt)-+).+ = - $v:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@table $root $($($k)-+).+ = (-$v) , $($rest)*);
    };

    // Parse positive number `key = +value`.
    (@table $root:ident $($($k:tt)-+).+ = + $v:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@table $root $($($k)-+).+ = ($v) , $($rest)*);
    };

    // Parse offset datetime `key = 1979-05-27T00:32:00.999999-07:00`.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt . $frac:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec . $frac - $tzh : $tzm) $($rest)*);
    };
    // Space instead of T.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt . $frac:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec . $frac - $tzh : $tzm) $($rest)*);
    };

    // Parse offset datetime `key = 1979-05-27T00:32:00-07:00`.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec - $tzh : $tzm) $($rest)*);
    };
    // Space instead of T.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec - $tzh : $tzm) $($rest)*);
    };

    // Parse local datetime `key = 1979-05-27T00:32:00.999999`.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt . $frac:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec . $frac) $($rest)*);
    };
    // Space instead of T.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt . $frac:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec . $frac) $($rest)*);
    };

    // Parse offset datetime `key = 1979-05-27T07:32:00Z` and local datetime `key = 1979-05-27T07:32:00`.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $dhr : $min : $sec) $($rest)*);
    };
    // Space instead of T.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $day T $hr : $min : $sec) $($rest)*);
    };

    // Parse local date `key = 1979-05-27`.
    (@table $root:ident $($($k:tt)-+).+ = $yr:tt - $mo:tt - $day:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($yr - $mo - $day) $($rest)*);
    };

    // Parse local time `key = 00:32:00.999999`.
    (@table $root:ident $($($k:tt)-+).+ = $hr:tt : $min:tt : $sec:tt . $frac:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($hr : $min : $sec . $frac) $($rest)*);
    };

    // Parse local time `key = 07:32:00`.
    (@table $root:ident $($($k:tt)-+).+ = $hr:tt : $min:tt : $sec:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@tabledatetime $root $($($k)-+).+ = ($hr : $min : $sec) $($rest)*);
    };

    // Parse any other type, probably string or boolean or number.
    (@table $root:ident $($($k:tt)-+).+ = $v:tt , $($rest:tt)*) => {
        $crate::macros::insert_toml(
            &mut $root,
            &[$(&concat!($("-", $crate::toml_internal!(@path $k),)+)[1..], )+],
            $crate::toml_internal!(@value $v));
        $crate::toml_internal!(@table $root $($rest)*);
    };

    // Parse a Datetime from string and continue in @table state.
    (@tabledatetime $root:ident $($($k:tt)-+).+ = ($($datetime:tt)*) $($rest:tt)*) => {
        $crate::macros::insert_toml(
            &mut $root,
            &[$(&concat!($("-", $crate::toml_internal!(@path $k),)+)[1..], )+],
            $crate::Value::Datetime(concat!($(stringify!($datetime)),+).parse().unwrap()));
        $crate::toml_internal!(@table $root $($rest)*);
    };

    // Base case of inline array.
    (@array $root:ident) => {};

    // Parse negative number `-value`.
    (@array $root:ident - $v:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@array $root (-$v) , $($rest)*);
    };

    // Parse positive number `+value`.
    (@array $root:ident + $v:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@array $root ($v) , $($rest)*);
    };

    // Parse offset datetime `1979-05-27T00:32:00.999999-07:00`.
    (@array $root:ident $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt . $frac:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $dhr : $min : $sec . $frac - $tzh : $tzm) $($rest)*);
    };
    // Space instead of T.
    (@array $root:ident $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt . $frac:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $day T $hr : $min : $sec . $frac - $tzh : $tzm) $($rest)*);
    };

    // Parse offset datetime `1979-05-27T00:32:00-07:00`.
    (@array $root:ident $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $dhr : $min : $sec - $tzh : $tzm) $($rest)*);
    };
    // Space instead of T.
    (@array $root:ident $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt - $tzh:tt : $tzm:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $day T $hr : $min : $sec - $tzh : $tzm) $($rest)*);
    };

    // Parse local datetime `1979-05-27T00:32:00.999999`.
    (@array $root:ident $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt . $frac:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $dhr : $min : $sec . $frac) $($rest)*);
    };
    // Space instead of T.
    (@array $root:ident $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt . $frac:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $day T $hr : $min : $sec . $frac) $($rest)*);
    };

    // Parse offset datetime `1979-05-27T07:32:00Z` and local datetime `1979-05-27T07:32:00`.
    (@array $root:ident $yr:tt - $mo:tt - $dhr:tt : $min:tt : $sec:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $dhr : $min : $sec) $($rest)*);
    };
    // Space instead of T.
    (@array $root:ident $yr:tt - $mo:tt - $day:tt $hr:tt : $min:tt : $sec:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $day T $hr : $min : $sec) $($rest)*);
    };

    // Parse local date `1979-05-27`.
    (@array $root:ident $yr:tt - $mo:tt - $day:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($yr - $mo - $day) $($rest)*);
    };

    // Parse local time `00:32:00.999999`.
    (@array $root:ident $hr:tt : $min:tt : $sec:tt . $frac:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($hr : $min : $sec . $frac) $($rest)*);
    };

    // Parse local time `07:32:00`.
    (@array $root:ident $hr:tt : $min:tt : $sec:tt , $($rest:tt)*) => {
        $crate::toml_internal!(@arraydatetime $root ($hr : $min : $sec) $($rest)*);
    };

    // Parse any other type, probably string or boolean or number.
    (@array $root:ident $v:tt , $($rest:tt)*) => {
        $root.push($crate::toml_internal!(@value $v));
        $crate::toml_internal!(@array $root $($rest)*);
    };

    // Parse a Datetime from string and continue in @array state.
    (@arraydatetime $root:ident ($($datetime:tt)*) $($rest:tt)*) => {
        $root.push($crate::Value::Datetime(concat!($(stringify!($datetime)),+).parse().unwrap()));
        $crate::toml_internal!(@array $root $($rest)*);
    };

    // No trailing comma required if the tokens are empty.
    (@trailingcomma ($($args:tt)*)) => {
        $crate::toml_internal!($($args)*);
    };

    // Tokens end with a trailing comma, do not append another one.
    (@trailingcomma ($($args:tt)*) ,) => {
        $crate::toml_internal!($($args)* ,);
    };

    // Tokens end with something other than comma, append a trailing comma.
    (@trailingcomma ($($args:tt)*) $last:tt) => {
        $crate::toml_internal!($($args)* $last ,);
    };

    // Not yet at the last token.
    (@trailingcomma ($($args:tt)*) $first:tt $($rest:tt)+) => {
        $crate::toml_internal!(@trailingcomma ($($args)* $first) $($rest)+);
    };
}

// Called when parsing a `key = value` pair.
// Inserts an entry into the table at the given path.
pub fn insert_toml(root: &mut Value, path: &[&str], value: Value) {
    *traverse(root, path) = value;
}

// Called when parsing an `[[array header]]`.
// Pushes an empty table onto the array at the given path.
pub fn push_toml(root: &mut Value, path: &[&str]) {
    let target = traverse(root, path);
    if !target.is_array() {
        *target = Value::Array(Array::new());
    }
    target
        .as_array_mut()
        .unwrap()
        .push(Value::Table(Table::new()));
}

fn traverse<'a>(root: &'a mut Value, path: &[&str]) -> &'a mut Value {
    let mut cur = root;
    for &key in path {
        // Lexical lifetimes :D
        let cur1 = cur;
        let cur2;

        // From the TOML spec:
        //
        // > Each double-bracketed sub-table will belong to the most recently
        // > defined table element above it.
        if cur1.is_array() {
            cur2 = cur1.as_array_mut().unwrap().last_mut().unwrap();
        } else {
            cur2 = cur1;
        };

        // We are about to index into this value, so it better be a table.
        if !cur2.is_table() {
            *cur2 = Value::Table(Table::new());
        }

        if !cur2.as_table().unwrap().contains_key(key) {
            // Insert an empty table for the next loop iteration to point to.
            let empty = Value::Table(Table::new());
            cur2.as_table_mut().unwrap().insert(key.to_owned(), empty);
        }

        // Step into the current table.
        cur = cur2.as_table_mut().unwrap().get_mut(key).unwrap();
    }
    cur
}