summaryrefslogtreecommitdiffstats
path: root/third_party/rust/paste/src/lib.rs
blob: 80c1b98f4696e40dafa77fa4d389a76439001492 (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
//! [![github]](https://github.com/dtolnay/paste) [![crates-io]](https://crates.io/crates/paste) [![docs-rs]](https://docs.rs/paste)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
//!
//! <br>
//!
//! The nightly-only [`concat_idents!`] macro in the Rust standard library is
//! notoriously underpowered in that its concatenated identifiers can only refer to
//! existing items, they can never be used to define something new.
//!
//! [`concat_idents!`]: https://doc.rust-lang.org/std/macro.concat_idents.html
//!
//! This crate provides a flexible way to paste together identifiers in a macro,
//! including using pasted identifiers to define new items.
//!
//! This approach works with any Rust compiler 1.31+.
//!
//! <br>
//!
//! # Pasting identifiers
//!
//! Within the `paste!` macro, identifiers inside `[<`...`>]` are pasted
//! together to form a single identifier.
//!
//! ```
//! use paste::paste;
//!
//! paste! {
//!     // Defines a const called `QRST`.
//!     const [<Q R S T>]: &str = "success!";
//! }
//!
//! fn main() {
//!     assert_eq!(
//!         paste! { [<Q R S T>].len() },
//!         8,
//!     );
//! }
//! ```
//!
//! <br><br>
//!
//! # More elaborate example
//!
//! The next example shows a macro that generates accessor methods for some
//! struct fields. It demonstrates how you might find it useful to bundle a
//! paste invocation inside of a macro\_rules macro.
//!
//! ```
//! use paste::paste;
//!
//! macro_rules! make_a_struct_and_getters {
//!     ($name:ident { $($field:ident),* }) => {
//!         // Define a struct. This expands to:
//!         //
//!         //     pub struct S {
//!         //         a: String,
//!         //         b: String,
//!         //         c: String,
//!         //     }
//!         pub struct $name {
//!             $(
//!                 $field: String,
//!             )*
//!         }
//!
//!         // Build an impl block with getters. This expands to:
//!         //
//!         //     impl S {
//!         //         pub fn get_a(&self) -> &str { &self.a }
//!         //         pub fn get_b(&self) -> &str { &self.b }
//!         //         pub fn get_c(&self) -> &str { &self.c }
//!         //     }
//!         paste! {
//!             impl $name {
//!                 $(
//!                     pub fn [<get_ $field>](&self) -> &str {
//!                         &self.$field
//!                     }
//!                 )*
//!             }
//!         }
//!     }
//! }
//!
//! make_a_struct_and_getters!(S { a, b, c });
//!
//! fn call_some_getters(s: &S) -> bool {
//!     s.get_a() == s.get_b() && s.get_c().is_empty()
//! }
//! #
//! # fn main() {}
//! ```
//!
//! <br><br>
//!
//! # Case conversion
//!
//! Use `$var:lower` or `$var:upper` in the segment list to convert an
//! interpolated segment to lower- or uppercase as part of the paste. For
//! example, `[<ld_ $reg:lower _expr>]` would paste to `ld_bc_expr` if invoked
//! with $reg=`Bc`.
//!
//! Use `$var:snake` to convert CamelCase input to snake\_case.
//! Use `$var:camel` to convert snake\_case to CamelCase.
//! These compose, so for example `$var:snake:upper` would give you SCREAMING\_CASE.
//!
//! The precise Unicode conversions are as defined by [`str::to_lowercase`] and
//! [`str::to_uppercase`].
//!
//! [`str::to_lowercase`]: https://doc.rust-lang.org/std/primitive.str.html#method.to_lowercase
//! [`str::to_uppercase`]: https://doc.rust-lang.org/std/primitive.str.html#method.to_uppercase
//!
//! <br>
//!
//! # Pasting documentation strings
//!
//! Within the `paste!` macro, arguments to a #\[doc ...\] attribute are
//! implicitly concatenated together to form a coherent documentation string.
//!
//! ```
//! use paste::paste;
//!
//! macro_rules! method_new {
//!     ($ret:ident) => {
//!         paste! {
//!             #[doc = "Create a new `" $ret "` object."]
//!             pub fn new() -> $ret { todo!() }
//!         }
//!     };
//! }
//!
//! pub struct Paste {}
//!
//! method_new!(Paste);  // expands to #[doc = "Create a new `Paste` object"]
//! ```

#![allow(
    clippy::derive_partial_eq_without_eq,
    clippy::doc_markdown,
    clippy::match_same_arms,
    clippy::module_name_repetitions,
    clippy::needless_doctest_main,
    clippy::too_many_lines
)]

extern crate proc_macro;

mod attr;
mod error;
mod segment;

use crate::attr::expand_attr;
use crate::error::{Error, Result};
use crate::segment::Segment;
use proc_macro::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
use std::char;
use std::iter;
use std::panic;

#[proc_macro]
pub fn paste(input: TokenStream) -> TokenStream {
    let mut contains_paste = false;
    let flatten_single_interpolation = true;
    match expand(
        input.clone(),
        &mut contains_paste,
        flatten_single_interpolation,
    ) {
        Ok(expanded) => {
            if contains_paste {
                expanded
            } else {
                input
            }
        }
        Err(err) => err.to_compile_error(),
    }
}

#[doc(hidden)]
#[proc_macro]
pub fn item(input: TokenStream) -> TokenStream {
    paste(input)
}

#[doc(hidden)]
#[proc_macro]
pub fn expr(input: TokenStream) -> TokenStream {
    paste(input)
}

fn expand(
    input: TokenStream,
    contains_paste: &mut bool,
    flatten_single_interpolation: bool,
) -> Result<TokenStream> {
    let mut expanded = TokenStream::new();
    let mut lookbehind = Lookbehind::Other;
    let mut prev_none_group = None::<Group>;
    let mut tokens = input.into_iter().peekable();
    loop {
        let token = tokens.next();
        if let Some(group) = prev_none_group.take() {
            if match (&token, tokens.peek()) {
                (Some(TokenTree::Punct(fst)), Some(TokenTree::Punct(snd))) => {
                    fst.as_char() == ':' && snd.as_char() == ':' && fst.spacing() == Spacing::Joint
                }
                _ => false,
            } {
                expanded.extend(group.stream());
                *contains_paste = true;
            } else {
                expanded.extend(iter::once(TokenTree::Group(group)));
            }
        }
        match token {
            Some(TokenTree::Group(group)) => {
                let delimiter = group.delimiter();
                let content = group.stream();
                let span = group.span();
                if delimiter == Delimiter::Bracket && is_paste_operation(&content) {
                    let segments = parse_bracket_as_segments(content, span)?;
                    let pasted = segment::paste(&segments)?;
                    let tokens = pasted_to_tokens(pasted, span)?;
                    expanded.extend(tokens);
                    *contains_paste = true;
                } else if flatten_single_interpolation
                    && delimiter == Delimiter::None
                    && is_single_interpolation_group(&content)
                {
                    expanded.extend(content);
                    *contains_paste = true;
                } else {
                    let mut group_contains_paste = false;
                    let is_attribute = delimiter == Delimiter::Bracket
                        && (lookbehind == Lookbehind::Pound || lookbehind == Lookbehind::PoundBang);
                    let mut nested = expand(
                        content,
                        &mut group_contains_paste,
                        flatten_single_interpolation && !is_attribute,
                    )?;
                    if is_attribute {
                        nested = expand_attr(nested, span, &mut group_contains_paste)?;
                    }
                    let group = if group_contains_paste {
                        let mut group = Group::new(delimiter, nested);
                        group.set_span(span);
                        *contains_paste = true;
                        group
                    } else {
                        group.clone()
                    };
                    if delimiter != Delimiter::None {
                        expanded.extend(iter::once(TokenTree::Group(group)));
                    } else if lookbehind == Lookbehind::DoubleColon {
                        expanded.extend(group.stream());
                        *contains_paste = true;
                    } else {
                        prev_none_group = Some(group);
                    }
                }
                lookbehind = Lookbehind::Other;
            }
            Some(TokenTree::Punct(punct)) => {
                lookbehind = match punct.as_char() {
                    ':' if lookbehind == Lookbehind::JointColon => Lookbehind::DoubleColon,
                    ':' if punct.spacing() == Spacing::Joint => Lookbehind::JointColon,
                    '#' => Lookbehind::Pound,
                    '!' if lookbehind == Lookbehind::Pound => Lookbehind::PoundBang,
                    _ => Lookbehind::Other,
                };
                expanded.extend(iter::once(TokenTree::Punct(punct)));
            }
            Some(other) => {
                lookbehind = Lookbehind::Other;
                expanded.extend(iter::once(other));
            }
            None => return Ok(expanded),
        }
    }
}

#[derive(PartialEq)]
enum Lookbehind {
    JointColon,
    DoubleColon,
    Pound,
    PoundBang,
    Other,
}

// https://github.com/dtolnay/paste/issues/26
fn is_single_interpolation_group(input: &TokenStream) -> bool {
    #[derive(PartialEq)]
    enum State {
        Init,
        Ident,
        Literal,
        Apostrophe,
        Lifetime,
        Colon1,
        Colon2,
    }

    let mut state = State::Init;
    for tt in input.clone() {
        state = match (state, &tt) {
            (State::Init, TokenTree::Ident(_)) => State::Ident,
            (State::Init, TokenTree::Literal(_)) => State::Literal,
            (State::Init, TokenTree::Punct(punct)) if punct.as_char() == '\'' => State::Apostrophe,
            (State::Apostrophe, TokenTree::Ident(_)) => State::Lifetime,
            (State::Ident, TokenTree::Punct(punct))
                if punct.as_char() == ':' && punct.spacing() == Spacing::Joint =>
            {
                State::Colon1
            }
            (State::Colon1, TokenTree::Punct(punct))
                if punct.as_char() == ':' && punct.spacing() == Spacing::Alone =>
            {
                State::Colon2
            }
            (State::Colon2, TokenTree::Ident(_)) => State::Ident,
            _ => return false,
        };
    }

    state == State::Ident || state == State::Literal || state == State::Lifetime
}

fn is_paste_operation(input: &TokenStream) -> bool {
    let mut tokens = input.clone().into_iter();

    match &tokens.next() {
        Some(TokenTree::Punct(punct)) if punct.as_char() == '<' => {}
        _ => return false,
    }

    let mut has_token = false;
    loop {
        match &tokens.next() {
            Some(TokenTree::Punct(punct)) if punct.as_char() == '>' => {
                return has_token && tokens.next().is_none();
            }
            Some(_) => has_token = true,
            None => return false,
        }
    }
}

fn parse_bracket_as_segments(input: TokenStream, scope: Span) -> Result<Vec<Segment>> {
    let mut tokens = input.into_iter().peekable();

    match &tokens.next() {
        Some(TokenTree::Punct(punct)) if punct.as_char() == '<' => {}
        Some(wrong) => return Err(Error::new(wrong.span(), "expected `<`")),
        None => return Err(Error::new(scope, "expected `[< ... >]`")),
    }

    let mut segments = segment::parse(&mut tokens)?;

    match &tokens.next() {
        Some(TokenTree::Punct(punct)) if punct.as_char() == '>' => {}
        Some(wrong) => return Err(Error::new(wrong.span(), "expected `>`")),
        None => return Err(Error::new(scope, "expected `[< ... >]`")),
    }

    if let Some(unexpected) = tokens.next() {
        return Err(Error::new(
            unexpected.span(),
            "unexpected input, expected `[< ... >]`",
        ));
    }

    for segment in &mut segments {
        if let Segment::String(string) = segment {
            if string.value.starts_with("'\\u{") {
                let hex = &string.value[4..string.value.len() - 2];
                if let Ok(unsigned) = u32::from_str_radix(hex, 16) {
                    if let Some(ch) = char::from_u32(unsigned) {
                        string.value.clear();
                        string.value.push(ch);
                        continue;
                    }
                }
            }
            if string.value.contains(&['#', '\\', '.', '+'][..])
                || string.value.starts_with("b'")
                || string.value.starts_with("b\"")
                || string.value.starts_with("br\"")
            {
                return Err(Error::new(string.span, "unsupported literal"));
            }
            let mut range = 0..string.value.len();
            if string.value.starts_with("r\"") {
                range.start += 2;
                range.end -= 1;
            } else if string.value.starts_with(&['"', '\''][..]) {
                range.start += 1;
                range.end -= 1;
            }
            string.value = string.value[range].replace('-', "_");
        }
    }

    Ok(segments)
}

fn pasted_to_tokens(mut pasted: String, span: Span) -> Result<TokenStream> {
    let mut tokens = TokenStream::new();

    #[cfg(not(no_literal_fromstr))]
    {
        use proc_macro::{LexError, Literal};
        use std::str::FromStr;

        if pasted.starts_with(|ch: char| ch.is_ascii_digit()) {
            let literal = match panic::catch_unwind(|| Literal::from_str(&pasted)) {
                Ok(Ok(literal)) => TokenTree::Literal(literal),
                Ok(Err(LexError { .. })) | Err(_) => {
                    return Err(Error::new(
                        span,
                        &format!("`{:?}` is not a valid literal", pasted),
                    ));
                }
            };
            tokens.extend(iter::once(literal));
            return Ok(tokens);
        }
    }

    if pasted.starts_with('\'') {
        let mut apostrophe = TokenTree::Punct(Punct::new('\'', Spacing::Joint));
        apostrophe.set_span(span);
        tokens.extend(iter::once(apostrophe));
        pasted.remove(0);
    }

    let ident = match panic::catch_unwind(|| Ident::new(&pasted, span)) {
        Ok(ident) => TokenTree::Ident(ident),
        Err(_) => {
            return Err(Error::new(
                span,
                &format!("`{:?}` is not a valid identifier", pasted),
            ));
        }
    };

    tokens.extend(iter::once(ident));
    Ok(tokens)
}