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
use rustc_ast::token::{self, Delimiter, Token};
use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
use rustc_ast_pretty::pprust::token_to_string;
use rustc_errors::{Applicability, PErr};
use rustc_span::symbol::kw;

use super::diagnostics::{
    report_suspicious_mismatch_block, same_indentation_level, TokenTreeDiagInfo,
};
use super::{StringReader, UnmatchedDelim};
use crate::Parser;

pub(super) struct TokenTreesReader<'psess, 'src> {
    string_reader: StringReader<'psess, 'src>,
    /// The "next" token, which has been obtained from the `StringReader` but
    /// not yet handled by the `TokenTreesReader`.
    token: Token,
    diag_info: TokenTreeDiagInfo,
}

impl<'psess, 'src> TokenTreesReader<'psess, 'src> {
    pub(super) fn lex_all_token_trees(
        string_reader: StringReader<'psess, 'src>,
    ) -> (TokenStream, Result<(), Vec<PErr<'psess>>>, Vec<UnmatchedDelim>) {
        let mut tt_reader = TokenTreesReader {
            string_reader,
            token: Token::dummy(),
            diag_info: TokenTreeDiagInfo::default(),
        };
        let (_open_spacing, stream, res) = tt_reader.lex_token_trees(/* is_delimited */ false);
        (stream, res, tt_reader.diag_info.unmatched_delims)
    }

    // Lex into a token stream. The `Spacing` in the result is that of the
    // opening delimiter.
    fn lex_token_trees(
        &mut self,
        is_delimited: bool,
    ) -> (Spacing, TokenStream, Result<(), Vec<PErr<'psess>>>) {
        // Move past the opening delimiter.
        let (_, open_spacing) = self.bump(false);

        let mut buf = Vec::new();
        loop {
            match self.token.kind {
                token::OpenDelim(delim) => buf.push(match self.lex_token_tree_open_delim(delim) {
                    Ok(val) => val,
                    Err(errs) => return (open_spacing, TokenStream::new(buf), Err(errs)),
                }),
                token::CloseDelim(delim) => {
                    return (
                        open_spacing,
                        TokenStream::new(buf),
                        if is_delimited { Ok(()) } else { Err(vec![self.close_delim_err(delim)]) },
                    );
                }
                token::Eof => {
                    return (
                        open_spacing,
                        TokenStream::new(buf),
                        if is_delimited { Err(vec![self.eof_err()]) } else { Ok(()) },
                    );
                }
                _ => {
                    // Get the next normal token.
                    let (this_tok, this_spacing) = self.bump(true);
                    buf.push(TokenTree::Token(this_tok, this_spacing));
                }
            }
        }
    }

    fn eof_err(&mut self) -> PErr<'psess> {
        let msg = "this file contains an unclosed delimiter";
        let mut err = self.string_reader.dcx().struct_span_err(self.token.span, msg);

        let unclosed_delimiter_show_limit = 5;
        let len = usize::min(unclosed_delimiter_show_limit, self.diag_info.open_braces.len());
        for &(_, span) in &self.diag_info.open_braces[..len] {
            err.span_label(span, "unclosed delimiter");
            self.diag_info.unmatched_delims.push(UnmatchedDelim {
                found_delim: None,
                found_span: self.token.span,
                unclosed_span: Some(span),
                candidate_span: None,
            });
        }

        if let Some((_, span)) = self.diag_info.open_braces.get(unclosed_delimiter_show_limit)
            && self.diag_info.open_braces.len() >= unclosed_delimiter_show_limit + 2
        {
            err.span_label(
                *span,
                format!(
                    "another {} unclosed delimiters begin from here",
                    self.diag_info.open_braces.len() - unclosed_delimiter_show_limit
                ),
            );
        }

        if let Some((delim, _)) = self.diag_info.open_braces.last() {
            report_suspicious_mismatch_block(
                &mut err,
                &self.diag_info,
                self.string_reader.psess.source_map(),
                *delim,
            )
        }
        err
    }

    fn lex_token_tree_open_delim(
        &mut self,
        open_delim: Delimiter,
    ) -> Result<TokenTree, Vec<PErr<'psess>>> {
        // The span for beginning of the delimited section.
        let pre_span = self.token.span;

        self.diag_info.open_braces.push((open_delim, self.token.span));

        // Lex the token trees within the delimiters.
        // We stop at any delimiter so we can try to recover if the user
        // uses an incorrect delimiter.
        let (open_spacing, tts, res) = self.lex_token_trees(/* is_delimited */ true);
        if let Err(errs) = res {
            return Err(self.unclosed_delim_err(tts, errs));
        }

        // Expand to cover the entire delimited token tree.
        let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
        let sm = self.string_reader.psess.source_map();

        let close_spacing = match self.token.kind {
            // Correct delimiter.
            token::CloseDelim(close_delim) if close_delim == open_delim => {
                let (open_brace, open_brace_span) = self.diag_info.open_braces.pop().unwrap();
                let close_brace_span = self.token.span;

                if tts.is_empty() && close_delim == Delimiter::Brace {
                    let empty_block_span = open_brace_span.to(close_brace_span);
                    if !sm.is_multiline(empty_block_span) {
                        // Only track if the block is in the form of `{}`, otherwise it is
                        // likely that it was written on purpose.
                        self.diag_info.empty_block_spans.push(empty_block_span);
                    }
                }

                // only add braces
                if let (Delimiter::Brace, Delimiter::Brace) = (open_brace, open_delim) {
                    // Add all the matching spans, we will sort by span later
                    self.diag_info.matching_block_spans.push((open_brace_span, close_brace_span));
                }

                // Move past the closing delimiter.
                self.bump(false).1
            }
            // Incorrect delimiter.
            token::CloseDelim(close_delim) => {
                let mut unclosed_delimiter = None;
                let mut candidate = None;

                if self.diag_info.last_unclosed_found_span != Some(self.token.span) {
                    // do not complain about the same unclosed delimiter multiple times
                    self.diag_info.last_unclosed_found_span = Some(self.token.span);
                    // This is a conservative error: only report the last unclosed
                    // delimiter. The previous unclosed delimiters could actually be
                    // closed! The lexer just hasn't gotten to them yet.
                    if let Some(&(_, sp)) = self.diag_info.open_braces.last() {
                        unclosed_delimiter = Some(sp);
                    };
                    for (brace, brace_span) in &self.diag_info.open_braces {
                        if same_indentation_level(sm, self.token.span, *brace_span)
                            && brace == &close_delim
                        {
                            // high likelihood of these two corresponding
                            candidate = Some(*brace_span);
                        }
                    }
                    let (_, _) = self.diag_info.open_braces.pop().unwrap();
                    self.diag_info.unmatched_delims.push(UnmatchedDelim {
                        found_delim: Some(close_delim),
                        found_span: self.token.span,
                        unclosed_span: unclosed_delimiter,
                        candidate_span: candidate,
                    });
                } else {
                    self.diag_info.open_braces.pop();
                }

                // If the incorrect delimiter matches an earlier opening
                // delimiter, then don't consume it (it can be used to
                // close the earlier one). Otherwise, consume it.
                // E.g., we try to recover from:
                // fn foo() {
                //     bar(baz(
                // }  // Incorrect delimiter but matches the earlier `{`
                if !self.diag_info.open_braces.iter().any(|&(b, _)| b == close_delim) {
                    self.bump(false).1
                } else {
                    // The choice of value here doesn't matter.
                    Spacing::Alone
                }
            }
            token::Eof => {
                // Silently recover, the EOF token will be seen again
                // and an error emitted then. Thus we don't pop from
                // self.open_braces here. The choice of spacing value here
                // doesn't matter.
                Spacing::Alone
            }
            _ => unreachable!(),
        };

        let spacing = DelimSpacing::new(open_spacing, close_spacing);

        Ok(TokenTree::Delimited(delim_span, spacing, open_delim, tts))
    }

    // Move on to the next token, returning the current token and its spacing.
    // Will glue adjacent single-char tokens together if `glue` is set.
    fn bump(&mut self, glue: bool) -> (Token, Spacing) {
        let (this_spacing, next_tok) = loop {
            let (next_tok, is_next_tok_preceded_by_whitespace) = self.string_reader.next_token();

            if is_next_tok_preceded_by_whitespace {
                break (Spacing::Alone, next_tok);
            } else if glue && let Some(glued) = self.token.glue(&next_tok) {
                self.token = glued;
            } else {
                let this_spacing = if next_tok.is_punct() {
                    Spacing::Joint
                } else if next_tok == token::Eof {
                    Spacing::Alone
                } else {
                    Spacing::JointHidden
                };
                break (this_spacing, next_tok);
            }
        };
        let this_tok = std::mem::replace(&mut self.token, next_tok);
        (this_tok, this_spacing)
    }

    fn unclosed_delim_err(
        &mut self,
        tts: TokenStream,
        mut errs: Vec<PErr<'psess>>,
    ) -> Vec<PErr<'psess>> {
        // If there are unclosed delims, see if there are diff markers and if so, point them
        // out instead of complaining about the unclosed delims.
        let mut parser = Parser::new(self.string_reader.psess, tts, None);
        let mut diff_errs = vec![];
        // Suggest removing a `{` we think appears in an `if`/`while` condition.
        // We want to suggest removing a `{` only if we think we're in an `if`/`while` condition,
        // but we have no way of tracking this in the lexer itself, so we piggyback on the parser.
        let mut in_cond = false;
        while parser.token != token::Eof {
            if let Err(diff_err) = parser.err_vcs_conflict_marker() {
                diff_errs.push(diff_err);
            } else if parser.is_keyword_ahead(0, &[kw::If, kw::While]) {
                in_cond = true;
            } else if matches!(
                parser.token.kind,
                token::CloseDelim(Delimiter::Brace) | token::FatArrow
            ) {
                // End of the `if`/`while` body, or the end of a `match` guard.
                in_cond = false;
            } else if in_cond && parser.token == token::OpenDelim(Delimiter::Brace) {
                // Store the `&&` and `let` to use their spans later when creating the diagnostic
                let maybe_andand = parser.look_ahead(1, |t| t.clone());
                let maybe_let = parser.look_ahead(2, |t| t.clone());
                if maybe_andand == token::OpenDelim(Delimiter::Brace) {
                    // This might be the beginning of the `if`/`while` body (i.e., the end of the
                    // condition).
                    in_cond = false;
                } else if maybe_andand == token::AndAnd && maybe_let.is_keyword(kw::Let) {
                    let mut err = parser.dcx().struct_span_err(
                        parser.token.span,
                        "found a `{` in the middle of a let-chain",
                    );
                    err.span_suggestion(
                        parser.token.span,
                        "consider removing this brace to parse the `let` as part of the same chain",
                        "",
                        Applicability::MachineApplicable,
                    );
                    err.span_label(
                        maybe_andand.span.to(maybe_let.span),
                        "you might have meant to continue the let-chain here",
                    );
                    errs.push(err);
                }
            }
            parser.bump();
        }
        if !diff_errs.is_empty() {
            for err in errs {
                err.cancel();
            }
            return diff_errs;
        }
        return errs;
    }

    fn close_delim_err(&mut self, delim: Delimiter) -> PErr<'psess> {
        // An unexpected closing delimiter (i.e., there is no matching opening delimiter).
        let token_str = token_to_string(&self.token);
        let msg = format!("unexpected closing delimiter: `{token_str}`");
        let mut err = self.string_reader.dcx().struct_span_err(self.token.span, msg);

        report_suspicious_mismatch_block(
            &mut err,
            &self.diag_info,
            self.string_reader.psess.source_map(),
            delim,
        );
        err.span_label(self.token.span, "unexpected closing delimiter");
        err
    }
}