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1a4d82fc | 1 | // Copyright 2015 The Rust Project Developers. See the COPYRIGHT |
223e47cc LB |
2 | // file at the top-level directory of this distribution and at |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
9e0c209e | 11 | use {ast, attr}; |
3157f602 | 12 | use syntax_pos::{Span, DUMMY_SP}; |
32a655c1 SL |
13 | use ext::base::{DummyResult, ExtCtxt, MacResult, SyntaxExtension}; |
14 | use ext::base::{NormalTT, TTMacroExpander}; | |
9e0c209e | 15 | use ext::expand::{Expansion, ExpansionKind}; |
1a4d82fc | 16 | use ext::tt::macro_parser::{Success, Error, Failure}; |
92a42be0 | 17 | use ext::tt::macro_parser::{MatchedSeq, MatchedNonterminal}; |
c30ab7b3 | 18 | use ext::tt::macro_parser::{parse, parse_failure_msg}; |
8bb4bdeb | 19 | use ext::tt::quoted; |
32a655c1 | 20 | use ext::tt::transcribe::transcribe; |
cc61c64b | 21 | use feature_gate::{self, emit_feature_err, Features, GateIssue}; |
476ff2be | 22 | use parse::{Directory, ParseSess}; |
476ff2be | 23 | use parse::parser::Parser; |
8bb4bdeb | 24 | use parse::token::{self, NtTT}; |
1a4d82fc | 25 | use parse::token::Token::*; |
476ff2be | 26 | use symbol::Symbol; |
8bb4bdeb | 27 | use tokenstream::{TokenStream, TokenTree}; |
223e47cc | 28 | |
7cac9316 XL |
29 | use std::collections::HashMap; |
30 | use std::collections::hash_map::Entry; | |
0531ce1d XL |
31 | |
32 | use rustc_data_structures::sync::Lrc; | |
1a4d82fc | 33 | |
9e0c209e SL |
34 | pub struct ParserAnyMacro<'a> { |
35 | parser: Parser<'a>, | |
9346a6ac AL |
36 | |
37 | /// Span of the expansion site of the macro this parser is for | |
38 | site_span: Span, | |
39 | /// The ident of the macro we're parsing | |
40 | macro_ident: ast::Ident | |
1a4d82fc JJ |
41 | } |
42 | ||
43 | impl<'a> ParserAnyMacro<'a> { | |
9e0c209e SL |
44 | pub fn make(mut self: Box<ParserAnyMacro<'a>>, kind: ExpansionKind) -> Expansion { |
45 | let ParserAnyMacro { site_span, macro_ident, ref mut parser } = *self; | |
46 | let expansion = panictry!(parser.parse_expansion(kind, true)); | |
47 | ||
48 | // We allow semicolons at the end of expressions -- e.g. the semicolon in | |
49 | // `macro_rules! m { () => { panic!(); } }` isn't parsed by `.parse_expr()`, | |
50 | // but `m!()` is allowed in expression positions (c.f. issue #34706). | |
51 | if kind == ExpansionKind::Expr && parser.token == token::Semi { | |
9cc50fc6 | 52 | parser.bump(); |
1a4d82fc | 53 | } |
e9174d1e | 54 | |
9e0c209e | 55 | // Make sure we don't have any tokens left to parse so we don't silently drop anything. |
83c7162d | 56 | let path = ast::Path::from_ident(macro_ident.with_span_pos(site_span)); |
cc61c64b | 57 | parser.ensure_complete_parse(&path, kind.name(), site_span); |
9e0c209e | 58 | expansion |
e9174d1e | 59 | } |
1a4d82fc JJ |
60 | } |
61 | ||
62 | struct MacroRulesMacroExpander { | |
63 | name: ast::Ident, | |
8bb4bdeb XL |
64 | lhses: Vec<quoted::TokenTree>, |
65 | rhses: Vec<quoted::TokenTree>, | |
92a42be0 | 66 | valid: bool, |
1a4d82fc JJ |
67 | } |
68 | ||
69 | impl TTMacroExpander for MacroRulesMacroExpander { | |
70 | fn expand<'cx>(&self, | |
71 | cx: &'cx mut ExtCtxt, | |
72 | sp: Span, | |
8bb4bdeb | 73 | input: TokenStream) |
1a4d82fc | 74 | -> Box<MacResult+'cx> { |
92a42be0 SL |
75 | if !self.valid { |
76 | return DummyResult::any(sp); | |
77 | } | |
1a4d82fc JJ |
78 | generic_extension(cx, |
79 | sp, | |
80 | self.name, | |
8bb4bdeb | 81 | input, |
85aaf69f SL |
82 | &self.lhses, |
83 | &self.rhses) | |
1a4d82fc JJ |
84 | } |
85 | } | |
86 | ||
7cac9316 XL |
87 | fn trace_macros_note(cx: &mut ExtCtxt, sp: Span, message: String) { |
88 | let sp = sp.macro_backtrace().last().map(|trace| trace.call_site).unwrap_or(sp); | |
3b2f2976 | 89 | let values: &mut Vec<String> = cx.expansions.entry(sp).or_insert_with(Vec::new); |
7cac9316 XL |
90 | values.push(message); |
91 | } | |
92 | ||
1a4d82fc | 93 | /// Given `lhses` and `rhses`, this is the new macro we create |
7cac9316 | 94 | fn generic_extension<'cx>(cx: &'cx mut ExtCtxt, |
1a4d82fc JJ |
95 | sp: Span, |
96 | name: ast::Ident, | |
8bb4bdeb XL |
97 | arg: TokenStream, |
98 | lhses: &[quoted::TokenTree], | |
99 | rhses: &[quoted::TokenTree]) | |
1a4d82fc JJ |
100 | -> Box<MacResult+'cx> { |
101 | if cx.trace_macros() { | |
7cac9316 | 102 | trace_macros_note(cx, sp, format!("expanding `{}! {{ {} }}`", name, arg)); |
1a4d82fc JJ |
103 | } |
104 | ||
105 | // Which arm's failure should we report? (the one furthest along) | |
106 | let mut best_fail_spot = DUMMY_SP; | |
c30ab7b3 | 107 | let mut best_fail_tok = None; |
1a4d82fc JJ |
108 | |
109 | for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers | |
92a42be0 | 110 | let lhs_tt = match *lhs { |
8bb4bdeb | 111 | quoted::TokenTree::Delimited(_, ref delim) => &delim.tts[..], |
3157f602 | 112 | _ => cx.span_bug(sp, "malformed macro lhs") |
92a42be0 SL |
113 | }; |
114 | ||
8bb4bdeb | 115 | match TokenTree::parse(cx, lhs_tt, arg.clone()) { |
92a42be0 SL |
116 | Success(named_matches) => { |
117 | let rhs = match rhses[i] { | |
118 | // ignore delimiters | |
8bb4bdeb | 119 | quoted::TokenTree::Delimited(_, ref delimed) => delimed.tts.clone(), |
3157f602 | 120 | _ => cx.span_bug(sp, "malformed macro rhs"), |
1a4d82fc | 121 | }; |
3b2f2976 XL |
122 | |
123 | let rhs_spans = rhs.iter().map(|t| t.span()).collect::<Vec<_>>(); | |
1a4d82fc | 124 | // rhs has holes ( `$id` and `$(...)` that need filled) |
3b2f2976 XL |
125 | let mut tts = transcribe(cx, Some(named_matches), rhs); |
126 | ||
127 | // Replace all the tokens for the corresponding positions in the macro, to maintain | |
128 | // proper positions in error reporting, while maintaining the macro_backtrace. | |
129 | if rhs_spans.len() == tts.len() { | |
130 | tts = tts.map_enumerated(|i, tt| { | |
131 | let mut tt = tt.clone(); | |
132 | let mut sp = rhs_spans[i]; | |
ea8adc8c | 133 | sp = sp.with_ctxt(tt.span().ctxt()); |
3b2f2976 XL |
134 | tt.set_span(sp); |
135 | tt | |
136 | }); | |
137 | } | |
7cac9316 XL |
138 | |
139 | if cx.trace_macros() { | |
140 | trace_macros_note(cx, sp, format!("to `{}`", tts)); | |
141 | } | |
142 | ||
476ff2be SL |
143 | let directory = Directory { |
144 | path: cx.current_expansion.module.directory.clone(), | |
145 | ownership: cx.current_expansion.directory_ownership, | |
54a0048b | 146 | }; |
7cac9316 | 147 | let mut p = Parser::new(cx.parse_sess(), tts, Some(directory), true, false); |
476ff2be | 148 | p.root_module_name = cx.current_expansion.module.mod_path.last() |
cc61c64b | 149 | .map(|id| id.name.as_str().to_string()); |
476ff2be | 150 | |
cc61c64b | 151 | p.process_potential_macro_variable(); |
1a4d82fc JJ |
152 | // Let the context choose how to interpret the result. |
153 | // Weird, but useful for X-macros. | |
d9579d0f | 154 | return Box::new(ParserAnyMacro { |
9e0c209e | 155 | parser: p, |
9346a6ac AL |
156 | |
157 | // Pass along the original expansion site and the name of the macro | |
158 | // so we can print a useful error message if the parse of the expanded | |
159 | // macro leaves unparsed tokens. | |
160 | site_span: sp, | |
161 | macro_ident: name | |
d9579d0f | 162 | }) |
92a42be0 | 163 | } |
ea8adc8c | 164 | Failure(sp, tok) => if sp.lo() >= best_fail_spot.lo() { |
1a4d82fc | 165 | best_fail_spot = sp; |
c30ab7b3 | 166 | best_fail_tok = Some(tok); |
92a42be0 SL |
167 | }, |
168 | Error(err_sp, ref msg) => { | |
169 | cx.span_fatal(err_sp.substitute_dummy(sp), &msg[..]) | |
1a4d82fc | 170 | } |
1a4d82fc JJ |
171 | } |
172 | } | |
e9174d1e | 173 | |
c30ab7b3 | 174 | let best_fail_msg = parse_failure_msg(best_fail_tok.expect("ran no matchers")); |
ea8adc8c XL |
175 | cx.span_err(best_fail_spot.substitute_dummy(sp), &best_fail_msg); |
176 | cx.trace_macros_diag(); | |
177 | DummyResult::any(sp) | |
1a4d82fc JJ |
178 | } |
179 | ||
180 | // Note that macro-by-example's input is also matched against a token tree: | |
181 | // $( $lhs:tt => $rhs:tt );+ | |
182 | // | |
183 | // Holy self-referential! | |
184 | ||
185 | /// Converts a `macro_rules!` invocation into a syntax extension. | |
0531ce1d | 186 | pub fn compile(sess: &ParseSess, features: &Features, def: &ast::Item) -> SyntaxExtension { |
476ff2be SL |
187 | let lhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("lhs")); |
188 | let rhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("rhs")); | |
223e47cc | 189 | |
7cac9316 XL |
190 | // Parse the macro_rules! invocation |
191 | let body = match def.node { | |
192 | ast::ItemKind::MacroDef(ref body) => body, | |
193 | _ => unreachable!(), | |
194 | }; | |
195 | ||
1a4d82fc | 196 | // The pattern that macro_rules matches. |
223e47cc | 197 | // The grammar for macro_rules! is: |
1a4d82fc | 198 | // $( $lhs:tt => $rhs:tt );+ |
223e47cc | 199 | // ...quasiquoting this would be nice. |
1a4d82fc | 200 | // These spans won't matter, anyways |
3157f602 | 201 | let argument_gram = vec![ |
0531ce1d | 202 | quoted::TokenTree::Sequence(DUMMY_SP, Lrc::new(quoted::SequenceRepetition { |
3157f602 | 203 | tts: vec![ |
8bb4bdeb XL |
204 | quoted::TokenTree::MetaVarDecl(DUMMY_SP, lhs_nm, ast::Ident::from_str("tt")), |
205 | quoted::TokenTree::Token(DUMMY_SP, token::FatArrow), | |
206 | quoted::TokenTree::MetaVarDecl(DUMMY_SP, rhs_nm, ast::Ident::from_str("tt")), | |
3157f602 | 207 | ], |
7cac9316 | 208 | separator: Some(if body.legacy { token::Semi } else { token::Comma }), |
8bb4bdeb | 209 | op: quoted::KleeneOp::OneOrMore, |
3157f602 | 210 | num_captures: 2, |
5bcae85e | 211 | })), |
3157f602 | 212 | // to phase into semicolon-termination instead of semicolon-separation |
0531ce1d | 213 | quoted::TokenTree::Sequence(DUMMY_SP, Lrc::new(quoted::SequenceRepetition { |
8bb4bdeb | 214 | tts: vec![quoted::TokenTree::Token(DUMMY_SP, token::Semi)], |
3157f602 | 215 | separator: None, |
8bb4bdeb | 216 | op: quoted::KleeneOp::ZeroOrMore, |
3157f602 | 217 | num_captures: 0 |
5bcae85e | 218 | })), |
3157f602 | 219 | ]; |
223e47cc | 220 | |
7cac9316 | 221 | let argument_map = match parse(sess, body.stream(), &argument_gram, None, true) { |
e9174d1e | 222 | Success(m) => m, |
c30ab7b3 SL |
223 | Failure(sp, tok) => { |
224 | let s = parse_failure_msg(tok); | |
2c00a5a8 | 225 | sess.span_diagnostic.span_fatal(sp.substitute_dummy(def.span), &s).raise(); |
c30ab7b3 SL |
226 | } |
227 | Error(sp, s) => { | |
2c00a5a8 | 228 | sess.span_diagnostic.span_fatal(sp.substitute_dummy(def.span), &s).raise(); |
e9174d1e SL |
229 | } |
230 | }; | |
223e47cc | 231 | |
92a42be0 SL |
232 | let mut valid = true; |
233 | ||
223e47cc | 234 | // Extract the arguments: |
7cac9316 | 235 | let lhses = match *argument_map[&lhs_nm] { |
92a42be0 | 236 | MatchedSeq(ref s, _) => { |
c30ab7b3 | 237 | s.iter().map(|m| { |
041b39d2 | 238 | if let MatchedNonterminal(ref nt) = *m { |
c30ab7b3 | 239 | if let NtTT(ref tt) = **nt { |
2c00a5a8 XL |
240 | let tt = quoted::parse(tt.clone().into(), true, sess, features, &def.attrs) |
241 | .pop().unwrap(); | |
041b39d2 | 242 | valid &= check_lhs_nt_follows(sess, features, &def.attrs, &tt); |
8bb4bdeb | 243 | return tt; |
c30ab7b3 | 244 | } |
3157f602 | 245 | } |
c30ab7b3 | 246 | sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
8bb4bdeb | 247 | }).collect::<Vec<quoted::TokenTree>>() |
92a42be0 | 248 | } |
9e0c209e | 249 | _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
223e47cc LB |
250 | }; |
251 | ||
7cac9316 | 252 | let rhses = match *argument_map[&rhs_nm] { |
92a42be0 | 253 | MatchedSeq(ref s, _) => { |
c30ab7b3 | 254 | s.iter().map(|m| { |
041b39d2 | 255 | if let MatchedNonterminal(ref nt) = *m { |
c30ab7b3 | 256 | if let NtTT(ref tt) = **nt { |
2c00a5a8 XL |
257 | return quoted::parse(tt.clone().into(), false, sess, features, &def.attrs) |
258 | .pop().unwrap(); | |
c30ab7b3 SL |
259 | } |
260 | } | |
261 | sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") | |
8bb4bdeb | 262 | }).collect::<Vec<quoted::TokenTree>>() |
92a42be0 | 263 | } |
9e0c209e | 264 | _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured rhs") |
223e47cc LB |
265 | }; |
266 | ||
92a42be0 | 267 | for rhs in &rhses { |
9e0c209e SL |
268 | valid &= check_rhs(sess, rhs); |
269 | } | |
270 | ||
271 | // don't abort iteration early, so that errors for multiple lhses can be reported | |
272 | for lhs in &lhses { | |
273 | valid &= check_lhs_no_empty_seq(sess, &[lhs.clone()]) | |
92a42be0 SL |
274 | } |
275 | ||
3b2f2976 | 276 | let expander: Box<_> = Box::new(MacroRulesMacroExpander { |
1a4d82fc | 277 | name: def.ident, |
3b2f2976 XL |
278 | lhses, |
279 | rhses, | |
280 | valid, | |
d9579d0f | 281 | }); |
223e47cc | 282 | |
7cac9316 XL |
283 | if body.legacy { |
284 | let allow_internal_unstable = attr::contains_name(&def.attrs, "allow_internal_unstable"); | |
3b2f2976 | 285 | let allow_internal_unsafe = attr::contains_name(&def.attrs, "allow_internal_unsafe"); |
0531ce1d XL |
286 | |
287 | let unstable_feature = attr::find_stability(&sess.span_diagnostic, | |
288 | &def.attrs, def.span).and_then(|stability| { | |
289 | if let attr::StabilityLevel::Unstable { issue, .. } = stability.level { | |
290 | Some((stability.feature, issue)) | |
291 | } else { | |
292 | None | |
293 | } | |
294 | }); | |
295 | ||
3b2f2976 XL |
296 | NormalTT { |
297 | expander, | |
298 | def_info: Some((def.id, def.span)), | |
299 | allow_internal_unstable, | |
0531ce1d XL |
300 | allow_internal_unsafe, |
301 | unstable_feature | |
3b2f2976 | 302 | } |
7cac9316 | 303 | } else { |
3b2f2976 | 304 | SyntaxExtension::DeclMacro(expander, Some((def.id, def.span))) |
7cac9316 | 305 | } |
1a4d82fc JJ |
306 | } |
307 | ||
cc61c64b | 308 | fn check_lhs_nt_follows(sess: &ParseSess, |
0531ce1d | 309 | features: &Features, |
041b39d2 | 310 | attrs: &[ast::Attribute], |
cc61c64b | 311 | lhs: "ed::TokenTree) -> bool { |
92a42be0 SL |
312 | // lhs is going to be like TokenTree::Delimited(...), where the |
313 | // entire lhs is those tts. Or, it can be a "bare sequence", not wrapped in parens. | |
7cac9316 | 314 | if let quoted::TokenTree::Delimited(_, ref tts) = *lhs { |
041b39d2 | 315 | check_matcher(sess, features, attrs, &tts.tts) |
7cac9316 XL |
316 | } else { |
317 | let msg = "invalid macro matcher; matchers must be contained in balanced delimiters"; | |
318 | sess.span_diagnostic.span_err(lhs.span(), msg); | |
319 | false | |
3157f602 | 320 | } |
1a4d82fc JJ |
321 | // we don't abort on errors on rejection, the driver will do that for us |
322 | // after parsing/expansion. we can report every error in every macro this way. | |
323 | } | |
324 | ||
9e0c209e SL |
325 | /// Check that the lhs contains no repetition which could match an empty token |
326 | /// tree, because then the matcher would hang indefinitely. | |
8bb4bdeb XL |
327 | fn check_lhs_no_empty_seq(sess: &ParseSess, tts: &[quoted::TokenTree]) -> bool { |
328 | use self::quoted::TokenTree; | |
9e0c209e SL |
329 | for tt in tts { |
330 | match *tt { | |
041b39d2 | 331 | TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => (), |
9e0c209e SL |
332 | TokenTree::Delimited(_, ref del) => if !check_lhs_no_empty_seq(sess, &del.tts) { |
333 | return false; | |
334 | }, | |
335 | TokenTree::Sequence(span, ref seq) => { | |
7cac9316 XL |
336 | if seq.separator.is_none() && seq.tts.iter().all(|seq_tt| { |
337 | match *seq_tt { | |
041b39d2 | 338 | TokenTree::MetaVarDecl(_, _, id) => id.name == "vis", |
7cac9316 XL |
339 | TokenTree::Sequence(_, ref sub_seq) => |
340 | sub_seq.op == quoted::KleeneOp::ZeroOrMore, | |
341 | _ => false, | |
9e0c209e | 342 | } |
7cac9316 XL |
343 | }) { |
344 | sess.span_diagnostic.span_err(span, "repetition matches empty token tree"); | |
345 | return false; | |
9e0c209e SL |
346 | } |
347 | if !check_lhs_no_empty_seq(sess, &seq.tts) { | |
348 | return false; | |
349 | } | |
350 | } | |
351 | } | |
352 | } | |
353 | ||
354 | true | |
355 | } | |
356 | ||
8bb4bdeb | 357 | fn check_rhs(sess: &ParseSess, rhs: "ed::TokenTree) -> bool { |
92a42be0 | 358 | match *rhs { |
8bb4bdeb XL |
359 | quoted::TokenTree::Delimited(..) => return true, |
360 | _ => sess.span_diagnostic.span_err(rhs.span(), "macro rhs must be delimited") | |
92a42be0 SL |
361 | } |
362 | false | |
363 | } | |
364 | ||
cc61c64b | 365 | fn check_matcher(sess: &ParseSess, |
0531ce1d | 366 | features: &Features, |
041b39d2 | 367 | attrs: &[ast::Attribute], |
cc61c64b | 368 | matcher: &[quoted::TokenTree]) -> bool { |
9cc50fc6 SL |
369 | let first_sets = FirstSets::new(matcher); |
370 | let empty_suffix = TokenSet::empty(); | |
9e0c209e | 371 | let err = sess.span_diagnostic.err_count(); |
041b39d2 | 372 | check_matcher_core(sess, features, attrs, &first_sets, matcher, &empty_suffix); |
9e0c209e | 373 | err == sess.span_diagnostic.err_count() |
9cc50fc6 SL |
374 | } |
375 | ||
376 | // The FirstSets for a matcher is a mapping from subsequences in the | |
377 | // matcher to the FIRST set for that subsequence. | |
378 | // | |
379 | // This mapping is partially precomputed via a backwards scan over the | |
380 | // token trees of the matcher, which provides a mapping from each | |
381 | // repetition sequence to its FIRST set. | |
382 | // | |
383 | // (Hypothetically sequences should be uniquely identifiable via their | |
384 | // spans, though perhaps that is false e.g. for macro-generated macros | |
385 | // that do not try to inject artificial span information. My plan is | |
386 | // to try to catch such cases ahead of time and not include them in | |
387 | // the precomputed mapping.) | |
388 | struct FirstSets { | |
389 | // this maps each TokenTree::Sequence `$(tt ...) SEP OP` that is uniquely identified by its | |
390 | // span in the original matcher to the First set for the inner sequence `tt ...`. | |
391 | // | |
392 | // If two sequences have the same span in a matcher, then map that | |
393 | // span to None (invalidating the mapping here and forcing the code to | |
394 | // use a slow path). | |
395 | first: HashMap<Span, Option<TokenSet>>, | |
396 | } | |
397 | ||
398 | impl FirstSets { | |
8bb4bdeb XL |
399 | fn new(tts: &[quoted::TokenTree]) -> FirstSets { |
400 | use self::quoted::TokenTree; | |
401 | ||
9cc50fc6 SL |
402 | let mut sets = FirstSets { first: HashMap::new() }; |
403 | build_recur(&mut sets, tts); | |
404 | return sets; | |
405 | ||
406 | // walks backward over `tts`, returning the FIRST for `tts` | |
407 | // and updating `sets` at the same time for all sequence | |
408 | // substructure we find within `tts`. | |
409 | fn build_recur(sets: &mut FirstSets, tts: &[TokenTree]) -> TokenSet { | |
410 | let mut first = TokenSet::empty(); | |
411 | for tt in tts.iter().rev() { | |
412 | match *tt { | |
041b39d2 | 413 | TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => { |
8bb4bdeb | 414 | first.replace_with(tt.clone()); |
9cc50fc6 | 415 | } |
32a655c1 | 416 | TokenTree::Delimited(span, ref delimited) => { |
9cc50fc6 | 417 | build_recur(sets, &delimited.tts[..]); |
8bb4bdeb | 418 | first.replace_with(delimited.open_tt(span)); |
9cc50fc6 SL |
419 | } |
420 | TokenTree::Sequence(sp, ref seq_rep) => { | |
421 | let subfirst = build_recur(sets, &seq_rep.tts[..]); | |
422 | ||
423 | match sets.first.entry(sp) { | |
424 | Entry::Vacant(vac) => { | |
425 | vac.insert(Some(subfirst.clone())); | |
426 | } | |
427 | Entry::Occupied(mut occ) => { | |
428 | // if there is already an entry, then a span must have collided. | |
429 | // This should not happen with typical macro_rules macros, | |
430 | // but syntax extensions need not maintain distinct spans, | |
431 | // so distinct syntax trees can be assigned the same span. | |
432 | // In such a case, the map cannot be trusted; so mark this | |
433 | // entry as unusable. | |
434 | occ.insert(None); | |
435 | } | |
436 | } | |
437 | ||
438 | // If the sequence contents can be empty, then the first | |
439 | // token could be the separator token itself. | |
440 | ||
441 | if let (Some(ref sep), true) = (seq_rep.separator.clone(), | |
442 | subfirst.maybe_empty) { | |
8bb4bdeb | 443 | first.add_one_maybe(TokenTree::Token(sp, sep.clone())); |
9cc50fc6 SL |
444 | } |
445 | ||
446 | // Reverse scan: Sequence comes before `first`. | |
8bb4bdeb | 447 | if subfirst.maybe_empty || seq_rep.op == quoted::KleeneOp::ZeroOrMore { |
9cc50fc6 SL |
448 | // If sequence is potentially empty, then |
449 | // union them (preserving first emptiness). | |
450 | first.add_all(&TokenSet { maybe_empty: true, ..subfirst }); | |
451 | } else { | |
452 | // Otherwise, sequence guaranteed | |
453 | // non-empty; replace first. | |
454 | first = subfirst; | |
455 | } | |
456 | } | |
457 | } | |
458 | } | |
459 | ||
7cac9316 | 460 | first |
9cc50fc6 SL |
461 | } |
462 | } | |
463 | ||
464 | // walks forward over `tts` until all potential FIRST tokens are | |
465 | // identified. | |
8bb4bdeb XL |
466 | fn first(&self, tts: &[quoted::TokenTree]) -> TokenSet { |
467 | use self::quoted::TokenTree; | |
468 | ||
9cc50fc6 SL |
469 | let mut first = TokenSet::empty(); |
470 | for tt in tts.iter() { | |
471 | assert!(first.maybe_empty); | |
472 | match *tt { | |
041b39d2 | 473 | TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => { |
8bb4bdeb | 474 | first.add_one(tt.clone()); |
9cc50fc6 SL |
475 | return first; |
476 | } | |
32a655c1 | 477 | TokenTree::Delimited(span, ref delimited) => { |
8bb4bdeb | 478 | first.add_one(delimited.open_tt(span)); |
9cc50fc6 SL |
479 | return first; |
480 | } | |
481 | TokenTree::Sequence(sp, ref seq_rep) => { | |
482 | match self.first.get(&sp) { | |
483 | Some(&Some(ref subfirst)) => { | |
484 | ||
485 | // If the sequence contents can be empty, then the first | |
486 | // token could be the separator token itself. | |
487 | ||
488 | if let (Some(ref sep), true) = (seq_rep.separator.clone(), | |
489 | subfirst.maybe_empty) { | |
8bb4bdeb | 490 | first.add_one_maybe(TokenTree::Token(sp, sep.clone())); |
9cc50fc6 SL |
491 | } |
492 | ||
493 | assert!(first.maybe_empty); | |
494 | first.add_all(subfirst); | |
3157f602 | 495 | if subfirst.maybe_empty || |
8bb4bdeb | 496 | seq_rep.op == quoted::KleeneOp::ZeroOrMore { |
9cc50fc6 SL |
497 | // continue scanning for more first |
498 | // tokens, but also make sure we | |
499 | // restore empty-tracking state | |
500 | first.maybe_empty = true; | |
501 | continue; | |
502 | } else { | |
503 | return first; | |
504 | } | |
505 | } | |
506 | ||
507 | Some(&None) => { | |
508 | panic!("assume all sequences have (unique) spans for now"); | |
509 | } | |
510 | ||
511 | None => { | |
512 | panic!("We missed a sequence during FirstSets construction"); | |
513 | } | |
514 | } | |
515 | } | |
516 | } | |
517 | } | |
518 | ||
519 | // we only exit the loop if `tts` was empty or if every | |
520 | // element of `tts` matches the empty sequence. | |
521 | assert!(first.maybe_empty); | |
7cac9316 | 522 | first |
9cc50fc6 SL |
523 | } |
524 | } | |
525 | ||
8bb4bdeb XL |
526 | // A set of `quoted::TokenTree`s, which may include `TokenTree::Match`s |
527 | // (for macro-by-example syntactic variables). It also carries the | |
9cc50fc6 SL |
528 | // `maybe_empty` flag; that is true if and only if the matcher can |
529 | // match an empty token sequence. | |
530 | // | |
531 | // The First set is computed on submatchers like `$($a:expr b),* $(c)* d`, | |
532 | // which has corresponding FIRST = {$a:expr, c, d}. | |
533 | // Likewise, `$($a:expr b),* $(c)+ d` has FIRST = {$a:expr, c}. | |
534 | // | |
535 | // (Notably, we must allow for *-op to occur zero times.) | |
536 | #[derive(Clone, Debug)] | |
537 | struct TokenSet { | |
8bb4bdeb | 538 | tokens: Vec<quoted::TokenTree>, |
9cc50fc6 SL |
539 | maybe_empty: bool, |
540 | } | |
541 | ||
542 | impl TokenSet { | |
543 | // Returns a set for the empty sequence. | |
544 | fn empty() -> Self { TokenSet { tokens: Vec::new(), maybe_empty: true } } | |
545 | ||
546 | // Returns the set `{ tok }` for the single-token (and thus | |
547 | // non-empty) sequence [tok]. | |
8bb4bdeb | 548 | fn singleton(tok: quoted::TokenTree) -> Self { |
9cc50fc6 SL |
549 | TokenSet { tokens: vec![tok], maybe_empty: false } |
550 | } | |
551 | ||
552 | // Changes self to be the set `{ tok }`. | |
553 | // Since `tok` is always present, marks self as non-empty. | |
8bb4bdeb | 554 | fn replace_with(&mut self, tok: quoted::TokenTree) { |
9cc50fc6 SL |
555 | self.tokens.clear(); |
556 | self.tokens.push(tok); | |
557 | self.maybe_empty = false; | |
558 | } | |
559 | ||
560 | // Changes self to be the empty set `{}`; meant for use when | |
561 | // the particular token does not matter, but we want to | |
562 | // record that it occurs. | |
563 | fn replace_with_irrelevant(&mut self) { | |
564 | self.tokens.clear(); | |
565 | self.maybe_empty = false; | |
566 | } | |
567 | ||
568 | // Adds `tok` to the set for `self`, marking sequence as non-empy. | |
8bb4bdeb | 569 | fn add_one(&mut self, tok: quoted::TokenTree) { |
9cc50fc6 SL |
570 | if !self.tokens.contains(&tok) { |
571 | self.tokens.push(tok); | |
572 | } | |
573 | self.maybe_empty = false; | |
574 | } | |
575 | ||
576 | // Adds `tok` to the set for `self`. (Leaves `maybe_empty` flag alone.) | |
8bb4bdeb | 577 | fn add_one_maybe(&mut self, tok: quoted::TokenTree) { |
9cc50fc6 SL |
578 | if !self.tokens.contains(&tok) { |
579 | self.tokens.push(tok); | |
580 | } | |
581 | } | |
582 | ||
583 | // Adds all elements of `other` to this. | |
584 | // | |
585 | // (Since this is a set, we filter out duplicates.) | |
586 | // | |
587 | // If `other` is potentially empty, then preserves the previous | |
588 | // setting of the empty flag of `self`. If `other` is guaranteed | |
589 | // non-empty, then `self` is marked non-empty. | |
590 | fn add_all(&mut self, other: &Self) { | |
591 | for tok in &other.tokens { | |
592 | if !self.tokens.contains(tok) { | |
593 | self.tokens.push(tok.clone()); | |
594 | } | |
595 | } | |
596 | if !other.maybe_empty { | |
597 | self.maybe_empty = false; | |
598 | } | |
599 | } | |
600 | } | |
601 | ||
602 | // Checks that `matcher` is internally consistent and that it | |
603 | // can legally by followed by a token N, for all N in `follow`. | |
604 | // (If `follow` is empty, then it imposes no constraint on | |
605 | // the `matcher`.) | |
606 | // | |
607 | // Returns the set of NT tokens that could possibly come last in | |
608 | // `matcher`. (If `matcher` matches the empty sequence, then | |
609 | // `maybe_empty` will be set to true.) | |
610 | // | |
611 | // Requires that `first_sets` is pre-computed for `matcher`; | |
612 | // see `FirstSets::new`. | |
9e0c209e | 613 | fn check_matcher_core(sess: &ParseSess, |
0531ce1d | 614 | features: &Features, |
041b39d2 | 615 | attrs: &[ast::Attribute], |
9cc50fc6 | 616 | first_sets: &FirstSets, |
8bb4bdeb | 617 | matcher: &[quoted::TokenTree], |
3157f602 | 618 | follow: &TokenSet) -> TokenSet { |
8bb4bdeb | 619 | use self::quoted::TokenTree; |
9cc50fc6 SL |
620 | |
621 | let mut last = TokenSet::empty(); | |
622 | ||
623 | // 2. For each token and suffix [T, SUFFIX] in M: | |
624 | // ensure that T can be followed by SUFFIX, and if SUFFIX may be empty, | |
625 | // then ensure T can also be followed by any element of FOLLOW. | |
626 | 'each_token: for i in 0..matcher.len() { | |
627 | let token = &matcher[i]; | |
628 | let suffix = &matcher[i+1..]; | |
629 | ||
630 | let build_suffix_first = || { | |
631 | let mut s = first_sets.first(suffix); | |
632 | if s.maybe_empty { s.add_all(follow); } | |
7cac9316 | 633 | s |
9cc50fc6 SL |
634 | }; |
635 | ||
636 | // (we build `suffix_first` on demand below; you can tell | |
637 | // which cases are supposed to fall through by looking for the | |
638 | // initialization of this variable.) | |
639 | let suffix_first; | |
640 | ||
641 | // First, update `last` so that it corresponds to the set | |
642 | // of NT tokens that might end the sequence `... token`. | |
643 | match *token { | |
041b39d2 | 644 | TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => { |
9cc50fc6 | 645 | let can_be_followed_by_any; |
041b39d2 | 646 | if let Err(bad_frag) = has_legal_fragment_specifier(sess, features, attrs, token) { |
9e0c209e | 647 | let msg = format!("invalid fragment specifier `{}`", bad_frag); |
8bb4bdeb | 648 | sess.span_diagnostic.struct_span_err(token.span(), &msg) |
cc61c64b XL |
649 | .help("valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, \ |
650 | `pat`, `ty`, `path`, `meta`, `tt`, `item` and `vis`") | |
3157f602 | 651 | .emit(); |
9cc50fc6 SL |
652 | // (This eliminates false positives and duplicates |
653 | // from error messages.) | |
654 | can_be_followed_by_any = true; | |
655 | } else { | |
8bb4bdeb | 656 | can_be_followed_by_any = token_can_be_followed_by_any(token); |
9cc50fc6 SL |
657 | } |
658 | ||
659 | if can_be_followed_by_any { | |
660 | // don't need to track tokens that work with any, | |
661 | last.replace_with_irrelevant(); | |
662 | // ... and don't need to check tokens that can be | |
663 | // followed by anything against SUFFIX. | |
664 | continue 'each_token; | |
665 | } else { | |
8bb4bdeb | 666 | last.replace_with(token.clone()); |
9cc50fc6 SL |
667 | suffix_first = build_suffix_first(); |
668 | } | |
669 | } | |
32a655c1 | 670 | TokenTree::Delimited(span, ref d) => { |
8bb4bdeb | 671 | let my_suffix = TokenSet::singleton(d.close_tt(span)); |
041b39d2 | 672 | check_matcher_core(sess, features, attrs, first_sets, &d.tts, &my_suffix); |
9cc50fc6 SL |
673 | // don't track non NT tokens |
674 | last.replace_with_irrelevant(); | |
675 | ||
676 | // also, we don't need to check delimited sequences | |
677 | // against SUFFIX | |
678 | continue 'each_token; | |
679 | } | |
680 | TokenTree::Sequence(sp, ref seq_rep) => { | |
681 | suffix_first = build_suffix_first(); | |
682 | // The trick here: when we check the interior, we want | |
683 | // to include the separator (if any) as a potential | |
684 | // (but not guaranteed) element of FOLLOW. So in that | |
685 | // case, we make a temp copy of suffix and stuff | |
686 | // delimiter in there. | |
687 | // | |
688 | // FIXME: Should I first scan suffix_first to see if | |
689 | // delimiter is already in it before I go through the | |
690 | // work of cloning it? But then again, this way I may | |
691 | // get a "tighter" span? | |
692 | let mut new; | |
693 | let my_suffix = if let Some(ref u) = seq_rep.separator { | |
694 | new = suffix_first.clone(); | |
8bb4bdeb | 695 | new.add_one_maybe(TokenTree::Token(sp, u.clone())); |
9cc50fc6 SL |
696 | &new |
697 | } else { | |
698 | &suffix_first | |
699 | }; | |
700 | ||
701 | // At this point, `suffix_first` is built, and | |
702 | // `my_suffix` is some TokenSet that we can use | |
703 | // for checking the interior of `seq_rep`. | |
041b39d2 XL |
704 | let next = check_matcher_core(sess, |
705 | features, | |
706 | attrs, | |
707 | first_sets, | |
708 | &seq_rep.tts, | |
709 | my_suffix); | |
9cc50fc6 SL |
710 | if next.maybe_empty { |
711 | last.add_all(&next); | |
712 | } else { | |
713 | last = next; | |
714 | } | |
715 | ||
716 | // the recursive call to check_matcher_core already ran the 'each_last | |
717 | // check below, so we can just keep going forward here. | |
718 | continue 'each_token; | |
719 | } | |
720 | } | |
721 | ||
722 | // (`suffix_first` guaranteed initialized once reaching here.) | |
723 | ||
724 | // Now `last` holds the complete set of NT tokens that could | |
725 | // end the sequence before SUFFIX. Check that every one works with `suffix`. | |
8bb4bdeb XL |
726 | 'each_last: for token in &last.tokens { |
727 | if let TokenTree::MetaVarDecl(_, ref name, ref frag_spec) = *token { | |
728 | for next_token in &suffix_first.tokens { | |
9e0c209e | 729 | match is_in_follow(next_token, &frag_spec.name.as_str()) { |
3157f602 | 730 | Err((msg, help)) => { |
8bb4bdeb XL |
731 | sess.span_diagnostic.struct_span_err(next_token.span(), &msg) |
732 | .help(help).emit(); | |
9cc50fc6 SL |
733 | // don't bother reporting every source of |
734 | // conflict for a particular element of `last`. | |
735 | continue 'each_last; | |
736 | } | |
737 | Ok(true) => {} | |
738 | Ok(false) => { | |
739 | let may_be = if last.tokens.len() == 1 && | |
740 | suffix_first.tokens.len() == 1 | |
741 | { | |
742 | "is" | |
743 | } else { | |
744 | "may be" | |
745 | }; | |
746 | ||
9e0c209e | 747 | sess.span_diagnostic.span_err( |
8bb4bdeb | 748 | next_token.span(), |
9cc50fc6 SL |
749 | &format!("`${name}:{frag}` {may_be} followed by `{next}`, which \ |
750 | is not allowed for `{frag}` fragments", | |
751 | name=name, | |
752 | frag=frag_spec, | |
8bb4bdeb | 753 | next=quoted_tt_to_string(next_token), |
3157f602 XL |
754 | may_be=may_be) |
755 | ); | |
9cc50fc6 SL |
756 | } |
757 | } | |
758 | } | |
759 | } | |
760 | } | |
761 | } | |
762 | last | |
763 | } | |
764 | ||
8bb4bdeb XL |
765 | fn token_can_be_followed_by_any(tok: "ed::TokenTree) -> bool { |
766 | if let quoted::TokenTree::MetaVarDecl(_, _, frag_spec) = *tok { | |
9cc50fc6 SL |
767 | frag_can_be_followed_by_any(&frag_spec.name.as_str()) |
768 | } else { | |
769 | // (Non NT's can always be followed by anthing in matchers.) | |
770 | true | |
771 | } | |
772 | } | |
773 | ||
774 | /// True if a fragment of type `frag` can be followed by any sort of | |
775 | /// token. We use this (among other things) as a useful approximation | |
776 | /// for when `frag` can be followed by a repetition like `$(...)*` or | |
777 | /// `$(...)+`. In general, these can be a bit tricky to reason about, | |
778 | /// so we adopt a conservative position that says that any fragment | |
779 | /// specifier which consumes at most one token tree can be followed by | |
780 | /// a fragment specifier (indeed, these fragments can be followed by | |
781 | /// ANYTHING without fear of future compatibility hazards). | |
782 | fn frag_can_be_followed_by_any(frag: &str) -> bool { | |
783 | match frag { | |
ff7c6d11 XL |
784 | "item" | // always terminated by `}` or `;` |
785 | "block" | // exactly one token tree | |
786 | "ident" | // exactly one token tree | |
787 | "meta" | // exactly one token tree | |
788 | "lifetime" | // exactly one token tree | |
3157f602 | 789 | "tt" => // exactly one token tree |
62682a34 SL |
790 | true, |
791 | ||
792 | _ => | |
793 | false, | |
794 | } | |
795 | } | |
796 | ||
797 | /// True if `frag` can legally be followed by the token `tok`. For | |
9cc50fc6 | 798 | /// fragments that can consume an unbounded number of tokens, `tok` |
62682a34 SL |
799 | /// must be within a well-defined follow set. This is intended to |
800 | /// guarantee future compatibility: for example, without this rule, if | |
801 | /// we expanded `expr` to include a new binary operator, we might | |
802 | /// break macros that were relying on that binary operator as a | |
803 | /// separator. | |
9cc50fc6 | 804 | // when changing this do not forget to update doc/book/macros.md! |
8bb4bdeb XL |
805 | fn is_in_follow(tok: "ed::TokenTree, frag: &str) -> Result<bool, (String, &'static str)> { |
806 | use self::quoted::TokenTree; | |
807 | ||
808 | if let TokenTree::Token(_, token::CloseDelim(_)) = *tok { | |
62682a34 SL |
809 | // closing a token tree can never be matched by any fragment; |
810 | // iow, we always require that `(` and `)` match, etc. | |
85aaf69f SL |
811 | Ok(true) |
812 | } else { | |
813 | match frag { | |
814 | "item" => { | |
815 | // since items *must* be followed by either a `;` or a `}`, we can | |
816 | // accept anything after them | |
817 | Ok(true) | |
818 | }, | |
819 | "block" => { | |
b039eaaf | 820 | // anything can follow block, the braces provide an easy boundary to |
85aaf69f SL |
821 | // maintain |
822 | Ok(true) | |
823 | }, | |
8bb4bdeb XL |
824 | "stmt" | "expr" => match *tok { |
825 | TokenTree::Token(_, ref tok) => match *tok { | |
85aaf69f SL |
826 | FatArrow | Comma | Semi => Ok(true), |
827 | _ => Ok(false) | |
8bb4bdeb XL |
828 | }, |
829 | _ => Ok(false), | |
85aaf69f | 830 | }, |
8bb4bdeb XL |
831 | "pat" => match *tok { |
832 | TokenTree::Token(_, ref tok) => match *tok { | |
9cc50fc6 | 833 | FatArrow | Comma | Eq | BinOp(token::Or) => Ok(true), |
0531ce1d | 834 | Ident(i, false) if i.name == "if" || i.name == "in" => Ok(true), |
85aaf69f | 835 | _ => Ok(false) |
8bb4bdeb XL |
836 | }, |
837 | _ => Ok(false), | |
85aaf69f | 838 | }, |
8bb4bdeb XL |
839 | "path" | "ty" => match *tok { |
840 | TokenTree::Token(_, ref tok) => match *tok { | |
9cc50fc6 SL |
841 | OpenDelim(token::DelimToken::Brace) | OpenDelim(token::DelimToken::Bracket) | |
842 | Comma | FatArrow | Colon | Eq | Gt | Semi | BinOp(token::Or) => Ok(true), | |
0531ce1d | 843 | Ident(i, false) if i.name == "as" || i.name == "where" => Ok(true), |
85aaf69f | 844 | _ => Ok(false) |
8bb4bdeb XL |
845 | }, |
846 | TokenTree::MetaVarDecl(_, _, frag) if frag.name == "block" => Ok(true), | |
847 | _ => Ok(false), | |
85aaf69f | 848 | }, |
ff7c6d11 XL |
849 | "ident" | "lifetime" => { |
850 | // being a single token, idents and lifetimes are harmless | |
85aaf69f SL |
851 | Ok(true) |
852 | }, | |
853 | "meta" | "tt" => { | |
854 | // being either a single token or a delimited sequence, tt is | |
855 | // harmless | |
856 | Ok(true) | |
857 | }, | |
cc61c64b XL |
858 | "vis" => { |
859 | // Explicitly disallow `priv`, on the off chance it comes back. | |
860 | match *tok { | |
861 | TokenTree::Token(_, ref tok) => match *tok { | |
862 | Comma => Ok(true), | |
0531ce1d | 863 | Ident(i, is_raw) if is_raw || i.name != "priv" => Ok(true), |
cc61c64b XL |
864 | ref tok => Ok(tok.can_begin_type()) |
865 | }, | |
866 | TokenTree::MetaVarDecl(_, _, frag) if frag.name == "ident" | |
867 | || frag.name == "ty" | |
868 | || frag.name == "path" => Ok(true), | |
869 | _ => Ok(false) | |
870 | } | |
871 | }, | |
8bb4bdeb | 872 | "" => Ok(true), // keywords::Invalid |
3157f602 XL |
873 | _ => Err((format!("invalid fragment specifier `{}`", frag), |
874 | "valid fragment specifiers are `ident`, `block`, \ | |
cc61c64b XL |
875 | `stmt`, `expr`, `pat`, `ty`, `path`, `meta`, `tt`, \ |
876 | `item` and `vis`")) | |
85aaf69f | 877 | } |
1a4d82fc | 878 | } |
223e47cc | 879 | } |
9cc50fc6 | 880 | |
cc61c64b | 881 | fn has_legal_fragment_specifier(sess: &ParseSess, |
0531ce1d | 882 | features: &Features, |
041b39d2 | 883 | attrs: &[ast::Attribute], |
cc61c64b | 884 | tok: "ed::TokenTree) -> Result<(), String> { |
9cc50fc6 | 885 | debug!("has_legal_fragment_specifier({:?})", tok); |
cc61c64b XL |
886 | if let quoted::TokenTree::MetaVarDecl(_, _, ref frag_spec) = *tok { |
887 | let frag_name = frag_spec.name.as_str(); | |
888 | let frag_span = tok.span(); | |
041b39d2 | 889 | if !is_legal_fragment_specifier(sess, features, attrs, &frag_name, frag_span) { |
cc61c64b | 890 | return Err(frag_name.to_string()); |
9cc50fc6 SL |
891 | } |
892 | } | |
893 | Ok(()) | |
894 | } | |
895 | ||
cc61c64b | 896 | fn is_legal_fragment_specifier(sess: &ParseSess, |
0531ce1d | 897 | features: &Features, |
041b39d2 | 898 | attrs: &[ast::Attribute], |
cc61c64b XL |
899 | frag_name: &str, |
900 | frag_span: Span) -> bool { | |
901 | match frag_name { | |
9cc50fc6 | 902 | "item" | "block" | "stmt" | "expr" | "pat" | |
8bb4bdeb | 903 | "path" | "ty" | "ident" | "meta" | "tt" | "" => true, |
ff7c6d11 | 904 | "lifetime" => { |
0531ce1d | 905 | if !features.macro_lifetime_matcher && |
ff7c6d11 XL |
906 | !attr::contains_name(attrs, "allow_internal_unstable") { |
907 | let explain = feature_gate::EXPLAIN_LIFETIME_MATCHER; | |
908 | emit_feature_err(sess, | |
909 | "macro_lifetime_matcher", | |
910 | frag_span, | |
911 | GateIssue::Language, | |
912 | explain); | |
913 | } | |
914 | true | |
915 | }, | |
cc61c64b | 916 | "vis" => { |
0531ce1d | 917 | if !features.macro_vis_matcher && |
ff7c6d11 | 918 | !attr::contains_name(attrs, "allow_internal_unstable") { |
cc61c64b XL |
919 | let explain = feature_gate::EXPLAIN_VIS_MATCHER; |
920 | emit_feature_err(sess, | |
921 | "macro_vis_matcher", | |
922 | frag_span, | |
923 | GateIssue::Language, | |
924 | explain); | |
925 | } | |
926 | true | |
927 | }, | |
9cc50fc6 SL |
928 | _ => false, |
929 | } | |
930 | } | |
8bb4bdeb XL |
931 | |
932 | fn quoted_tt_to_string(tt: "ed::TokenTree) -> String { | |
933 | match *tt { | |
934 | quoted::TokenTree::Token(_, ref tok) => ::print::pprust::token_to_string(tok), | |
041b39d2 | 935 | quoted::TokenTree::MetaVar(_, name) => format!("${}", name), |
8bb4bdeb | 936 | quoted::TokenTree::MetaVarDecl(_, name, kind) => format!("${}:{}", name, kind), |
7cac9316 XL |
937 | _ => panic!("unexpected quoted::TokenTree::{{Sequence or Delimited}} \ |
938 | in follow set checker"), | |
8bb4bdeb XL |
939 | } |
940 | } |