1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
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.
11 use ast::{TokenTree, TtDelimited, TtSequence, TtToken};
13 use codemap::{Span, DUMMY_SP};
14 use ext::base::{ExtCtxt, MacResult, SyntaxExtension};
15 use ext::base::{NormalTT, TTMacroExpander};
16 use ext::tt::macro_parser::{Success, Error, Failure};
17 use ext::tt::macro_parser::{NamedMatch, MatchedSeq, MatchedNonterminal};
18 use ext::tt::macro_parser::{parse, parse_or_else};
19 use parse::lexer::{new_tt_reader, new_tt_reader_with_doc_flag};
20 use parse::parser::Parser;
21 use parse::attr::ParserAttr;
22 use parse::token::{special_idents, gensym_ident, NtTT, Token};
23 use parse::token::Token::*;
28 use util::small_vector::SmallVector;
30 use std::cell::RefCell;
33 struct ParserAnyMacro<'a> {
34 parser: RefCell<Parser<'a>>,
37 impl<'a> ParserAnyMacro<'a> {
38 /// Make sure we don't have any tokens left to parse, so we don't
39 /// silently drop anything. `allow_semi` is so that "optional"
40 /// semicolons at the end of normal expressions aren't complained
41 /// about e.g. the semicolon in `macro_rules! kapow { () => {
42 /// panic!(); } }` doesn't get picked up by .parse_expr(), but it's
43 /// allowed to be there.
44 fn ensure_complete_parse(&self, allow_semi: bool) {
45 let mut parser = self.parser.borrow_mut();
46 if allow_semi && parser.token == token::Semi {
49 if parser.token != token::Eof {
50 let token_str = parser.this_token_to_string();
51 let msg = format!("macro expansion ignores token `{}` and any \
54 let span = parser.span;
55 parser.span_err(span, &msg[]);
60 impl<'a> MacResult for ParserAnyMacro<'a> {
61 fn make_expr(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Expr>> {
62 let ret = self.parser.borrow_mut().parse_expr();
63 self.ensure_complete_parse(true);
66 fn make_pat(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Pat>> {
67 let ret = self.parser.borrow_mut().parse_pat();
68 self.ensure_complete_parse(false);
71 fn make_items(self: Box<ParserAnyMacro<'a>>) -> Option<SmallVector<P<ast::Item>>> {
72 let mut ret = SmallVector::zero();
74 let mut parser = self.parser.borrow_mut();
75 // so... do outer attributes attached to the macro invocation
76 // just disappear? This question applies to make_methods, as
78 match parser.parse_item_with_outer_attributes() {
79 Some(item) => ret.push(item),
83 self.ensure_complete_parse(false);
87 fn make_methods(self: Box<ParserAnyMacro<'a>>) -> Option<SmallVector<P<ast::Method>>> {
88 let mut ret = SmallVector::zero();
90 let mut parser = self.parser.borrow_mut();
94 let attrs = parser.parse_outer_attributes();
95 ret.push(parser.parse_method(attrs, ast::Inherited))
99 self.ensure_complete_parse(false);
103 fn make_stmt(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Stmt>> {
104 let attrs = self.parser.borrow_mut().parse_outer_attributes();
105 let ret = self.parser.borrow_mut().parse_stmt(attrs);
106 self.ensure_complete_parse(true);
111 struct MacroRulesMacroExpander {
113 imported_from: Option<ast::Ident>,
114 lhses: Vec<Rc<NamedMatch>>,
115 rhses: Vec<Rc<NamedMatch>>,
118 impl TTMacroExpander for MacroRulesMacroExpander {
119 fn expand<'cx>(&self,
120 cx: &'cx mut ExtCtxt,
122 arg: &[ast::TokenTree])
123 -> Box<MacResult+'cx> {
124 generic_extension(cx,
134 /// Given `lhses` and `rhses`, this is the new macro we create
135 fn generic_extension<'cx>(cx: &'cx ExtCtxt,
138 imported_from: Option<ast::Ident>,
139 arg: &[ast::TokenTree],
140 lhses: &[Rc<NamedMatch>],
141 rhses: &[Rc<NamedMatch>])
142 -> Box<MacResult+'cx> {
143 if cx.trace_macros() {
144 println!("{}! {{ {} }}",
145 token::get_ident(name),
146 print::pprust::tts_to_string(arg));
149 // Which arm's failure should we report? (the one furthest along)
150 let mut best_fail_spot = DUMMY_SP;
151 let mut best_fail_msg = "internal error: ran no matchers".to_string();
153 for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers
155 MatchedNonterminal(NtTT(ref lhs_tt)) => {
156 let lhs_tt = match **lhs_tt {
157 TtDelimited(_, ref delim) => &delim.tts[],
158 _ => cx.span_fatal(sp, "malformed macro lhs")
160 // `None` is because we're not interpolating
161 let arg_rdr = new_tt_reader_with_doc_flag(&cx.parse_sess().span_diagnostic,
165 .map(|x| (*x).clone())
168 match parse(cx.parse_sess(), cx.cfg(), arg_rdr, lhs_tt) {
169 Success(named_matches) => {
170 let rhs = match *rhses[i] {
171 // okay, what's your transcriber?
172 MatchedNonterminal(NtTT(ref tt)) => {
175 TtDelimited(_, ref delimed) => delimed.tts.clone(),
176 _ => cx.span_fatal(sp, "macro rhs must be delimited"),
179 _ => cx.span_bug(sp, "bad thing in rhs")
181 // rhs has holes ( `$id` and `$(...)` that need filled)
182 let trncbr = new_tt_reader(&cx.parse_sess().span_diagnostic,
186 let mut p = Parser::new(cx.parse_sess(), cx.cfg(), box trncbr);
187 p.check_unknown_macro_variable();
188 // Let the context choose how to interpret the result.
189 // Weird, but useful for X-macros.
190 return box ParserAnyMacro {
191 parser: RefCell::new(p),
192 } as Box<MacResult+'cx>
194 Failure(sp, ref msg) => if sp.lo >= best_fail_spot.lo {
196 best_fail_msg = (*msg).clone();
198 Error(sp, ref msg) => cx.span_fatal(sp, &msg[])
201 _ => cx.bug("non-matcher found in parsed lhses")
204 cx.span_fatal(best_fail_spot, &best_fail_msg[]);
207 // Note that macro-by-example's input is also matched against a token tree:
208 // $( $lhs:tt => $rhs:tt );+
210 // Holy self-referential!
212 /// Converts a `macro_rules!` invocation into a syntax extension.
213 pub fn compile<'cx>(cx: &'cx mut ExtCtxt,
214 def: &ast::MacroDef) -> SyntaxExtension {
216 let lhs_nm = gensym_ident("lhs");
217 let rhs_nm = gensym_ident("rhs");
219 // The pattern that macro_rules matches.
220 // The grammar for macro_rules! is:
221 // $( $lhs:tt => $rhs:tt );+
222 // ...quasiquoting this would be nice.
223 // These spans won't matter, anyways
224 let match_lhs_tok = MatchNt(lhs_nm, special_idents::tt, token::Plain, token::Plain);
225 let match_rhs_tok = MatchNt(rhs_nm, special_idents::tt, token::Plain, token::Plain);
226 let argument_gram = vec!(
228 Rc::new(ast::SequenceRepetition {
230 TtToken(DUMMY_SP, match_lhs_tok),
231 TtToken(DUMMY_SP, token::FatArrow),
232 TtToken(DUMMY_SP, match_rhs_tok)],
233 separator: Some(token::Semi),
237 //to phase into semicolon-termination instead of
238 //semicolon-separation
240 Rc::new(ast::SequenceRepetition {
241 tts: vec![TtToken(DUMMY_SP, token::Semi)],
248 // Parse the macro_rules! invocation (`none` is for no interpolations):
249 let arg_reader = new_tt_reader(&cx.parse_sess().span_diagnostic,
253 let argument_map = parse_or_else(cx.parse_sess(),
258 // Extract the arguments:
259 let lhses = match *argument_map[lhs_nm] {
260 MatchedSeq(ref s, _) => /* FIXME (#2543) */ (*s).clone(),
261 _ => cx.span_bug(def.span, "wrong-structured lhs")
264 for lhs in lhses.iter() {
265 check_lhs_nt_follows(cx, &**lhs, def.span);
268 let rhses = match *argument_map[rhs_nm] {
269 MatchedSeq(ref s, _) => /* FIXME (#2543) */ (*s).clone(),
270 _ => cx.span_bug(def.span, "wrong-structured rhs")
273 let exp = box MacroRulesMacroExpander {
275 imported_from: def.imported_from,
280 NormalTT(exp, Some(def.span))
283 fn check_lhs_nt_follows(cx: &mut ExtCtxt, lhs: &NamedMatch, sp: Span) {
284 // lhs is going to be like MatchedNonterminal(NtTT(TtDelimited(...))), where the entire lhs is
285 // those tts. Or, it can be a "bare sequence", not wrapped in parens.
287 &MatchedNonterminal(NtTT(ref inner)) => match &**inner {
288 &TtDelimited(_, ref tts) => {
289 check_matcher(cx, tts.tts.iter(), &Eof);
291 tt @ &TtSequence(..) => {
292 check_matcher(cx, Some(tt).into_iter(), &Eof);
294 _ => cx.span_bug(sp, "wrong-structured lhs for follow check (didn't find \
295 a TtDelimited or TtSequence)")
297 _ => cx.span_bug(sp, "wrong-structured lhs for follow check (didn't find a \
298 MatchedNonterminal)")
300 // we don't abort on errors on rejection, the driver will do that for us
301 // after parsing/expansion. we can report every error in every macro this way.
304 // returns the last token that was checked, for TtSequence. this gets used later on.
305 fn check_matcher<'a, I>(cx: &mut ExtCtxt, matcher: I, follow: &Token)
306 -> Option<(Span, Token)> where I: Iterator<Item=&'a TokenTree> {
307 use print::pprust::token_to_string;
311 // 2. For each token T in M:
312 let mut tokens = matcher.peekable();
313 while let Some(token) = tokens.next() {
314 last = match *token {
315 TtToken(sp, MatchNt(ref name, ref frag_spec, _, _)) => {
316 // ii. If T is a simple NT, look ahead to the next token T' in
318 let next_token = match tokens.peek() {
319 // If T' closes a complex NT, replace T' with F
320 Some(&&TtToken(_, CloseDelim(_))) => follow.clone(),
321 Some(&&TtToken(_, ref tok)) => tok.clone(),
322 Some(&&TtSequence(sp, _)) => {
324 format!("`${0}:{1}` is followed by a \
325 sequence repetition, which is not \
326 allowed for `{1}` fragments",
327 name.as_str(), frag_spec.as_str())
331 // die next iteration
332 Some(&&TtDelimited(_, ref delim)) => delim.close_token(),
333 // else, we're at the end of the macro or sequence
334 None => follow.clone()
337 let tok = if let TtToken(_, ref tok) = *token { tok } else { unreachable!() };
338 // If T' is in the set FOLLOW(NT), continue. Else, reject.
340 &Eof => return Some((sp, tok.clone())),
341 _ if is_in_follow(cx, &next_token, frag_spec.as_str()) => continue,
343 cx.span_err(sp, format!("`${0}:{1}` is followed by `{2}`, which \
344 is not allowed for `{1}` fragments",
345 name.as_str(), frag_spec.as_str(),
346 token_to_string(next)).as_slice());
351 TtSequence(sp, ref seq) => {
352 // iii. Else, T is a complex NT.
353 match seq.separator {
354 // If T has the form $(...)U+ or $(...)U* for some token U,
355 // run the algorithm on the contents with F set to U. If it
356 // accepts, continue, else, reject.
358 let last = check_matcher(cx, seq.tts.iter(), u);
360 // Since the delimiter isn't required after the last
361 // repetition, make sure that the *next* token is
362 // sane. This doesn't actually compute the FIRST of
363 // the rest of the matcher yet, it only considers
364 // single tokens and simple NTs. This is imprecise,
365 // but conservatively correct.
366 Some((span, tok)) => {
367 let fol = match tokens.peek() {
368 Some(&&TtToken(_, ref tok)) => tok.clone(),
369 Some(&&TtDelimited(_, ref delim)) => delim.close_token(),
371 cx.span_err(sp, "sequence repetition followed by \
372 another sequence repetition, which is not allowed");
377 check_matcher(cx, Some(&TtToken(span, tok.clone())).into_iter(),
383 // If T has the form $(...)+ or $(...)*, run the algorithm
384 // on the contents with F set to the token following the
385 // sequence. If it accepts, continue, else, reject.
387 let fol = match tokens.peek() {
388 Some(&&TtToken(_, ref tok)) => tok.clone(),
389 Some(&&TtDelimited(_, ref delim)) => delim.close_token(),
391 cx.span_err(sp, "sequence repetition followed by another \
392 sequence repetition, which is not allowed");
397 check_matcher(cx, seq.tts.iter(), &fol)
402 // i. If T is not an NT, continue.
405 TtDelimited(_, ref tts) => {
406 // if we don't pass in that close delimiter, we'll incorrectly consider the matcher
407 // `{ $foo:ty }` as having a follow that isn't `RBrace`
408 check_matcher(cx, tts.tts.iter(), &tts.close_token())
415 fn is_in_follow(cx: &ExtCtxt, tok: &Token, frag: &str) -> bool {
416 if let &CloseDelim(_) = tok {
422 // since items *must* be followed by either a `;` or a `}`, we can
423 // accept anything after them
427 // anything can follow block, the braces provide a easy boundary to
433 FatArrow | Comma | Semi => true,
439 FatArrow | Comma | Eq => true,
445 Comma | FatArrow | Colon | Eq | Gt => true,
446 Ident(i, _) if i.as_str() == "as" => true,
451 // being a single token, idents are harmless
455 // being either a single token or a delimited sequence, tt is
459 _ => cx.bug(format!("unrecognized builtin nonterminal {}",