bjoernager/rust
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Improve some documentation.

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This commit is contained in:
Paul Stansifer 2012-07-27 17:32:15 -07:00
parent 19922fcd93
commit a28812cfd6
1 changed files with 20 additions and 14 deletions
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34
src/libsyntax/ext/tt/macro_rules.rs
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@ -5,12 +5,10 @@ import ast::{ident, matcher_, matcher, match_tok,
import parse::lexer::{new_tt_reader, tt_reader_as_reader, reader};
import parse::token::{FAT_ARROW, SEMI, LBRACE, RBRACE, nt_matchers, nt_tt};
import parse::parser::{parser, SOURCE_FILE};
import earley_parser::{parse, success, failure, named_match,
import earley_parser::{parse, parse_or_else, success, failure, named_match,
matched_seq, matched_nonterminal};
import std::map::hashmap;
fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
arg: ~[ast::token_tree]) -> base::mac_result {
// these spans won't matter, anyways
@ -18,6 +16,9 @@ fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
{node: m, span: {lo: 0u, hi: 0u, expn_info: none}}
}
// The grammar for macro_rules! is:
// $( $lhs:mtcs => $rhs:tt );+
// ...quasiquoting this would be nice.
let argument_gram = ~[
ms(match_seq(~[
ms(match_nonterminal(@~"lhs",@~"matchers", 0u)),
@ -25,43 +26,48 @@ fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
ms(match_nonterminal(@~"rhs",@~"tt", 1u)),
], some(SEMI), false, 0u, 2u))];
// Parse the macro_rules! invocation (`none` is for no interpolations):
let arg_reader = new_tt_reader(cx.parse_sess().span_diagnostic,
cx.parse_sess().interner, none, arg);
let arguments = alt parse(cx.parse_sess(), cx.cfg(),
arg_reader as reader, argument_gram) {
success(m) { m }
failure(sp, msg) { cx.span_fatal(sp, msg); }
};
let argument_map = parse_or_else(cx.parse_sess(), cx.cfg(),
arg_reader as reader, argument_gram);
let lhses = alt arguments.get(@~"lhs") {
// Extract the arguments:
let lhses:~[@named_match] = alt argument_map.get(@~"lhs") {
@matched_seq(s, sp) { s }
_ { cx.span_bug(sp, ~"wrong-structured lhs") }
};
let rhses = alt arguments.get(@~"rhs") {
let rhses:~[@named_match] = alt argument_map.get(@~"rhs") {
@matched_seq(s, sp) { s }
_ { cx.span_bug(sp, ~"wrong-structured rhs") }
};
// Given `lhses` and `rhses`, this is the new macro we create
fn generic_extension(cx: ext_ctxt, sp: span, arg: ~[ast::token_tree],
lhses: ~[@named_match], rhses: ~[@named_match])
-> mac_result {
// Which arm's failure should we report? (the one furthest along)
let mut best_fail_spot = {lo: 0u, hi: 0u, expn_info: none};
let mut best_fail_msg = ~"internal error: ran no matchers";
let s_d = cx.parse_sess().span_diagnostic;
let itr = cx.parse_sess().interner;
for lhses.eachi() |i, lhs| {
for lhses.eachi() |i, lhs| { // try each arm's matchers
alt lhs {
@matched_nonterminal(nt_matchers(mtcs)) {
// `none` is because we're not interpolating
let arg_rdr = new_tt_reader(s_d, itr, none, arg) as reader;
alt parse(cx.parse_sess(), cx.cfg(), arg_rdr, mtcs) {
success(m) {
let rhs = alt rhses[i] {
success(named_matches) {
let rhs = alt rhses[i] { // okay, what's your transcriber?
@matched_nonterminal(nt_tt(@tt)) { tt }
_ { cx.span_bug(sp, ~"bad thing in rhs") }
};
let trncbr = new_tt_reader(s_d, itr, some(m), ~[rhs]);
// rhs has holes ( `$id` and `$(...)` that need filled)
let trncbr = new_tt_reader(s_d, itr, some(named_matches),
~[rhs]);
let p = parser(cx.parse_sess(), cx.cfg(),
trncbr as reader, SOURCE_FILE);
ret mr_expr(p.parse_expr());