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This commit is contained in:
Mark Mansi 2018-01-24 23:10:39 -06:00
parent b01b481db3
commit 02d1d92878
1 changed files with 26 additions and 2 deletions
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28
src/libsyntax/ext/tt/macro_parser.rs
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@ -469,9 +469,13 @@ fn inner_parse_loop(
else {
eof_items.push(item);
}
} else {
}
// We are in the middle of a matcher.
else {
// Look at what token in the matcher we are trying to match the current token (`token`)
// against. Depending on that, we may generate new items.
match item.top_elts.get_tt(idx) {
/* need to descend into sequence */
// Need to descend into a sequence
TokenTree::Sequence(sp, seq) => {
if seq.op == quoted::KleeneOp::ZeroOrMore {
// Examine the case where there are 0 matches of this sequence
@ -499,11 +503,16 @@ fn inner_parse_loop(
top_elts: Tt(TokenTree::Sequence(sp, seq)),
}));
}
// We need to match a metavar (but the identifier is invalid)... this is an error
TokenTree::MetaVarDecl(span, _, id) if id.name == keywords::Invalid.name() => {
if sess.missing_fragment_specifiers.borrow_mut().remove(&span) {
return Error(span, "missing fragment specifier".to_string());
}
}
// We need to match a metavar with a valid ident... call out to the black-box
// parser by adding an item to `bb_items`.
TokenTree::MetaVarDecl(_, _, id) => {
// Built-in nonterminals never start with these tokens,
// so we can eliminate them from consideration.
@ -511,6 +520,13 @@ fn inner_parse_loop(
bb_items.push(item);
}
}
// We need to descend into a delimited submatcher or a doc comment. To do this, we
// push the current matcher onto a stack and push a new item containing the
// submatcher onto `cur_items`.
//
// At the beginning of the loop, if we reach the end of the delimited submatcher,
// we pop the stack to backtrack out of the descent.
seq @ TokenTree::Delimited(..) | seq @ TokenTree::Token(_, DocComment(..)) => {
let lower_elts = mem::replace(&mut item.top_elts, Tt(seq));
let idx = item.idx;
@ -521,15 +537,23 @@ fn inner_parse_loop(
item.idx = 0;
cur_items.push(item);
}
// We just matched a normal token. We can just advance the parser.
TokenTree::Token(_, ref t) if token_name_eq(t, token) => {
item.idx += 1;
next_items.push(item);
}
// There was another token that was not `token`... This means we can't add any
// rules. NOTE that this is not necessarily an error unless _all_ items in
// `cur_items` end up doing this. There may still be some other matchers that do
// end up working out.
TokenTree::Token(..) | TokenTree::MetaVar(..) => {}
}
}
}
// Yay a successful parse (so far)!
Success(())
}