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Replace the String in ParseResult::Failure with Token.
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This lets us delay creation of failure messages until they are needed,
which avoids ~1.6M allocations in html5ever.
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nnethercote committed Oct 21, 2016
1 parent e382267 commit b817cf8
Showing 3 changed files with 31 additions and 15 deletions.
19 changes: 13 additions & 6 deletions src/libsyntax/ext/tt/macro_parser.rs
Original file line number Diff line number Diff line change
@@ -251,14 +251,22 @@ pub fn nameize(p_s: &ParseSess, ms: &[TokenTree], res: &[Rc<NamedMatch>])

pub enum ParseResult<T> {
Success(T),
/// Arm failed to match
Failure(syntax_pos::Span, String),
/// Arm failed to match. If the second parameter is `token::Eof`, it
/// indicates an unexpected end of macro invocation. Otherwise, it
/// indicates that no rules expected the given token.
Failure(syntax_pos::Span, Token),
/// Fatal error (malformed macro?). Abort compilation.
Error(syntax_pos::Span, String)
}

pub fn parse_failure_msg(tok: Token) -> String {
match tok {
token::Eof => "unexpected end of macro invocation".to_string(),
_ => format!("no rules expected the token `{}`", pprust::token_to_string(&tok)),
}
}

pub type NamedParseResult = ParseResult<HashMap<Ident, Rc<NamedMatch>>>;
pub type PositionalParseResult = ParseResult<Vec<Rc<NamedMatch>>>;

/// Perform a token equality check, ignoring syntax context (that is, an
/// unhygienic comparison)
@@ -446,7 +454,7 @@ pub fn parse(sess: &ParseSess,
} else if eof_eis.len() > 1 {
return Error(sp, "ambiguity: multiple successful parses".to_string());
} else {
return Failure(sp, "unexpected end of macro invocation".to_string());
return Failure(sp, token::Eof);
}
} else {
if (!bb_eis.is_empty() && !next_eis.is_empty())
@@ -467,8 +475,7 @@ pub fn parse(sess: &ParseSess,
}
))
} else if bb_eis.is_empty() && next_eis.is_empty() {
return Failure(sp, format!("no rules expected the token `{}`",
pprust::token_to_string(&tok)));
return Failure(sp, tok);
} else if !next_eis.is_empty() {
/* Now process the next token */
while !next_eis.is_empty() {
19 changes: 12 additions & 7 deletions src/libsyntax/ext/tt/macro_rules.rs
Original file line number Diff line number Diff line change
@@ -16,7 +16,7 @@ use ext::expand::{Expansion, ExpansionKind};
use ext::placeholders;
use ext::tt::macro_parser::{Success, Error, Failure};
use ext::tt::macro_parser::{MatchedSeq, MatchedNonterminal};
use ext::tt::macro_parser::parse;
use ext::tt::macro_parser::{parse, parse_failure_msg};
use parse::ParseSess;
use parse::lexer::new_tt_reader;
use parse::parser::{Parser, Restrictions};
@@ -100,7 +100,7 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,

// Which arm's failure should we report? (the one furthest along)
let mut best_fail_spot = DUMMY_SP;
let mut best_fail_msg = "internal error: ran no matchers".to_string();
let mut best_fail_tok = None;

for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers
let lhs_tt = match *lhs {
@@ -139,17 +139,18 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,
macro_ident: name
})
}
Failure(sp, msg) => if sp.lo >= best_fail_spot.lo {
Failure(sp, tok) => if sp.lo >= best_fail_spot.lo {
best_fail_spot = sp;
best_fail_msg = msg;
best_fail_tok = Some(tok);
},
Error(err_sp, ref msg) => {
cx.span_fatal(err_sp.substitute_dummy(sp), &msg[..])
}
}
}

cx.span_fatal(best_fail_spot.substitute_dummy(sp), &best_fail_msg[..]);
let best_fail_msg = parse_failure_msg(best_fail_tok.expect("ran no matchers"));
cx.span_fatal(best_fail_spot.substitute_dummy(sp), &best_fail_msg);
}

pub struct MacroRulesExpander;
@@ -227,8 +228,12 @@ pub fn compile(sess: &ParseSess, def: &ast::MacroDef) -> SyntaxExtension {

let argument_map = match parse(sess, &Vec::new(), arg_reader, &argument_gram) {
Success(m) => m,
Failure(sp, str) | Error(sp, str) => {
panic!(sess.span_diagnostic.span_fatal(sp.substitute_dummy(def.span), &str));
Failure(sp, tok) => {
let s = parse_failure_msg(tok);
panic!(sess.span_diagnostic.span_fatal(sp.substitute_dummy(def.span), &s));
}
Error(sp, s) => {
panic!(sess.span_diagnostic.span_fatal(sp.substitute_dummy(def.span), &s));
}
};

Original file line number Diff line number Diff line change
@@ -25,6 +25,7 @@ use syntax::ext::base::{ExtCtxt, MacResult, DummyResult, MacEager};
use syntax::ext::build::AstBuilder;
use syntax::ext::tt::macro_parser::{MatchedSeq, MatchedNonterminal};
use syntax::ext::tt::macro_parser::{Success, Failure, Error};
use syntax::ext::tt::macro_parser::parse_failure_msg;
use syntax::ptr::P;
use syntax_pos::Span;
use rustc_plugin::Registry;
@@ -58,8 +59,11 @@ fn expand_mbe_matches(cx: &mut ExtCtxt, sp: Span, args: &[TokenTree])
_ => unreachable!()
}
}
Failure(_, s) | Error(_, s) => {
panic!("expected Success, but got Error/Failure: {}", s);
Failure(_, tok) => {
panic!("expected Success, but got Failure: {}", parse_failure_msg(tok));
}
Error(_, s) => {
panic!("expected Success, but got Error: {}", s);
}
};

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