371bf0eda2
Remove the old FOLLOW checking (aka `check_matcher_old`). It was supposed to be removed at the next release cycle but is still in the tree since like 6 months. Potential breaking change, since some cases (such as #25658) will change from a warning to an error. But the warning stating that it will be a hard error in the next release has been there for 6 months now. I think it's safe to break this code. ^_^
852 lines
33 KiB
Rust
852 lines
33 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
use ast::{self, TokenTree};
|
|
use codemap::{Span, DUMMY_SP};
|
|
use ext::base::{DummyResult, ExtCtxt, MacResult, SyntaxExtension};
|
|
use ext::base::{NormalTT, TTMacroExpander};
|
|
use ext::tt::macro_parser::{Success, Error, Failure};
|
|
use ext::tt::macro_parser::{MatchedSeq, MatchedNonterminal};
|
|
use ext::tt::macro_parser::parse;
|
|
use parse::lexer::new_tt_reader;
|
|
use parse::parser::{Parser, Restrictions};
|
|
use parse::token::{self, gensym_ident, NtTT, Token};
|
|
use parse::token::Token::*;
|
|
use print;
|
|
use ptr::P;
|
|
|
|
use util::small_vector::SmallVector;
|
|
|
|
use std::cell::RefCell;
|
|
use std::collections::{HashMap};
|
|
use std::collections::hash_map::{Entry};
|
|
use std::rc::Rc;
|
|
|
|
struct ParserAnyMacro<'a> {
|
|
parser: RefCell<Parser<'a>>,
|
|
|
|
/// Span of the expansion site of the macro this parser is for
|
|
site_span: Span,
|
|
/// The ident of the macro we're parsing
|
|
macro_ident: ast::Ident
|
|
}
|
|
|
|
impl<'a> ParserAnyMacro<'a> {
|
|
/// Make sure we don't have any tokens left to parse, so we don't
|
|
/// silently drop anything. `allow_semi` is so that "optional"
|
|
/// semicolons at the end of normal expressions aren't complained
|
|
/// about e.g. the semicolon in `macro_rules! kapow { () => {
|
|
/// panic!(); } }` doesn't get picked up by .parse_expr(), but it's
|
|
/// allowed to be there.
|
|
fn ensure_complete_parse(&self, allow_semi: bool, context: &str) {
|
|
let mut parser = self.parser.borrow_mut();
|
|
if allow_semi && parser.token == token::Semi {
|
|
parser.bump();
|
|
}
|
|
if parser.token != token::Eof {
|
|
let token_str = parser.this_token_to_string();
|
|
let msg = format!("macro expansion ignores token `{}` and any \
|
|
following",
|
|
token_str);
|
|
let span = parser.span;
|
|
let mut err = parser.diagnostic().struct_span_err(span, &msg[..]);
|
|
let msg = format!("caused by the macro expansion here; the usage \
|
|
of `{}!` is likely invalid in {} context",
|
|
self.macro_ident, context);
|
|
err.span_note(self.site_span, &msg[..])
|
|
.emit();
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'a> MacResult for ParserAnyMacro<'a> {
|
|
fn make_expr(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Expr>> {
|
|
let ret = panictry!(self.parser.borrow_mut().parse_expr());
|
|
self.ensure_complete_parse(true, "expression");
|
|
Some(ret)
|
|
}
|
|
fn make_pat(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Pat>> {
|
|
let ret = panictry!(self.parser.borrow_mut().parse_pat());
|
|
self.ensure_complete_parse(false, "pattern");
|
|
Some(ret)
|
|
}
|
|
fn make_items(self: Box<ParserAnyMacro<'a>>) -> Option<SmallVector<P<ast::Item>>> {
|
|
let mut ret = SmallVector::zero();
|
|
while let Some(item) = panictry!(self.parser.borrow_mut().parse_item()) {
|
|
ret.push(item);
|
|
}
|
|
self.ensure_complete_parse(false, "item");
|
|
Some(ret)
|
|
}
|
|
|
|
fn make_impl_items(self: Box<ParserAnyMacro<'a>>)
|
|
-> Option<SmallVector<ast::ImplItem>> {
|
|
let mut ret = SmallVector::zero();
|
|
loop {
|
|
let mut parser = self.parser.borrow_mut();
|
|
match parser.token {
|
|
token::Eof => break,
|
|
_ => ret.push(panictry!(parser.parse_impl_item()))
|
|
}
|
|
}
|
|
self.ensure_complete_parse(false, "item");
|
|
Some(ret)
|
|
}
|
|
|
|
fn make_stmts(self: Box<ParserAnyMacro<'a>>)
|
|
-> Option<SmallVector<ast::Stmt>> {
|
|
let mut ret = SmallVector::zero();
|
|
loop {
|
|
let mut parser = self.parser.borrow_mut();
|
|
match parser.token {
|
|
token::Eof => break,
|
|
_ => match parser.parse_stmt() {
|
|
Ok(maybe_stmt) => match maybe_stmt {
|
|
Some(stmt) => ret.push(stmt),
|
|
None => (),
|
|
},
|
|
Err(mut e) => {
|
|
e.emit();
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
self.ensure_complete_parse(false, "statement");
|
|
Some(ret)
|
|
}
|
|
|
|
fn make_ty(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Ty>> {
|
|
let ret = panictry!(self.parser.borrow_mut().parse_ty());
|
|
self.ensure_complete_parse(false, "type");
|
|
Some(ret)
|
|
}
|
|
}
|
|
|
|
struct MacroRulesMacroExpander {
|
|
name: ast::Ident,
|
|
imported_from: Option<ast::Ident>,
|
|
lhses: Vec<TokenTree>,
|
|
rhses: Vec<TokenTree>,
|
|
valid: bool,
|
|
}
|
|
|
|
impl TTMacroExpander for MacroRulesMacroExpander {
|
|
fn expand<'cx>(&self,
|
|
cx: &'cx mut ExtCtxt,
|
|
sp: Span,
|
|
arg: &[TokenTree])
|
|
-> Box<MacResult+'cx> {
|
|
if !self.valid {
|
|
return DummyResult::any(sp);
|
|
}
|
|
generic_extension(cx,
|
|
sp,
|
|
self.name,
|
|
self.imported_from,
|
|
arg,
|
|
&self.lhses,
|
|
&self.rhses)
|
|
}
|
|
}
|
|
|
|
/// Given `lhses` and `rhses`, this is the new macro we create
|
|
fn generic_extension<'cx>(cx: &'cx ExtCtxt,
|
|
sp: Span,
|
|
name: ast::Ident,
|
|
imported_from: Option<ast::Ident>,
|
|
arg: &[TokenTree],
|
|
lhses: &[TokenTree],
|
|
rhses: &[TokenTree])
|
|
-> Box<MacResult+'cx> {
|
|
if cx.trace_macros() {
|
|
println!("{}! {{ {} }}",
|
|
name,
|
|
print::pprust::tts_to_string(arg));
|
|
}
|
|
|
|
// 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();
|
|
|
|
for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers
|
|
let lhs_tt = match *lhs {
|
|
TokenTree::Delimited(_, ref delim) => &delim.tts[..],
|
|
_ => cx.span_bug(sp, "malformed macro lhs")
|
|
};
|
|
|
|
match TokenTree::parse(cx, lhs_tt, arg) {
|
|
Success(named_matches) => {
|
|
let rhs = match rhses[i] {
|
|
// ignore delimiters
|
|
TokenTree::Delimited(_, ref delimed) => delimed.tts.clone(),
|
|
_ => cx.span_bug(sp, "malformed macro rhs"),
|
|
};
|
|
// rhs has holes ( `$id` and `$(...)` that need filled)
|
|
let trncbr = new_tt_reader(&cx.parse_sess().span_diagnostic,
|
|
Some(named_matches),
|
|
imported_from,
|
|
rhs);
|
|
let mut p = Parser::new(cx.parse_sess(), cx.cfg(), Box::new(trncbr));
|
|
p.filename = cx.filename.clone();
|
|
p.mod_path_stack = cx.mod_path_stack.clone();
|
|
p.restrictions = match cx.in_block {
|
|
true => Restrictions::NO_NONINLINE_MOD,
|
|
false => Restrictions::empty(),
|
|
};
|
|
p.check_unknown_macro_variable();
|
|
// Let the context choose how to interpret the result.
|
|
// Weird, but useful for X-macros.
|
|
return Box::new(ParserAnyMacro {
|
|
parser: RefCell::new(p),
|
|
|
|
// Pass along the original expansion site and the name of the macro
|
|
// so we can print a useful error message if the parse of the expanded
|
|
// macro leaves unparsed tokens.
|
|
site_span: sp,
|
|
macro_ident: name
|
|
})
|
|
}
|
|
Failure(sp, ref msg) => if sp.lo >= best_fail_spot.lo {
|
|
best_fail_spot = sp;
|
|
best_fail_msg = (*msg).clone();
|
|
},
|
|
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[..]);
|
|
}
|
|
|
|
// Note that macro-by-example's input is also matched against a token tree:
|
|
// $( $lhs:tt => $rhs:tt );+
|
|
//
|
|
// Holy self-referential!
|
|
|
|
/// Converts a `macro_rules!` invocation into a syntax extension.
|
|
pub fn compile<'cx>(cx: &'cx mut ExtCtxt,
|
|
def: &ast::MacroDef) -> SyntaxExtension {
|
|
|
|
let lhs_nm = gensym_ident("lhs");
|
|
let rhs_nm = gensym_ident("rhs");
|
|
|
|
// The pattern that macro_rules matches.
|
|
// The grammar for macro_rules! is:
|
|
// $( $lhs:tt => $rhs:tt );+
|
|
// ...quasiquoting this would be nice.
|
|
// These spans won't matter, anyways
|
|
let match_lhs_tok = MatchNt(lhs_nm, token::str_to_ident("tt"));
|
|
let match_rhs_tok = MatchNt(rhs_nm, token::str_to_ident("tt"));
|
|
let argument_gram = vec!(
|
|
TokenTree::Sequence(DUMMY_SP,
|
|
Rc::new(ast::SequenceRepetition {
|
|
tts: vec![
|
|
TokenTree::Token(DUMMY_SP, match_lhs_tok),
|
|
TokenTree::Token(DUMMY_SP, token::FatArrow),
|
|
TokenTree::Token(DUMMY_SP, match_rhs_tok)],
|
|
separator: Some(token::Semi),
|
|
op: ast::KleeneOp::OneOrMore,
|
|
num_captures: 2
|
|
})),
|
|
//to phase into semicolon-termination instead of
|
|
//semicolon-separation
|
|
TokenTree::Sequence(DUMMY_SP,
|
|
Rc::new(ast::SequenceRepetition {
|
|
tts: vec![TokenTree::Token(DUMMY_SP, token::Semi)],
|
|
separator: None,
|
|
op: ast::KleeneOp::ZeroOrMore,
|
|
num_captures: 0
|
|
})));
|
|
|
|
|
|
// Parse the macro_rules! invocation (`none` is for no interpolations):
|
|
let arg_reader = new_tt_reader(&cx.parse_sess().span_diagnostic,
|
|
None,
|
|
None,
|
|
def.body.clone());
|
|
|
|
let argument_map = match parse(cx.parse_sess(),
|
|
cx.cfg(),
|
|
arg_reader,
|
|
&argument_gram) {
|
|
Success(m) => m,
|
|
Failure(sp, str) | Error(sp, str) => {
|
|
panic!(cx.parse_sess().span_diagnostic
|
|
.span_fatal(sp.substitute_dummy(def.span), &str[..]));
|
|
}
|
|
};
|
|
|
|
let mut valid = true;
|
|
|
|
// Extract the arguments:
|
|
let lhses = match **argument_map.get(&lhs_nm.name).unwrap() {
|
|
MatchedSeq(ref s, _) => {
|
|
s.iter().map(|m| match **m {
|
|
MatchedNonterminal(NtTT(ref tt)) => {
|
|
valid &= check_lhs_nt_follows(cx, tt);
|
|
(**tt).clone()
|
|
}
|
|
_ => cx.span_bug(def.span, "wrong-structured lhs")
|
|
}).collect()
|
|
}
|
|
_ => cx.span_bug(def.span, "wrong-structured lhs")
|
|
};
|
|
|
|
let rhses = match **argument_map.get(&rhs_nm.name).unwrap() {
|
|
MatchedSeq(ref s, _) => {
|
|
s.iter().map(|m| match **m {
|
|
MatchedNonterminal(NtTT(ref tt)) => (**tt).clone(),
|
|
_ => cx.span_bug(def.span, "wrong-structured rhs")
|
|
}).collect()
|
|
}
|
|
_ => cx.span_bug(def.span, "wrong-structured rhs")
|
|
};
|
|
|
|
for rhs in &rhses {
|
|
valid &= check_rhs(cx, rhs);
|
|
}
|
|
|
|
let exp: Box<_> = Box::new(MacroRulesMacroExpander {
|
|
name: def.ident,
|
|
imported_from: def.imported_from,
|
|
lhses: lhses,
|
|
rhses: rhses,
|
|
valid: valid,
|
|
});
|
|
|
|
NormalTT(exp, Some(def.span), def.allow_internal_unstable)
|
|
}
|
|
|
|
fn check_lhs_nt_follows(cx: &mut ExtCtxt, lhs: &TokenTree) -> bool {
|
|
// lhs is going to be like TokenTree::Delimited(...), where the
|
|
// entire lhs is those tts. Or, it can be a "bare sequence", not wrapped in parens.
|
|
match lhs {
|
|
&TokenTree::Delimited(_, ref tts) => check_matcher(cx, &tts.tts),
|
|
_ => {
|
|
cx.span_err(lhs.get_span(), "invalid macro matcher; matchers must \
|
|
be contained in balanced delimiters");
|
|
false
|
|
}
|
|
}
|
|
// we don't abort on errors on rejection, the driver will do that for us
|
|
// after parsing/expansion. we can report every error in every macro this way.
|
|
}
|
|
|
|
fn check_rhs(cx: &mut ExtCtxt, rhs: &TokenTree) -> bool {
|
|
match *rhs {
|
|
TokenTree::Delimited(..) => return true,
|
|
_ => cx.span_err(rhs.get_span(), "macro rhs must be delimited")
|
|
}
|
|
false
|
|
}
|
|
|
|
fn check_matcher(cx: &mut ExtCtxt, matcher: &[TokenTree]) -> bool {
|
|
let first_sets = FirstSets::new(matcher);
|
|
let empty_suffix = TokenSet::empty();
|
|
let err = cx.parse_sess.span_diagnostic.err_count();
|
|
check_matcher_core(cx, &first_sets, matcher, &empty_suffix);
|
|
err == cx.parse_sess.span_diagnostic.err_count()
|
|
}
|
|
|
|
// The FirstSets for a matcher is a mapping from subsequences in the
|
|
// matcher to the FIRST set for that subsequence.
|
|
//
|
|
// This mapping is partially precomputed via a backwards scan over the
|
|
// token trees of the matcher, which provides a mapping from each
|
|
// repetition sequence to its FIRST set.
|
|
//
|
|
// (Hypothetically sequences should be uniquely identifiable via their
|
|
// spans, though perhaps that is false e.g. for macro-generated macros
|
|
// that do not try to inject artificial span information. My plan is
|
|
// to try to catch such cases ahead of time and not include them in
|
|
// the precomputed mapping.)
|
|
struct FirstSets {
|
|
// this maps each TokenTree::Sequence `$(tt ...) SEP OP` that is uniquely identified by its
|
|
// span in the original matcher to the First set for the inner sequence `tt ...`.
|
|
//
|
|
// If two sequences have the same span in a matcher, then map that
|
|
// span to None (invalidating the mapping here and forcing the code to
|
|
// use a slow path).
|
|
first: HashMap<Span, Option<TokenSet>>,
|
|
}
|
|
|
|
impl FirstSets {
|
|
fn new(tts: &[TokenTree]) -> FirstSets {
|
|
let mut sets = FirstSets { first: HashMap::new() };
|
|
build_recur(&mut sets, tts);
|
|
return sets;
|
|
|
|
// walks backward over `tts`, returning the FIRST for `tts`
|
|
// and updating `sets` at the same time for all sequence
|
|
// substructure we find within `tts`.
|
|
fn build_recur(sets: &mut FirstSets, tts: &[TokenTree]) -> TokenSet {
|
|
let mut first = TokenSet::empty();
|
|
for tt in tts.iter().rev() {
|
|
match *tt {
|
|
TokenTree::Token(sp, ref tok) => {
|
|
first.replace_with((sp, tok.clone()));
|
|
}
|
|
TokenTree::Delimited(_, ref delimited) => {
|
|
build_recur(sets, &delimited.tts[..]);
|
|
first.replace_with((delimited.open_span,
|
|
Token::OpenDelim(delimited.delim)));
|
|
}
|
|
TokenTree::Sequence(sp, ref seq_rep) => {
|
|
let subfirst = build_recur(sets, &seq_rep.tts[..]);
|
|
|
|
match sets.first.entry(sp) {
|
|
Entry::Vacant(vac) => {
|
|
vac.insert(Some(subfirst.clone()));
|
|
}
|
|
Entry::Occupied(mut occ) => {
|
|
// if there is already an entry, then a span must have collided.
|
|
// This should not happen with typical macro_rules macros,
|
|
// but syntax extensions need not maintain distinct spans,
|
|
// so distinct syntax trees can be assigned the same span.
|
|
// In such a case, the map cannot be trusted; so mark this
|
|
// entry as unusable.
|
|
occ.insert(None);
|
|
}
|
|
}
|
|
|
|
// If the sequence contents can be empty, then the first
|
|
// token could be the separator token itself.
|
|
|
|
if let (Some(ref sep), true) = (seq_rep.separator.clone(),
|
|
subfirst.maybe_empty) {
|
|
first.add_one_maybe((sp, sep.clone()));
|
|
}
|
|
|
|
// Reverse scan: Sequence comes before `first`.
|
|
if subfirst.maybe_empty || seq_rep.op == ast::KleeneOp::ZeroOrMore {
|
|
// If sequence is potentially empty, then
|
|
// union them (preserving first emptiness).
|
|
first.add_all(&TokenSet { maybe_empty: true, ..subfirst });
|
|
} else {
|
|
// Otherwise, sequence guaranteed
|
|
// non-empty; replace first.
|
|
first = subfirst;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return first;
|
|
}
|
|
}
|
|
|
|
// walks forward over `tts` until all potential FIRST tokens are
|
|
// identified.
|
|
fn first(&self, tts: &[TokenTree]) -> TokenSet {
|
|
let mut first = TokenSet::empty();
|
|
for tt in tts.iter() {
|
|
assert!(first.maybe_empty);
|
|
match *tt {
|
|
TokenTree::Token(sp, ref tok) => {
|
|
first.add_one((sp, tok.clone()));
|
|
return first;
|
|
}
|
|
TokenTree::Delimited(_, ref delimited) => {
|
|
first.add_one((delimited.open_span,
|
|
Token::OpenDelim(delimited.delim)));
|
|
return first;
|
|
}
|
|
TokenTree::Sequence(sp, ref seq_rep) => {
|
|
match self.first.get(&sp) {
|
|
Some(&Some(ref subfirst)) => {
|
|
|
|
// If the sequence contents can be empty, then the first
|
|
// token could be the separator token itself.
|
|
|
|
if let (Some(ref sep), true) = (seq_rep.separator.clone(),
|
|
subfirst.maybe_empty) {
|
|
first.add_one_maybe((sp, sep.clone()));
|
|
}
|
|
|
|
assert!(first.maybe_empty);
|
|
first.add_all(subfirst);
|
|
if subfirst.maybe_empty || seq_rep.op == ast::KleeneOp::ZeroOrMore {
|
|
// continue scanning for more first
|
|
// tokens, but also make sure we
|
|
// restore empty-tracking state
|
|
first.maybe_empty = true;
|
|
continue;
|
|
} else {
|
|
return first;
|
|
}
|
|
}
|
|
|
|
Some(&None) => {
|
|
panic!("assume all sequences have (unique) spans for now");
|
|
}
|
|
|
|
None => {
|
|
panic!("We missed a sequence during FirstSets construction");
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// we only exit the loop if `tts` was empty or if every
|
|
// element of `tts` matches the empty sequence.
|
|
assert!(first.maybe_empty);
|
|
return first;
|
|
}
|
|
}
|
|
|
|
// A set of Tokens, which may include MatchNt tokens (for
|
|
// macro-by-example syntactic variables). It also carries the
|
|
// `maybe_empty` flag; that is true if and only if the matcher can
|
|
// match an empty token sequence.
|
|
//
|
|
// The First set is computed on submatchers like `$($a:expr b),* $(c)* d`,
|
|
// which has corresponding FIRST = {$a:expr, c, d}.
|
|
// Likewise, `$($a:expr b),* $(c)+ d` has FIRST = {$a:expr, c}.
|
|
//
|
|
// (Notably, we must allow for *-op to occur zero times.)
|
|
#[derive(Clone, Debug)]
|
|
struct TokenSet {
|
|
tokens: Vec<(Span, Token)>,
|
|
maybe_empty: bool,
|
|
}
|
|
|
|
impl TokenSet {
|
|
// Returns a set for the empty sequence.
|
|
fn empty() -> Self { TokenSet { tokens: Vec::new(), maybe_empty: true } }
|
|
|
|
// Returns the set `{ tok }` for the single-token (and thus
|
|
// non-empty) sequence [tok].
|
|
fn singleton(tok: (Span, Token)) -> Self {
|
|
TokenSet { tokens: vec![tok], maybe_empty: false }
|
|
}
|
|
|
|
// Changes self to be the set `{ tok }`.
|
|
// Since `tok` is always present, marks self as non-empty.
|
|
fn replace_with(&mut self, tok: (Span, Token)) {
|
|
self.tokens.clear();
|
|
self.tokens.push(tok);
|
|
self.maybe_empty = false;
|
|
}
|
|
|
|
// Changes self to be the empty set `{}`; meant for use when
|
|
// the particular token does not matter, but we want to
|
|
// record that it occurs.
|
|
fn replace_with_irrelevant(&mut self) {
|
|
self.tokens.clear();
|
|
self.maybe_empty = false;
|
|
}
|
|
|
|
// Adds `tok` to the set for `self`, marking sequence as non-empy.
|
|
fn add_one(&mut self, tok: (Span, Token)) {
|
|
if !self.tokens.contains(&tok) {
|
|
self.tokens.push(tok);
|
|
}
|
|
self.maybe_empty = false;
|
|
}
|
|
|
|
// Adds `tok` to the set for `self`. (Leaves `maybe_empty` flag alone.)
|
|
fn add_one_maybe(&mut self, tok: (Span, Token)) {
|
|
if !self.tokens.contains(&tok) {
|
|
self.tokens.push(tok);
|
|
}
|
|
}
|
|
|
|
// Adds all elements of `other` to this.
|
|
//
|
|
// (Since this is a set, we filter out duplicates.)
|
|
//
|
|
// If `other` is potentially empty, then preserves the previous
|
|
// setting of the empty flag of `self`. If `other` is guaranteed
|
|
// non-empty, then `self` is marked non-empty.
|
|
fn add_all(&mut self, other: &Self) {
|
|
for tok in &other.tokens {
|
|
if !self.tokens.contains(tok) {
|
|
self.tokens.push(tok.clone());
|
|
}
|
|
}
|
|
if !other.maybe_empty {
|
|
self.maybe_empty = false;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Checks that `matcher` is internally consistent and that it
|
|
// can legally by followed by a token N, for all N in `follow`.
|
|
// (If `follow` is empty, then it imposes no constraint on
|
|
// the `matcher`.)
|
|
//
|
|
// Returns the set of NT tokens that could possibly come last in
|
|
// `matcher`. (If `matcher` matches the empty sequence, then
|
|
// `maybe_empty` will be set to true.)
|
|
//
|
|
// Requires that `first_sets` is pre-computed for `matcher`;
|
|
// see `FirstSets::new`.
|
|
fn check_matcher_core(cx: &mut ExtCtxt,
|
|
first_sets: &FirstSets,
|
|
matcher: &[TokenTree],
|
|
follow: &TokenSet) -> TokenSet {
|
|
use print::pprust::token_to_string;
|
|
|
|
let mut last = TokenSet::empty();
|
|
|
|
// 2. For each token and suffix [T, SUFFIX] in M:
|
|
// ensure that T can be followed by SUFFIX, and if SUFFIX may be empty,
|
|
// then ensure T can also be followed by any element of FOLLOW.
|
|
'each_token: for i in 0..matcher.len() {
|
|
let token = &matcher[i];
|
|
let suffix = &matcher[i+1..];
|
|
|
|
let build_suffix_first = || {
|
|
let mut s = first_sets.first(suffix);
|
|
if s.maybe_empty { s.add_all(follow); }
|
|
return s;
|
|
};
|
|
|
|
// (we build `suffix_first` on demand below; you can tell
|
|
// which cases are supposed to fall through by looking for the
|
|
// initialization of this variable.)
|
|
let suffix_first;
|
|
|
|
// First, update `last` so that it corresponds to the set
|
|
// of NT tokens that might end the sequence `... token`.
|
|
match *token {
|
|
TokenTree::Token(sp, ref tok) => {
|
|
let can_be_followed_by_any;
|
|
if let Err(bad_frag) = has_legal_fragment_specifier(tok) {
|
|
cx.struct_span_err(sp, &format!("invalid fragment specifier `{}`", bad_frag))
|
|
.help("valid fragment specifiers are `ident`, `block`, \
|
|
`stmt`, `expr`, `pat`, `ty`, `path`, `meta`, `tt` \
|
|
and `item`")
|
|
.emit();
|
|
// (This eliminates false positives and duplicates
|
|
// from error messages.)
|
|
can_be_followed_by_any = true;
|
|
} else {
|
|
can_be_followed_by_any = token_can_be_followed_by_any(tok);
|
|
}
|
|
|
|
if can_be_followed_by_any {
|
|
// don't need to track tokens that work with any,
|
|
last.replace_with_irrelevant();
|
|
// ... and don't need to check tokens that can be
|
|
// followed by anything against SUFFIX.
|
|
continue 'each_token;
|
|
} else {
|
|
last.replace_with((sp, tok.clone()));
|
|
suffix_first = build_suffix_first();
|
|
}
|
|
}
|
|
TokenTree::Delimited(_, ref d) => {
|
|
let my_suffix = TokenSet::singleton((d.close_span, Token::CloseDelim(d.delim)));
|
|
check_matcher_core(cx, first_sets, &d.tts, &my_suffix);
|
|
// don't track non NT tokens
|
|
last.replace_with_irrelevant();
|
|
|
|
// also, we don't need to check delimited sequences
|
|
// against SUFFIX
|
|
continue 'each_token;
|
|
}
|
|
TokenTree::Sequence(sp, ref seq_rep) => {
|
|
suffix_first = build_suffix_first();
|
|
// The trick here: when we check the interior, we want
|
|
// to include the separator (if any) as a potential
|
|
// (but not guaranteed) element of FOLLOW. So in that
|
|
// case, we make a temp copy of suffix and stuff
|
|
// delimiter in there.
|
|
//
|
|
// FIXME: Should I first scan suffix_first to see if
|
|
// delimiter is already in it before I go through the
|
|
// work of cloning it? But then again, this way I may
|
|
// get a "tighter" span?
|
|
let mut new;
|
|
let my_suffix = if let Some(ref u) = seq_rep.separator {
|
|
new = suffix_first.clone();
|
|
new.add_one_maybe((sp, u.clone()));
|
|
&new
|
|
} else {
|
|
&suffix_first
|
|
};
|
|
|
|
// At this point, `suffix_first` is built, and
|
|
// `my_suffix` is some TokenSet that we can use
|
|
// for checking the interior of `seq_rep`.
|
|
let next = check_matcher_core(cx, first_sets, &seq_rep.tts, my_suffix);
|
|
if next.maybe_empty {
|
|
last.add_all(&next);
|
|
} else {
|
|
last = next;
|
|
}
|
|
|
|
// the recursive call to check_matcher_core already ran the 'each_last
|
|
// check below, so we can just keep going forward here.
|
|
continue 'each_token;
|
|
}
|
|
}
|
|
|
|
// (`suffix_first` guaranteed initialized once reaching here.)
|
|
|
|
// Now `last` holds the complete set of NT tokens that could
|
|
// end the sequence before SUFFIX. Check that every one works with `suffix`.
|
|
'each_last: for &(_sp, ref t) in &last.tokens {
|
|
if let MatchNt(ref name, ref frag_spec) = *t {
|
|
for &(sp, ref next_token) in &suffix_first.tokens {
|
|
match is_in_follow(cx, next_token, &frag_spec.name.as_str()) {
|
|
Err((msg, help)) => {
|
|
cx.struct_span_err(sp, &msg).help(help).emit();
|
|
// don't bother reporting every source of
|
|
// conflict for a particular element of `last`.
|
|
continue 'each_last;
|
|
}
|
|
Ok(true) => {}
|
|
Ok(false) => {
|
|
let may_be = if last.tokens.len() == 1 &&
|
|
suffix_first.tokens.len() == 1
|
|
{
|
|
"is"
|
|
} else {
|
|
"may be"
|
|
};
|
|
|
|
cx.span_err(
|
|
sp,
|
|
&format!("`${name}:{frag}` {may_be} followed by `{next}`, which \
|
|
is not allowed for `{frag}` fragments",
|
|
name=name,
|
|
frag=frag_spec,
|
|
next=token_to_string(next_token),
|
|
may_be=may_be)
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
last
|
|
}
|
|
|
|
fn token_can_be_followed_by_any(tok: &Token) -> bool {
|
|
if let &MatchNt(_, ref frag_spec) = tok {
|
|
frag_can_be_followed_by_any(&frag_spec.name.as_str())
|
|
} else {
|
|
// (Non NT's can always be followed by anthing in matchers.)
|
|
true
|
|
}
|
|
}
|
|
|
|
/// True if a fragment of type `frag` can be followed by any sort of
|
|
/// token. We use this (among other things) as a useful approximation
|
|
/// for when `frag` can be followed by a repetition like `$(...)*` or
|
|
/// `$(...)+`. In general, these can be a bit tricky to reason about,
|
|
/// so we adopt a conservative position that says that any fragment
|
|
/// specifier which consumes at most one token tree can be followed by
|
|
/// a fragment specifier (indeed, these fragments can be followed by
|
|
/// ANYTHING without fear of future compatibility hazards).
|
|
fn frag_can_be_followed_by_any(frag: &str) -> bool {
|
|
match frag {
|
|
"item" | // always terminated by `}` or `;`
|
|
"block" | // exactly one token tree
|
|
"ident" | // exactly one token tree
|
|
"meta" | // exactly one token tree
|
|
"tt" => // exactly one token tree
|
|
true,
|
|
|
|
_ =>
|
|
false,
|
|
}
|
|
}
|
|
|
|
/// True if `frag` can legally be followed by the token `tok`. For
|
|
/// fragments that can consume an unbounded number of tokens, `tok`
|
|
/// must be within a well-defined follow set. This is intended to
|
|
/// guarantee future compatibility: for example, without this rule, if
|
|
/// we expanded `expr` to include a new binary operator, we might
|
|
/// break macros that were relying on that binary operator as a
|
|
/// separator.
|
|
// when changing this do not forget to update doc/book/macros.md!
|
|
fn is_in_follow(_: &ExtCtxt, tok: &Token, frag: &str) -> Result<bool, (String, &'static str)> {
|
|
if let &CloseDelim(_) = tok {
|
|
// closing a token tree can never be matched by any fragment;
|
|
// iow, we always require that `(` and `)` match, etc.
|
|
Ok(true)
|
|
} else {
|
|
match frag {
|
|
"item" => {
|
|
// since items *must* be followed by either a `;` or a `}`, we can
|
|
// accept anything after them
|
|
Ok(true)
|
|
},
|
|
"block" => {
|
|
// anything can follow block, the braces provide an easy boundary to
|
|
// maintain
|
|
Ok(true)
|
|
},
|
|
"stmt" | "expr" => {
|
|
match *tok {
|
|
FatArrow | Comma | Semi => Ok(true),
|
|
_ => Ok(false)
|
|
}
|
|
},
|
|
"pat" => {
|
|
match *tok {
|
|
FatArrow | Comma | Eq | BinOp(token::Or) => Ok(true),
|
|
Ident(i) if (i.name.as_str() == "if" ||
|
|
i.name.as_str() == "in") => Ok(true),
|
|
_ => Ok(false)
|
|
}
|
|
},
|
|
"path" | "ty" => {
|
|
match *tok {
|
|
OpenDelim(token::DelimToken::Brace) | OpenDelim(token::DelimToken::Bracket) |
|
|
Comma | FatArrow | Colon | Eq | Gt | Semi | BinOp(token::Or) => Ok(true),
|
|
MatchNt(_, ref frag) if frag.name.as_str() == "block" => Ok(true),
|
|
Ident(i) if i.name.as_str() == "as" || i.name.as_str() == "where" => Ok(true),
|
|
_ => Ok(false)
|
|
}
|
|
},
|
|
"ident" => {
|
|
// being a single token, idents are harmless
|
|
Ok(true)
|
|
},
|
|
"meta" | "tt" => {
|
|
// being either a single token or a delimited sequence, tt is
|
|
// harmless
|
|
Ok(true)
|
|
},
|
|
_ => Err((format!("invalid fragment specifier `{}`", frag),
|
|
"valid fragment specifiers are `ident`, `block`, \
|
|
`stmt`, `expr`, `pat`, `ty`, `path`, `meta`, `tt` \
|
|
and `item`"))
|
|
}
|
|
}
|
|
}
|
|
|
|
fn has_legal_fragment_specifier(tok: &Token) -> Result<(), String> {
|
|
debug!("has_legal_fragment_specifier({:?})", tok);
|
|
if let &MatchNt(_, ref frag_spec) = tok {
|
|
let s = &frag_spec.name.as_str();
|
|
if !is_legal_fragment_specifier(s) {
|
|
return Err(s.to_string());
|
|
}
|
|
}
|
|
Ok(())
|
|
}
|
|
|
|
fn is_legal_fragment_specifier(frag: &str) -> bool {
|
|
match frag {
|
|
"item" | "block" | "stmt" | "expr" | "pat" |
|
|
"path" | "ty" | "ident" | "meta" | "tt" => true,
|
|
_ => false,
|
|
}
|
|
}
|