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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* Token-affiliated data structures except for TokenKind (defined in its own
* header).
*/
#ifndef frontend_Token_h
#define frontend_Token_h
#include "mozilla/Assertions.h" // MOZ_ASSERT
#include <stdint.h> // uint32_t
#include "frontend/ParserAtom.h" // TaggedParserAtomIndex, TrivialTaggedParserAtomIndex
#include "frontend/TokenKind.h" // js::frontend::TokenKind
#include "js/RegExpFlags.h" // JS::RegExpFlags
namespace js {
namespace frontend {
struct TokenPos {
uint32_t begin = 0; // Offset of the token's first code unit.
uint32_t end = 0; // Offset of 1 past the token's last code unit.
TokenPos() = default;
TokenPos(uint32_t begin, uint32_t end) : begin(begin), end(end) {}
// Return a TokenPos that covers left, right, and anything in between.
static TokenPos box(const TokenPos& left, const TokenPos& right) {
MOZ_ASSERT(left.begin <= left.end);
MOZ_ASSERT(left.end <= right.begin);
MOZ_ASSERT(right.begin <= right.end);
return TokenPos(left.begin, right.end);
}
bool operator==(const TokenPos& bpos) const {
return begin == bpos.begin && end == bpos.end;
}
bool operator!=(const TokenPos& bpos) const {
return begin != bpos.begin || end != bpos.end;
}
bool operator<(const TokenPos& bpos) const { return begin < bpos.begin; }
bool operator<=(const TokenPos& bpos) const { return begin <= bpos.begin; }
bool operator>(const TokenPos& bpos) const { return !(*this <= bpos); }
bool operator>=(const TokenPos& bpos) const { return !(*this < bpos); }
bool encloses(const TokenPos& pos) const {
return begin <= pos.begin && pos.end <= end;
}
};
enum DecimalPoint { NoDecimal = false, HasDecimal = true };
// The only escapes found in IdentifierName are of the Unicode flavor.
enum class IdentifierEscapes { None, SawUnicodeEscape };
enum class NameVisibility { Public, Private };
class TokenStreamShared;
struct Token {
private:
// The lexical grammar of JavaScript has a quirk around the '/' character.
// As the spec puts it:
//
// > There are several situations where the identification of lexical input
// > elements is sensitive to the syntactic grammar context that is consuming
// > the input elements. This requires multiple goal symbols for the lexical
// > grammar. [...] The InputElementRegExp goal symbol is used in all
// > syntactic grammar contexts where a RegularExpressionLiteral is permitted
// > [...] In all other contexts, InputElementDiv is used as the lexical
// > goal symbol.
//
// https://tc39.github.io/ecma262/#sec-lexical-and-regexp-grammars
//
// What "sensitive to the syntactic grammar context" means is, the parser has
// to tell the TokenStream whether to interpret '/' as division or
// RegExp. Because only one or the other (or neither) will be legal at that
// point in the program, and only the parser knows which one.
//
// But there's a problem: the parser often gets a token, puts it back, then
// consumes it later; or (equivalently) peeks at a token, leaves it, peeks
// again later, then finally consumes it. Of course we don't actually re-scan
// the token every time; we cache it in the TokenStream. This leads to the
// following rule:
//
// The parser must not pass SlashIsRegExp when getting/peeking at a token
// previously scanned with SlashIsDiv; or vice versa.
//
// That way, code that asks for a SlashIsRegExp mode will never get a cached
// Div token. But this rule is easy to screw up, because tokens are so often
// peeked at on Parser.cpp line A and consumed on line B, where |A-B| is
// thousands of lines. We therefore enforce it with the frontend's most
// annoying assertion (in verifyConsistentModifier), and provide
// Modifier::SlashIsInvalid to help avoid tripping it.
//
// This enum belongs in TokenStream, but C++, so we define it here and
// typedef it there.
enum Modifier {
// Parse `/` and `/=` as the division operators. (That is, use
// InputElementDiv as the goal symbol.)
SlashIsDiv,
// Parse `/` as the beginning of a RegExp literal. (That is, use
// InputElementRegExp.)
SlashIsRegExp,
// Neither a Div token nor a RegExp token is syntactically valid here. When
// the parser calls `getToken(SlashIsInvalid)`, it must be prepared to see
// either one (and throw a SyntaxError either way).
//
// It's OK to use SlashIsInvalid to get a token that was originally scanned
// with SlashIsDiv or SlashIsRegExp. The reverse--peeking with
// SlashIsInvalid, then getting with another mode--is not OK. If either Div
// or RegExp is syntactically valid here, use the appropriate modifier.
SlashIsInvalid,
};
friend class TokenStreamShared;
public:
/** The type of this token. */
TokenKind type;
/** The token's position in the overall script. */
TokenPos pos;
union {
private:
friend struct Token;
TrivialTaggedParserAtomIndex atom;
struct {
/** Numeric literal's value. */
double value;
/** Does the numeric literal contain a '.'? */
DecimalPoint decimalPoint;
} number;
/** Regular expression flags; use charBuffer to access source chars. */
JS::RegExpFlags reflags;
} u;
#ifdef DEBUG
/** The modifier used to get this token. */
Modifier modifier;
#endif
// Mutators
void setName(TaggedParserAtomIndex name) {
MOZ_ASSERT(type == TokenKind::Name || type == TokenKind::PrivateName);
u.atom = TrivialTaggedParserAtomIndex::from(name);
}
void setAtom(TaggedParserAtomIndex atom) {
MOZ_ASSERT(type == TokenKind::String || type == TokenKind::TemplateHead ||
type == TokenKind::NoSubsTemplate);
u.atom = TrivialTaggedParserAtomIndex::from(atom);
}
void setRegExpFlags(JS::RegExpFlags flags) {
MOZ_ASSERT(type == TokenKind::RegExp);
u.reflags = flags;
}
void setNumber(double n, DecimalPoint decimalPoint) {
MOZ_ASSERT(type == TokenKind::Number);
u.number.value = n;
u.number.decimalPoint = decimalPoint;
}
// Type-safe accessors
TaggedParserAtomIndex name() const {
MOZ_ASSERT(type == TokenKind::Name || type == TokenKind::PrivateName);
return u.atom;
}
TaggedParserAtomIndex atom() const {
MOZ_ASSERT(type == TokenKind::String || type == TokenKind::TemplateHead ||
type == TokenKind::NoSubsTemplate);
return u.atom;
}
JS::RegExpFlags regExpFlags() const {
MOZ_ASSERT(type == TokenKind::RegExp);
return u.reflags;
}
double number() const {
MOZ_ASSERT(type == TokenKind::Number);
return u.number.value;
}
DecimalPoint decimalPoint() const {
MOZ_ASSERT(type == TokenKind::Number);
return u.number.decimalPoint;
}
};
} // namespace frontend
} // namespace js
#endif // frontend_Token_h
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