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Bug 885695 - Simplify detection of legacy generators. r=Waldo, r=jorendorff

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This commit is contained in:
Andy Wingo 2013-08-06 13:01:51 +02:00
parent dee2ecf218
commit 59af52fe96
3 changed files with 73 additions and 169 deletions
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213
js/src/frontend/Parser.cpp
View File

@ -1051,6 +1051,8 @@ Parser<ParseHandler>::functionBody(FunctionSyntaxKind kind, FunctionBodyType typ
JS_ASSERT(pc->sc->isFunctionBox());
JS_ASSERT(!pc->funHasReturnExpr && !pc->funHasReturnVoid);
uint32_t startYieldOffset = pc->lastYieldOffset;
Node pn;
if (type == StatementListBody) {
pn = statements();
@ -1067,13 +1069,24 @@ Parser<ParseHandler>::functionBody(FunctionSyntaxKind kind, FunctionBodyType typ
pn = handler.newReturnStatement(kid, handler.getPosition(kid));
if (!pn)
return null();
}
if (pc->sc->asFunctionBox()->isLegacyGenerator()) {
if (pc->lastYieldOffset != startYieldOffset) {
JS_ASSERT(pc->isLegacyGenerator());
if (kind == Arrow) {
reportWithOffset(ParseError, false, pc->lastYieldOffset,
JSMSG_YIELD_IN_ARROW, js_yield_str);
return null();
}
if (type == ExpressionBody) {
reportBadReturn(pn, ParseError,
JSMSG_BAD_GENERATOR_RETURN,
JSMSG_BAD_ANON_GENERATOR_RETURN);
return null();
}
pc->sc->asFunctionBox()->setIsLegacyGenerator();
} else {
JS_ASSERT(!pc->isLegacyGenerator());
}
/* Check for falling off the end of a function that returns a value. */
@ -2253,10 +2266,6 @@ Parser<ParseHandler>::functionArgsAndBodyGeneric(Node pn, HandleFunction fun, Fu
}
// Parse the function body.
Maybe<GenexpGuard<ParseHandler> > yieldGuard;
if (kind == Arrow)
yieldGuard.construct(this);
FunctionBodyType bodyType = StatementListBody;
if (tokenStream.getToken(TokenStream::Operand) != TOK_LC) {
tokenStream.ungetToken();
@ -2268,9 +2277,6 @@ Parser<ParseHandler>::functionArgsAndBodyGeneric(Node pn, HandleFunction fun, Fu
if (!body)
return false;
if (!yieldGuard.empty() && !yieldGuard.ref().checkValidBody(body, JSMSG_YIELD_IN_ARROW))
return false;
if (fun->name() && !checkStrictBinding(fun->name(), pn))
return false;
@ -4410,18 +4416,31 @@ Parser<ParseHandler>::returnStatementOrYieldExpression()
// Legacy generators are identified by the presence of "yield" in their
// bodies. We only see "yield" as TOK_YIELD in JS 1.7+.
if (isYield) {
JS_ASSERT(tokenStream.versionNumber() >= JSVERSION_1_7);
if (!abortIfSyntaxParser())
return null();
// If we're within parens, we won't know if this is a generator
// expression until we see a |for| token, so we have to delay flagging
// the current function.
if (pc->parenDepth == 0) {
pc->sc->asFunctionBox()->setIsLegacyGenerator();
if (pc->isLegacyGenerator()) {
// We are in a legacy generator: a function that has already seen a
// yield.
JS_ASSERT(pc->sc->isFunctionBox());
JS_ASSERT(pc->lastYieldOffset != ParseContext<ParseHandler>::NoYieldOffset);
} else {
pc->yieldCount++;
pc->yieldOffset = begin;
// We are in a code that has not seen a yield, and in JS 1.8 so
// "yield" parsed as TOK_YIELD. Try to transition to being a legacy
// generator.
JS_ASSERT(tokenStream.currentToken().type == TOK_YIELD);
JS_ASSERT(pc->lastYieldOffset == ParseContext<ParseHandler>::NoYieldOffset);
if (!pc->sc->isFunctionBox()) {
report(ParseError, false, null(), JSMSG_BAD_RETURN_OR_YIELD, js_yield_str);
return null();
}
pc->generatorParseMode = ParseContext<ParseHandler>::LegacyGenerator;
}
pc->lastYieldOffset = begin;
}
// Parse an optional operand.
@ -4466,7 +4485,7 @@ Parser<ParseHandler>::returnStatementOrYieldExpression()
if (!pn)
return null();
if (pc->funHasReturnExpr && pc->sc->asFunctionBox()->isLegacyGenerator()) {
if (pc->funHasReturnExpr && pc->isLegacyGenerator()) {
/* As in Python (see PEP-255), disallow return v; in generators. */
reportBadReturn(pn, ParseError, JSMSG_BAD_GENERATOR_RETURN,
JSMSG_BAD_ANON_GENERATOR_RETURN);
@ -5415,117 +5434,6 @@ class CompExprTransplanter
bool transplant(ParseNode *pn);
};
/*
* A helper for lazily checking for the presence of illegal |yield| or
* |arguments| tokens inside of legacy generator expressions. This must be done
* lazily since we don't know whether we're in a legacy generator expression
* until we see the "for" token after we've already parsed the body expression.
* (For ES6 generator comprehensions, we won't need this lazy check because the
* |for| is at the beginning.)
*
* Use in any context which may turn out to be inside a legacy generator
* expression. This includes parenthesized expressions and argument lists, and
* it includes the tail of legacy generator expressions.
*
* The guard will keep track of any |yield| or |arguments| tokens that occur while
* parsing the body. As soon as the parser reaches the end of the body expression,
* call endBody() to reset the context's state, and then immediately call:
*
* - checkValidBody() if this *did* turn out to be a legacy generator expression
* - maybeNoteLegacyGenerator() if this *did not* turn out to be a legacy
* generator expression
*/
template <typename ParseHandler>
class GenexpGuard
{
Parser<ParseHandler> *parser;
uint32_t startYieldCount;
typedef typename ParseHandler::Node Node;
public:
explicit GenexpGuard(Parser<ParseHandler> *parser)
: parser(parser)
{
ParseContext<ParseHandler> *pc = parser->pc;
if (pc->parenDepth == 0) {
pc->yieldCount = 0;
pc->yieldOffset = 0;
}
startYieldCount = pc->yieldCount;
pc->parenDepth++;
}
void endBody();
bool checkValidBody(Node pn, unsigned err = JSMSG_BAD_GENEXP_BODY);
bool maybeNoteLegacyGenerator(Node pn);
};
template <typename ParseHandler>
void
GenexpGuard<ParseHandler>::endBody()
{
parser->pc->parenDepth--;
}
/*
* Check whether a |yield| or |arguments| token has been encountered in the
* body expression, and if so, report an error.
*
* Call this after endBody() when determining that the body *was* in a
* generator expression.
*/
template <typename ParseHandler>
bool
GenexpGuard<ParseHandler>::checkValidBody(Node pn, unsigned err)
{
ParseContext<ParseHandler> *pc = parser->pc;
if (pc->yieldCount > startYieldCount) {
uint32_t offset = pc->yieldOffset
? pc->yieldOffset
: (pn ? parser->handler.getPosition(pn)
: parser->pos()).begin;
parser->reportWithOffset(ParseError, false, offset, err, js_yield_str);
return false;
}
return true;
}
/*
* Check whether a |yield| token has been encountered in the body expression,
* and if so, note that the current function is a generator function.
*
* Call this after endBody() when determining that the body *was not* in a
* generator expression.
*/
template <typename ParseHandler>
bool
GenexpGuard<ParseHandler>::maybeNoteLegacyGenerator(Node pn)
{
ParseContext<ParseHandler> *pc = parser->pc;
// yieldCount is only incremented when we see yield in JS 1.7+ code.
if (pc->yieldCount > 0) {
if (!pc->sc->isFunctionBox()) {
// FIXME: This error should be detected eagerly, when the yield is
// seen.
parser->report(ParseError, false, ParseHandler::null(),
JSMSG_BAD_RETURN_OR_YIELD, js_yield_str);
return false;
}
pc->sc->asFunctionBox()->setIsLegacyGenerator();
if (pc->funHasReturnExpr) {
// At the time we saw the yield, we might not have set
// isLegacyGenerator yet.
parser->reportBadReturn(pn, ParseError,
JSMSG_BAD_GENERATOR_RETURN, JSMSG_BAD_ANON_GENERATOR_RETURN);
return false;
}
}
return true;
}
/*
* Any definitions nested within the comprehension expression of a generator
* expression must move "down" one static level, which of course increases the
@ -5817,7 +5725,7 @@ Parser<FullParseHandler>::comprehensionTail(ParseNode *kid, unsigned blockid, bo
pn2->pn_iflags |= JSITER_FOREACH;
MUST_MATCH_TOKEN(TOK_LP, JSMSG_PAREN_AFTER_FOR);
GenexpGuard<FullParseHandler> guard(this);
uint32_t startYieldOffset = pc->lastYieldOffset;
RootedPropertyName name(context);
tt = tokenStream.getToken();
@ -5874,14 +5782,10 @@ Parser<FullParseHandler>::comprehensionTail(ParseNode *kid, unsigned blockid, bo
return null();
MUST_MATCH_TOKEN(TOK_RP, JSMSG_PAREN_AFTER_FOR_CTRL);
guard.endBody();
if (isGenexp) {
if (!guard.checkValidBody(pn2))
return null();
} else {
if (!guard.maybeNoteLegacyGenerator(pn2))
return null();
if (isGenexp && pc->lastYieldOffset != startYieldOffset) {
reportWithOffset(ParseError, false, pc->lastYieldOffset,
JSMSG_BAD_GENEXP_BODY, js_yield_str);
return null();
}
switch (tt) {
@ -6111,12 +6015,12 @@ template <typename ParseHandler>
typename ParseHandler::Node
Parser<ParseHandler>::assignExprWithoutYield(unsigned msg)
{
GenexpGuard<ParseHandler> yieldGuard(this);
uint32_t startYieldOffset = pc->lastYieldOffset;
Node res = assignExpr();
yieldGuard.endBody();
if (res) {
if (!yieldGuard.checkValidBody(res, msg))
return null();
if (res && pc->lastYieldOffset != startYieldOffset) {
reportWithOffset(ParseError, false, pc->lastYieldOffset,
msg, js_yield_str);
return null();
}
return res;
}
@ -6128,15 +6032,13 @@ Parser<ParseHandler>::argumentList(Node listNode)
if (tokenStream.matchToken(TOK_RP, TokenStream::Operand))
return true;
GenexpGuard<ParseHandler> guard(this);
uint32_t startYieldOffset = pc->lastYieldOffset;
bool arg0 = true;
do {
Node argNode = assignExpr();
if (!argNode)
return false;
if (arg0)
guard.endBody();
if (handler.isOperationWithoutParens(argNode, PNK_YIELD) &&
tokenStream.peekToken() == TOK_COMMA) {
@ -6145,8 +6047,11 @@ Parser<ParseHandler>::argumentList(Node listNode)
}
#if JS_HAS_GENERATOR_EXPRS
if (tokenStream.matchToken(TOK_FOR)) {
if (!guard.checkValidBody(argNode))
if (pc->lastYieldOffset != startYieldOffset) {
reportWithOffset(ParseError, false, pc->lastYieldOffset,
JSMSG_BAD_GENEXP_BODY, js_yield_str);
return false;
}
argNode = generatorExpr(argNode);
if (!argNode)
return false;
@ -6154,11 +6059,8 @@ Parser<ParseHandler>::argumentList(Node listNode)
report(ParseError, false, argNode, JSMSG_BAD_GENERATOR_SYNTAX, js_generator_str);
return false;
}
} else
}
#endif
if (arg0 && !guard.maybeNoteLegacyGenerator(argNode))
return false;
arg0 = false;
handler.addList(listNode, argNode);
@ -6784,7 +6686,7 @@ Parser<ParseHandler>::parenExpr(bool *genexp)
if (genexp)
*genexp = false;
GenexpGuard<ParseHandler> guard(this);
uint32_t startYieldOffset = pc->lastYieldOffset;
/*
* Always accept the 'in' operator in a parenthesized expression,
@ -6798,12 +6700,14 @@ Parser<ParseHandler>::parenExpr(bool *genexp)
if (!pn)
return null();
guard.endBody();
#if JS_HAS_GENERATOR_EXPRS
if (tokenStream.matchToken(TOK_FOR)) {
if (!guard.checkValidBody(pn))
if (pc->lastYieldOffset != startYieldOffset) {
reportWithOffset(ParseError, false, pc->lastYieldOffset,
JSMSG_BAD_GENEXP_BODY, js_yield_str);
return null();
}
if (handler.isOperationWithoutParens(pn, PNK_COMMA)) {
report(ParseError, false, null(),
JSMSG_BAD_GENERATOR_SYNTAX, js_generator_str);
@ -6822,12 +6726,9 @@ Parser<ParseHandler>::parenExpr(bool *genexp)
handler.setEndPosition(pn, pos().end);
*genexp = true;
}
} else
}
#endif /* JS_HAS_GENERATOR_EXPRS */
if (!guard.maybeNoteLegacyGenerator(pn))
return null();
return pn;
}

27
js/src/frontend/Parser.h
View File

@ -105,10 +105,19 @@ struct ParseContext : public GenericParseContext
const unsigned staticLevel; /* static compilation unit nesting level */
uint32_t parenDepth; /* nesting depth of parens that might turn out
to be generator expressions */
uint32_t yieldCount; /* number of |yield| tokens encountered at
non-zero depth in current paren tree */
// Functions start off being parsed as NotGenerator.
// NotGenerator transitions to LegacyGenerator on parsing "yield" in JS 1.7.
enum GeneratorParseMode { NotGenerator, LegacyGenerator };
GeneratorParseMode generatorParseMode;
// lastYieldOffset stores the offset of the last yield that was parsed.
// NoYieldOffset is its initial value.
static const uint32_t NoYieldOffset = UINT32_MAX;
uint32_t lastYieldOffset;
bool isGenerator() const { return generatorParseMode != NotGenerator; }
bool isLegacyGenerator() const { return generatorParseMode == LegacyGenerator; }
Node blockNode; /* parse node for a block with let declarations
(block with its own lexical scope) */
private:
@ -192,11 +201,6 @@ struct ParseContext : public GenericParseContext
bool generateFunctionBindings(ExclusiveContext *cx, LifoAlloc &alloc,
InternalHandle<Bindings*> bindings) const;
public:
uint32_t yieldOffset; /* offset of a yield expression that might
be an error if we turn out to be inside
a generator expression. Zero means
there isn't one. */
private:
ParseContext **parserPC; /* this points to the Parser's active pc
and holds either |this| or one of
@ -246,13 +250,12 @@ struct ParseContext : public GenericParseContext
blockChain(prs->context),
maybeFunction(maybeFunction),
staticLevel(staticLevel),
parenDepth(0),
yieldCount(0),
generatorParseMode(NotGenerator),
lastYieldOffset(NoYieldOffset),
blockNode(ParseHandler::null()),
decls_(prs->context, prs->alloc),
args_(prs->context),
vars_(prs->context),
yieldOffset(0),
parserPC(&prs->pc),
oldpc(prs->pc),
lexdeps(prs->context),

2
js/src/tests/js1_8/genexps/regress-634472.js
View File

@ -58,7 +58,7 @@ const cases = [
{ expr: "(yield, 1 for (x in []))", top: JSMSG_TOP_YIELD, fun: JSMSG_YIELD_PAREN, gen: JSMSG_YIELD_PAREN, desc: "simple yield in list in genexp" },
{ expr: "(yield 1, 2 for (x in []))", top: JSMSG_TOP_YIELD, fun: JSMSG_YIELD_PAREN, gen: JSMSG_YIELD_PAREN, desc: "yield w/ arg in list in genexp" },
{ expr: "(1, yield for (x in []))", top: JSMSG_TOP_YIELD, fun: JSMSG_GENERIC, gen: JSMSG_GENERIC, desc: "simple yield at end of list in genexp" },
{ expr: "(1, yield 2 for (x in []))", top: JSMSG_TOP_YIELD, fun: { simple: JSMSG_GENEXP_YIELD, call: JSMSG_BAD_GENERATOR_SYNTAX },
{ expr: "(1, yield 2 for (x in []))", top: JSMSG_TOP_YIELD, fun: { simple: JSMSG_GENEXP_YIELD, call: JSMSG_GENEXP_YIELD },
gen: JSMSG_GENEXP_YIELD, desc: "yield w/ arg at end of list in genexp" },
{ expr: "((yield) for (x in []))", top: JSMSG_TOP_YIELD, fun: JSMSG_GENEXP_YIELD, gen: JSMSG_GENEXP_YIELD, desc: "simple yield, parenthesized in genexp" },
{ expr: "((yield 1) for (x in []))", top: JSMSG_TOP_YIELD, fun: JSMSG_GENEXP_YIELD, gen: JSMSG_GENEXP_YIELD, desc: "yield w/ arg, parenthesized in genexp" },