349851 - "yield \n ,3" compiles, but its decompilation does not

Status: VERIFIED FIXED

(Core :: JavaScript Engine, defect, P1)

Description

[Jesse Ruderman]

> function(){ yield 
  ,3 }
function () { yield, 3; }

> function () { yield, 3; }
syntax error

I don't know where the bug lies -- it could be that the first is accepted, the way the first decompiles, or that the second is not accepted.

Comment 1

[Jeff Walden [:Waldo]]

def foo():
  yield 12,42

returns the tuple (12, 42);

def foo():
  yield, 42

is a syntax error, because top-level yield statements require parenthesization in Python.  Enclosing parentheses results in a generator which yields None and on .next() throws StopIteration.

The latest ES4 dump on developer.m.o/es4/ gives the yield expression as "yield" AssignmentExpression without any [no line break here] between the two (as occurs with |return|, |continue|, and a few other constructs).  My tendency would be to insert [no line break here] in the production to conform with return.  If this were done, the former example would be a syntax error on the second line (",3"), and the latter would demonstrate the same behavior as the second Python example given here with parentheses inserted around the |yield|.  If this isn't done, then I think both examples should be equivalent (yield undefined, on .next() throw).

Comment 2

[Brendan Eich [:brendan]]

Attachment: fix

Python doesn't have the comma operator at lower precedence than assignment, but JS does -- still, we need to reject yield, 3 and yield\n, 3 equally (also 1, yield\n, 3 -- hence the placement of the error check).

/be

Comment 3

[Brendan Eich [:brendan]]

Fixed on trunk.

/be

Comment 4

[Bob Clary [:bc] (inactive)]

Checking in regress-349851.js;
/cvsroot/mozilla/js/tests/js1_7/geniter/regress-349851.js,v  <--  regress-349851.js
initial revision: 1.1

Comment 5

[Bob Clary [:bc] (inactive)]

verified fixed 1.9 20060903 windows/mac*/linux

Comment 6

[Mike Schroepfer]

Comment on attachment 236366 [details] [diff] [review]
fix

a=schrep for drivers.

Comment 7

[Brendan Eich [:brendan]]

Fixed on the 1.8 branch.

/be

Comment 8

[Bob Clary [:bc] (inactive)]

verified fixed 1.8 20060906 windows/mac*/linux