Consider the following JavaScript code fragment:
var x=foo.
if (a>b) -bar;
If this showed up in real code, it would probably be either as a typo where
either the actual property name for foo was left off or because of a mental
lapse by an old Smalltalk programmer who was used to using . instead of ; to
terminate statements. Regardless, it will validly parse identically to the
following single line formulation:
var x=foo.if(a>b)-bar;
The ES5 grammar for a dotted property access is:
CallExpression ::
CallExpression . IdentifierName
Where IdentifierName includes all possible identifiers including reserved
words. The above confusion could have been avoided if we had instead defined
things as:
CallExpression ::
CallExpression . Identifier
CallExpression . [no LineTerminator here] ReservedWord
Is this the grammar we should have used for ES5? It's too late to make this
change in the ES5 spec. but if we had consensus that this is how it should be
specified in Harmony we might also get the emerging ES5 implementations to also
follow this interpretations.
Thoughts? It's kind of hooky to have semi-arbitrary restrictions on line
terminator placement. But we already have them in order to make semi-colon
insertion more sane and arguably such restrictions reasonably go hand-in-hand
with allowing context sensitive use of reserved words.
Allen
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