Pratap came up with an issue in reviewing the ES3.1 draft that I don't have a
good answer to:
Sections 7 and 5.1.2 mention InputElementDiv and InputElementRegExp.
7 "There are two goal symbols for the lexical grammar. The InputElementDiv
symbol is used in those syntactic grammar contexts where a division (/) or
division-assignment (/=) operator is permitted. The InputElementRegExp symbol
is used in other syntactic grammar contexts."
Where in the grammar (or elsewhere) does it define **when** these two contexts
are used?
There are no subsequent references to InputElementDiv or InputElementRegExp in
either the grammars or the prose of the specification. Nor, is there any
reference to RegularExpressionLiteral in the syntactic grammar or supporting
prose.
So how am I as a language implementer reading this specification supposed to
know that:
var rx = /a*z/;
is a valid expression whose RHS is an RegualrExpressionLiteral? The best
explanation I can come up with for this interpretation solely from the
specification is that the production to the right of the "=" in
VariableDeclaration is an AssignmentExpression that can reduce to
ConditionalExpression and since ConditionExpression doesn't describe any
non-parenthesized expressions that begin with "/" or "=/" I should use
InputElementRegExp and accept a RegularExpressionLiteral as a
PrimaryExpression. (and there really isn't anything in the specification that
tells me to make that last leap. Actually, I don't really think that the
specification actually says that the above example is valid.)
This isn't a new ES3.1 problem. Nothing has changed from the ES3 specification
in this regard. Am I missing something obvious? Obviously this can't be
unambiguously specified in the grammar but it sure seems like there should be
some sort of comprehensible specification of exactly when
RegularExpressionLiteral is allowed.
Allen
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