On 2015/03/10 19:36:19, caitp wrote:
On 2015/03/10 19:29:44, marja wrote:
> I'm confused! I always thought that the rule is "a semicolon is inserted
*only*
> if it's a syntax error without the semicolon".
>
> Is this no longer true? What's going on here? Is there an additional
restriction
> that there cannot be a line feed between params and arrow, independent
of
ASI?
From
`https://people.mozilla.org/~jorendorff/es6-draft.html#sec-grammar-notation`
```
If the phrase “[no LineTerminator here]” appears in the right-hand side
of a
production of the syntactic grammar, it indicates that the production is a
restricted production: it may not be used if a LineTerminator occurs in
the
input stream at the indicated position. For example, the production:
ThrowStatement :
throw [no LineTerminator here] Expression ;
indicates that the production may not be used if a LineTerminator occurs
in
the
script between the throw token and the Expression.
```
Since the arrow function production requires that there is no line
terminator
before the `=>`, then we need to treat it as though there was a semicolon.
`var
fn = (a)\n` would be perfectly valid in ES5, so it's still valid in ES6,
but
there's a syntax error if the next statement starts with `=>`.
To be fair, the restriction in this case makes no sense since you would get
a
syntax error in either case.
IIRC, the [no LineTerminator here] was added for future extensions. We have
talked about allowing `=> {}` (optional params) and then the case `x\n=>{}`
would be ambiguous.
https://codereview.chromium.org/987203003/
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