On Mar 14, 2014, at 10:50 AM, Russell Leggett <russell.legg...@gmail.com> wrote:
> I completely agree with this. It looks like a modifier.
This is a good point, and folks working on the Square transpiler noticed this,
too. I think there's a more surgical fix, though (and I'm not entertaining
major syntax redesign at this point). In fact it's one with precedent in JS. In
statements, we allow both expressions and declarations, which is a syntactic
overlap. But visually people expect something that looks like a declaration in
that context to be a declaration, so the lookahead restriction breaks the tie
in favor of declarations.
I think we're seeing the exact same phenomenon with `export default` -- the
modifiers make it look more like a declaration context. So I think we should
consider doing the same thing as we do for ExpressionStatement:
ExportDeclaration :
...
export default FunctionDeclaration ;
export default ClassDeclaration ;
export default [lookahead !in { function, class }] AssignmentExpression
;
This actually results in no net change to the language syntax, but it allows us
to change the scoping rules so that function and class declarations scope to
the entire module:
// function example
export default function foo() { ... }
...
foo();
// class example
export default class Foo { ... }
...
let x = new Foo(...);
// expression example
export default { x: 1, y: 2, z: 3 };
I argue that not only does this avoid violating surprise, it's not any more of
a special-casing logic than we already have with ExpressionStatement, because
it's the same phenomenon: a context that allows a formally ambiguous union of
two productions, but whose context strongly suggests the declaration
interpretation over the expression interpretation in the overlapping cases.
Dave
_______________________________________________
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
