On Thu, Jan 30, 2014 at 10:59 AM, John Barton <[email protected]>wrote:
> > > > On Thu, Jan 30, 2014 at 7:54 AM, Brendan Eich <[email protected]> wrote: > >> John Lenz wrote: >> >>> Generally, I've always thought of: >>> >>> "if (x) ..." as equivalent to "if (x) { ... }" >>> >> >> let and const (and class) are block-scoped. {...} in your "if (x) {...}" >> is a block. An unbraced consequent is not a block, and you can't have a >> "conditional let binding". >> >> The restriction avoids nonsense such as >> >> let x = 0; { if (y) let x = 42; alert(x); } >> >> What pray tell is going on here, in your model? > > > I'm with John: the alert should say 0 and I can't see why that is not > obvious. > It's not obvious at all -- what happens when you drop the initial `let x = 0;` and you just have `{ if (y) let x = 42; alert(x); }` -- now what happens? Is x declared or not? To my mind `if (y) let x = 42;` reads like it's own 1-line noop block -- at least, that's what I'd expect of the scope. So while it could be allowed in that sense, it'd only serve as a footgun when y is true.
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