On 2/11/2014 11:04 AM, Allen Wirfs-Brock wrote:
I can't find any explicit mention of this in the meeting notes [1]
where we decided to make Symbol a primitive type with a wrapper class.
However, I made the appropriate changes to the spec. immediately
after that meeting when the discussion was fresh in my mind and I
still think that throwing on Symbol(sym) is the right thing to do:
For the other primitive/wrapper types the following conventions apply:
new Wrapper(prim) //always creates a new Wrapper instances
wrapping the supplied primitive value
Wrapper(prim) //always returns a primitive value derived
by coercing the argument to the appropriate primitive type. Returns
prim if same type.
At [1] we made different decisions for symbols and Symbol wrappers :
new Symbol(arg) // always throws, we don't support explicit
creation of Symbol wrapper objects
Symbol(arg) // always returns a new, not previously
observed, primitive symbol value
One consideration is that it still is possible end up with a Symbol
wrapper and with the current spec there's no way to unwrap it. The
argument for having a Symbol wrapper at all was to enabled prototypal
inheritance, so, in theory, we want to enable people to add methods to
Symbol.prototype. When non-strict methods on Symbol.prototype are
called, they'll encounter a wrapped Symbol object that they can't do
much with since they can never get at the underlying Symbol primitive.
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