Hello,
In the latest ES.next draft(May 4), section 10.5.3 Function Declaration
Instantiation step 5 is following
5. For each String argName in parameterNames, in list order do
> a. Let alreadyDeclared be the result of calling env’s HasBinding
> concrete method passing argName as the argument.
> b. NOTE Duplicate parameter names can only occur in non-strict code.
> c. If alreadyDeclared is false, then
> i. Call env’s CreateMutableBinding concrete method passing argName
> as the argument.
> d. If strict is false, then
> i. Call env’s InitializeBinding concrete method passing argName, and
> undefined as the arguments.
In the step d-i, if strict is false, engine always call
env.InitializeBinding(argName, undefined).
But if code is non-strict mode, duplicate parameter names may be provided.
And section 10.2.1.1.8, InitializeBinding, step 2 is following
2. Assert: envRec must have an uninitialised binding for N.
So for example,
// this is non-strict function
function test(a, a) {
}
test(1, 1);
engine execute above script and raise assertion failure because of calling
InitializeBinding to the same name twice.
So I suggest changing like this
c. If alreadyDeclared is false, then
> i. Call env’s CreateMutableBinding concrete method passing argName
> as the argument.
> ii. If strict is false, then
> 1. Call env’s InitializeBinding concrete method passing argName,
> and undefined as the arguments.
If I missed something, please point out.
Regards,
Yusuke Suzuki
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