Can't use typedarray macro with generics

[jdm]

It is not possible to write a function that accepts a generic type that's bounded by TypedArrayElement and extracts a typed array from a JSObject pointer. The macro doesn't like typedarray!(in(cx) let foo: TypedArray<T> = ...) because it accepts an ident, not a ty, and making it accept a ty yields $crate::typedarray::TypedArray<T>::from(...) which is obviously incorrect.

[emilio]

We had some custom code for making the no_jsmanaged_fieds macro work with generics IIRC, probably we can do something similar.