Cut down on casts in forEachChild

[ghost]

Use one cast for each node kind, not one cast per property.

[ahejlsberg]

Did you check whether this impacts performance, particularly in the binder? The existing casts have zero run-time cost (because they're compiled away), but the changes you are introducing do, and this is a very time critical function. Also, eventually we're going to switch the Node type to be a proper discriminated union and then we won't need the casts at all.

I'd prefer just leaving things the way there are here.

[mhegazy]

I am not sure i see much value in this reorganization. the type assertions do not get removed, they just reorganized, but now we have some additional code to execute at runtime.

closing for now.