[BUG] Luau reports typechecking error on strict

[Aloroid]

Describe the bug

Luau currently reports a type error in strict mode for code generated for the client.
This is due to when using :WaitForChild, the return value is Instance while we know that it's a RemoteEvent.
The function FireServer does not exist on type Instance thus correctly reporting an error.

Reproduction

Just generate any code for the client. It should cause a type error in strict mode.

Expected behavior

The generated code should not give off any type error.

Potential Fix

Typecast the resulting return value to be RemoteEvent / UnreliableRemoteEvent

[ArchLand64]

I believe a better fix to this problem is to just assert the class of the instance received, because the instance received could actually be something other than a RemoteEvent. That looks like

assert(reliable:IsA("RemoteEvent"))
assert(unreliable:IsA("UnreliableRemoteEvent"))