"A reactive whose class declares the listed traits." _t is a phantom slot typed against typeof Cls.traits; listed keys must resolve to non-null. Pure constraint — doesn't imply Cell<T>; intersect with Writable<Cell<T>> / Read<T> for capability.
_t
typeof Cls.traits
Cell<T>
Writable<Cell<T>>
Read<T>
"A reactive whose class declares the listed traits."
_tis a phantom slot typed againsttypeof Cls.traits; listed keys must resolve to non-null. Pure constraint — doesn't implyCell<T>; intersect withWritable<Cell<T>>/Read<T>for capability.