createBaseShapeValidator

The fields every shape has, whatever its type — everything but props.

Used for a shape whose type this build has no props map for. Forward compatibility is about props: a newer generation of the format may carry props this build cannot describe, and those must survive a round trip. It says nothing about x being a number or index being an index key, which are true of every shape record there has ever been. Passing an unknown type through untouched let { x: "NOT A NUMBER" } into the store.