Extend a non-persistable type?

Is the following possible?

entity type Manufacturer extends MetricEvaluatable schema name "MNFCT"

using extends vs mixes?

Looks like server sees the silliness and makes the fix automatically

So heres whats REALLY happenning.

the syntax extends is just syntax sugar (httpfs://en.wikipedia.org/wiki/Syntactic_sugar) and is treated equivalently to mixes. You can think of it as if everytime you type extends A mixes B, C the platform treats it as mixes A, B, C.

The real rule is that you can only MIXIN 1 persistable type.

When you mixin a persistable type, the documentation is rendered as extends

This might change in the future where extends and mixes are really different.