The foundational abstraction for input and output to commands
The fundamental error type for the evaluation engine. These cases represent different kinds of errors
the evaluator might face, along with helpful spans to label. An error renderer will take this error value
and pass it into an error viewer to display to the user.
The syntactic shapes that values must match to be passed into a command. You can think of this as the type-checking that occurs when you call a function.
Core structured values that pass through the pipeline in Nushell.