Go value decoding and nested cue.Value

[verdverm]

On the most recent community call, @rogpeppe mentioned an idea about something like this I think

val: {
  a: 1
  b: [string]: int
}

type Val struct {
  A int
  B cue.Value
}

var v Val
val.Decode(&v)

where

• a nested CUE value will be decoded into a cue.Value Go field
• incomplete CUE would now be possible. would this extend to the A field in this example?

Generally, can you expand on this idea here?

• is it possible to have a catchall Go field, such that any fields that are in the value but not the Go struct get put in an "overflow" field
• how can I exclude a field from being included from decoding? such that if I have an internal Go field, I don't want an accidental extra CUE field to fill it in during decoding