internal/encoding/gotypes: disjunctions of many kinds are not TODOs

We are aware that we are not handling these for now.
Much like how `#structOne | #structTwo` generates `map[string]any`,
disjunctions of different kinds like `string | int` generate `any`.
We can do better in the future if we wish to, but there is no good way
to represent sum types in Go today.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I92685ff0287003e4a39989d92ae122cdbed36ca6
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1207250
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>

Author: mvdan

cmd/cue/cmd/testdata/script/exp_gengotypes.txtar

@@ -638,13 +638,13 @@ type Types struct {
 
 	Duration string/* CUE time.Duration */ `json:"Duration,omitempty"`
 
-	StringOrInt any/* TODO: IncompleteKind: (int|string) */ `json:"StringOrInt,omitempty"`
+	StringOrInt any/* CUE disjunction: (int|string) */ `json:"StringOrInt,omitempty"`
 
-	StringOrIntDefault any/* TODO: IncompleteKind: (int|string) */ `json:"StringOrIntDefault,omitempty"`
+	StringOrIntDefault any/* CUE disjunction: (int|string) */ `json:"StringOrIntDefault,omitempty"`
 
-	NullOrStruct any/* TODO: IncompleteKind: (null|struct) */ `json:"NullOrStruct,omitempty"`
+	NullOrStruct any/* CUE disjunction: (null|struct) */ `json:"NullOrStruct,omitempty"`
 
-	NullOrString any/* TODO: IncompleteKind: (null|string) */ `json:"NullOrString,omitempty"`
+	NullOrString any/* CUE disjunction: (null|string) */ `json:"NullOrString,omitempty"`
 
 	NumericBounds any/* CUE number; int64 or float64 */ `json:"NumericBounds,omitempty"`
 

internal/encoding/gotypes/generate.go

@@ -316,6 +316,12 @@ func (g *generator) emitType(val cue.Value, optional bool) error {
 	// TODO: uint64 would be marginally better than int64 for unsigned integer types
 
 	default:
+		// A disjunction of various kinds cannot be represented in Go, as it does not have sum types.
+		// Also see the potential approaches in the TODO about disjunctions of structs.
+		if op, _ := val.Expr(); op == cue.OrOp {
+			g.appendf("any /* CUE disjunction: %s */", k)
+			break
+		}
 		g.appendf("any /* TODO: IncompleteKind: %s */", k)
 	}
 	return nil