[GitHub] [beam] lostluck commented on a diff in pull request #25203: Fix interface{} in iter& emit type of DoFn in Go

["lostluck (via GitHub)" <gi...@apache.org>]

lostluck commented on code in PR #25203:
URL: https://github.com/apache/beam/pull/25203#discussion_r1089568225


##########
sdks/go/pkg/beam/core/funcx/output.go:
##########
@@ -84,6 +84,9 @@ func unfoldEmit(t reflect.Type) ([]reflect.Type, bool, error) {
 		if ok, err := isInParam(t.In(i)); !ok {
 			return nil, false, errors.Wrap(err, errIllegalParametersInEmit)
 		}
+		if t.In(i).Kind() == reflect.Interface || (t.In(i).Kind() == reflect.Pointer && t.In(i).Elem().Kind() == reflect.Interface) {
+			panic("Type interface{} isn't a supported PCollection type")

Review Comment:
   If there's an error return, one should return an error instead of panicking. Panicking is generally a last resort thing, and rarely when one can return an error instead.



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