cue: more conversions to new style templates

Change-Id: I5476eaf5fb2d6cc09fc9848d0dd711ddcb6c249c
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/3865
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/encoding/protobuf/parse.go b/encoding/protobuf/parse.go
index e70601c..917f7fd 100644
--- a/encoding/protobuf/parse.go
+++ b/encoding/protobuf/parse.go
@@ -519,7 +519,7 @@
 
 		// All keys are converted to strings.
 		// TODO: support integer keys.
-		f.Label = &ast.TemplateLabel{Ident: ast.NewIdent("_")}
+		f.Label = ast.NewList(ast.NewIdent("string"))
 		f.Value = p.toExpr(x.Position, p.resolve(x.Position, x.Type, x.Options))
 
 		name := p.ident(x.Position, x.Name)