Reject options that cannot take effect, and skip entries that are not data

template.go

@@ -143,6 +143,9 @@ func checkTokens(format string, fields map[string]node) error {
 				continue // a root reference; its target is checked at New (see linkRefs)
 			}
 			if _, ok := fields[name]; !ok {
+				if isOption(name) {
+					return fmt.Errorf("token {%s}: %q is an option, never a field", t.body, name)
+				}
 				return fmt.Errorf("token {%s}: no field %q", t.body, name)
 			}
 		}