deploy: 5379e04ce4

home/exceptions/index.md

@@ -909,6 +909,18 @@ Example message
 [json.exception.type_error.318] duplicate object key 'red'
 ```
 
+### json.exception.type_error.321
+
+A discarded value (one created by [`parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) with a callback that returns `false` for the value, or by default-constructing a [`basic_json`](https://json.nlohmann.me/api/basic_json/index.md) with [`value_t::discarded`](https://json.nlohmann.me/api/basic_json/value_t/index.md)) was passed to a binary serialization function, either directly or nested in an array or object. There is no way to represent a discarded value in CBOR, MessagePack, UBJSON, BJData, or BSON.
+
+Example message
+
+Serializing `[1, 2]` to CBOR, where the second element was discarded by a parser callback:
+
+```
+[json.exception.type_error.321] cannot serialize discarded value to CBOR
+```
+
 ## Out of range
 
 This exception is thrown in case a library function is called on an input parameter that exceeds the expected range, for instance, in the case of array indices or nonexisting object keys.