mars-dev, I am seeing the same behavior in 5.3.7 and 5.2.18.

I don't believe this is a valid query. JPA 2.1 says:

update_statement :: = update_clause [where_clause] 

update_clause ::= UPDATE entity_name [[AS] identification_variable]
SET update_item {, update_item}*

update_item ::= [identification_variable.]{single_valued_embeddable_object_field.}*
{state_field | single_valued_object_field} = new_value

It also says:

"A single_valued_object_field is designated by the name of an association field in a one-to-one or
many-to-one relationship or a field of embeddable class type. The type of a
single_valued_object_field is the abstract schema type of the related entity or embeddable class."

IIUC, e.user.assignTo is not an Event state_field or single_valued_object_field., it is a User state_field.

Guillaume Smet, WDYT? Should this be rejected?