The type information from context is missing when using the CriteriaBuilder.selectCase(Expression<? extends C> expression).when(C condition, Expression<? extends R> result).
It's working however perfectly when using CriteriaBuilder.selectCase().when(Expression<Boolean> condition, Expression<? extends R> result).

By debugging the code, it appears that the type information from expression is not reused in condition, which leads to type conversion errors.