JPA + custom type + Number + NumberExpression throws IllegalArgument Unsupported target type

[HonoluluHenk]

Observed vs. expected behavior

(This is a continuation from the original QueryDSL issue #3550)

When using the following Combination

• a custom type extending Number (imho this seems to trigger the strange behavior)
• a custom @Converter/AttributeConverter (also happens with all other Hibernate custom types like UserType)
• a NumberExpression in the JPAQuery: sumAggregate() (formerly: sum())

Example:

var result = new JPAQuery<>(em)
		.select(myEntity.myCustomNumber.sumAggregate())
		.from(myEntity)
		.fetchOne();

Actual outcome:

java.lang.IllegalArgumentException: Unsupported target type : MyCustomNumber is thrown instead of a valid result.

Expected outcome:

The query-result.

Steps to reproduce

I created a reproducer with unit tests showing what works and what doesn't: https://github.com/dvbern/bug-reproducers-querydsl-jpa-hibernate6/tree/openfeign

Environment

Querydsl version: 6.0.0.RC1

Querydsl module: querydsl-jpa

Database: any (e.g. hsqldb, postgresql)

JDK: 17 (but the stacktrace indicates this is not a JDK-problem)