TempDir in a base class not initialized

[vmj]

Issue description

The @TempDir doesn't work in base class.

How to reproduce

Given a build.gradle file:

plugins {
    id 'groovy'
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation 'org.spockframework:spock-core:2.0-M4-groovy-2.5'
}

test {
    useJUnitPlatform()
}

and a src/test/groovy/BaseSpec.groovy file:

import spock.lang.Specification
import spock.lang.TempDir

import java.nio.file.Path

class BaseSpec extends Specification {
    @TempDir Path tmp
}

and a src/test/groovy/FileSpec.groovy file:

class FileSpec extends BaseSpec {
    void "test"() {
        expect:
        tmp != null
    }
}

when the test is executed

gradle test

then it fails

Condition not satisfied:

tmp != null
|   |
|   false
null

Versions

• Spock 2.0-M4
• Gradle 6.7
• Java 11

openjdk version "11.0.9" 2020-10-20 LTS
OpenJDK Runtime Environment Zulu11.43+21-CA (build 11.0.9+11-LTS)
OpenJDK 64-Bit Server VM Zulu11.43+21-CA (build 11.0.9+11-LTS, mixed mode)

• Groovy 2.5.12 (from transitive dependencies of Spock)
• IntelliJ IDEA, but also reproduced in command line
• macOS 10.15.7