Power assertion broken for non-static inner class after upgrade to Groovy 3.0.8

[szpak]

Issue description

Power assertion has broken for non-static inner class after upgrade to Groovy 3.0.8.

How to reproduce

class PowerAssertionRegressionGroovy380Spec extends Specification {

  def test() {
    expect:
    new NonStaticInnerClass() == null
  }

  class NonStaticInnerClass {
    String toString() { "nsi" }
  }

}

fails wtih Groovy 3.0.7 with:

Condition not satisfied:

new NonStaticInnerClass() == null
|                         |
nsi                       false

Expected :null
Actual   :

With Groovy 3.0.8 there is:

Condition not satisfied:

new NonStaticInnerClass() == null
                          |
                          null

Expected :
Actual   :

The same assertion with plain Groovy (without Spock) works fine.

Additional Environment information

Spock master, Groovy 3.0.8

Additional information

The test for that case was added in autumn 2020 in #930.

Sample failure: https://github.com/spockframework/spock/pull/1316/checks?check_run_id=2475170792#step:6:130

[leonard84]

@Vampire would you take a look, as you did the original fix.

From what I can see is that the check expr == THIS_EXPRESSION in
for (Expression expr : expressions) converted.add(expr == THIS_EXPRESSION ? (T) expr : convert(expr));
does not match anymore, since the expr instance of this is different from the constant.

@paulk-asert do you know of any changes in groovy that might cause this?

[leonard84]

I think apache/groovy#1531 is the culprit, we will have to update the implicit this check.

[Vampire]

Yes, you are totally right.
See PR #1319