Spurious incremental CompilerTest failure

[niloc132]

https://github.com/gwtproject/gwt/actions/runs/8483890223/attempts/1

I believe I've seen this at least once before - something is going wrong either in the compiler or in the test code, causing com.google.gwt.dev.CompilerTest to fail "randomly". Every test method that validates incremental changes ends up failing with a stack trace something like this:

  <testcase classname="com.google.gwt.dev.CompilerTest" name="testChangeJsType" time="2.888">
    <failure message="expected:&lt;[com.foo.Bar, com.foo.Foo]&gt; but was:&lt;[java.util.Map, com.foo.Bar, java.util.Set, com.foo.Foo, java.util.List]&gt;" type="junit.framework.AssertionFailedError">junit.framework.AssertionFailedError: expected:&lt;[com.foo.Bar, com.foo.Foo]&gt; but was:&lt;[java.util.Map, com.foo.Bar, java.util.Set, com.foo.Foo, java.util.List]&gt;
	at com.google.gwt.dev.CompilerTest.compileToJs(CompilerTest.java:2739)
	at com.google.gwt.dev.CompilerTest.compileToJs(CompilerTest.java:2677)
	at com.google.gwt.dev.CompilerTest.checkRecompiledModifiedApp(CompilerTest.java:2637)
	at com.google.gwt.dev.CompilerTest.testChangeJsType(CompilerTest.java:1252)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
</failure>
  </testcase>

Every failure looks like this - as if Set, Map, and List had somehow also changed through simulated user actions.

Every failure included those three classes (I didn't see any others, but didn't exhaustively search), and every failure was specific to recompilation. Not all recompilation tests failed in this way though, for example testIncrementalRecompile_bridgeMethodOverrideChain and testIncrementalRecompile_jsPropertyConsistencyCheck did not fail in this way.

Failing CompilerTest.xml attached (but renamed with .txt suffix).
TEST-com.google.gwt.dev.CompilerTest.xml.txt