allow getStub to return something after AST is GC-ed

java/java-tests/testSrc/com/intellij/psi/StubAstSwitchTest.groovy

@@ -27,6 +27,7 @@ import com.intellij.psi.stubs.StubElement
 import com.intellij.psi.stubs.StubTree
 import com.intellij.psi.util.PsiTreeUtil
 import com.intellij.reference.SoftReference
+import com.intellij.testFramework.LeakHunter
 import com.intellij.testFramework.fixtures.LightCodeInsightFixtureTestCase
 import com.intellij.util.GCUtil
 
@@ -161,8 +162,8 @@ class B {
     assert file.treeElement
 
     GCUtil.tryGcSoftlyReachableObjects()
-    assert !file.stub
     assert !file.treeElement
+    assert file.stub
 
     assert psiClass.nameIdentifier
     assert !file.stub
@@ -190,8 +191,8 @@ class B {
     assert file.classes[0].nameIdentifier
     GCUtil.tryGcSoftlyReachableObjects()
 
-    assert !((PsiFileImpl)file).getTreeElement()
-    assert !((PsiFileImpl)file).getStub()
+    assert !((PsiFileImpl)file).treeElement
+    assertNoStubLoaded(file)
 
     assert file.classes[0].methods[0].modifierList.hasExplicitModifier(PsiModifier.STATIC)
     assert !((PsiFileImpl)file).getTreeElement()
@@ -204,11 +205,12 @@ class B {
     GCUtil.tryGcSoftlyReachableObjects()
 
     assert !file.treeElement
-    assert !file.greenStub
-
-    assert PsiAnchor.create(psiClass) instanceof PsiAnchor.StubIndexReference
+    assertNoStubLoaded(file)
     StubElement hardRefToStub = file.greenStub
     assert hardRefToStub
+    assert hardRefToStub == file.stub
+
+    assert file.node
 
     GCUtil.tryGcSoftlyReachableObjects()
     assert !file.treeElement
@@ -218,6 +220,10 @@ class B {
     assert !file.treeElement
   }
 
+  private static assertNoStubLoaded(PsiFile file) {
+    LeakHunter.checkLeak(file, StubTree) { candidate -> candidate.root.psi == file }
+  }
+
   void "test node is not deeply parsed when loaded in green stub presence"() {
     PsiFileImpl file = (PsiFileImpl)myFixture.addFileToProject("a.java", "class A<T>{}")
     def stubTree = file.stubTree