StackOverflowError while editing RxJava 4

[akarnokd]

Ever since I've started editing RxJava 4, https://github.com/ReactiveX/RxJava, the IDE keeps crashing with a StackOverflowError, especially if I have a temporary compilation error during editing.

Imported via default Buildship Gradle.

Eclipse IDE for Enterprise Java and Web Developers (includes Incubating components)

Version: 2026-03 (4.39.0)
Build id: 20260305-0817

How to reproduce:

Break some classes, such as Observable.java, fix it, break it, fix it. Eventually the error will popup and the IDE wants to quit. Very annoying.

I don't think I can provide a "small reproducing example" because the issue seems to be popping up with a complex project.

StackOverflowError.txt

Excerpt:

java.lang.StackOverflowError
	at org.eclipse.jdt.internal.core.JavaElement.hashCode(JavaElement.java:507)
	at java.base/java.util.HashMap.hash(HashMap.java:338)
	at java.base/java.util.HashMap.getNode(HashMap.java:576)
	at java.base/java.util.HashMap.get(HashMap.java:564)
	at org.eclipse.jdt.internal.core.NameLookup.seekTypesInWorkingCopies(NameLookup.java:1730)
	at org.eclipse.jdt.internal.core.NameLookup.seekTypes(NameLookup.java:1472)
	at org.eclipse.jdt.internal.core.NameLookup.findType(NameLookup.java:1026)
	at org.eclipse.jdt.internal.core.NameLookup.findType(NameLookup.java:837)
	at org.eclipse.jdt.internal.core.NameLookup.findType(NameLookup.java:735)
	at org.eclipse.jdt.internal.core.SearchableEnvironment.find(SearchableEnvironment.java:200)
	at org.eclipse.jdt.internal.core.SearchableEnvironment.findType(SearchableEnvironment.java:575)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.fromSplitPackageOrOracle(LookupEnvironment.java:520)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.lambda$1(LookupEnvironment.java:384)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForTypeFromModules(LookupEnvironment.java:487)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForType(LookupEnvironment.java:383)
	at org.eclipse.jdt.internal.compiler.lookup.PackageBinding.getTypeOrPackage(PackageBinding.java:277)
	at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.findImport(CompilationUnitScope.java:620)
	at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.resolveImports(CompilationUnitScope.java:320)
	at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.checkAndSetImports(CompilationUnitScope.java:271)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment$CompleteTypeBindingsSteps.perform(LookupEnvironment.java:220)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.completeTypeBindings(LookupEnvironment.java:677)
	at org.eclipse.jdt.internal.codeassist.impl.Engine.accept(Engine.java:151)
	at org.eclipse.jdt.internal.codeassist.SelectionEngine.accept(SelectionEngine.java:313)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForType(LookupEnvironment.java:434)
	at org.eclipse.jdt.internal.compiler.lookup.PackageBinding.getTypeOrPackage(PackageBinding.java:277)
	at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.findImport(CompilationUnitScope.java:620)
	at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.resolveImports(CompilationUnitScope.java:320)
	at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.checkAndSetImports(CompilationUnitScope.java:271)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment$CompleteTypeBindingsSteps.perform(LookupEnvironment.java:220)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.completeTypeBindings(LookupEnvironment.java:677)
	at org.eclipse.jdt.internal.codeassist.impl.Engine.accept(Engine.java:151)
[...]