This repository contains small example that reproduces issue #6664 of the checker-framework.
With checker-framework 4.43 and 4.44 the compilation with the checker-frameworks crashes with the error message
Error in AnnotatedTypeMirror.fromExpression(RegexAnnotatedTypeFactory, either.map(Arrays::asList)): Enclosing type not found: type: Object supertype: Either<A extends Object, B extends Object>
version 4.42 compiles the code without problems.
This issue is fixed with typetools/checker-framework#6692.