A lambda given to stream().filter() that modifies the elements leaves the source list @NotModified #115

fernflower (test-oss/fernflower, main sources; maddi 8a38863c8, maddi-mod 6ed8f49f), GenericMain:

public static List<TypeAnnotationWriteHelper> getGenericTypeAnnotations(
    int argIndex, List<TypeAnnotationWriteHelper> typeAnnWriteHelpers) {
  return typeAnnWriteHelpers.stream().filter(typeAnnWriteHelper -> {
    StructTypePathEntry entry = typeAnnWriteHelper.getPaths().peek();
    boolean inGeneric = entry != null && entry.getTypeArgumentIndex() == argIndex
                        && entry.getTypePathEntryKind() == StructTypePathEntry.Kind.TYPE.getId();
    if (inGeneric) typeAnnWriteHelper.getPaths().pop();   // modifies the element's own Deque
    return inGeneric;
  }).collect(Collectors.toList());
}

with TypeAnnotationWriteHelper.getPaths() returning its private final Deque<StructTypePathEntry> paths field.

Results: typeAnnWriteHelpers has unmodifiedParameter: 1 and structurallyUnmodifiedParameter: 1. The structural
claim may stand (the helpers are the list's elements, hidden content), but the deep one does not: every element for
which inGeneric holds has its paths deque popped. The modification happens in a lambda that Stream.filter
applies to the stream's elements, which are the list's elements, and it does not reach the parameter.
ExprProcessor.writeTypeAnnotationBeforeType has the same shape and the same result for its list of helpers.

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