Major Description
I hit this bug while dog-food eating (attempting to upgrade http://jirasearch.mikemccandless.com from 4.6.x to 6.x):
If you ask AnalyzingInfixSuggester for suggestions, but 1) you do not require all terms to match, and 2) you provide a context for filtering the results, then you'll get back results that did not match any of the terms from the user's query but did match solely the context filter.