Original post from forum 
"I found out that compass does a dictionary lookup for alias fields in a query, hence a query for "foo (alias:bar)" could suggest "foo (alias:baz)". To me, this doesn't make sense, as bar isn't ever meant to be added to the dictionary. I'd suggest to add
if ("alias".equals(term.field())) return term;
to the QueryTermVisitor in DefaultLuceneSpellCheckManager.suggest(CompassQuery) (sorry, can't provide a patch right now)"
The solution might not be as trivial as expected though. As a workaround, one could make sure that all used aliases are in the dictionary.