Don't use deduplicated predecessors in mapper-created duplication check #589
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inducer
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inducer
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inducer
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add comment explaining use of NonUniqueDirectPredecessorsGetter rename NonUniqueDirectPredecessorsGetter -> ListOfDirectPredecessorsGetter make DirectPredecessorsGetter not a Mapper fix docstrings
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DirectPredecessorsGetterreturns a deduplicated set of predecessors, which causes problems with the "mapper-created duplication" check inTransformMapper. Example: Suppose anIndexLambdahas two bindings that are duplicates of each other. When applying a mapper that deduplicates the DAG, such asCopyMapper, the recursion will deduplicate these two arrays, which means that a newIndexLambdamust be created. This should not trigger the mapper-created duplicate error, because it should see that one of the predecessors has changed. However becauseDirectPredecessorsGetterdeduplicates internally (by virtue of returning aFrozenOrderedSet), it will report that theIndexLambdahas only one predecessor. Subsequently, the duplication check won't see that a predecessor has changed, and it will trigger the error.This change adds a
ListOfDirectPredecessorsGetterthat returns a list instead of a set and uses that to implement the duplication check.