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ASF GitHub Bot commented on FLINK-3042: --------------------------------------- Github user twalthr commented on a diff in the pull request: https://github.com/apache/flink/pull/2337#discussion_r77984002 --- Diff: flink-core/src/main/java/org/apache/flink/api/java/typeutils/TypeExtractor.java --- @@ -792,12 +832,40 @@ else if (t instanceof Class) { return null; } - + + @SuppressWarnings({"unchecked", "rawtypes"}) private <IN1> TypeInformation<?> createTypeInfoFromInput(TypeVariable<?> returnTypeVar, ArrayList<Type> inputTypeHierarchy, Type inType, TypeInformation<IN1> inTypeInfo) { TypeInformation<?> info = null; - + + // use a factory to find corresponding type information to type variable + final ArrayList<Type> factoryHierarchy = new ArrayList<>(inputTypeHierarchy); + final TypeInfoFactory<?> factory = getClosestFactory(factoryHierarchy, inType); + if (factory != null) { + // the type that defines the factory is last in factory hierarchy + final Type factoryDefiningType = factoryHierarchy.get(factoryHierarchy.size() - 1); + // defining type has generics, the factory need to be asked for a mapping of subtypes to type information + if (factoryDefiningType instanceof ParameterizedType) { --- End diff -- Yes, because we try to create type information from the input in this method. This only works if a type variable connects input with output. `Map<InType<A>, OutType<A>>` > Define a way to let types create their own TypeInformation > ---------------------------------------------------------- > > Key: FLINK-3042 > URL: https://issues.apache.org/jira/browse/FLINK-3042 > Project: Flink > Issue Type: Improvement > Components: Core > Affects Versions: 0.10.0 > Reporter: Stephan Ewen > Assignee: Timo Walther > Fix For: 1.0.0 > > > Currently, introducing new Types that should have specific TypeInformation > requires > - Either integration with the TypeExtractor > - Or manually constructing the TypeInformation (potentially at every place) > and using type hints everywhere. > I propose to add a way to allow classes to create their own TypeInformation > (like a static method "createTypeInfo()"). > To support generic nested types (like Optional / Either), the type extractor > would provide a Map of what generic variables map to what types (deduced from > the input). The class can use that to create the correct nested > TypeInformation (possibly by calling the TypeExtractor again, passing the Map > of generic bindings). -- This message was sent by Atlassian JIRA (v6.3.4#6332)