Improved Inference for Checking Type Annotations
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Date
2005-02-16T08:53:42Z
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Abstract
We consider type inference in the Hindley/Milner system extended with type annotations and constraints with a particular focus on Haskell-style type classes.
We observe that standard inference algorithms are incomplete in the presence of nested type annotations.
To improve the situation we introduce a novel inference scheme for checking type annotations. Our inference scheme is also incomplete in general but improves over existing implementations as found e.g.~in the Glasgow Haskell Compiler (GHC). For certain cases (e.g.~Haskell 98) our inference scheme is complete. Our approach has been fully implemented as part of the Chameleon system (experimental version of Haskell).