Finite subtype inference with explicit polymorphism

Finite subtype inference occupies a middle ground between Hindley-Milner-ty pe inference (as in ML) and subtype inference with recursively constrained types. It refers to subtype inference where only finite types are allowed a s solutions. This approach avoids some open problems with general subtype i nference, and has practical motivation where recursively constrained types are not appropriate. This paper presents algorithms for finite subtype infe rence, including checking for entailment of inferred types against explicit ly declared polymorphic types. This resolves for finite types a problem tha t is still open for recursively constrained types. Some motivation for this work, particularly for finite types and explicit polymorphism, is in provi ding subtype inference for first-class container objects with polymorphic m ethods. (C) 2001 Elsevier Science B.V. All rights reserved.