when trying to look up the state of this proposal, I noticed: - there seem to be two parallel versions (probably signatures is an older form, and all references ought to point to annotations instead?): http://hackage.haskell.org/trac/haskell-prime/wiki/HaskellExtensions points to: http://hackage.haskell.org/trac/haskell-prime/wiki/PartialTypeSigs http://hackage.haskell.org/trac/haskell-prime/ticket/40 whereas http://hackage.haskell.org/trac/haskell-prime/report/9 points to: http://hackage.haskell.org/trac/haskell-prime/wiki/PartialTypeAnnotations http://hackage.haskell.org/trac/haskell-prime/ticket/86 - the proposal focusses on using "_" as a place holder for unspecified parts of a type or context, without discussing the alternative I'd favour: instead of introducing holes in types and contexts to leave parts of a declaration unspecified, why not use type subsumption? the idea being, that instead of declaring the precise type, one would declare an upper bound on the type, and the precise type inferred needs to be subsumed by the one declared. type and context syntax would remain unchanged, but in addition to "::" for precise type annotations, there'd be ":::" (or "::<", or whatever) to indicate the difference in intended semantics. pro: would easily allow for omission of type details or parts of context (a type with more context, or with more specific type components, is subsumed by the declaration) cons: as long as we only specify an upper bound, the inferred type could be more specific than we'd like (we can't say that we don't want context, or that some type variable must not be instantiated) cheers, claus