id,summary,reporter,owner,description,type,status,priority,resolution,keywords,cc,topic,difficulty,mentor
81,Implement a better type checker for yhc,malcolm.wallace,none,"The implementation of type inference in yhc (also used in nhc98) is occasionally incorrect, always difficult to understand and modify, and entirely undocumented.  As a result, there is no hope of extending it to deal with multi-parameter type classes, functional dependencies, associated types, GADTs, rank-N, or any of the other exciting and widely-used type-system extensions.  The solution - rip it out and replace it completely.  There are a few key requirements:  it must be maintainable, it must be correct, it must give reasonable error messages.  Speed is not a goal.

Ideally, you will also implement one or more of the extensions noted above.  There are opportunities to engage with cutting-edge type techniques like constraint-based resolution, or just to go for plain and simple H-M-style.

= Interested Mentors =
 * Malcolm Wallace <[mailto:malcolm.wallace@cs.york.ac.uk]>

= Interested Students =
 * Charles Blundell <[mailto:blundellc@googlemail.com]>
 * Kenn Knowles <[mailto:kknowles@soe.ucsc.edu]>",proposed-project,closed,OK,wontfix,"types, compilers",,YHC,1 person Summer,not-accepted