• Simon Peyton Jones's avatar
    Re-do superclass solving (again); fixes #10423 · 1189196c
    Simon Peyton Jones authored
    TcInstDcls.tcSuperClasses was getting increasingly baroque as a
    succession of tickets (#10423 being the latest) pointed out that
    my cunning plan was not so cunning.
    The big issue is how to restrict the evidence that we generate
    for superclass constraints in an instance declaration to avoid
    superclass loops.  See Note [Recursive superclasses] in TcInstDcls
    which explains the plan.
    The question is how to implement the plan.  The new implementation is
    much neater, and is described in Note [Solving superclass constraints]
    in TcInstDcls.
TcInteract.hs 93.6 KB