• Richard Eisenberg's avatar
    Fix #13819 by refactoring TypeEqOrigin.uo_thing · c2417b87
    Richard Eisenberg authored
    The uo_thing field of TypeEqOrigin is used to track the
    "thing" (either term or type) that has the type (kind) stored
    in the TypeEqOrigin fields. Previously, this was sometimes a
    proper Core Type, which needed zonking and tidying. Now, it
    is only HsSyn: much simpler, and the error messages now use
    the user-written syntax.
    
    But this aspect of uo_thing didn't cause #13819; it was the
    sibling field uo_arity that did. uo_arity stored the number
    of arguments of uo_thing, useful when reporting something
    like "should have written 2 fewer arguments". We wouldn't want
    to say that if the thing didn't have two arguments. However,
    in practice, GHC was getting this wrong, and this message
    didn't seem all that helpful. Furthermore, the calculation
    of the number of arguments is what caused #13819 to fall over.
    This patch just removes uo_arity. In my opinion, the change
    to error messages is a nudge in the right direction.
    
    Test case: typecheck/should_fail/T13819
    c2417b87
Inst.hs 31.5 KB