• Simon Peyton Jones's avatar
    Fix a TyVar bug in the flattener · 0a851903
    Simon Peyton Jones authored
    A year ago I gave up on trying to rigorously separate TyVars
    from TcTyVars, and instead allowed TyVars to appear rather more
    freely in types examined by the constraint solver:
       commit 18d0bdd3
       Author: Simon Peyton Jones <simonpj@microsoft.com>
       Date:   Wed Nov 23 16:00:00 2016 +0000
       Allow TyVars in TcTypes
    See Note [TcTyVars in the typechecker] in TcType.
    However, TcFlatten.flatten_tyvar1 turned out to treat
    a TyVar specially, and implicitly assumed that it could
    not have an equality constraint in the inert set.  Wrong!
    This caused Trac #14450.  Fortunately it is easily fixed,
    by deleting code.
TcType.hs 103 KB