[Git][ghc/ghc][wip/T23070-unify] Wibble

[Simon Peyton Jones (@simonpj)]

Simon Peyton Jones pushed to branch wip/T23070-unify at Glasgow Haskell Compiler / GHC


Commits:
3d0ab24e by Simon Peyton Jones at 2023-04-28T22:24:19+01:00
Wibble

- - - - -


1 changed file:

- compiler/GHC/Tc/Solver/Equality.hs


Changes:

=====================================
compiler/GHC/Tc/Solver/Equality.hs
=====================================
@@ -1509,9 +1509,11 @@ canEqCanLHSHetero ev eq_rel swapped lhs1 ps_xi1 ki1 xi2 ps_xi2 ki2
 --        type_ev :: (xi2 |> kind_co) ~r# lhs1
 
   = do { (kind_co, rewriters) <- mk_kind_eq   -- :: ki1 ~N ki2
-       ; if isEmptyRewriterSet rewriters
+       ; if isWanted ev && isEmptyRewriterSet rewriters
               -- Made kinds equal with no deferred rewrites so we must have done
               -- some unifications; start again to do the zonking
+              -- For Givens we never want to go round again,
+              -- and the rewriter set is empty, so we must check isWanted.
          then startAgainWith (mkNonCanonical ev)
          else
     do { let lhs_redn = mkReflRedn role ps_xi1



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3d0ab24ebe588d800b3559a7a56f993ea2830d3a

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3d0ab24ebe588d800b3559a7a56f993ea2830d3a
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