[commit: ghc] wip/type-app: Argument types *can* get instantiated. (9b9f3c7)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/type-app
Link       : http://ghc.haskell.org/trac/ghc/changeset/9b9f3c7d3a215d2e271dc5d6f92c8bd37e9cdfe6/ghc

>---------------------------------------------------------------

commit 9b9f3c7d3a215d2e271dc5d6f92c8bd37e9cdfe6
Author: Richard Eisenberg <eir at cis.upenn.edu>
Date:   Wed Aug 5 11:52:23 2015 -0400

    Argument types *can* get instantiated.


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9b9f3c7d3a215d2e271dc5d6f92c8bd37e9cdfe6
 compiler/typecheck/TcUnify.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/typecheck/TcUnify.hs b/compiler/typecheck/TcUnify.hs
index d6e5b75..04f8498 100644
--- a/compiler/typecheck/TcUnify.hs
+++ b/compiler/typecheck/TcUnify.hs
@@ -683,7 +683,7 @@ tc_sub_type_ds eq_orig inst_orig ctxt ty_actual ty_expected
       = -- See Note [Co/contra-variance of subsumption checking]
         do { res_wrap <- tc_sub_type_ds eq_orig inst_orig ctxt act_res exp_res
            ; arg_wrap
-               <- tc_sub_type eq_orig (Shouldn'tHappenOrigin "tc_sub_type_ds")
+               <- tc_sub_type eq_orig (GivenOrigin (SigSkol GenSigCtxt exp_arg))
                               ctxt exp_arg act_arg
            ; return (mkWpFun arg_wrap res_wrap exp_arg exp_res) }
                -- arg_wrap :: exp_arg ~ act_arg