[commit: ghc] master: Don't instantaite when typechecking a pattern synonym (1221f81)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/1221f8104bb5123c18bd5b840cde9ab2e71247d5/ghc

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

commit 1221f8104bb5123c18bd5b840cde9ab2e71247d5
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Mon Oct 24 16:59:03 2016 +0100

    Don't instantaite when typechecking a pattern synonym
    
    Fixes most of the cases in Trac #12762


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

1221f8104bb5123c18bd5b840cde9ab2e71247d5
 compiler/typecheck/TcPatSyn.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/typecheck/TcPatSyn.hs b/compiler/typecheck/TcPatSyn.hs
index 05d98ff..81c5e2c 100644
--- a/compiler/typecheck/TcPatSyn.hs
+++ b/compiler/typecheck/TcPatSyn.hs
@@ -72,7 +72,7 @@ tcInferPatSynDecl PSB{ psb_id = lname@(L _ name), psb_args = details,
        ; let (arg_names, rec_fields, is_infix) = collectPatSynArgInfo details
        ; (tclvl, wanted, ((lpat', args), pat_ty))
             <- pushLevelAndCaptureConstraints  $
-               tcInferInst $ \ exp_ty ->
+               tcInferNoInst $ \ exp_ty ->
                tcPat PatSyn lpat exp_ty $
                mapM tcLookupId arg_names