Kill varSetElemsWellScoped in quantifyTyVars

varSetElemsWellScoped introduces unnecessary non-determinism in
inferred type signatures.
Removing this instance required changing the representation of
TcDepVars to use deterministic sets.
This is the last occurence of varSetElemsWellScoped, allowing me to
finally remove it.

Test Plan:
./validate
I will update the expected outputs when commiting, some reordering
of type variables in types is expected.

Reviewers: goldfire, simonpj, austin, bgamari

Reviewed By: simonpj

Subscribers: thomie, simonmar

Differential Revision: https://phabricator.haskell.org/D2135

GHC Trac Issues: #4012

1 files changed, 6 insertions, 6 deletions

diff --git a/testsuite/tests/typecheck/should_fail/T9109.stderr b/testsuite/tests/typecheck/should_fail/T9109.stderr
index 6a08318ac0..71d88efdc8 100644
--- a/testsuite/tests/typecheck/should_fail/T9109.stderr
+++ b/testsuite/tests/typecheck/should_fail/T9109.stderr
@@ -1,15 +1,15 @@
 
 T9109.hs:8:13: error:
-    • Couldn't match expected type ‘t1’ with actual type ‘Bool’
-        ‘t1’ is untouchable
-          inside the constraints: t ~ Bool
+    • Couldn't match expected type ‘t’ with actual type ‘Bool’
+        ‘t’ is untouchable
+          inside the constraints: t1 ~ Bool
           bound by a pattern with constructor: GBool :: G Bool,
                    in an equation for ‘foo’
           at T9109.hs:8:5-9
-      ‘t1’ is a rigid type variable bound by
-        the inferred type of foo :: G t -> t1 at T9109.hs:8:1
+      ‘t’ is a rigid type variable bound by
+        the inferred type of foo :: G t1 -> t at T9109.hs:8:1
       Possible fix: add a type signature for ‘foo’
     • In the expression: True
       In an equation for ‘foo’: foo GBool = True
     • Relevant bindings include
-        foo :: G t -> t1 (bound at T9109.hs:8:1)
+        foo :: G t1 -> t (bound at T9109.hs:8:1)