From de3b0a27948e17413385fee86fccd7e918d7c49a Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Mon, 30 Nov 2020 13:41:54 -0800
Subject: [PATCH] it works

---
 gpkit/constraints/costed.py |  3 +--
 gpkit/constraints/set.py    | 11 +++--------
 gpkit/nomials/math.py       |  4 ----
 gpkit/tests/t_nomials.py    |  2 +-
 4 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index b6f0cfece..62eed1c08 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -23,8 +23,7 @@ def __init__(self, cost, constraints, substitutions=None):
         subs = {k: k.value for k in self.cost.vks if "value" in k.descr}
         if substitutions:
             subs.update(substitutions)
-        ConstraintSet.__init__(self, constraints, subs)
-        self.vks.update(self.cost.vks)
+        ConstraintSet.__init__(self, constraints, subs, bonusvks=self.cost.vks)
 
     def constrained_varkeys(self):
         "Return all varkeys in the cost and non-ConstraintSet constraints"
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 1c7fc6edb..b8a54b288 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -65,7 +65,7 @@ class ConstraintSet(list, ReprMixin):
     unique_varkeys, idxlookup = frozenset(), {}
     _name_collision_varkeys = None
 
-    def __init__(self, constraints, substitutions=None):  # pylint: disable=too-many-branches,too-many-statements
+    def __init__(self, constraints, substitutions=None, *, bonusvks=None):  # pylint: disable=too-many-branches,too-many-statements
         if isinstance(constraints, dict):
             keys, constraints = sort_constraints_dict(constraints)
             self.idxlookup = {k: i for i, k in enumerate(keys)}
@@ -90,6 +90,8 @@ def __init__(self, constraints, substitutions=None):  # pylint: disable=too-many
                 raise badelement(self, i, constraint,
                                  " It had not yet been initialized!")
         self.substitutions.vks = self.vks
+        if bonusvks:
+            self.vks.update(bonusvks)
         if substitutions:
             self.substitutions.update(substitutions)
         for key in self.vks:
@@ -117,13 +119,6 @@ def _update(self, constraint):
         self.bounded.update(constraint.bounded)
         for bound, solutionset in constraint.meq_bounded.items():
             self.meq_bounded[bound].update(solutionset)
-        # if not isinstance(constraint, ConstraintSet):
-        #     if hasattr(constraint, "substitutions"):
-        #         del constraint.substitutions
-        #     del constraint.bounded
-        #     del constraint.vks
-        #     if constraint.meq_bounded:
-        #         del constraint.meq_bounded
 
     def __getitem__(self, key):
         if key in self.idxlookup:
diff --git a/gpkit/nomials/math.py b/gpkit/nomials/math.py
index 9dde76cd1..b172a5062 100644
--- a/gpkit/nomials/math.py
+++ b/gpkit/nomials/math.py
@@ -76,10 +76,6 @@ def diff(self, var):
         -------
         Signomial (or Posynomial or Monomial)
         """
-        # varset = self.varkeys[var]
-        # if len(varset) > 1:
-        #     raise ValueError("multiple variables %s found for key %s"
-        #                      % (list(varset), var))
         var = var.key
         if var not in self.vks:
             diff = NomialMap({EMPTY_HV: 0.0})
diff --git a/gpkit/tests/t_nomials.py b/gpkit/tests/t_nomials.py
index ec5540a8b..e6176fb00 100644
--- a/gpkit/tests/t_nomials.py
+++ b/gpkit/tests/t_nomials.py
@@ -375,7 +375,7 @@ def test_diff(self):
         self.assertEqual(x.diff(y), 0)
         self.assertEqual((y**2).diff(y), 2*y)
         self.assertEqual((x + y**2).diff(y), 2*y)
-        self.assertEqual((x + y**2).diff("x"), 1)
+        self.assertEqual((x + y**2).diff(x.key), 1)
         self.assertEqual((x + x*y**2).diff(y), 2*x*y)  # pylint: disable=no-member
         self.assertEqual((2*y).diff(y), 2)  # pylint: disable=no-member
         # test with units