chore: payments are virtual objects.

Unit tests do not have makeKind or makeWeakStore and Swingset tests fail with little information.

packages/ERTP/src/issuer.js

@@ -1,7 +1,7 @@
-// Copyright (C) 2019 Agoric, under Apache License 2.0
-
 // @ts-check
 
+/* global makeWeakStore */
+
 import { assert, details as X } from '@agoric/assert';
 import { makeExternalStore } from '@agoric/store';
 import { E } from '@agoric/eventual-send';
@@ -12,6 +12,7 @@ import { isPromise } from '@agoric/promise-kit';
 import { makeAmountMath, MathKind } from './amountMath';
 import { makeFarName, ERTPKind } from './interfaces';
 import { coerceDisplayInfo } from './displayInfo';
+import { makePaymentMaker } from './payment';
 
 import './types';
 
@@ -43,17 +44,10 @@ function makeIssuerKit(
   const { add } = amountMath;
   const empty = amountMath.getEmpty();
 
-  const {
-    makeInstance: makePayment,
-    makeWeakStore: makePaymentWeakStore,
-  } = makeExternalStore('payment', () =>
-    Far(makeFarName(allegedName, ERTPKind.PAYMENT), {
-      getAllegedBrand: () => brand,
-    }),
-  );
+  const makePayment = makePaymentMaker(allegedName, brand);
 
   /** @type {WeakStore<Payment, Amount>} */
-  const paymentLedger = makePaymentWeakStore();
+  const paymentLedger = makeWeakStore('payment');
 
   function assertKnownPayment(payment) {
     assert(paymentLedger.has(payment), X`payment not found for ${allegedName}`);

packages/ERTP/src/payment.js

@@ -0,0 +1,24 @@
+/* global makeKind */
+
+// @ts-check
+
+import { Far } from '@agoric/marshal';
+import { makeFarName, ERTPKind } from './interfaces';
+
+export const makePaymentMaker = (allegedName, brand) => {
+  const paymentVOMaker = state => {
+    return {
+      init: b => (state.brand = b),
+      self: Far(makeFarName(allegedName, ERTPKind.PAYMENT), {
+        getAllegedBrand: () => state.brand,
+      }),
+    };
+  };
+
+  const paymentMaker = makeKind(paymentVOMaker);
+
+  const makePayment = () => paymentMaker(brand);
+
+  return makePayment;
+}
+