Fix tests (#7)

I made a few small mistakes in #4, causing the tests to break. This
fixes it.

Blocked by #5.

src/structs/types.ts

@@ -690,8 +690,8 @@ export function union<First extends AnyStruct, Rest extends AnyStruct[]>(
     type: 'union',
     schema: null,
     coercer(value) {
-      for (const { validate } of Structs) {
-        const [error, coerced] = validate(value, { coerce: true });
+      for (const InnerStruct of Structs) {
+        const [error, coerced] = InnerStruct.validate(value, { coerce: true });
         if (!error) {
           return coerced;
         }

src/utils.ts

@@ -199,7 +199,8 @@ export function* run<Type, Schema>(
     yield [failure, undefined];
   }
 
-  for (const [innerKey, innerValue, innerStruct] of struct.entries(
+  // eslint-disable-next-line prefer-const
+  for (let [innerKey, innerValue, innerStruct] of struct.entries(
     value,
     context,
   )) {
@@ -220,8 +221,7 @@ export function* run<Type, Schema>(
 
         yield [result[0], undefined];
       } else if (coerce) {
-        // eslint-disable-next-line no-param-reassign
-        value = result[1];
+        innerValue = result[1];
 
         if (innerKey === undefined) {
           // eslint-disable-next-line no-param-reassign