Channel.select: Complain if not passed an array.

lib/index.js

@@ -331,39 +331,42 @@ Channel.from = values => {
 };
 
 Channel.of = (...values) => Channel.from(values);
-
 Channel.isChannel = arg => prototype.isPrototypeOf(arg);
 
 Channel.select = methodPromises =>
   Object.assign(
     new Promise((resolve, reject) => {
-      methodPromises.forEach(async promise => {
+      try {
-        try {
+        methodPromises.forEach(async promise => {
-          promise.prethen(() => {
-            // We've been given a heads-up that this method will complete first
-            // so cancel the other method calls.
-            methodPromises.forEach(other => {
-              if (other !== promise) {
-                other.cancel();
-              }
-            });
-          });
-
           try {
-            await promise;
+            promise.prethen(() => {
-          } catch (exception) {
+              // We've been given a heads-up that this method will complete first
-            reject(exception);
+              // so cancel the other method calls.
-                `Channel.select accepts only promises returned by push & shift.`
+              methodPromises.forEach(other => {
-          }
+                if (other !== promise) {
+                  other.cancel();
+                }
+              });
+            });
 
-          resolve(promise.channel);
+            try {
-        } catch (exception) {
+              await promise;
-          reject(
+            } catch (exception) {
-            new TypeError(
+              reject(exception);
-            )
+            }
-          );
+
-        }
+            resolve(promise.channel);
-      });
+          } catch (exception) {
+            reject(
+              new TypeError(
+                `Channel.select accepts only promises returned by push & shift.`
+              )
+            );
+          }
+        });
+      } catch (exception) {
+        reject(new TypeError(`Channel.select: Argument must be an array.`));
+      }
     }),
     {
       cancel: () => Promise.all(methodPromises.map(promise => promise.cancel()))

test/index.js

@@ -124,6 +124,12 @@ describe(`Channel`, function() {
       await Channel.select([Promise.resolve()]);
     }, new TypeError(`Channel.select accepts only promises returned by push & shift.`));
   });
+
+  it(`complains if not given an array`, function() {
+    assertRejects(async () => {
+      await Channel.select(Channel.of(0).shift(), Channel.of(1).shift());
+    }, new TypeError(`Channel.select: Argument must be an array.`));
+  });
 });
 
 describe(`functional interface`, async function() {