Better error message.

mbostock · mbostock · commit e0baa30f62c7 · 2020-03-17T10:06:36.000-07:00
diff --git a/src/generators/queue.js b/src/generators/queue.js
@@ -6,7 +6,9 @@ export default function(initialize) {
   const dispose = initialize(push);
 
   if (dispose != null && typeof dispose !== "function") {
-    throw new Error("invalid dispose");
+    throw new Error(typeof dispose.then === "function"
+        ? "async initializers are not supported"
+        : "initializer returned something, but not a dispose function");
   }
 
   function push(x) {

Original file line number	Diff line number	Diff line change
`@@ -6,7 +6,9 @@ export default function(initialize) {`
`6`	`6`	`const dispose = initialize(push);`
`7`	`7`
`8`	`8`	`if (dispose != null && typeof dispose !== "function") {`
`9`		`- throw new Error("invalid dispose");`
	`9`	`+ throw new Error(typeof dispose.then === "function"`
	`10`	`+ ? "async initializers are not supported"`
	`11`	`+ : "initializer returned something, but not a dispose function");`
`10`	`12`	`}`
`11`	`13`
`12`	`14`	`function push(x) {`