Temporarily use SHA1 for type hashes, and clarify unrecognized-rule error

src/type-hash.js

@@ -5,6 +5,7 @@
 
 const mapObj = require("map-obj");
 const objectHash = require("object-hash");
+const util = require("util");
 
 const filterTypeRules = require("./util/filter-type-rules");
 
@@ -116,7 +117,7 @@ function hashType(type, level = 0, seenTypes = new Map()) {
 				};
 			}
 		} else {
-			throw new Error("Foo");
+			throw new Error(`Unrecognized rule type: ${util.inspect(rule)}`);
 		}
 
 		for (let [seenRule, seenLevel] of seenTypes) {
@@ -159,7 +160,7 @@ function hashType(type, level = 0, seenTypes = new Map()) {
 
 module.exports = function generateTypeHash(type) {
 	return objectHash(hashType(type), {
-		algorithm: "sha256",
+		algorithm: "sha1", /* FIXME: Switch to SHA256, after figuring out how to make this work in Webpack */
 		respectFunctionNames: false,
 		respectFunctionProperties: false
 	}).slice(0, 6);