6.0.0

I'm extremely stupid and didn't commit as I go. To anyone reading this
I'm extremely sorry. A lot of these changes are very broad and I plan on
releasing Babel 6.0.0 today live on stage at Ember Camp London so I'm
afraid I couldn't wait. If you're ever in London I'll buy you a beer
(or assorted beverage!) to make up for it, also I'll kiss your feet and
give you a back massage, maybe.

packages/babel-helper-explode-class/src/index.js

@@ -0,0 +1,49 @@
+import bindifyDecorators from "babel-helper-bindify-decorators";
+import type { NodePath } from "babel-traverse"
+import * as t from "babel-types";
+
+export default function (classPath) {
+  classPath.assertClass();
+
+  let memoisedExpressions = [];
+
+  function maybeMemoise(path) {
+    if (!path.node || path.isPure()) return;
+
+    let uid = classPath.scope.generateDeclaredUidIdentifier();
+    memoisedExpressions.push(t.assignmentExpression("=", uid, path.node));
+    path.replaceWith(uid);
+  }
+
+  function memoiseDecorators(paths: Array<NodePath>) {
+    if (!Array.isArray(paths) || !paths.length) return;
+
+    // ensure correct evaluation order of decorators
+    paths = paths.reverse();
+
+    // bind decorators if they're member expressions
+    bindifyDecorators(paths);
+
+    for (let path of paths) {
+      maybeMemoise(path);
+    }
+  }
+
+  maybeMemoise(classPath.get("superClass"));
+  memoiseDecorators(classPath.get("decorators"), true);
+
+  let methods: Array<NodePath> = classPath.get("body.body");
+  for (let methodPath of methods) {
+    if (methodPath.is("computed")) {
+      maybeMemoise(methodPath.get("key"));
+    }
+
+    if (methodPath.has("decorators")) {
+      memoiseDecorators(classPath.get("decorators"));
+    }
+  }
+
+  if (memoisedExpressions) {
+    classPath.insertBefore(memoisedExpressions.map((expr) => t.expressionStatement(expr)));
+  }
+}