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-function-name/src/index.js

@@ -0,0 +1,164 @@
+/* @flow */
+
+import getFunctionArity from "babel-helper-get-function-arity";
+import template from "babel-template";
+import * as t from "babel-types";
+
+let buildPropertyMethodAssignmentWrapper = template(`
+  (function (FUNCTION_KEY) {
+    function FUNCTION_ID() {
+      return FUNCTION_KEY.apply(this, arguments);
+    }
+
+    FUNCTION_ID.toString = function () {
+      return FUNCTION_KEY.toString();
+    }
+
+    return FUNCTION_ID;
+  })(FUNCTION)
+`);
+
+let buldGeneratorPropertyMethodAssignmentWrapper = template(`
+  (function (FUNCTION_KEY) {
+    function* FUNCTION_ID() {
+      return yield* FUNCTION_KEY.apply(this, arguments);
+    }
+
+    FUNCTION_ID.toString = function () {
+      return FUNCTION_KEY.toString();
+    };
+
+    return FUNCTION_ID;
+  })(FUNCTION)
+`);
+
+let visitor = {
+  "ReferencedIdentifier|BindingIdentifier"(path, state) {
+    // check if this node matches our function id
+    if (path.node.name !== state.name) return;
+
+    // check that we don't have a local variable declared as that removes the need
+    // for the wrapper
+    let localDeclar = path.scope.getBindingIdentifier(state.name);
+    if (localDeclar !== state.outerDeclar) return;
+
+    state.selfReference = true;
+    path.stop();
+  }
+};
+
+function wrap(state, method, id, scope) {
+  if (state.selfReference) {
+    if (scope.hasBinding(id.name) && !scope.hasGlobal(id.name)) {
+      // we can just munge the local binding
+      scope.rename(id.name);
+    } else {
+      // need to add a wrapper since we can't change the references
+      let build = buildPropertyMethodAssignmentWrapper;
+      if (method.generator) build = buldGeneratorPropertyMethodAssignmentWrapper;
+      let template = build({
+        FUNCTION: method,
+        FUNCTION_ID: id,
+        FUNCTION_KEY: scope.generateUidIdentifier(id.name)
+      }).expression;
+      template.callee._skipModulesRemap = true;
+      
+      // shim in dummy params to retain function arity, if you try to read the
+      // source then you'll get the original since it's proxied so it's all good
+      let params = template.callee.body.body[0].params;
+      for (let i = 0, len = getFunctionArity(method); i < len; i++) {
+        params.push(scope.generateUidIdentifier("x"));
+      }
+
+      return template;
+    }
+  }
+
+  method.id = id;
+  scope.getProgramParent().references[id.name] = true;
+}
+
+function visit(node, name, scope) {
+  let state = {
+    selfAssignment: false,
+    selfReference:  false,
+    outerDeclar:    scope.getBindingIdentifier(name),
+    references:     [],
+    name:           name
+  };
+
+  // check to see if we have a local binding of the id we're setting inside of
+  // the function, this is important as there are caveats associated
+
+  let binding = scope.getOwnBinding(name);
+
+  if (binding) {
+    if (binding.kind === "param") {
+      // safari will blow up in strict mode with code like:
+      //
+      //   let t = function t(t) {};
+      //
+      // with the error:
+      //
+      //   Cannot declare a parameter named 't' as it shadows the name of a
+      //   strict mode function.
+      //
+      // this isn't to the spec and they've invented this behaviour which is
+      // **extremely** annoying so we avoid setting the name if it has a param
+      // with the same id
+      state.selfReference = true;
+    } else {
+      // otherwise it's defined somewhere in scope like:
+      //
+      //   let t = function () {
+      //     let t = 2;
+      //   };
+      //
+      // so we can safely just set the id and move along as it shadows the
+      // bound function id
+    }
+  } else if (state.outerDeclar || scope.hasGlobal(name)) {
+    scope.traverse(node, visitor, state);
+  }
+
+  return state;
+}
+
+export default function ({ node, parent, scope, id }) {
+  // has an `id` so we don't need to infer one
+  if (node.id) return;
+
+  if ((t.isObjectProperty(parent) || t.isObjectMethod(parent, { kind: "method" })) && (!parent.computed || t.isLiteral(parent.key))) {
+    // { foo() {} };
+    id = parent.key;
+  } else if (t.isVariableDeclarator(parent)) {
+    // let foo = function () {};
+    id = parent.id;
+
+    if (t.isIdentifier(id)) {
+      let binding = scope.parent.getBinding(id.name);
+      if (binding && binding.constant && scope.getBinding(id.name) === binding) {
+        // always going to reference this method
+        node.id = id;
+        return;
+      }
+    }
+  } else if (!id) {
+    return;
+  }
+
+  let name;
+  if (id && t.isLiteral(id)) {
+    name = id.value;
+  } else if (id && t.isIdentifier(id)) {
+    name = id.name;
+  } else {
+    return;
+  }
+
+  name = t.toBindingIdentifierName(name);
+  id = t.identifier(name);
+
+  let state = visit(node, name, scope);
+  return wrap(state, node, id, scope) || node;
+}