message: add return types for List<T> in collections.ts
diff: @@ -58,7 +58,7 @@ export class List<T> {
  constructor(public isHead: boolean, public data: T) {
  }
  - clear() {
  + clear(): void {
  if (this.isHead) {
  this.prev = this;
  this.next = this;
  @@ -74,24 +74,24 @@ export class List<T> {
  return (entry);
  }
  - dequeue() {
  + dequeue(): T {
  if (!this.empty()) {
  let removedEntry = ListRemoveEntry(this.next);
  return removedEntry.data;
  }
  }
  - enqueue(data: T) {
  + enqueue(data: T): List<T> {
  return this.add(data);
  }
  - walk(fn: (data: T, l: List<T>) => void) {
  + walk(fn: (data: T, l: List<T>) => void): void {
  for (var entry = this.next; !(entry.isHead); entry = entry.next) {
  fn(entry.data, entry);
  }
  }
  - some(fn: (data: T, l: List<T>) => boolean, rev?: boolean) {
  + some(fn: (data: T, l: List<T>) => boolean, rev?: boolean): T {
  for (var entry = <List<T>>this; !(entry.isHead); entry = rev ? entry.prev : entry.next) {
  if (fn(entry.data, entry)) {
  return (entry.data);
  @@ -116,7 +116,7 @@ export class List<T> {
  }
  }
  - last() {
  + last(): T {
  if (!this.empty()) {
  return (this.prev.data);
  }
  