Upgraded supported TypeScript version to v2.7.

[aleppard]

This PR upgrades compatibility to TypeScript v2.7. It also adds the yield* operator to JavaScript and JSX.

First some minor parsing improvements:

You can now name anonymous functions, e.g.

object = {
     field: function myFunction(arg1) { return arg1; }
}

Assertion typing (casting) is now supported in for statements, e.g.

let object = {"field1":5, "field2:"value"};
for (let [field, value] of Object.entries(object) as [string, any]) {
}

You can now export type aliases, e.g.

export type MyType = {
    field: number, 
    field2: string, 
}

(and they don't need to end with a semi-colon).

Union, intersection type aliases can now start with a leading | or &, e.g.

type EmployeeType =
     | "employee"
     | "manager";

See microsoft/TypeScript#12386

Tuples (and function parameter lists) can have a trailing comma:

[string, number,]

See microsoft/TypeScript#28893

Upgrades based on TypeScript versions:

TypeScript v0.9

You can now declare namespaces, e.g.

declare namespace myLib {
}

See https://www.typescriptlang.org/docs/handbook/declaration-files/by-example.html

TypeScript v1.8

Boolean, number and string literal types are now supported, e.g.

export type CharityStatsJson = {
    type: "single" | "multi"; 
    type: 1 | 2; 
    type: false | 1 | 2; 

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-1-8.html#type-parameters-as-constraints

TypeScript v2.0

Added non-null assertion operator, e.g.

let s = e!.name; // Assert that e is non-null and access name

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-0.html#non-null-assertion-operator

Added undefined type, e.g.

let y: number | undefined;

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-0.html#null--and-undefined-aware-types

Added never type, e.g.

function error(message: string): never {
  throw new Error(message);
}

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-0.html#the-never-type

TypeScript v2.1

Added keyof and indexed access types, e.g.

interface Person {
  name: string;
  age: number;
  location: string;
}
type Key = keyof Person; // "name" | "age" | "location"
type Age = Person["age"]; 

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-1.html#keyof-and-lookup-types

TypeScript v2.2

Added object type, e.g.

declare function create(o: object | null): void;

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-2.html#object-type

TypeScript v2.3

Added yield* operator to JavaScript, TypeScript & JSX.

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-3.html#generators

Added generic parameter defaults, e.g.

function genericParameterWithDefault<T = DefaultType>(field: T) {}

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-3.html#generic-parameter-defaults

TypeScript v2.7

Added unique symbol type, e.g.

declare const Foo: unique symbol;

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-7.html#unique-symbol

[teverett]

@aleppard thanks!