Add using namespace statement

[ruochenjia]

Suggestion

🔍 Search Terms

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

Add a statement similar to using namespace NS; in C++, that allows to append members of an object/namespace/module to the global scope or function scope during compile time.

📃 Motivating Example

Using namespace in global scope

TypeScript:

module NS {
  var a = 0;
  var b = "a";
}

using namespace NS;
b = "b";
a++;

Compiled JavaScript:

NS.b = "b";
NS.a++;

Using namespace in function scope

TypeScript:

module NS {
  var a = 0;
  var b = "a";
}

function c() {
  using namespace NS;
  a++;
  b = "";
}

Compiled JavaScript:

function c() {
  NS.a++;
  NS.b = "";
}

Using namespace not allowed

module NS {
  var a = 0;
  var window = null;
}

// error here as 'window' is already declared
using namespace NS;

Extending another module

module A {
  var a = 0;
  var b = 1;
}

module B {
  using namespace A;
  var c = 10;
}

console.log(B.a); // 0
console.log(B.c); // 10

💻 Use Cases

Currently, I have to use ModuleName.memberName statement to access a member declared inside a module. This doesn't have many effects when you only have a few references, but I have far more than the acceptable amount just in one file. It makes your function lines longer, affects the readability of the code, and wastes a lot of time on just on typing out the module name.

[MartinJohns]

Duplicate of #11775. You should also check the viability checklist again. Point 3 is definitely wrong.

[IllusionMH]

Why this one is checked?

This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)

How it's different from with?
In a sense "how it would avoid problems that usually caused by with"?

[Josh-Cena]

Not to mention that using declarations are already taken by the resource management feature ^^

[fatcerberus]

Not to mention that using declarations are already taken by the resource management feature ^^

To be fair, C# uses it for both purposes. That said, yeah, this doesn't even come close to meeting the viability criteria.