Object literal not recognized as namespace

[texastoland]

TypeScript Version: 3.1.0xxxxx

Search Terms:

namespace empty object literal and https://github.com/Microsoft/TypeScript/tree/master/tests/cases

Code

var ns = {};     // recognized as a declaration for a namespace `ns`
ns.constant = 1; // recognized as a declaration for var `constant`
// ^^^^^^^^ <- Property 'constant' does not exist on type '{}'.

Expected behavior:

TypeScript 2.8 adds support for understanding more namespace patterns in .js files. Empty object literals declarations on top level, just like functions and classes, are now recognized as as namespace declarations in JavaScript.

Release notes (source)

Actual behavior:

Compile error.

Playground Link:

Playground

Related Issues:

I'm migrating a codebase and tried a few minor variations unsuccessfully.

[texastoland]

patterns in .js files

Ugh I just realized I converted my file to .ts. Is this feature specific to @ts-check?

[AlCalzone]

Yes, this is specific to JavaScript. In TypeScript you should declare the intended type of your variables beforehand. One exception will come for function types:
#26368