`export as namespace` still allows access via properties in module files

TypeScript Version: 3.8.0-dev.20200119

Search Terms: export as namespace

Code

someModule.d.ts:

export function foo (bar: string): void;
export as namespace someModule;

index.ts:

import { foo } from './someModule';

someModule.foo;
window.someModule.foo;
globalThis.someModule.foo;

Expected behavior:

All of the attempts to access someModule as a global namespace in index.ts should result in compile-time errors, as index.ts is not a script file.

Actual behavior:

window.someModule.foo and globalThis.someModule.foo do NOT result in compile-time errors.

Playground Link: N/A (requires multiple files)

Related Issues: None found

Reproduce the issue with the two files shown, someModule.d.ts and index.ts, using the reported TypeScript version or a current build. Compare diagnostics for direct, window, and globalThis access, then trace the compiler handling of export as namespace. Done means all three global-namespace accesses in the module file produce compile-time errors.