awaited operator is not added to the return types of async functions

[falsandtru]

TypeScript Version: 3.7.x-dev.201xxxxx

Search Terms:

Code

async function f<T>(a: T): Promise<T> {
    return a;
}
async function g<T>(a: T) {
    return a;
}
g(Promise.resolve(0));

Expected behavior:
Return type of f is invalid because the correct type is Promise<awaited T>.
Return types of g are Promise<awaited T> and Promise<number>.
Actual behavior:
Return type of f is valid although the correct type is Promise<awaited T>.
Return types of g are Promise<T> and Promise<Promise<number>>.

Playground Link: https://www.typescriptlang.org/play/index.html?ts=3.9.0-dev.20200324&ssl=1&ssc=1&pln=7&pc=23#code/IYZwngdgxgBAZgV2gFwJYHsLwDwBUB8AFMAFwy4CUZACgE7oC2qIApnvjAN4BQMfMtFsgS0swANzcAvt1CRYiFBiwBzdsTKUuvfoOGiYE6dxWE6jZiwB0gkOgA2ANxaEADBQrigA

Related Issues:

[falsandtru]

@rbuckton @amcasey @RyanCavanaugh @sandersn Since this bug would easily make wrong errors in user tests, this should be fixed soon.