no-unused-expression should permit await

[andy-hanson]

The following code causes a linter error:

async function f(foo: Promise<void>): Promise<number> {
    await foo
    return 0
}

The output I get is:

src/foo.ts[2, 2]: expected an assignment or function call

Here's my tslint.json:

{
    "rules": {
        "no-unused-expression": true
    }
}

[jkillian]

Thanks for the bug report @andy-hanson. I bet the issue comes from not handling await statements correctly. What versions of tsc does this apply to with which compiler settings? I know async/await support is still somewhat limited, correct?

[andy-hanson]

This is tested with typescript 1.7.5, using tslint src/*.ts --target ES6. await foo() does work, as does const x = await foo.

[jkillian]

@andy-hanson This is fixed on master now, and we'll likely do a release on NPM within the next week or so.

[adidahiya]

fix is available in tslint@next (v3.2.2-dev.1)