GeezerVison

TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the perf test suite on this PR at c44f1a4. You can monitor the build here. It should now contribute to this PR's status checks.

Update: The results are in!

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at c44f1a4. You can monitor the build here. It should now contribute to this PR's status checks.

Anders Hejlsberg (@ahejlsberg)
The results of the perf run you requested are in!

TypeScript Bot (@typescript-bot) pack this

Heya Andrew Casey (@amcasey), I've started to run the tarball bundle task on this PR at d6d9dd7. You can monitor the build here. It should now contribute to this PR's status checks.

Hey Andrew Casey (@amcasey), I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
    "devDependencies": {
        "typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/63158/artifacts?artifactName=tgz&fileId=A987F38F6364514260C7A68F64FA1F26CC816EB374A422F9891F2C151AB1791A02&fileName=/typescript-3.8.0-insiders.20200204.tgz"
    }
}

and then running npm install.

There is also a playground for this build.

10-run average from the original machine shows a 7% improvement. Very nice!

This change fixes a failure in checking in @types/mongoose of the form:

interface E {
    stack: string;
}
declare var y: E | undefined
declare var x: E;
var x = y; // error expected here, but none given
x.stack

It's very surprising to me that we didn't give an error here before. Note that we did give an error for number | undefined.

Maybe it's because we weren't strictly checking duplicate declaration sites before. Normal code like var x: E | undefined = y gives the error before this change.