Debugger pauses on promise rejection even though it is handled/caught (TypeScript)

[eyelidlessness]

Issue Type: Bug

When I'm debugging code that wraps a synchronous function in an async function, if the synchronous function throws and an async caller catches, the debugger treats error/rejection as unhandled.

Previously, I had seen this issue when an error was thrown synchronously within an async function before an await (as described in #5213 (comment)). I was able to fix the problem by making the function in question synchronous (its async behavior had been refactored out already). But the problem has reappeared after I restarted VSCode yesterday (so I have to figure it's related to an update that may have been installed on restart?).

Repro code (compiler target is es2016):

const syncThrowFn = () => {
    // Debugger pauses here
    throw new Error('welp');
};

const wrapAsAsync = <T extends Function>(fn: T) => {
    return async () => {
        return fn();
    };
};

const wrappedAsyncThrowFn = wrapAsAsync(syncThrowFn);

const asyncFn = async (): Promise<Error | void> => {
    try {
        await wrappedAsyncThrowFn();
    }
    catch (error) {
        return error;
    }
};

asyncFn().then((error: Error) => {
    // Logs the error as expected
    console.log('error', error);
});

"Uncaught Exceptions" is checked, "All Exceptions" is not.

I'm not sure this is related to to #1746 because:

1. The debugger correctly identifies the error (it's not undefined).
2. The debugger correctly identifies the pause as being caused by a promise rejection (it says "paused on promise rejection" in the top of the Call Stack panel.

VS Code version: Code 1.23.1 (d0182c3, 2018-05-10T16:03:31.083Z)
OS version: Darwin x64 15.6.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz (8 x 2800)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled rasterization: enabled video_decode: enabled video_encode: enabled vpx_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	4, 4, 4
Memory (System)	16.00GB (0.25GB free)
Process Argv	/Users/gnosis/Applications/Development/Visual Studio Code.app/Contents/MacOS/Electron
Screen Reader	no
VM	0%

Extensions (14)

Extension	Author (truncated)	Version
output-colorizer	IBM	0.1.2
bbcode	Squ	0.0.2
gitlens	eam	8.3.2
flow-for-vscode	flo	0.8.1
theme-macos-classic	hua	1.1.1
theme-karyfoundation-themes	kar	18.0.1
camelcasenavigation	map	0.3.42
sidetest	mat	1.1.0
theme-monokai-pro-vscode	mon	1.1.6
typescript-javascript-grammar	ms-	0.0.41
debugger-for-chrome	msj	4.4.3
vscode-icons	rob	7.23.0
trailing-spaces	sha	0.2.11
cursor-align	yo1	1.0.4

(1 theme extensions excluded)

[eyelidlessness]

It's possible I'm misunderstanding what's covered by #1746. If so I'd understand if this is closed as duplicate. But if this is in fact covered by #1746, it seems that issue should be marked as a bug, not as a feature request. It seems pretty clear that it's a defect that handled promise rejections are being treated as uncaught.

[roblourens]

This is still #1746. I don't have a good way to fix it, I'm really at the mercy of the runtime, this is why chrome devtools shows the same behavior. The way TS downcompiles async/await, the runtime doesn't actually know whether the error is handled later on or not. If you run this using native async/await, it works as expected.