Inlay hints displayed twice for folded functions/objects

[IllusionMH]

Issue Type: Bug

Related to #129465 and #129381

Steps to reproduce:

1. Enable "typescript.inlayHints.variableTypes.enabled": true and "typescript.inlayHints.functionLikeReturnTypes.enabled": true or corresponding JS settings.

2. Create new TS or JS file and paste next code:

function test() {
    // code here
}

const obj = {
    a: 'test'
};

function testFolded() {
    // code here
}

const objFolded = {
    a: 'test'
};

3. Fold testFolded and objFolded

TS Version 4.4.0-dev.20210708

VS Code version: Code - Insiders 1.59.0-insider (e437d42, 2021-07-28T05:13:47.114Z)
OS version: Windows_NT x64 10.0.19041
Restricted Mode: No

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz (12 x 3192)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled skia_renderer: enabled_on video_decode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	31.72GB (18.24GB free)
Process Argv	--crash-reporter-id cf52dbde-2c94-45c3-9bf3-45d8b9966b04
Screen Reader	no
VM	0%

Extensions: none

A/B Experiments

vsliv695:30137379
vsins829:30139715
vsliv368cf:30146710
vsreu685:30147344
python383cf:30185419
pythonvspyt602:30291494
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vswsl492cf:30256198
pythonvspyt639:30291487
pythontb:30258533
vspre833:30321513
pythonptprofiler:30281269
vsdfh931cf:30280410
vshan820:30294714
pythondataviewer:30285072
vscus158:30321503
pythonvsuse255:30319630
vscod805cf:30301675
pythonvspyt200:30323110
vscextlangct:30310089
vsccppwt:30312692
pythonvssor306:30340298
bridge0708:30335490

[IllusionMH]

/assign @mjbvz

[mjbvz]

@jrieken / @hediet Can you please take a look? I believe that folding generates two new requests for inlay hints that VS Code then displays incorrectly.

Here's the TS server trace from folding testFolded with only "javascript.inlayHints.functionLikeReturnTypes.enabled": true:

[Trace  - 19:50:26.340] <semantic> Sending request: provideInlayHints (78). Response expected: yes. Current queue length: 0
Arguments: {
    "file": "^untitled:Untitled-1",
    "start": 0,
    "length": 93
}
[Trace  - 19:50:26.341] <semantic> Response received: provideInlayHints (78). Request took 1 ms. Success: true 
Result: [
    {
        "text": ": void",
        "position": {
            "line": 1,
            "offset": 16
        },
        "kind": "Type",
        "whitespaceBefore": true
    },
    {
        "text": ": void",
        "position": {
            "line": 9,
            "offset": 22
        },
        "kind": "Type",
        "whitespaceBefore": true
    }
]
[Trace  - 19:50:26.341] <semantic> Sending request: provideInlayHints (79). Response expected: yes. Current queue length: 0
Arguments: {
    "file": "^untitled:Untitled-1",
    "start": 111,
    "length": 39
}
[Trace  - 19:50:26.342] <semantic> Response received: provideInlayHints (79). Request took 2 ms. Success: true 
Result: [
    {
        "text": ": void",
        "position": {
            "line": 9,
            "offset": 22
        },
        "kind": "Type",
        "whitespaceBefore": true
    }
]

The position of the hints seem correct to me. I don't know why VS Code requests the hints twice here though (or why it needs to re-request any hints on folding in this case since no new code became visible)

[hediet]

These are the visible ranges:

And vscode sends two requests, one for each range.
For some reason, each reuqest returns one inlay hint, so in total, there are 2 inlay hints:

@Kingwl do you have an idea why this is?

To me, it looks like a bug in the provider, there should not be a result for the second request.

[Kingwl]

Emmmmmm... I think I know the reason.

In the tsserver. For each request, we will get the hint in the area that overlay with the visible range (not strictly included).
Honestly, I don't know about this behavior. We may could de-duplicate these items?

[hediet]

Can't you just filter out all inlay hints whose position is not in the requested range?

[Kingwl]

Well, do you prefer to do it in vscode or ts side?