Include documentation from a variable's type when you hover the variable

Issue Type: Feature request

I had hoped to see the description for the type when hovering over the value via intellisense, etc.

When I hover over context.slot I can see “The slot the disk is in.” yet when I try hovering over const slot I see just the type. Is there anything to enable this? Even setting slot to Slot manually it still only shows the type.

 /** The slot the disk is in. */
type Slot = string;

interface Context {
    /** The slot the disk is in. */
    slot?: Slot
}

const func = (context: Context): Context => {
    const x = context.slot;
    const slot: Slot = context.slot;

    return {
        slot: x || slot
    };
};

func({
    slot: '1'
}).slot;

VS Code version: Code 1.43.2 (0ba0ca52957102ca3527cf479571617f0de6ed50, 2020-03-24T07:34:57.037Z) OS version: Darwin x64 19.2.0

System Info

Item	Value
CPUs	Intel® Core™ i5 CPU M 520 @ 2.40GHz (4 x 2400)
GPU Status	2d_canvas: unavailable_software flash_3d: disabled_software flash_stage3d: disabled_software flash_stage3d_baseline: disabled_software gpu_compositing: disabled_software metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: disabled_off rasterization: disabled_software skia_renderer: disabled_off_ok video_decode: disabled_software viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: unavailable_software webgl2: unavailable_software
Load (avg)	1, 1, 2
Memory (System)	8.00GB (0.79GB free)
Process Argv	.
Screen Reader	no
VM	0%

Extensions (27)

Extension	Author (truncated)	Version
go-outliner	766	0.1.20
npm-intellisense	chr	1.3.0
path-intellisense	chr	1.4.2
jsrefactor	cms	2.20.5
vue-peek	dar	1.0.2
vscode-eslint	dba	2.1.2
EditorConfig	Edi	0.14.5
vscode-npm-script	eg2	0.3.11
flow-for-vscode	flo	1.5.0
todo-tree	Gru	0.0.171
docthis	joe	0.7.1
vscode-home-assistant	kee	1.6.1
dotenv	mik	1.0.1
vscode-docker	ms-	1.0.0
csharp	ms-	1.21.16
atom-keybindings	ms-	3.0.6
cpptools	ms-	0.27.0
Go	ms-	0.13.1
vscode-typescript-next	ms-	3.9.20200408
go-doc	msy	0.1.1
hide-gitignored	npx	1.1.0
vetur	oct	0.24.0
vscode-graphql	Pri	0.2.14
json-template	sto	0.3.1
vscode-icons	vsc	10.0.0
vscode-wakatime	Wak	4.0.0
vscode-go-autotest	win	1.6.0

(2 theme extensions excluded)

[mesqueeb]

@RyanCavanaugh @mjbvz

Here is a real use case of mine. I have a library that uses certain types through the entire library. Sometimes as function param types, sometimes as return types, etc…

The library then exposes a set of functions the dev that uses my library must implement.

In all cases below, IF there is no extra documentation provided for wherever MyProp is used, I would like it to fall back to the documentation of MyProp:

/**
 * Documentation on MyProp I want everything below to fall back to
 */
type MyProp = string

type SomeType = {
  n: number
  myProp: MyProp
}

type AnotherType = {
  x: string
  myProp: MyProp
}

type MyTuple = [MyProp, boolean]

export type ActionDevNeedsToImplement1 = (myProp: MyProp, n: number, x: string) => void
export type ActionDevNeedsToImplement2 = (someType: SomeType) => void
export type ActionDevNeedsToImplement3 = (anotherType: AnotherType) => void
export type ActionDevNeedsToImplement4 = (myTuple: MyTuple) => void

const action1: ActionDevNeedsToImplement1 = (myProp, n, x) => {
  // ❌ no documentation when hovering over `myProp`
  // ✅ documentation when the dev writes `myProp: MyProp` in the params and hovers over MyProp instead
  
  // requirements:
  // the library creator needs to export `MyProp`
}
const action2: ActionDevNeedsToImplement2 = (someType: SomeType) => {
  // ❌ no documentation on `MyProp` when hovering over `SomeType`
  // ❌ impossible to retrieve the documentation, because:
  //    the dev only sees this when hovering over SomeType
  //    { n: number, myProp: string }
}
const action3: ActionDevNeedsToImplement3 = (anotherType: AnotherType) => {
  // same as above
}
const action4: ActionDevNeedsToImplement4 = (myTuple: MyTuple) => {
  // same as above
}

My developers are having a hard time in all the cases above to know exactly what MyProp has to represent, unless I duplicate the documentation through all types underneath MyProp.

I want to avoid this duplication of documentation issue.

This is the reason this is an important feature request by @OmgImAlexis and myself.

If there are better ways to solve my issues without adding this feature and without duplication of documentation, please advise.

[mjbvz]

Awaiting More Feedback means that we’d like feedback from more members of the community on whether this features would be useful