Hotkey to get type information for the selected expression

[alisabzevari]

Intellij has a very useful feature called "show type info" that shows type information for the selected expression. For example, consider the following code:

function fn(count: number, str: string) {
	return str + count;
}

In Intellij IDEA it is possible to select str + count expression and press alt + = and get the result type of the selected expression (string in the example).

I think this feature would be very beneficial specially in the languages that type inference is very important. Although I am not sure this repository is the right place to ask for this feature.

[mjbvz]

Alternative: https://marketplace.visualstudio.com/items?itemName=MartinJohns.inline-types

TS can implement this using the existing VS Code apis. Not sure if there are enough other use cases that we need a dedicated api

[jrieken]

@alisabzevari You can today already press Cmd+K Cmd+I to show the hover programmatically. That will show all hovers - usually it's just the type hover but it rare cases it might be more. Is that enough to make you happy?

[alisabzevari]

So, here is a more interesting example:

import _ from "lodash";

const students = [
	{ id: 1, age: 20, points: [10, 12, 15] },
	{ id: 1, age: 25, points: [1, 12, 20] },
	{ id: 1, age: 18, points: [17, 10, 15] }
];

const sumAge = _.chain(students)
	.map(s => s.age)
	.sum()
	.value()

Usually, when dealing with chaining of calls, every function call (like map and sum) accept s certain input type and return a different type. Now, if I want to know what is the result type of _.chain(students).map(s => s.age).sum() it is only possible by removing the .value() in the end and look at the variable type by using Cmd+K Cmd+I.
In intellij it is possible to select a part of the expression and get type information for that selected part.

Here are some screenshots in intellij using this feature:

As you can see, cursor is on articleId. Now if I press alt+= the following menu will open:

So I can select which expression I want to get type info for. When I select Favorites.articleId, it shows the type info (only for that selected expression):

Note that, generic type parameters are resolved here. If I select the other expression from the menu, the following result will appear:

And here is another example, selecting the whole statement:

This feature does not exist in vscode.

[mjbvz]

@jrieken One problem with the VS Code hover api and UX is that hover uses a position instead of a selection range. A hover provider could decide to use the current selection if the cursor position is within it but this could result in a confusing UX

[alisabzevari]

I think this feature does not contradict with hover feature. This is how I image them together:

• User can hover over (mouse cursor) an identifier and get type information for that identifier.
• User can hit ctrl+k ctrl+i while not selecting anything and type information should be shown for the identifier currently under the caret (keyboard cursor).
• User can hit ctrl+k ctrl+i to get type information for the currently selected expression.

[Ciantic]

Now this is broken, I can't anymore copy & paste the type definition from the "Ctrl+K Ctrk+i", I get these darn abbreviations with three dots:

let ffprobe_video_stream: {
    index: number;
    codec_name: string;
    codec_long_name: string;
    profile: string;
    codec_type: string;
    codec_time_base: string;
    codec_tag_string: string;
    codec_tag: string;
    width: number;
    height: number;
    ... 22 more ...;
    tags: {
        ...;
    };
}

This thee dots abbreviation is some new addition, can we disable that? I constantly copy & paste the type definitions, ctrl+k ctrl+i is now useless for me.

EDIT I'm creating a bug report, this is bad: #66405

[mjbvz]

Closing this since it has not gotten a significant number of 👍 over the past two years

[ciuncan]

This is a pretty significant missing feature in VS Code that I've been missin ever since I started using it. Type annotations are being used more and more frequently even by languages of dynamic nature like Python, TypeScript, etc. Coming from a Scala background, I've been using this feature of IntelliJ idea to get the inferred type of a selected expression. It is quite inconvenient to assign a selection to a variable each time just to see its type, not just coding yourself but especially if you are reviewing a code or reading a library source or a previous work.

I'd suggest reopening this issue as it is clearly not out of scope of VS Code since the type hint is already a feature of it.

[Troyx21]

Please reopen this!!!

[aksh1618]

I worked around this by remapping Show or focus hover (Ctrl+k Ctrl+i by default) to Ctrl+Shift+P (I'm coming from IntelliJ IDEA). This works for rust, although it shows the check/clippy lint etc. as well.