Better display representation for intersection types

I'm not sure if this has been discussed before, but join types are mostly unreadable. I think the type should be prettified somehow before being displayed to the user.

TypeScript Version:

1.8

Code

type T1 = {};
type T2 = {test: number};
type J = T1 & T2;

Expected behavior:

var x: J;
typeof x; // {test: number}

Actual behavior:

var x: J;
typeof x; // {} & {test: number}

👍
I use intersections a lot and I would love to have this feature.

so just to be clear is the request 1. to remove the empty object type if exists, or 2. to collapse all types. i.e.:

type T = { } & { a: number } & { b: string };

var x: T; // What is x? 
            // 1. { a: number } & { b: string }
            // 2. { a: number, b: string }

The second actually.

ok one more clarification, i assume this only applies to anonymous types. so 2.a would be the desired behavior.

class C { c: boolean; }

type T = C & { a: number } & { b: string };

var x: T; // What is x? 
            // 2.a C & { a: number; b: string }
            // 2.b { a: number, b: string; c: boolean }

I suppose it's better to limit this to anonymous types, or else it could rapidly go out of control with "big" named types, and you'll lose some type information.

related #6070

Accepting PRs, with a big caveat. This is actually quite a bit trickier than it appears because of how the compiler handles anonymous self-referential types. A PR here should be accompanied by a large test suite of recursively self-referential types to ensure there aren't any lingering runaway recursion bugs.

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Better display representation for intersection types #7705

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Better display representation for intersection types #7705

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JabX commented on Apr 13, 2016

mhegazy commented on Apr 13, 2016

louy commented on Apr 13, 2016

mhegazy commented on Apr 13, 2016

JabX commented on Apr 14, 2016

zpdDG4gta8XKpMCd commented on Apr 22, 2016

RyanCavanaugh commented on May 9, 2016

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