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}

[louy]

The second actually.

[RyanCavanaugh]

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.

See also comments in #8228.