Language service: open Type.id

I am using language service to "traverse" the program, and I would like very much to "remember" which types and symbols I already saw, and to cache my computation results for them. Performance boost and avoiding infinite loops.

The compiler very helpfully supplies id for Type, Symbol and Node, and it seems to be "really, really" unique for symbols and nodes, and "relatively unique" (i.e. within a given typechecker) for types.

The problem is, however, that, unlike nodes and symbols, types hide their ids behind the "internal" qualifier and the lack of accessor function, making them not legally visible to me as a consumer of the language service. Of course, this being JavaScript, nothing prevents me from accessing them anyway, and that is what I currently do, but this is not ideal, because I am not protected from the code evolution in the future.

So it seems to me that nothing stands in the way of adding a getTypeId method to the typechecker, unless I'm missing something very important.

Inizia con src/compiler/checker.ts e src/compiler/types.ts, prestando particolare attenzione alla definizione di Type e alla gestione esistente dell’identità del typechecker descritta nell’issue. Traccia come vengono dichiarate e testate le API pubbliche di language-service e type-checker, quindi determina cosa è necessario per un accessor supportato dell’identificatore di tipo e verifica che l’identificatore esposto rimanga utile all’interno di un typechecker.