Parsing index siganture types is broken

First - thank you so much for the incredible work you've done on this. I'm doing something very unorthodox with my fork, making a language variant that allows people to define type names with unescaped whitespace as part of the type name (yes, very stupid. I have reasons.). As a result, I'm refactoring almost the entire repository to make this possible. I have encountered an error while trying to recompute your `checker/definitions/internal.ts.d.bin` asset, as of course my work adjusted the binary format. It appears that there's an error in parsing index type signatures, it blows up on parsing this: interface Array<T> { [index: number]: T; } It's upset that there isn't a corresponding ] to the opening [. I'll report back if I find a solution, but it might be good if you add internal.ts.d.bin generation into your regular test suite to catch this in the future, as it looks like it's a very old regression.