Pre-parsed stdlib

[sbarzowski]

@mqliang wrote in #89:

It would be very interesting if we can dump ast as go source files, then we can dump ast of stdlib as go source code, and embed it into vm, thus avoid parsing stdlib every time. Any idea?

I think we should look into it. It sound quite easy.

[mqliang]

I tried to dump ast using go-spew (https://github.com/davecgh/go-spew), it's practicable: about 7w line source code is generated.

The problem is: we need fork go-spew and modify its source code to make the generated files meet go's syntax.

[sbarzowski]

My feeling is that the easiest and most maintainable way would be to do it by hand (without go-spew), i.e. have a function that does a type switch over ast nodes and formats each of them into a go source code representation. There are just ~30 AST node types IIRC. This will give us full control over the output and let us specially handle location information, aliased nodes and other complex cases. I think that with some helper functions the boilerplate could be minimal.

[mqliang]

utter(github.com/kortschak/utter) works. See experiment: #101

The only problem is: we need make ALL fields of AST node as public, then the dumped source code can be put in any package. Otherwise, we must put the source code in the "ast" package.

[mqliang]

#82 will also benefit from this.