You can't manipulate ASTs (ie, Zig code), but nothing stops you from parsing string literals however you want.

For example, I wrote a PEG-like parser combinator library in Zig. Using it currently [looks like this](https://github.com/CurtisFenner/zsmol/blob/87de4c77dd8543011...). However, as a library, I ^could provide a function that looks like

    pub const UnionDefinition = comb.fromLiteral(
        \\ _: KeyUnion
        \\ union_name: TypeIden
        \\ generics: Generics?
        \\ implements: Implements?
        \\ _: PuncCurlyOpen
        \\ fields: Field*
        \\ members: FunctionDef*
        \\ _: PuncCurlyClose 
   );

etc. But, I find reading the code as it is good enough for now that I didn't want to spend time implementing such a library.

[^]: Being able to create brand new types at `comptime` isn't [yet implemented](https://github.com/ziglang/zig/issues/383), so this can't quite be done yet, though you could fake it with `get`/`set` methods instead of real fields