Preserve source filenames during inlining

[sunshowers]

Thanks again for releasing version 0.4!

Looks like there's one more thing I need, which is the ability to report errors in the parsed syn::File. For that the main thing I need is to be able to map span data back to the files it came from.

How does this design sound?

• Add an attribute to every inlined file with, say: #[syn_inline_mod_source_path = "..."]. Readers can then look through the attributes (add an API to syn-inline-mod to do so for convenience).
• Add a method to InlinerBuilder which configures whether these annotations should be inserted (default false).

I'm planning to publish a crate that ties together syn-inline-mod and codespan-reporting so that tools can report custom errors.

[dtolnay]

#[path = "..."] would work for this.

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6b6184af84dfcd3a6adbb6c7aca4a7d4

[sunshowers]

Thanks! My concern with using path is that with transitive includes it is relative to the file that included it, but for consumers of syn-inline-mod the path that's most useful would be with respect to the same base (relative or absolute) as the initial path passed in.