# spanr
A tool for procedural macro authors to be able to interactively view and debug
the `Span`s on generated code.
## Screenshot
## Example usage
```rust
#[proc_macro_attribute]
pub fn act_zero(_attr: TokenStream, item: TokenStream) -> TokenStream {
let res = match act_zero_impl(item) {
Ok(tokens) => tokens,
Err(e) => e.to_compile_error(),
};
// Save the visualization to a file
spanr::save_html(res.clone(), "tokens.html").unwrap();
res.into()
}
```
## Building
This crate relies on unstable features from the `proc-macro2` crate, so it must
be built using a nightly compiler, and the `RUSTFLAGS` environment variable
must be configured:
```bash
RUSTFLAGS='--cfg procmacro2_semver_exempt'
```
