rustc_macros/
current_version.rs

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1use proc_macro::TokenStream;
2use proc_macro2::Span;
3use quote::quote;
4
5pub(crate) fn current_version(_input: TokenStream) -> TokenStream {
6    let env_var = "CFG_RELEASE";
7    TokenStream::from(match RustcVersion::parse_cfg_release(env_var) {
8        Ok(RustcVersion { major, minor, patch }) => quote!(
9            // The produced literal has type `rustc_session::RustcVersion`.
10            Self { major: #major, minor: #minor, patch: #patch }
11        ),
12        Err(err) => syn::Error::new(Span::call_site(), format!("{env_var} env var: {err}"))
13            .into_compile_error(),
14    })
15}
16
17struct RustcVersion {
18    major: u16,
19    minor: u16,
20    patch: u16,
21}
22
23impl RustcVersion {
24    fn parse_cfg_release(env_var: &str) -> Result<Self, Box<dyn std::error::Error>> {
25        let value = proc_macro::tracked_env::var(env_var)?;
26        Self::parse_str(&value)
27            .ok_or_else(|| format!("failed to parse rustc version: {:?}", value).into())
28    }
29
30    fn parse_str(value: &str) -> Option<Self> {
31        // Ignore any suffixes such as "-dev" or "-nightly".
32        let mut components = value.split('-').next().unwrap().splitn(3, '.');
33        let major = components.next()?.parse().ok()?;
34        let minor = components.next()?.parse().ok()?;
35        let patch = components.next().unwrap_or("0").parse().ok()?;
36        Some(RustcVersion { major, minor, patch })
37    }
38}
rustc_macros/current_version.rs

rustc_macros/
current_version.rs
