| use proc_macro::TokenStream; |
| use proc_macro2::Span; |
| use quote::quote; |
| use syn::parse::{Parse, ParseStream}; |
| use syn::{parenthesized, parse_macro_input, LitStr, Token}; |
| |
| pub struct Input { |
| variable: LitStr, |
| } |
| |
| mod kw { |
| syn::custom_keyword!(env); |
| } |
| |
| impl Parse for Input { |
| // Input syntax is `env!("CFG_RELEASE")` to facilitate grepping. |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let paren; |
| input.parse::<kw::env>()?; |
| input.parse::<Token![!]>()?; |
| parenthesized!(paren in input); |
| let variable: LitStr = paren.parse()?; |
| Ok(Input { variable }) |
| } |
| } |
| |
| pub(crate) fn current_version(input: TokenStream) -> TokenStream { |
| let input = parse_macro_input!(input as Input); |
| |
| TokenStream::from(match RustcVersion::parse_env_var(&input.variable) { |
| Ok(RustcVersion { major, minor, patch }) => quote!( |
| Self { major: #major, minor: #minor, patch: #patch } |
| ), |
| Err(err) => syn::Error::new(Span::call_site(), err).into_compile_error(), |
| }) |
| } |
| |
| struct RustcVersion { |
| major: u16, |
| minor: u16, |
| patch: u16, |
| } |
| |
| impl RustcVersion { |
| fn parse_env_var(env_var: &LitStr) -> Result<Self, Box<dyn std::error::Error>> { |
| let value = proc_macro::tracked_env::var(env_var.value())?; |
| Self::parse_str(&value) |
| .ok_or_else(|| format!("failed to parse rustc version: {:?}", value).into()) |
| } |
| |
| fn parse_str(value: &str) -> Option<Self> { |
| // Ignore any suffixes such as "-dev" or "-nightly". |
| let mut components = value.split('-').next().unwrap().splitn(3, '.'); |
| let major = components.next()?.parse().ok()?; |
| let minor = components.next()?.parse().ok()?; |
| let patch = components.next().unwrap_or("0").parse().ok()?; |
| Some(RustcVersion { major, minor, patch }) |
| } |
| } |