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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 })
}
}
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