src/vendor/failure_derive/build.rs

   1 use std::env;
   2 use std::process::Command;
   3 use std::str;
   4 use std::str::FromStr;
   5
   6 fn main() {
   7     if rustc_has_dyn_trait() {
   8         println!("cargo:rustc-cfg=has_dyn_trait");
   9     }
  10 }
  11
  12 fn rustc_has_dyn_trait() -> bool {
  13     let rustc = match env::var_os("RUSTC") {
  14         Some(rustc) => rustc,
  15         None => return false,
  16     };
  17
  18     let output = match Command::new(rustc).arg("--version").output() {
  19         Ok(output) => output,
  20         Err(_) => return false,
  21     };
  22
  23     let version = match str::from_utf8(&output.stdout) {
  24         Ok(version) => version,
  25         Err(_) => return false,
  26     };
  27
  28     let mut pieces = version.split('.');
  29     if pieces.next() != Some("rustc 1") {
  30         return true;
  31     }
  32
  33     let next = match pieces.next() {
  34         Some(next) => next,
  35         None => return false,
  36     };
  37
  38     u32::from_str(next).unwrap_or(0) >= 27
  39 }