build: add back support for Rust 1.12

In older versions of Rust, the build.rs file is not auto-detected, so we
add it to the Cargo.toml. Moreover, the existing build.rs was not
compatible with older Rust versions because of the use of eprintln! and
short-hand struct initialization. We fix that.

Closes #140, Closes #141

2 files changed, 11 insertions, 5 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 8d612f6..5a1f1d8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,6 +11,7 @@ categories = ["encoding", "parsing"]
 keywords = ["byte", "endian", "big-endian", "little-endian", "binary"]
 license = "Unlicense OR MIT"
 exclude = ["/ci/*"]
+build = "build.rs"
 
 [lib]
 name = "byteorder"
diff --git a/build.rs b/build.rs
index a2c8d18..002135b 100644
--- a/build.rs
+++ b/build.rs
@@ -1,12 +1,17 @@
 use std::env;
 use std::ffi::OsString;
+use std::io::{self, Write};
 use std::process::Command;
 
 fn main() {
     let version = match Version::read() {
         Ok(version) => version,
         Err(err) => {
-            eprintln!("failed to parse `rustc --version`: {}", err);
+            writeln!(
+                &mut io::stderr(),
+                "failed to parse `rustc --version`: {}",
+                err
+            ).unwrap();
             return;
         }
     };
@@ -57,7 +62,7 @@ impl Version {
             }
             num.push(c);
         }
-        let major = num.parse::<u32>().map_err(|e| e.to_string())?;
+        let major = try!(num.parse::<u32>().map_err(|e| e.to_string()));
 
         num.clear();
         for c in parts[1].chars() {
@@ -66,7 +71,7 @@ impl Version {
             }
             num.push(c);
         }
-        let minor = num.parse::<u32>().map_err(|e| e.to_string())?;
+        let minor = try!(num.parse::<u32>().map_err(|e| e.to_string()));
 
         num.clear();
         for c in parts[2].chars() {
@@ -75,8 +80,8 @@ impl Version {
             }
             num.push(c);
         }
-        let patch = num.parse::<u32>().map_err(|e| e.to_string())?;
+        let patch = try!(num.parse::<u32>().map_err(|e| e.to_string()));
 
-        Ok(Version { major, minor, patch })
+        Ok(Version { major: major, minor: minor, patch: patch })
     }
 }