Give better errors when build-manifest fails

src/tools/build-manifest/src/main.rs

@@ -193,6 +193,12 @@ macro_rules! t {
             Err(e) => panic!("{} failed with {}", stringify!($e), e),
         }
     };
+    ($e:expr, $extra:expr) => {
+        match $e {
+            Ok(e) => e,
+            Err(e) => panic!("{} failed with {}: {}", stringify!($e), e, $extra),
+        }
+    };
 }
 
 struct Builder {
@@ -584,7 +590,7 @@ impl Builder {
         self.shipped_files.insert(name.clone());
 
         let dst = self.output.join(name);
-        t!(fs::write(&dst, contents));
+        t!(fs::write(&dst, contents), format!("failed to create manifest {}", dst.display()));
     }
 
     fn write_shipped_files(&self, path: &Path) {

src/tools/build-manifest/src/versions.rs

@@ -117,6 +117,9 @@ impl Versions {
             Some(version) => Ok(version.clone()),
             None => {
                 let version_info = self.load_version_from_tarball(package)?;
+                if *package == PkgType::Rust && version_info.version.is_none() {
+                    panic!("missing version info for toolchain");
+                }
                 self.versions.insert(package.clone(), version_info.clone());
                 Ok(version_info)
             }
@@ -131,6 +134,7 @@ impl Versions {
             Ok(file) => file,
             Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
                 // Missing tarballs do not return an error, but return empty data.
+                println!("warning: missing tarball {}", tarball.display());
                 return Ok(VersionInfo::default());
             }
             Err(err) => return Err(err.into()),