[DO NOT MERGE][BETA] What does compiletest see in opt-dist?

src/ci/github-actions/jobs.yml

@@ -79,7 +79,7 @@ envs:
     # - not running `opt-dist`'s post-optimization smoke tests on the resulting toolchain
     #
     # If you *want* these to happen however, temporarily uncomment it before triggering a try build.
-    DIST_TRY_BUILD: 1
+    #DIST_TRY_BUILD: 1
 
   auto:
     <<: *production

src/tools/compiletest/src/main.rs

@@ -18,6 +18,16 @@ fn main() {
 
     let config = Arc::new(parse_config(env::args().collect()));
 
+    eprintln!("INFO: compiletest was told channel=`{}`", config.channel);
+    eprintln!("INFO: rustc -vV reports:");
+    eprintln!(
+        "{}",
+        String::from_utf8(
+            std::process::Command::new(&config.rustc_path).arg("-vV").output().unwrap().stdout
+        )
+        .unwrap()
+    );
+
     if !config.has_html_tidy && config.mode == Mode::Rustdoc {
         eprintln!("warning: `tidy` (html-tidy.org) is not installed; diffs will not be generated");
     }

src/tools/opt-dist/src/tests.rs

@@ -25,6 +25,8 @@ pub fn run_tests(env: &Environment) -> anyhow::Result<()> {
     let host_triple = env.host_tuple();
     let version = find_dist_version(&dist_dir)?;
 
+    let channel = version_to_channel(&version);
+
     // Extract rustc, libstd, cargo and src archives to create the optimized sysroot
     let rustc_dir = extract_dist_dir(&format!("rustc-{version}-{host_triple}"))?.join("rustc");
     let libstd_dir = extract_dist_dir(&format!("rust-std-{version}-{host_triple}"))?
@@ -61,9 +63,13 @@ pub fn run_tests(env: &Environment) -> anyhow::Result<()> {
     assert!(llvm_config.is_file());
 
     let config_content = format!(
-        r#"profile = "user"
+        r#"
+profile = "user"
 change-id = 115898
 
+[rust]
+channel = "{channel}"
+
 [build]
 rustc = "{rustc}"
 cargo = "{cargo}"
@@ -116,3 +122,13 @@ fn find_dist_version(directory: &Utf8Path) -> anyhow::Result<String> {
         archive.strip_prefix("reproducible-artifacts-").unwrap().split_once('-').unwrap();
     Ok(version.to_string())
 }
+
+/// Roughly convert a version string (`nightly`, `beta`, or `1.XY.Z`) to channel string (`nightly`,
+/// `beta` or `stable`).
+fn version_to_channel(version_str: &str) -> &'static str {
+    match version_str {
+        "nightly" => "nightly",
+        "beta" => "beta",
+        _ => "stable",
+    }
+}