Fix review comments

Cargo.lock

@@ -3640,6 +3640,7 @@ dependencies = [
  "rustc_macros",
  "rustc_serialize",
  "rustc_span",
+ "smallvec",
  "tracing",
  "unic-langid",
 ]

compiler/rustc_error_messages/Cargo.toml

@@ -16,6 +16,7 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
+smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 tracing = "0.1"
 unic-langid = { version = "0.9.0", features = ["macros"] }
 # tidy-alphabetical-end

compiler/rustc_error_messages/src/lib.rs

@@ -21,6 +21,7 @@ use intl_memoizer::concurrent::IntlLangMemoizer;
 use rustc_data_structures::sync::IntoDynSyncSend;
 use rustc_macros::{Decodable, Encodable};
 use rustc_span::Span;
+use smallvec::SmallVec;
 use tracing::{instrument, trace};
 pub use unic_langid::{LanguageIdentifier, langid};
 
@@ -106,8 +107,7 @@ impl From<Vec<FluentError>> for TranslationBundleError {
 /// (overriding any conflicting messages).
 #[instrument(level = "trace")]
 pub fn fluent_bundle(
-    sysroot: PathBuf,
-    default_sysroot: PathBuf,
+    sysroot_candidates: SmallVec<[PathBuf; 2]>,
     requested_locale: Option<LanguageIdentifier>,
     additional_ftl_path: Option<&Path>,
     with_directionality_markers: bool,
@@ -141,7 +141,7 @@ pub fn fluent_bundle(
     // If the user requests the default locale then don't try to load anything.
     if let Some(requested_locale) = requested_locale {
         let mut found_resources = false;
-        for mut sysroot in [sysroot, default_sysroot] {
+        for mut sysroot in sysroot_candidates {
             sysroot.push("share");
             sysroot.push("locale");
             sysroot.push(requested_locale.to_string());

compiler/rustc_interface/src/interface.rs

@@ -18,7 +18,7 @@ use rustc_parse::parser::attr::AllowLeadingUnsafe;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
 use rustc_session::config::{self, Cfg, CheckCfg, ExpectedValues, Input, OutFileName};
-use rustc_session::filesearch::get_or_default_sysroot;
+use rustc_session::filesearch::sysroot_with_fallback;
 use rustc_session::parse::ParseSess;
 use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, lint};
 use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMapInputs};
@@ -442,8 +442,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
             let temps_dir = config.opts.unstable_opts.temps_dir.as_deref().map(PathBuf::from);
 
             let bundle = match rustc_errors::fluent_bundle(
-                config.opts.sysroot.clone(),
-                get_or_default_sysroot(),
+                sysroot_with_fallback(&config.opts.sysroot),
                 config.opts.unstable_opts.translate_lang.clone(),
                 config.opts.unstable_opts.translate_additional_ftl.as_deref(),
                 config.opts.unstable_opts.translate_directionality_markers,

compiler/rustc_interface/src/util.rs

@@ -345,14 +345,10 @@ pub fn rustc_path<'a>() -> Option<&'a Path> {
 }
 
 fn get_rustc_path_inner(bin_path: &str) -> Option<PathBuf> {
-    Some(filesearch::get_or_default_sysroot()).iter().find_map(|sysroot| {
-        let candidate = sysroot.join(bin_path).join(if cfg!(target_os = "windows") {
-            "rustc.exe"
-        } else {
-            "rustc"
-        });
-        candidate.exists().then_some(candidate)
-    })
+    let candidate = filesearch::get_or_default_sysroot()
+        .join(bin_path)
+        .join(if cfg!(target_os = "windows") { "rustc.exe" } else { "rustc" });
+    candidate.exists().then_some(candidate)
 }
 
 #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable