5 files changed, 19 insertions, 23 deletions
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index d2c03e588ff..d733e32f209 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -842,6 +842,11 @@ pub struct NextSolverConfig {
     /// This is only `true` if `coherence` is also enabled.
     pub globally: bool,
 }
+impl Default for NextSolverConfig {
+    fn default() -> Self {
+        NextSolverConfig { coherence: true, globally: false }
+    }
+}
 
 #[derive(Clone)]
 pub enum Input {
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index d63276db493..f9964b59a94 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -403,7 +403,7 @@ mod desc {
     pub(crate) const parse_unpretty: &str = "`string` or `string=string`";
     pub(crate) const parse_treat_err_as_bug: &str = "either no value or a non-negative number";
     pub(crate) const parse_next_solver_config: &str =
-        "a comma separated list of solver configurations: `globally` (default), and `coherence`";
+        "either `globally` (when used without an argument), `coherence` (default) or `no`";
     pub(crate) const parse_lto: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), `thin`, `fat`, or omitted";
     pub(crate) const parse_linker_plugin_lto: &str =
@@ -1123,27 +1123,16 @@ mod parse {
         }
     }
 
-    pub(crate) fn parse_next_solver_config(
-        slot: &mut Option<NextSolverConfig>,
-        v: Option<&str>,
-    ) -> bool {
+    pub(crate) fn parse_next_solver_config(slot: &mut NextSolverConfig, v: Option<&str>) -> bool {
         if let Some(config) = v {
-            let mut coherence = false;
-            let mut globally = true;
-            for c in config.split(',') {
-                match c {
-                    "globally" => globally = true,
-                    "coherence" => {
-                        globally = false;
-                        coherence = true;
-                    }
-                    _ => return false,
-                }
-            }
-
-            *slot = Some(NextSolverConfig { coherence: coherence || globally, globally });
+            *slot = match config {
+                "no" => NextSolverConfig { coherence: false, globally: false },
+                "coherence" => NextSolverConfig { coherence: true, globally: false },
+                "globally" => NextSolverConfig { coherence: true, globally: true },
+                _ => return false,
+            };
         } else {
-            *slot = Some(NextSolverConfig { coherence: true, globally: true });
+            *slot = NextSolverConfig { coherence: true, globally: true };
         }
 
         true
@@ -1914,7 +1903,7 @@ options! {
         "the size at which the `large_assignments` lint starts to be emitted"),
     mutable_noalias: bool = (true, parse_bool, [TRACKED],
         "emit noalias metadata for mutable references (default: yes)"),
-    next_solver: Option<NextSolverConfig> = (None, parse_next_solver_config, [TRACKED],
+    next_solver: NextSolverConfig = (NextSolverConfig::default(), parse_next_solver_config, [TRACKED],
         "enable and configure the next generation trait solver used by rustc"),
     nll_facts: bool = (false, parse_bool, [UNTRACKED],
         "dump facts from NLL analysis into side files (default: no)"),
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 9781c746520..3d44810e7dd 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -66,7 +66,7 @@ impl GatedSpans {
 #[derive(Default)]
 pub struct SymbolGallery {
     /// All symbols occurred and their first occurrence span.
-    pub symbols: Lock<FxHashMap<Symbol, Span>>,
+    pub symbols: Lock<FxIndexMap<Symbol, Span>>,
 }
 
 impl SymbolGallery {
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index d67e69fe0fb..27879d817b2 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -454,6 +454,8 @@ impl Session {
         let bin_path = filesearch::make_target_bin_path(&self.sysroot, config::host_triple());
         let fallback_sysroot_paths = filesearch::sysroot_candidates()
             .into_iter()
+            // Ignore sysroot candidate if it was the same as the sysroot path we just used.
+            .filter(|sysroot| *sysroot != self.sysroot)
             .map(|sysroot| filesearch::make_target_bin_path(&sysroot, config::host_triple()));
         let search_paths = std::iter::once(bin_path).chain(fallback_sysroot_paths);
 
diff --git a/compiler/rustc_session/src/utils.rs b/compiler/rustc_session/src/utils.rs
index 37528a4425f..9182789cf02 100644
--- a/compiler/rustc_session/src/utils.rs
+++ b/compiler/rustc_session/src/utils.rs
@@ -137,7 +137,7 @@ pub fn extra_compiler_flags() -> Option<(Vec<String>, bool)> {
             let content = if arg.len() == a.len() {
                 // A space-separated option, like `-C incremental=foo` or `--crate-type rlib`
                 match args.next() {
-                    Some(arg) => arg.to_string(),
+                    Some(arg) => arg,
                     None => continue,
                 }
             } else if arg.get(a.len()..a.len() + 1) == Some("=") {