Use `Rc<[Symbol]>` instead of `Vec<Symbol>` to reduce # of allocs

5 files changed, 15 insertions, 14 deletions

diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index bc86ffa852b..fff54814a38 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -138,13 +138,14 @@ fn call_intrinsic(cx: &ExtCtxt<'_>,
                   -> P<ast::Expr> {
     let intrinsic_allowed_via_allow_internal_unstable = cx
         .current_expansion.mark.expn_info().unwrap()
-        .allow_internal_unstable.iter()
-        .any(|&s| s == "core_intrinsics");
+        .allow_internal_unstable.map_or(false, |features| features.iter().any(|&s|
+            s == "core_intrinsics"
+        ));
     if intrinsic_allowed_via_allow_internal_unstable {
         span = span.with_ctxt(cx.backtrace());
     } else { // Avoid instability errors with user defined curstom derives, cc #36316
         let mut info = cx.current_expansion.mark.expn_info().unwrap();
-        info.allow_internal_unstable = vec![Symbol::intern("core_intrinsics")];
+        info.allow_internal_unstable = Some(vec![Symbol::intern("core_intrinsics")].into());
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(info);
         span = span.with_ctxt(SyntaxContext::empty().apply_mark(mark));
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index dacc54d272b..719f9a4b3fd 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -60,7 +60,7 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
                      NormalTT {
                         expander: Box::new($f as MacroExpanderFn),
                         def_info: None,
-                        allow_internal_unstable: Vec::new(),
+                        allow_internal_unstable: None,
                         allow_internal_unsafe: false,
                         local_inner_macros: false,
                         unstable_feature: None,
@@ -103,9 +103,9 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
              NormalTT {
                 expander: Box::new(format::expand_format_args),
                 def_info: None,
-                allow_internal_unstable: vec![
+                allow_internal_unstable: Some(vec![
                     Symbol::intern("fmt_internals"),
-                ],
+                ].into()),
                 allow_internal_unsafe: false,
                 local_inner_macros: false,
                 unstable_feature: None,
@@ -115,9 +115,9 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
              NormalTT {
                  expander: Box::new(format::expand_format_args_nl),
                  def_info: None,
-                 allow_internal_unstable: vec![
+                 allow_internal_unstable: Some(vec![
                      Symbol::intern("fmt_internals"),
-                 ],
+                 ].into()),
                  allow_internal_unsafe: false,
                  local_inner_macros: false,
                  unstable_feature: None,
diff --git a/src/libsyntax_ext/proc_macro_decls.rs b/src/libsyntax_ext/proc_macro_decls.rs
index f198739d104..5730081ce01 100644
--- a/src/libsyntax_ext/proc_macro_decls.rs
+++ b/src/libsyntax_ext/proc_macro_decls.rs
@@ -333,10 +333,10 @@ fn mk_decls(
         call_site: DUMMY_SP,
         def_site: None,
         format: MacroAttribute(Symbol::intern("proc_macro")),
-        allow_internal_unstable: vec![
+        allow_internal_unstable: Some(vec![
             Symbol::intern("rustc_attrs"),
             Symbol::intern("proc_macro_internals"),
-        ],
+        ].into()),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: hygiene::default_edition(),
diff --git a/src/libsyntax_ext/test.rs b/src/libsyntax_ext/test.rs
index e2bea0c8b07..37186246548 100644
--- a/src/libsyntax_ext/test.rs
+++ b/src/libsyntax_ext/test.rs
@@ -66,10 +66,10 @@ pub fn expand_test_or_bench(
             call_site: DUMMY_SP,
             def_site: None,
             format: MacroAttribute(Symbol::intern("test")),
-            allow_internal_unstable: vec![
+            allow_internal_unstable: Some(vec![
                 Symbol::intern("rustc_attrs"),
                 Symbol::intern("test"),
-            ],
+            ].into()),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),
diff --git a/src/libsyntax_ext/test_case.rs b/src/libsyntax_ext/test_case.rs
index a581c282193..1ed1ab0a07b 100644
--- a/src/libsyntax_ext/test_case.rs
+++ b/src/libsyntax_ext/test_case.rs
@@ -41,10 +41,10 @@ pub fn expand(
             call_site: DUMMY_SP,
             def_site: None,
             format: MacroAttribute(Symbol::intern("test_case")),
-            allow_internal_unstable: vec![
+            allow_internal_unstable: Some(vec![
                 Symbol::intern("test"),
                 Symbol::intern("rustc_attrs"),
-            ],
+            ].into()),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),