Rollup merge of #49030 - Zoxc:misc, r=michaelwoerister

Misc changes from my parallel rustc branch

r? @michaelwoerister

2 files changed, 10 insertions, 2 deletions

diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 9b83d5510fb..5a7b7e9ceca 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -184,8 +184,12 @@ impl SpanData {
     }
 }
 
-// The interner in thread-local, so `Span` shouldn't move between threads.
+// The interner is pointed to by a thread local value which is only set on the main thread
+// with parallelization is disabled. So we don't allow Span to transfer between threads
+// to avoid panics and other errors, even though it would be memory safe to do so.
+#[cfg(not(parallel_queries))]
 impl !Send for Span {}
+#[cfg(not(parallel_queries))]
 impl !Sync for Span {}
 
 impl PartialOrd for Span {
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index 0cba094da64..098eafef258 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -83,8 +83,12 @@ impl Decodable for Ident {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Symbol(u32);
 
-// The interner in thread-local, so `Symbol` shouldn't move between threads.
+// The interner is pointed to by a thread local value which is only set on the main thread
+// with parallelization is disabled. So we don't allow Symbol to transfer between threads
+// to avoid panics and other errors, even though it would be memory safe to do so.
+#[cfg(not(parallel_queries))]
 impl !Send for Symbol { }
+#[cfg(not(parallel_queries))]
 impl !Sync for Symbol { }
 
 impl Symbol {