[libSyntax] Pass RC<RawSyntax> by reference whenever possible

Author: ahoppen

include/swift/Syntax/Syntax.h

@@ -66,7 +66,7 @@ class Syntax {
   SyntaxKind getKind() const;
 
   /// Get the shared raw syntax.
-  const RC<RawSyntax> getRaw() const;
+  const RC<RawSyntax> &getRaw() const;
 
   /// Get an ID for this node that is stable across incremental parses
   SyntaxNodeId getId() const { return getRaw()->getId(); }

include/swift/Syntax/SyntaxData.h

@@ -60,7 +60,7 @@ class RefCountedBox final
 
   RefCountedBox(const T Data) : Data(Data) {}
 
-  static RC<RefCountedBox<T>> make(const T Data) {
+  static RC<RefCountedBox<T>> make(const T &Data) {
     return RC<RefCountedBox<T>>{new RefCountedBox(Data)};
   }
 };

lib/Syntax/Syntax.cpp

@@ -17,7 +17,7 @@
 using namespace swift;
 using namespace swift::syntax;
 
-const RC<RawSyntax> Syntax::getRaw() const { return Data.getRaw(); }
+const RC<RawSyntax> &Syntax::getRaw() const { return Data.getRaw(); }
 
 SyntaxKind Syntax::getKind() const {
   return getRaw()->getKind();