Merge pull request #9926 from 9999years/fix-cycle-detection-in-nix-repl

Fix cycle detection in `nix repl`

(cherry picked from commit e190c20c3394fd1a5cd9be1afc3f30ab32dcd36b)
Change-Id: Ie385e781b9f0b7171ca653bcd53a990bb41f9e4b

src/libexpr/print.cc

@@ -150,7 +150,7 @@ struct ImportantFirstAttrNameCmp
     }
 };
 
-typedef std::set<Value *> ValuesSeen;
+typedef std::set<const void *> ValuesSeen;
 
 class Printer
 {
@@ -260,7 +260,7 @@ private:
 
     void printAttrs(Value & v, size_t depth)
     {
-        if (seen && !seen->insert(&v).second) {
+        if (seen && !seen->insert(v.attrs).second) {
             printRepeated();
             return;
         }