nix flake show: Use evaluation cache

1 files changed, 9 insertions, 2 deletions

diff --git a/src/libexpr/symbol-table.hh b/src/libexpr/symbol-table.hh
index 7ba5e1c14..4eb6dac81 100644
--- a/src/libexpr/symbol-table.hh
+++ b/src/libexpr/symbol-table.hh
@@ -28,6 +28,12 @@ public:
         return s == s2.s;
     }
 
+    // FIXME: remove
+    bool operator == (std::string_view s2) const
+    {
+        return s->compare(s2) == 0;
+    }
+
     bool operator != (const Symbol & s2) const
     {
         return s != s2.s;
@@ -68,9 +74,10 @@ private:
     Symbols symbols;
 
 public:
-    Symbol create(const string & s)
+    Symbol create(std::string_view s)
     {
-        std::pair<Symbols::iterator, bool> res = symbols.insert(s);
+        // FIXME: avoid allocation if 's' already exists in the symbol table.
+        std::pair<Symbols::iterator, bool> res = symbols.emplace(std::string(s));
         return Symbol(&*res.first);
     }