return string_views from forceString*

once a string has been forced we already have dynamic storage allocated for it,
so we can easily reuse that storage instead of copying.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libexpr/primops/context.cc b/src/libexpr/primops/context.cc
index a239c06da..cd7eeb588 100644
--- a/src/libexpr/primops/context.cc
+++ b/src/libexpr/primops/context.cc
@@ -180,7 +180,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
             }
             for (auto elem : iter->value->listItems()) {
                 auto name = state.forceStringNoCtx(*elem, *iter->pos);
-                context.insert("!" + name + "!" + string(i.name));
+                context.insert(concatStrings("!", name, "!", i.name));
             }
         }
     }