diff options
Diffstat (limited to 'src/libexpr/nixexpr.cc')
| -rw-r--r-- | src/libexpr/nixexpr.cc | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc index 5c67b74ca6c6..289e923c3311 100644 --- a/src/libexpr/nixexpr.cc +++ b/src/libexpr/nixexpr.cc @@ -233,7 +233,12 @@ Expr substitute(const ATermMap & subs, Expr e) if (matchVar(e, name)) { Expr sub = subs.get(name); - return sub ? makeClosed(sub) : e; + Expr wrapped; + /* Add a "closed" wrapper around terms that aren't already + closed. The check is necessary to prevent repeated + wrapping, e.g., closed(closed(closed(...))), which kills + caching. */ + return sub ? (matchClosed(sub, wrapped) ? sub : makeClosed(sub)) : e; } /* In case of a function, filter out all variables bound by this |