diff options
Diffstat (limited to 'src/libexpr/eval.cc')
| -rw-r--r-- | src/libexpr/eval.cc | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 0623e4953239..5ae4d6de8edc 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -201,6 +201,11 @@ Expr evalExpr2(EvalState & state, Expr e) cons == "List")) return e; + /* The `Closed' constructor is just a way to prevent substitutions + into expressions not containing free variables. */ + if (atMatch(m, e) >> "Closed" >> e1) + return evalExpr(state, e1); + /* Any encountered variables must be undeclared or primops. */ if (atMatch(m, e) >> "Var" >> name) { PrimOp0 primOp = (PrimOp0) lookupPrimOp(state.primOps0, name); |