* In `nix-env', look for derivations inside attribute sets that have

the `recurseForDerivations' attribute set to `true'.

src/libexpr/eval.hh

@@ -55,6 +55,7 @@ Expr evalFile(EvalState & state, const Path & path);
 /* Specific results. */
 string evalString(EvalState & state, Expr e);
 Path evalPath(EvalState & state, Expr e);
+bool evalBool(EvalState & state, Expr e);
 ATermList evalList(EvalState & state, Expr e);
 ATerm coerceToString(Expr e);