* Added an experimental feature suggested by Andres: ellipses ("...")

  in attribute set pattern matches.  This allows defining a function
  that takes *at least* the listed attributes, while ignoring
  additional attributes.  For instance,

    {stdenv, fetchurl, fuse, ...}:
    
    stdenv.mkDerivation {
      ...
    };
    
  defines a function that requires an attribute set that contains the 
  specified attributes but ignores others.  The main advantage is that
  we can then write in all-packages.nix

    aefs = import ../bla/aefs pkgs;

  instead of

    aefs = import ../bla/aefs {
      inherit stdenv fetchurl fuse;
    };

  This saves a lot of typing (not to mention not having to update
  all-packages.nix with purely mechanical changes).  It saves as much
  typing as the "args: with args;" style, but has the advantage that
  the function arguments are properly declared (not implicit in what
  the body of the "with" uses).

1 files changed, 3 insertions, 2 deletions

diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index b2d775abbcc2..d96b5be97fb9 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -114,12 +114,13 @@ static void varsBoundByPattern(ATermMap & map, Pattern pat)
 {
     ATerm name;
     ATermList formals;
-    Pattern pat1, pat2;    
+    Pattern pat1, pat2;
+    ATermBool ellipsis;
     /* Use makeRemoved() so that it can be used directly in
        substitute(). */
     if (matchVarPat(pat, name))
         map.set(name, makeRemoved());
-    else if (matchAttrsPat(pat, formals)) { 
+    else if (matchAttrsPat(pat, formals, ellipsis)) { 
         for (ATermIterator i(formals); i; ++i) {
             ATerm d1;
             if (!matchFormal(*i, name, d1)) abort();