* Refactoring: combine functions that take an attribute set and

functions that take a single argument (plain lambdas) into one AST
  node (Function) that contains a Pattern node describing the
  arguments.  Current patterns are single lazy arguments (VarPat) and
  matching against an attribute set (AttrsPat).

  This refactoring allows other kinds of patterns to be added easily,
  such as Haskell-style @-patterns, or list pattern matching.

src/libexpr/primops.cc

@@ -120,11 +120,9 @@ static Expr prim_isNull(EvalState & state, const ATermVector & args)
 static Expr prim_isFunction(EvalState & state, const ATermVector & args)
 {
     Expr e = evalExpr(state, args[0]);
-    ATermList formals;
-    ATerm name, body, pos;
-    return makeBool(
-        matchFunction(e, formals, body, pos) ||
-        matchFunction1(e, name, body, pos));
+    Pattern pat;
+    ATerm body, pos;
+    return makeBool(matchFunction(e, pat, body, pos));
 }