From ca00aa11714921804afb490d0613086f549fb894 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Tue, 15 May 2007 12:14:37 +0000
Subject: [PATCH] * Allow empty argument lists in function definitions (e.g.,
 `{}:   bla').  Also allow trailing commas (`{x, y,}: ...') as a unintented  
 consequence.  Hopefully the reduce/reduce conflict won't cause any  
 problems.

---
 src/libexpr/parser.y                | 1 +
 tests/lang/eval-okay-empty-args.exp | 1 +
 tests/lang/eval-okay-empty-args.nix | 1 +
 3 files changed, 3 insertions(+)
 create mode 100644 tests/lang/eval-okay-empty-args.exp
 create mode 100644 tests/lang/eval-okay-empty-args.nix

diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 3540058b..1c06240f 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -249,6 +249,7 @@ expr_list
 formals
   : formal ',' formals { $$ = ATinsert($3, $1); } /* idem - right recursive */
   | formal { $$ = ATinsert(ATempty, $1); }
+  | { $$ = ATempty; }
   ;
 
 formal
diff --git a/tests/lang/eval-okay-empty-args.exp b/tests/lang/eval-okay-empty-args.exp
new file mode 100644
index 00000000..c386bbc8
--- /dev/null
+++ b/tests/lang/eval-okay-empty-args.exp
@@ -0,0 +1 @@
+Str("ab",[])
diff --git a/tests/lang/eval-okay-empty-args.nix b/tests/lang/eval-okay-empty-args.nix
new file mode 100644
index 00000000..78c133af
--- /dev/null
+++ b/tests/lang/eval-okay-empty-args.nix
@@ -0,0 +1 @@
+({}: {x,y,}: "${x}${y}") {} {x = "a"; y = "b";}