Add support for variadic parameters

Everything was already in place, but not used for variadic parameters.

On the other hand fixed parameters sets are currently bugged, as they don't
reject extra arguments (they act like variadic parameters set). This commit adds
a TODO mentionning that.

Nix/Eval.hs

@@ -93,10 +93,15 @@ atomText (NUri uri) = uri
 buildArgument :: Params (NValue m) -> NValue m -> ValueSet m
 buildArgument paramSpec arg = either error id $ case paramSpec of
     Param name -> return $ Map.singleton name arg
-    ParamSet (FixedParamSet s) Nothing -> lookupParamSet s
-    ParamSet (FixedParamSet s) (Just name) ->
-      Map.insert name arg <$> lookupParamSet s
-    ParamSet _ _ -> error "Can't yet handle variadic param sets"
+    -- TODO FixedParamSet should check that no extra args are passed
+    ParamSet paramSet setName ->
+      let actualParamSet = case paramSet of
+            FixedParamSet s -> s
+            VariadicParamSet s -> s
+          maybeAddSet = case setName of
+            Just name -> Map.insert name arg
+            Nothing -> id
+      in maybeAddSet <$> lookupParamSet actualParamSet
   where
     go env k def = maybe (Left err) return $ Map.lookup k env <|> def
       where err = "Could not find " ++ show k

tests/EvalTests.hs

@@ -36,6 +36,12 @@ case_function_set_two_arg = constantEqualStr "2" "({ a, b ? 3 }: b - a) { a = 1;
 case_function_definition_uses_environment :: Assertion
 case_function_definition_uses_environment = constantEqualStr "3" "let f = (let a=1; in x: x+a); in f 2"
 
+case_function_atpattern :: Assertion
+case_function_atpattern = constantEqualStr "2" "(({a}@attrs:attrs) {a=2;}).a"
+
+case_function_ellipsis :: Assertion
+case_function_ellipsis = constantEqualStr "2" "(({a, ...}@attrs:attrs) {a=0; b=2;}).b"
+
 tests :: TestTree
 tests = $testGroupGenerator