implement async function call with `@call`

this removes the last usage of var args in zig std lib

2 files changed, 9 insertions, 3 deletions

diff --git a/lib/std/builtin.zig b/lib/std/builtin.zig
index b3a80dc317..4c57915f92 100644
--- a/lib/std/builtin.zig
+++ b/lib/std/builtin.zig
@@ -382,6 +382,9 @@ pub const CallOptions = struct {
         /// Equivalent to function call syntax.
         auto,
 
+        /// Equivalent to async keyword used with function call syntax.
+        async_kw,
+
         /// Prevents tail call optimization. This guarantees that the return
         /// address will point to the callsite, as opposed to the callsite's
         /// callsite. If the call is otherwise required to be tail-called
diff --git a/lib/std/event/group.zig b/lib/std/event/group.zig
index 9feb99148b..d9076ef78d 100644
--- a/lib/std/event/group.zig
+++ b/lib/std/event/group.zig
@@ -60,16 +60,19 @@ pub fn Group(comptime ReturnType: type) type {
         /// allocated by the group and freed by `wait`.
         /// `func` must be async and have return type `ReturnType`.
         /// Thread-safe.
-        pub fn call(self: *Self, comptime func: var, args: ...) error{OutOfMemory}!void {
-            var frame = try self.allocator.create(@Frame(func));
+        pub fn call(self: *Self, comptime func: var, args: var) error{OutOfMemory}!void {
+            var frame = try self.allocator.create(@typeOf(@call(.{ .modifier = .async_kw }, func, args)));
+            errdefer self.allocator.destroy(frame);
             const node = try self.allocator.create(AllocStack.Node);
+            errdefer self.allocator.destroy(node);
             node.* = AllocStack.Node{
                 .next = undefined,
                 .data = Node{
-                    .handle = @asyncCall(frame, {}, func, args),
+                    .handle = frame,
                     .bytes = std.mem.asBytes(frame),
                 },
             };
+            frame.* = @call(.{ .modifier = .async_kw }, func, args);
             self.alloc_stack.push(node);
         }