heap.create で分かりにくいエラー (std/heap.zen 中で error[E04001]: use of undefined value) が出るもの

alloc_error.zen

const std = @import("std");
const heap = std.heap;

var buffer: [4096]u8 = undefined;
var allocator = heap.FixedBufferAllocator{ .buffer = &buffer };

fn Node(comptime T: type) type {
    return struct {
        next: ?*Node(T),
        data: T,
    };
}

fn newNode(data: var) heap.Allocator.Error!*Node(@typeOf(data)) {
    var node = try heap.create(&allocator, Node(@typeOf(data)));
    node.next = null;
    node.data = data;
    return node;
}

pub fn main() anyerror!void {
    // var node = newNode(@is(i32, 10)); // これなら OK
    var node = newNode(10); // .../std/heap.zen:121:56: error[E04001]: use of undefined value
    std.debug.warn("{}\n", node);
}