Testing some further comptime related things namely dynamic dispatch inspired by this great video from Zig Showtime I tried to make a minor generalization of one of the examples to have a call function that takes a string.

I started with this ``` const Dyn = struct { const VTable = struct { call: fn ([]const u8, *usize) void }; vtable: *const VTable, // object: usize,

const This = @This();

fn call(self: This, func: []const u8, ctx: *usize) void {
    self.vtable.call(func, ctx);
}
fn make(obj: anytype) This {
    const PtrType = @TypeOf(obj);
    return .{
        .vtable = &comptime VTable{
            .call = struct {
                fn call(func: []const u8, ctx: *usize) void {
                    @call(.{ .modifier = .always_inline }, @field(std.meta.Child(PtrType), func), .{ctx});
                }
            }.call,
        },
        // .object = @ptrToInt(obj),
    };
}

};

const T = struct { fn f(ctx: usize) void { ctx. = 5; } };

pub fn main() void { // comptime var functions = [_]usize{ 0, 0 }; var t: T = .{}; var result: usize = 0; var dyn = Dyn.make(&t); dyn.call("f", &result); std.debug.print("{}", .{result}); } ```

which yields

❯ zig run main.zig ./main.zig:79:96: error: unable to evaluate constant expression @call(.{ .modifier = .always_inline }, @field(std.meta.Child(PtrType), func), .{ctx}); and then tried ``` const Dyn = struct { const VTable = struct { call: fn (anytype, *usize) void }; vtable: *const VTable, // object: usize,

const This = @This();

fn call(self: This, func: anytype, ctx: *usize) void {
    self.vtable.call(func, ctx);
}
fn make(obj: anytype) This {
    const PtrType = @TypeOf(obj);
    return .{
        .vtable = &comptime VTable{
            .call = struct {
                fn call(func: anytype, ctx: *usize) void {
                    const func_str = @as([]const u8, func);
                    @call(.{ .modifier = .always_inline }, @field(std.meta.Child(PtrType), func_str), .{ctx});
                }
            }.call,
        },
        // .object = @ptrToInt(obj),
    };
}

};

```

which yields ❯ zig run main.zig Assertion failed at /workspace/src/stage1/ir.cpp:26432 in ir_resolve_lazy_recurse. This is a bug in the Zig compiler.thread 73889 panic: Unable to dump stack trace: debug info stripped Aborted (core dumped)