Values of type must be comptime-known

Question

I've the below in my code:

var routeRegister = std.StringHashMap(*const fn (response: *http.Server.Response) void).init(allocator);
try routes.init(&routeRegister);
defer routeRegister.deinit();

const some_data_info = @typeInfo(@TypeOf(routeRegister));
print("{}\n", .{some_data_info});

But I got the below error:

/usr/lib/zig/std/fmt.zig:662:22: error: values of type '[]const builtin.Type.StructField' must be comptime-known, but index value is runtime-known
                for (value, 0..) |elem, i| {
                     ^~~~~
/usr/lib/zig/std/builtin.zig:318:15: note: struct requires comptime because of this field
        type: type,
              ^~~~
/usr/lib/zig/std/builtin.zig:318:15: note: types are not available at runtime
        type: type,
              ^~~~
/usr/lib/zig/std/builtin.zig:321:20: note: struct requires comptime because of this field
        alignment: comptime_int,
                   ^~~~~~~~~~~~

I tried:

var routeRegister = comptime std.StringHashMap(*const fn (response: *http.Server.Response) void);
try routeRegister.init(allocator);

But got:

server.zig:99:13: error: variable of type 'type' must be const or comptime
        var routeRegister = comptime std.StringHashMap(*const fn (response: *http.Server.Response) void);
            ^~~~~~~~~~~~~
server.zig:99:13: note: types are not available at runtime

Answer 1

The second error occurs because std.StringHashMap returns a type. Just declare it constant (you can also declare it outside of any function):

const RouteRegister = std.StringHashMap(*const fn (response: *http.Server.Response) void);
var routeRegister = RouteRegister.init(allocator);

The first error occurs because @typeInfo returns std.builtin.Type, which cannot be formatted by the default formatter. Just remove @typeInfo and print the type directly:

print("{}\n", .{ @TypeOf(routeRegister) });
// or just
print("{}\n", .{ RouteRegister });