I cannot initialize a global variable with the stdout in zig:

var out = std.io.getStdOut().writer();

Then I tried to initialize in the fn main and declare the global variables as optional (initialized by null).

My problem is that I don't know which is the type of std.io.getStdOut().writer();.

I tried something like:

var out: std.fs.Writer? = null
//...
fn main() !void {
   out = std.io.getStdOut().writer();
   //...
   out.print("ok: {}", "ok");
}

Also I tried reflection:

var stdout: @typeInfo(@TypeOf(std.io.getStdOut().writer())).Fn.return_type.? = null;

I need to know how I can declare a variable or a function returning a Writer (i.e. something that has the usual print function inside).

Edited

Tied twice using zig version 0.12.0-dev.1150+3c22cecee and 0.11.0

With writer.zig file containing:

const std = @import("std");

var out = std.io.getStdOut().writer();

pub fn main() anyerror!void {
    try out.print("{any}\n", .{@TypeOf(out)});
}

I get error: unable to evaluate comptime expression

zig build-exe writer.zig && writer.exe                           
C:\bin\zig\lib\std\os\windows.zig:1944:28: error: unable to evaluate comptime expression
                break :blk asm volatile (
                           ^~~
C:\bin\zig\lib\std\os\windows.zig:1959:15: note: called from here
    return teb().ProcessEnvironmentBlock;
           ~~~^~
C:\bin\zig\lib\std\io.zig:37:30: note: called from here
        return os.windows.peb().ProcessParameters.hStdOutput;
               ~~~~~~~~~~~~~~^~
C:\bin\zig\lib\std\io.zig:51:34: note: called from here
        .handle = getStdOutHandle(),
                  ~~~~~~~~~~~~~~~^~
writer.zig:3:27: note: called from here
var out = std.io.getStdOut().writer();
          ~~~~~~~~~~~~~~~~^~
referenced by:
    main: writer.zig:6:9
    callMain: C:\bin\zig\lib\std\start.zig:583:32
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

It works for me on a Ubuntu/Linux machine. I assume it is a Windows-specific bug:

% cat test.zig

const std = @import("std");

var out = std.io.getStdOut().writer();

pub fn main() anyerror!void {
    try out.print("{any}\n", .{@TypeOf(out)});
}

% zig build-exe test.zig && ./test
io.writer.Writer(fs.file.File,error{AccessDenied,Unexpected,DiskQuota,FileTooBig,InputOutput,NoSpaceLeft,DeviceBusy,InvalidArgument,BrokenPipe,SystemResources,OperationAborted,NotOpenForWriting,LockViolation,WouldBlock,ConnectionResetByPeer},(function 'write'))

The last line gives you the returned type.