findInstancesDir

    fn findInstancesDir(
        gpa: Allocator,
        io: Io,
        registry: *Registry,
        environ_map: *const Environ.Map,
    ) error{ OutOfMemory, PathNotFound }!Dir {
        // First, try getting the packages cache path from the registry.
        // This only seems to exist when the path is different from the default.
        method1: {
            return findInstancesDirViaSetup(gpa, io, registry) catch |err| switch (err) {
                error.OutOfMemory => |e| return e,
                error.PathNotFound => break :method1,
            };
        }
        // Otherwise, try to get the path from the .dll that would have been
        // loaded via COM for SetupConfiguration.
        method2: {
            return findInstancesDirViaCLSID(gpa, io, registry) catch |err| switch (err) {
                error.OutOfMemory => |e| return e,
                error.PathNotFound => break :method2,
            };
        }
        // If that can't be found, fall back to manually appending
        // `Microsoft\VisualStudio\Packages\_Instances` to %PROGRAMDATA%
        method3: {
            const program_data = std.zig.EnvVar.PROGRAMDATA.get(environ_map) orelse break :method3;

            if (!std.fs.path.isAbsolute(program_data)) break :method3;

            const instances_path = try Dir.path.join(gpa, &.{
                program_data, "Microsoft", "VisualStudio", "Packages", "_Instances",
            });
            defer gpa.free(instances_path);

            return Dir.openDirAbsolute(io, instances_path, .{ .iterate = true }) catch break :method3;
        }
        return error.PathNotFound;
    }