findFromRoot

    fn findFromRoot(
        gpa: Allocator,
        io: Io,
        roots_key: Registry.Key,
        roots_subkey: []const u16,
        prefix: []const u8,
    ) error{ OutOfMemory, InstallationNotFound, PathTooLong, VersionTooLong }!Installation {
        const path = path: {
            const path_w_maybe_with_trailing_slash = roots_key.getString(gpa, .{ .name = roots_subkey }, .wtf16) catch |err| switch (err) {
                error.NotAString,
                error.ValueNameNotFound,
                error.StringNotFound,
                => return error.InstallationNotFound,

                error.OutOfMemory => |e| return e,
            };
            defer gpa.free(path_w_maybe_with_trailing_slash);

            if (!std.fs.path.isAbsoluteWindowsWtf16(path_w_maybe_with_trailing_slash)) {
                return error.InstallationNotFound;
            }

            const path_w = std.mem.trimEnd(u16, path_w_maybe_with_trailing_slash, L("\\/"));
            break :path try std.unicode.wtf16LeToWtf8Alloc(gpa, path_w);
        };
        errdefer gpa.free(path);

        const version = version: {
            var buf: [Dir.max_path_bytes]u8 = undefined;
            const sdk_lib_dir_path = std.mem.print(buf[0..], "{s}\\Lib\\", .{path}) catch |err| switch (err) {
                error.NoSpaceLeft => return error.PathTooLong,
            };
            if (!Dir.path.isAbsolute(sdk_lib_dir_path)) return error.InstallationNotFound;

            // enumerate files in sdk path looking for latest version
            var sdk_lib_dir = Dir.openDirAbsolute(io, sdk_lib_dir_path, .{
                .iterate = true,
            }) catch |err| switch (err) {
                error.NameTooLong => return error.PathTooLong,
                else => return error.InstallationNotFound,
            };
            defer sdk_lib_dir.close(io);

            var iterator = sdk_lib_dir.iterate();
            const versions = try iterateAndFilterByVersion(&iterator, gpa, io, prefix);
            if (versions.len == 0) return error.InstallationNotFound;
            defer {
                for (versions[1..]) |version| gpa.free(version);
                gpa.free(versions);
            }
            break :version versions[0];
        };
        errdefer gpa.free(version);

        return .{ .path = path, .version = version };
    }