Make a public alias for the return type of std.typecons.scoped

[dlangBugzillaToGithub]

dhasenan (@dhasenan) reported this on 2018-11-08T16:31:01Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=19379

Description

The documentation for std.typecons.scoped says to use typeof() to identify the type.

I know the arguments for keeping the actual type opaque. We've been over it with std.regex.Captures and so forth. It would be really great to have a way to name that type succinctly so you can use it in fields, pass it as a parameter (by reference obviously), instantiate templates of it, explicitly name variable types, that kind of thing, without having to use aliases everywhere.

Example of someone getting confused by how to use it without that sort of type naming: https://forum.dlang.org/thread/tnwyxmraefedcbypugqp@forum.dlang.org