On 04/15/2016 06:50 AM, Kenji Hara via Digitalmars-d wrote:

You should recall the history of inout.
http://wiki.dlang.org/DIP2

At first, It has designed to temporarily squash mutable/const/immutable
qualifiers on function argument inside function body. Therefore when
inout qualifier appears in function return type, but doesn't on
parameter types, we defined it an error.

However, I concluded that we can remove the restriction. When an inout
object arises from thin air, no one holds the qualifier of its real
instance. It means, the returned inout object can be converted to
arbitrary qualifiers without type system breaking.

Two years ago I opened an enhancement issue:
https://issues.dlang.org/show_bug.cgi?id=13006

And posted a pull request.
https://github.com/D-Programming-Language/dmd/pull/3740

I do recall the history. The enhancement is sensible in a frame of mind "we need to keep inout" but I'm looking at top level and thinking, crap we can put up with a little duplication if we get rid of inout. It's just a prime example of apparently simple idea gone bonkers.

In all of my recent code I've avoided inout and didn't miss it one bit. There's no need for it - I replace it with one-liners that forward to template functions, which in turn deduce qualifiers and all is great.