`alias newSymbol = existingSymbol` or `alias existingSymbol newSymbol`

[David Nadlinger via Digitalmars-d]

On Tuesday, 28 October 2014 at 08:29:22 UTC, Jonathan M Davis via 
Digitalmars-d wrote:
> I see no reason to say anything about the alias syntax in the 
> style guide.

Consistency, and thus less confusion/mental overhead.

I don't think that you'll be able to make a strong case for 
"Either it should be considered fine to use, or we should 
deprecate it." If we started with a clean slate today, there 
wouldn't be a good reason to include the old syntax. It is an 
outlier as we've generally moved away from C-style ordering of 
types/declarations, and also can't do inline templates. And if we 
agree that the new syntax is to be preferred – and it seems like 
except for you we pretty unambiguously do –, I don't see why we 
shouldn't put that out as an official recommendation.

Of course, breaking legacy code over this by deprecating the old 
syntax might ultimately not be worth it. I don't see how this can 
be construed as an argument against putting it in the style 
guide, however. In fact, if we planned to deprecate it anyway, 
this would rather be a reason _not_ to to bother with putting it 
in the style guide first.

To summarize why the new syntax is better than the old one:
  - It's more straightforward for newcomers, its order is the same 
as for basic assignments. If you somehow find that unnatural like 
you've claimed earlier, then you've merely trained your brain to 
read alias assignments backwards compared to assign expressions.

  - Arguably the new syntax also makes it easier to skim-read the 
code, as the most important part (the symbol introduced) is at 
the beginning of the line, not hidden after some potentially 
multi-line template instantiation. Granted, you might say that 
this is not very relevant, but I think you'd find it hard to 
argue that the syntax is _less_ readable.

  - The new syntax also has the advantage that it allows to easily 
declare template aliases, for example:
---
alias Seq(T...) = T;
---

By the way, "using" is regularly recommended for use in C++11 and 
up now instead of "typedef" for much the same reasons (just look 
at the CppCon talks for some data points).

David