I updated a small template-heavy experimental library mostly for compile-time introspection I write some time ago. The last time I updated the code was probably using 2.065, but might also have been as old as 2.063.

The code doesn't use much of the standard library, mostly parts of std.traits and std.typetuple.TypeTuple. While upgrading, I only encountered a single bug (https://issues.dlang.org/show_bug.cgi?id=14820), which might have been there for a long time as I didn't check when it was introduced - I hit it when adding additional unittests when I got weird compile-time errors.

There was however a breaking change that caused most of my templates to fail. My templates supports both built-in types, user-defined types and values. In order to do this, both templates of `T` and `alias T` has to be created. In previous versions of the compiler, user-defined types always picked the `alias T` version first, while the newest compiler picks `T` for all types.  I found the old behavior pretty weird, so I'm all in favor of the change though.

    // 1
    template Tmlp(T) {}
    // 2
    template Tmpl(alias T) {}

    struct S {}
    Tmpl!S; // 2 on 2.065 (/2.063?), 1 on 2.067

There's still an odd difference between built-in and user-defined types:

    template OnlyAlias(alias T) {}
    struct S {}
    OnlyAlias!S; // works
    OnlyAlias!int; // doesn't work

I also had to make some dub related changes and a simple import because `chain` moved from `std.algorithm` to `std.range`.

Just a little experience-report for upgrading between compiler versions. I'm one of the people that is pro breaking-changes.  Keep in mind that this is a small project of just 4351 LOC where a lot is tests and documentation and nearly no use of phobos or druntime.

Anyway - happy to see breaking changes that improves the language.

On Wednesday, 22 July 2015 at 15:50:13 UTC, simendsjo wrote:

>     // 1
>     template Tmlp(T) {}
>     // 2
>     template Tmpl(alias T) {}

I'm assuming thats a typo

On Thursday, 23 July 2015 at 13:20:32 UTC, Nicholas Wilson wrote:
> On Wednesday, 22 July 2015 at 15:50:13 UTC, simendsjo wrote:
>
>>     // 1
>>     template Tmlp(T) {}
>>     // 2
>>     template Tmpl(alias T) {}
>
> I'm assuming thats a typo

Yes. I just wrote the code in the post without trying to compile it. I'm not as good at caching typos as the compiler.

On 2015-07-23 15:58, simendsjo wrote:

> I'm not as good at caching typos as the compiler.

caching -> catching :)

-- 
/Jacob Carlborg