Better static assertion on template contraints with 'models'

[atilaneves]

This is similar to the work done on this PR, which is now dependent on the current one.

The idea is to have compiler error messages when a type that was intended to satisfy a template constraint but doesn't. Currently, when a template contraint isn't satisfied by accident, it's hard to know why. This PR attempts to make that process easier, with a similar intent as C++ concepts.

Also, I wanted to add a static assert if models is true but checkXXX doesn't compile; I didn't because I'd have to move the isFoo and checkFoo functions used in the accompanying unit tests to global scope.

[JackStouffer]

Can you add the Params and Returns sections.

[MetaLang]

Doesn't this entail massive code bloat as you're importing at least one module per check?

[atilaneves]

Only if it was already going to fail to compile, so no.

[atilaneves]

@JackStouffer Will do
@MetaLang Code bloat how? First of all, that import only happens if the template contraint fails, so it won't compile anyway. Secondly, the import only makes the checkXXX function visible from std.traits; whoever is using models has to have imported the module where checkXXX is.

[DmitryOlshansky]

The idea is to have compiler error messages when a type that was intended to satisfy a template constraint but doesn't. Currently, when a template contraint isn't satisfied by accident, it's hard to know why. This PR attempts to make that process easier, with a similar intent as C++ concepts.

Looks cute. Will review later ...

[schuetzm]

It's ugly that in the UDA version you have to repeat the type's name...

[atilaneves]

@schuetzm I agree, but there's nothing I can do about that.

[JackStouffer]

Adding in another ddoc-ed unit test in front of this with range type check examples would be helpful as that's the most common use case.

[atilaneves]

I'd have to change isInputRange first and I wanted to make the changes orthogonal.

[atilaneves]

@JackStouffer That's not possible since isInputRange doesn't have a corresponding checkInputRange. That's done in a different PR.

[burner]

import std.algorithm.searching : countUntil;

[JackStouffer]

This sounds like something that would be good for a dub release. If it's popular and works then it can be reconsidered for Phobos.

[wilzbach]

Looks cute. Will review later ... [more than 1 year ago]
It's ugly that in the UDA version you have to repeat the type's name...
This sounds like something that would be good for a dub release. If it's popular and works then it can be reconsidered for Phobos.

While I like the idea too, I am inclined to close this as there still seems to be no consensus after one year & going the DUB or DIP road make more sense than getting stalled here?

@ others: What do you think?