[refactor] Simplify parameter mismatch error code

[ntrel]

• Use one OutBuffer instead of 3, reducing memory allocations.
• Avoid repeating common string messages.
• Add a missing test for typesafe variadics.

[dlang-bot]

Thanks for your pull request and interest in making D better, @ntrel! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the annotated coverage diff directly on GitHub with CodeCov's browser extension
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + dmd#8263"

[jacob-carlborg]

Seems a bit unnecessary to duplicate the whole format string when the only difference is rvalue. Perhaps rvalue can be passed as a parameter to printf as well?

[wilzbach]

Yep, last time I tried something in this direction, it was complained that this increases the binary size.
It's just "cannot pass%s" and then rv ? " rvalue" : "", no?

[ntrel]

Fix is here: ntrel@6219e5e

[wilzbach]

Cool. Would you mind submitting it as PR too? Thanks!