Fix 12371: C++20: Requires clause on a constructor

[pfultz2]

No description provided.

[chrchr-github]

We have other issues with requires too. Should we simplify (i.e. remove) those clauses somehow?

[pfultz2]

Should we simplify (i.e. remove) those clauses somehow?

How would we simplify them? If we remove them then we cant apply checkers to the clause.

[chrchr-github]

Not applying checkers (which don't exist yet) seems better than throwing various syntax errors. What errors could we detect in a requires clause anyway?

[pfultz2]

Not applying checkers (which don't exist yet)

There are checkers that already exist but may need some tweaking to detect the issue.

What errors could we detect in a requires clause anyway?

If you wrote something like requires std::integral<T> || std::integral<T> we could detect the same expression on both sides.

[chrchr-github]

If you wrote something like requires std::integral<T> || std::integral<T> we could detect the same expression on both sides.

Fair enough. I wonder though how many places need to be tweaked so that requires is handled correctly.