Fix Issue 19731: throw away semantic3 run after return type inference to avoid missing invariants

[FeepingCreature]

This avoids a case where forcing semantic3 via querying the return type of a struct member function led it to ignore invariants, because they were not yet determined at that point, and later on semantic3 had already run.

I don't like this solution, but I don't know enough DMD to come up with something better. At least it should be a cornercase - auto functions aren't that common, hopefully.

edit: The point of this PR is mostly to run the CI pipeline to flush out possible (likely) breakage, and to softly poll for a better approach.

edit: OH GOD IT BROKE EVERYTHING

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19731	normal	auto struct methods whose address is taken don't test invariants

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#9448"

[FeepingCreature]

Gonna close it for now. This doesn't work.