Track last index in parameter marshalling

[jtschuster]

Tracks the last index marshalled in the interop generators to ensure we don't cleanup any unmarshalled elements.

To determine if the lastElementMarshalled variable is used, we need to generate the cleanup stage, which can be expensive. We also could generate _ = __param_lastIndexMarshalled if there is no cleanup so that there is no warning for an unused variable, but we don't need to generate the cleanup stage twice.

We'll need more testing around the ComInterfaceGenerator, but I would like to get this into preview 6 for LibraryImportGenerator.

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Issue Details

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Tracks the last index marshalled in the interop generators to ensure we don't cleanup any unmarshalled elements.

To determine if the lastElementMarshalled variable is used, we need to generate the cleanup stage, which can be expensive. We also could generate _ = __param_lastIndexMarshalled if there is no cleanup so that there is no warning for an unused variable, but we don't need to generate the cleanup stage twice.

We'll need more testing around the ComInterfaceGenerator, but I would like to get this into preview 6 for LibraryImportGenerator.

Author:	jtschuster
Assignees:	-
Labels:	area-System.Runtime.InteropServices
Milestone:	-

[jkoritzinsky]

As long as we don't generate invalid code for GeneratedComInterface, I'm supportive of getting this in for P6

[jkoritzinsky]

It looks like the unit tests all timed out in CI, but only for the LibraryImportGenerator unit tests. Very odd.

[jtschuster]

Looks like this probably does hurt perf significantly enough to cause some timeouts. I made #88060 as an alternative.

[jtschuster]

#88060 was accepted instead of this one