fix issue 12490 - No "Error: , has no effect" Error for comma expression LHS

[ghost]

Following a comment in sideeffect.d on how to check the LHS.

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	12490	normal	No "Error: , has no effect" Error for comma expression LHS

Testing this PR locally

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

dub run digger -- build "master + dmd#11377"

[ghost]

ping