This issue is referenced in source.
It tracks scenarios that were identified as needing more work for indexers.

• Nullability
• Revisit Length/Count extension properties in various scenarios (list/spread patterns, collection expressions, ...)
• Test dictionary initializer scenario with extension indexer
• Will want to handle Index/Range indexers in list/spread patterns
• We need to test RefSafetyAnalysis.MethodInfo.ReplaceWithExtensionImplementation
• ORPA
• Null-coalescing assignment
• Scenarios where there's an implicit conversion on the receiver
• Confirm that indexers trigger the inferrability check
• Caller expression attribute

Relates to test plan #76130