Version Used: 4.12.0-3.24558.5 (21192bf)

Steps to Reproduce:

1. Clone https://github.com/CommunityToolkit/dotnet
2. Checkout dev/more-analyzers (or Add more analyzers, enable unit tests for partial properties CommunityToolkit/dotnet#1010)
3. Remove the [Ignore] from InvalidPartialPropertyLevelObservablePropertyAttributeAnalyzer_OnImplementedProperty_GeneratedByAnotherGenerator_Warns
4. Put a breakpoint in the RegisterSymbolAction callback in InvalidPartialPropertyLevelObservablePropertyAttributeAnalyzer
5. Run the test
6. Verify that the callback is never executed
7. Comment out the [GeneratedCode] attribute on the partial property implementation in that test
8. Run the test again
9. Verify the callback is now hit (??!)

Expected Behavior:

The RegisterSymbolAction callback should work as expected in both cases.

Actual Behavior:

The RegisterSymbolAction callback is apparently not called at all if you leave the attribute on the implementation part.