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Add empty CSharp15 test project (#81512)
Fix stdlib inconsistency between core and fx compiler (#79911)
Switch code that was using Assert.True/False as a replacement for .Fail
Validate pooled objects in compiler tests (#82784)
Sort usings
Organize VB imports
More cases
Avoid storing information about unrelated assemblies in AssembliesToWhichInternalAccessHasBeenDetermined (#81959)