The LLVM rebranch added an “AllowUnknownKeys” setting to llvm::yaml::Input, which lets us rip out a lot of marginal code and encourages a broader rework of access note error diagnosis:
• Access note warnings and errors are now diagnosed as they’re found during YAML parsing
• They now have proper SourceLocs inside the .accessnotes file
• They’re now tested using -verify-additional-file instead of FileCheck
• A lot of gross duct tape is now gone
