This issue exists to track work that has to be done for Chisel 8.

Can Be Done Before Release

• Deprecate chisel3.experimental.ExtModule, change to chisel3.ExtModule. ([core] Deprecate ExtModule, Params in experimental #5101)
• Deprecate chisel3.experimental.*Param, change to chisel3.*Param. ([core] Deprecate ExtModule, Params in experimental #5101)
• Deprecate HasExtModule*. ([core] Deprecate ExtModule utility traits #5102)
• Deprecate BlackBox. ([core] Deprecate BlackBox in favor of ExtModule #5103)
• Change deprecation on TargetDirAnnotation and alias in chisel3
• Change deprecation on Annotation and alias in chisel3
• Change deprecation on MustDeduplicateAnnotation and move into chisel3.
• Remove internal (main) uses of os-lib (test and build uses are fine).
• Deprecate --use-legacy-width
• Deprecate Double support in properties

Right Before Release

• Move chisel3.experimental.ExtModule to chisel3.ExtModule.
• Move chisel3.experimental.*Param to chisel3.*Param.
• Remove HasExtModule*.
• Remove BlackBox.
• Remove IntrinsicModule.
• Delete firrtl IR
• Replace all deprecated case classes with classes
• Fix naming of some verification functions, e.g. cover._applyWithSourceLine
• Change Data equality to be structural for types and referential for values, get rid of BoxedData in Instantiate
• Delete deprecated ChiselStage methods
• Delete deprecated Lookupable and @instantiable related APIs
• Move TargetDirAnnotation into chisel3
• Move Annotation into chisel3
• Move MustDeduplicateAnnotation into chisel3.
• Delete os-lib as a [main] dependency (nothing against it, but it constrains users to use the same major version as us and doesn't add that much value in our own use).
• Stop publishing for Scala <= 2.13.8 (Can't publish for them with Java 17 - Stop publishing for Scala 2.13.0 to 2.13.8 #5202)
• Bump Mill
• Delete deprecated stuff related to Lookupable and IsInstantiable (just Modules are now instantiable?)
• Switch Chisel's logging to stderr - Log warnings and errors to stderr instead of stdout #5213
• Delete Double support for properties
• Delete Convert stage
• Delete CIRCTConverter