types.scala refactoring notes

types-refactoring.md

Typers.scala refactoring

Motivation

• Coral mutable state in prepration for thread-safe subtyping / glb / type printing.
• Side benefit: Impose structure on gargantuan source file.
  • Comments in the file that delimit sections are a code smell to me.

What's in there?

• Type ADT
• Subtyping / Equivalence
• LUB/GLB
• Base Class calculation
• TypeTraverser / TypeCollector / TypeMap
  • Many instances of these for specific purposes.
  • common owner
  • adaptToNewRun
• Type constraint solving
• Miscellania

Proposed structure

• Types
  • Type ADT
• TypeComparers
  • Subtyping / Equivalence
• LubGlbs
• TypeMaps
  • Base classes for type-map/collect/traverse
  • Implemenatations (perhaps split non-trivial ones like common owner to separate files?)
• TypeToStrings

New subpackage: scala.reflect.internal.types?

Refactoring methodology.

Impose Structure

• Keep things compiling after each edit.
  • Temporarily loosen access of referenced privates to public
• Keep methods in the same order as Types.
• Restore private once things are grouped accordingly.
  • or private[types] if need be.
• No other changes in the first refactoring step.

Coral State

• Analyse the usage of each item of mutable state.
  • Record unique stack trace to the state with Origins.
• Remove all mutable state the top level. Either.
  • move groups of methods that use them into a nested class which has a copy of that state as fields.
  • Pass the state through the call chain
    • as an extra mutable parameter
    • or an extra immutable parameter + an extra immutable return value.

Typers.scala or Types.scala?