Investigate prior art for adding types after GA

[markcowl]

Because new types may clash with names in user specs or external libraries, examine how other languages handle adding types after 1.0

[markcowl]

Overview of C-Sharp and .Net Versioning

.Net and C-Sharp allow breaking changes across their release types, but minimize them. While new language features have been introduced in minor releases, more recent versions tend to treat these features as preview until the next major release., using preview versions or using one of the mechanisms below, through which new features can be marked as volatile or preview in non-preview releases.

Identifying Stable and Volatile APIs

• Preview Features
• Experimental Features

Preview Features

Preview Features require a configuration opt-in to all preview features. These are reserved for features that include or require new compiler or runtime features

Experimental Features

Experimental features throw a specific diagnostic when used, each used feature requires a separate suppression - these are normally confined to new types only.

Handling Breaking Changes

• Both C-Sharp and .Net allow breaking changes in PATCH and Minor releases, and have done so for several reasons
  • Fixes for unintended behavior (bug fixes)
  • Breaks for new reserved words
  • Breaks for new fundamental language features
  • Narrowing allowed syntax for existing features
  • Breaks to enable new (or future) features