Design Meeting Notes, 4/23/2024

[DanielRosenwasser]

Notes courtesy of @RyanCavanaugh

• Error on references to literal enum members in conditions #58264
  • Disallow truthy checks on enum values since they're not variable
  • Yep, seems good
• Add transpileDeclaration API method #58261 transpileDeclaration
  • Emits .d.ts instead of .js like transpileModule
  • Implies additional required flags, of course
  • We need a minimal lib file to make everything work out for Symbol. references
  • Quick discussion of symbol freshness under ID
  • This is the requested "reference implementation" of a syntactic declaration emitter
  • Yep, seems good
  • Merge whenever (pre- or post-beta)
  • Jake to review
• New --enforceReadonly compiler option to enforce read-only semantics in type relations #58296 --enforceReadonly
  • Long has it been rumored
  • Changes the subtype relation to disallow mutable properties to alias readonly ones
  • Tweaks the definition of as const to also "fit" the contextual type by relaxing readonly inferences that would have caused a failure
  • Most other work is in making the lib compile again, particularly prototype
  • This is heckin' breaky but tends not to find many real issues since aliased mutation is rare
  • Need to update the DOM generator
  • What's the uptake plan?
    • Hope your dependencies did a good job
    • skipLibCheck might let you get away with it
  • What's the plan for DT?
    • Turn it on in new types
    • Roll out as people are able to
    • Patience!
    • Maybe try automating adding readonly "everywhere" and back it off from tests
      • Are we really doing 8,000 PRs??
  • What about methods overwritten by a readonly property?
    • Currenty allowed, but probably shouldn't be
    • Confusing because methods are only mostly not mutated