Suggestion Backlog Slog, 8/6/2018

[RyanCavanaugh]

• Proposal: Variadic Kinds -- Give specific types to variadic functions #5453 Variadic kinds - what use cases remain here?
• Disallow expressions of type void to be used in truthiness checks #26234 Disallow truthy checks of void
• out of range index in a tuple magically works #5203 Disallow OOB access on tuples
• Polymorphic "this" for static members #5863 Static polymorphic this
• T[K] should be never when T is never #23005 T[K] should be never when K is never
• Using string enum as key in {[key]: Type} throws not an index signature #22892 string enum object should be indexable type
• esModuleInterop should work even when compiling to esnext modules #22851 esModuleInterop should work when target = esnext
• Abstract classes that implement interfaces shouldn't require method signatures #22815 Abstract classes that implement interfaces shouldn't require method signatures
• Casting to Partial<x> seems to be errorful #22806 Partial<T> should be a weak type
• parameter initializer is bound to the wrong variable #22769 Allow unshadowed parameter initializer references in ES6+
• Typing number of children in TSX #22759 Let JSX children be subject to tupleness
• Bitwise enum initializer: compile-time constant but not allowed as a type reference? #22709 Allow references to literal-ish-initialized enums in type positions
• Proposal: Overload Function.bind for when no argArray is provided. #22669 Add a new overload to Function#bind
• Proposal: Easier Migration with Loose Mode in TypeScript Files #22665 Add a mode to make TS act like JS
• tsconfig cannot be specified along with an explicit list of files to compile - TS5042 #22649 Combine tsconfig with file list
• Inferred type symbol in conditional type should be visible-but-banned in falsy arm #22610 Keep infer variable in scope in false arm of conditional type
• Proposal: better type narrowing in overloaded functions through overload set pruning #22609 Do some type guards based on overload when a good discriminant is present
• Provide a back-compat mechanism for bundled .d.ts files in package.json #22605 Provide a back-compat mechanism for bundled .d.ts files in package.json
• typeof union.membername errors. #22598 Allow speculative union type property access in typeof (expression) operands
• Mapped types enumerating keys in string behave poorly #22509 Something something mapped types
• Any number can be assigned to enum member type #22311 Error on out-of-scope literal assigned to enum
• Allow bitwise test on undefined #22230 Allow implicit undefined->0 coercion under strictNullChecks for bitwise ops
• foo.ts is resolved before foo.d.ts even if the latter is in files[] #22208 Prefer .d.ts over .ts if it's in files array
• "...args: infer" on an overloaded function chooses only one function head #26136 Arg union type inference for overloads
• Add a strict flag forbidding impossible generic declarations #26129 Forbid illogical generic declarations

[RyanCavanaugh]

• Proposal: Variadic Kinds -- Give specific types to variadic functions #5453 Variadic kinds
  • Currently we allow you to capture tuples in variadic rest positions
  • But the tuples themselves cannot contain rests
  • This would allow deconstruction of tuples
  • What functions would be typable with this that currently aren't?
    • Promisify
  • Should we close holes that allow people to write trivial turing machines in the type system?
    • ??
• Disallow expressions of type void to be used in truthiness checks #26234 Disallow testing void exprs
  • Breaking change
  • All goodness
  • Found bugs in us and VS Code
  • Found "type errors" in a couple other projects
• out of range index in a tuple magically works #5203 OOB on tuples should be errors
  • 👍
• Polymorphic "this" for static members #5863 Polymorphic this
  • Static inheritance in signatures is plainly unsound
  • So calls to the polymorphic this are right out
  • Isn't what people want just the non-signature side?
  • Do people want instance-this or static-this ?
  • Representation vs checking
  • Discuss soundness
• T[K] should be never when T is never #23005 T[K] should be never
  • 👍
• Using string enum as key in {[key]: Type} throws not an index signature #22892 String enums should be indexed types
  • Our dot behavior makes this a bad idea
• Abstract classes that implement interfaces shouldn't require method signatures #22815 Interface members in abstract classes
  • Should we copy them automatically?
    • It's presumably what you want
  • What happens to optional members?
    • They become... abstract optional? What is that even?
      • How do you not-implement an optional abstract member?
    • Need to avoid hop-skip-jump problem
  • Post some questions on this
• Casting to Partial<x> seems to be errorful #22806 Partial<T> should be weak?
  • It is
  • Weak checking applies to assignability, not comparability
  • WIA
• parameter initializer is bound to the wrong variable #22769 Parameter initializers
  • Allow in ES6, error in downlevel only
• Typing number of children in TSX #22759 Allow tuples in JSX children
  • 👍
• Bitwise enum initializer: compile-time constant but not allowed as a type reference? #22709 Enum literals
  • There are actually many kinds of enums under the hood
  • Union enums only get created when only bare literals (or nothing) are initializers
  • These kinds of enums behave differently
  • You might want one or the other and this is how you choose
  • WIA; would be a BC
• Any number can be assigned to enum member type #22311 Out-of-range enum assignment
  • Back compat problem
  • Not really a trap
  • Problem for e.g. mod flags
  • Maybe disallow in strict
• Allow bitwise test on undefined #22230 undefined/null in & / |
  • 👎
• "...args: infer" on an overloaded function chooses only one function head #26136 Inference of unions from argument lists
  • Would this imply filtering if you weren't capturing the whole argument list?
  • No (spreading back would be a nightmare)

[jcalz]

WIA

Wounded in action?

EDIT: It suddenly occurs to me that this is probably "Works As Intended" as acronymized by Yoda. nmv...

[RyanCavanaugh]

Well, it's accepted
Wondering if actionable
We're imitating ActionScript