Suggestion Backlog Slog, 2/5/2018

[RyanCavanaugh]

• TypeScript 2.0 change in IterableResult<T> makes implementing iterators harder #11375 Improve definition of IteratorResult to make implementing iterators more ergonomic
• Consider allowing access to UMD globals from modules #10178 Allow access to UMD globals from modules
• Conversion to number using unary plus doesn't work properly with null #21574 What are allowed operands of unary + ?
• Generic { new(...args: any[]): T } parameter doesn't work for abstract classes #5843 Are abstract classes constructable?
• Type narrowing should be abandoned after an operation with potential side effects  #13904 Remove narrowings of sibling properties after method calls
• Generics extending unions cannot be narrowed #13995 Narrowability / comparability of (primitive) union-constrained generics?
  • Dupe?
• Arrow functions of a class show up on prototype #20922 Own properties appear in class prototype definition
• Suggestion: narrower parameters for NumberConstructor #20754 Tighten argument type to Number constructor
• In a union, types with index signatures should contribute types to all properties #21141 Index signatures should cause sibling union constituents' properties to appear on the surrounding type
• Strict function check failure due to union type with matching parameters in the unioned interfaces #20714 (defies summarization?)
• strictPropertyInitialization with subclasses that refine the types of properties #20911 Redeclaration of a property in a derived class should not required additional initialization
• generic type inference for boolean literals fails #19896 Do... something different with boolean inference?
• Outline unknown decision points

[zpdDG4gta8XKpMCd]

can we please return top types where they belong?: #21644

[RyanCavanaugh]

• TypeScript 2.0 change in IterableResult<T> makes implementing iterators harder #11375 Improve definition of IteratorResult to make implementing iterators more ergonomic
  • Was originally done to fix for/of
    • We could special-case it, maybe?
  • Do the break and turn it into a union type
  • And fix for/or inference
  • Do it now before more people write iterators
  • Try it and make sure nothing explodes 👍
• Consider allowing access to UMD globals from modules #10178 Allow access to UMD globals from modules
  • Could work around it with a lint rule
  • Catching a React error is too valuable to miss
  • Still no workarounds
  • Consider a /// directive to enable globals on a per-file basis
• Conversion to number using unary plus doesn't work properly with null #21574 What are allowed operands of unary + ?
  • Notes
    • +null is 0
    • +undefined is NaN
    • +"" is 0
  • Fine as-is
• Suggestion: narrower parameters for NumberConstructor #20754 Tighten argument type to Number constructor
  • Currently takes any
  • Uninvoked functions are generally problematic
  • The error message the dev got was correct!
  • Passing to Number is idiomatic "convert this"
  • Lots of functions broadly accept "Anything except a function" (e.g. JSON.stringify)
  • Kinda sad that object domain includes function
  • No clear fix for this that doesn't break other stuff
  • Is there room for a type that means "non-callable objects" ?
  • Fine as-is
• Generic { new(...args: any[]): T } parameter doesn't work for abstract classes #5843 Are abstract classes constructable?
  • There is no type that represents "an allowed RHS of instanceof" for some LHS
  • Not a huge loss of expressitivity by saying Function as the second arg of isType
  • Won't Fix
• Type narrowing should be abandoned after an operation with potential side effects  #13904 Remove narrowings of sibling properties after method calls
  • Would be a huge breaking change
  • More sound
  • "I'm flabbergasted that you would even propose this"
  • Completely unworkable without massive new type system mechanics
• Generics extending unions cannot be narrowed #13995 Narrowability / comparability of (primitive) union-constrained generics?
  • Dupe?
  • Can't be done without subtraction types
  • Are unittype-union-constrained generics special?
  • Could constrain to A & (A | B) inside the if ?
  • Can't currently narrow a constrained generic
  • AMF on account of complexity/perf concerns
• Arrow functions of a class show up on prototype #20922 Own properties appear in class prototype definition
  • 👎 breaking change with no clear upside
• In a union, types with index signatures should contribute types to all properties #21141 Index signatures should cause sibling union constituents' properties to appear on the surrounding type
  • 👍 see if it breaks anything

Out of time

• strictPropertyInitialization with subclasses that refine the types of properties #20911 Redeclaration of a property in a derived class should not require additional initialization
  • Discussed but did not agree on anything in particular
• Strict function check failure due to union type with matching parameters in the unioned interfaces #20714 (defies summarization?)
• generic type inference for boolean literals fails #19896 Do... something different?
• Outline unknown decision points
  • Ryan to take offline