Suggestion Backlog Slog, 3/13/2017

[RyanCavanaugh]

• Proposal: JSX.ElementType #13890 JSX.ElementType to define the type of <Tag /> expressions
• Warning when writing a generator function without any yield #13847 Enforce generator functions to contain at least one yield
• Control flow doesn't recognise undefined check #12600 Discriminated unions of non-unit-type-discriminated unions
• Operator '+' cannot be applied to types 'T' and 'T'. #12410 Allow operator + on string|number-constrained T ?
• [Proposal] External Module Type #13231 [Proposal] External Module Type
• Generic decorators - could they receive some default type arguments? #2607 Generic decorators - could they receive some default type arguments?
• Distinguish declaration file and js file when the option “Keep comments in TypeScript compiler output" is turned on #11774 Distinguish declaration file and js file when the option “Keep comments in TypeScript compiler output" is turned on
• Suggestion: Add abstract static methods in classes and static methods in interfaces #14600 abstract static in classes
• Mapped types over keyof T should be subtypes of types with string index signatures #14548 keyof t should be a subtype of string
• Proposal: quoted and unquoted property names distinct #14267 Quoted vs unquoted property names
• Compiler generates code that uses an undefined variable when decorating properties that have nullable types #13955 Narrowing of type parameters extending unions
• Type narrowing should be abandoned after an operation with potential side effects  #13904 Resetting narrowing after operations with side effects
• Suggestion: option to include undefined in index signatures #13778 Flag to include undefined in index signatures
• Proposal: Add an "exclusive or" (^) operator #14094 ^ operator to create disjoint types

[RyanCavanaugh]

• Proposal: JSX.ElementType #13890 JSX.ElementType to define the type of <Tag /> expressions
  • e.g. type JSXElement<T> = T;
  • What does this framework look like?
  • Ryan to investigate
• Warning when writing a generator function without any yield #13847 Enforce generator functions to contain at least one yield
  • What does this code actually do?
    • ...
  • It is valid
  • Not true that all generators must yield
    • This is, sort of, how you would write an empty iterator
  • Suspicious to have a return but no yield return
  • Who is writing this and why?
  • 👍 cannot have return without yield return
    • put a yield return in an unreachable position if you really intended to do this
• Control flow doesn't recognise undefined check #12600 Discriminated unions of non-unit-type-discriminated unions
  • It'd be great
  • Let's do it
  • Adds complexity, especially in switch statements with complex labels
  • Assigning to Anders, tentative 2.4?
• Operator '+' cannot be applied to types 'T' and 'T'. #12410 Allow operator + on string|number-constrained T ?
  • For T extends string, T + T should be string
  • For T extends number, T + T should be number
    • And for other arithmetic ops here as well
  • For T extends string | number, T + T is still an error
  • 👍
• Distinguish declaration file and js file when the option “Keep comments in TypeScript compiler output" is turned on #11774 Distinguish declaration file and js file when the option “Keep comments in TypeScript compiler output" is turned on
  • --preserveDeclarationComments ?
  • Could compile twice, or remove comments from a JS file with any number of tools
  • If you care about size, you're already minifying
  • 👎 Flag Soup
• Suggestion: Add abstract static methods in classes and static methods in interfaces #14600 abstract static in classes
  • Sidebar discussion on substitutability of static side of classes
  • Are abstract methods callable?
    • ... only indirectly?
    • wat
    • So it's useless?
  • AMF
• Mapped types over keyof T should be subtypes of types with string index signatures #14548 keyof t should be a subtype of string
  • Real issue: A mapped type over a string-keyed thing should be assignable to the base type
  • 👍
• Suggestion: option to include undefined in index signatures #13778 Flag to include undefined in index signatures
  • Would be enormously painful... why?
  • Would need special logic for for/of
  • What code to people intend to write?
  • Another flag? --allArraysAreDangerous
  • Allow overwriting / overriding of index signatures?
  • This just doesn't seem palatable
  • What happened when they hacked the lib.d.ts?
  • AMF

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Out of time

• Generic decorators - could they receive some default type arguments? #2607 Generic decorators - could they receive some default type arguments?
• [Proposal] External Module Type #13231 [Proposal] External Module Type
• Type narrowing should be abandoned after an operation with potential side effects  #13904 Resetting narrowing after operations with side effects
• Compiler generates code that uses an undefined variable when decorating properties that have nullable types #13955 Narrowing of type parameters extending unions
• Proposal: Add an "exclusive or" (^) operator #14094 ^ operator to create disjoint types
• Proposal: quoted and unquoted property names distinct #14267 Quoted vs unquoted property names