Suggestion Backlog Slog, 2/25/2019

[RyanCavanaugh]

• Show unused public properties and methods #29293 Identify unused public methods
  • "unused" ?
    • Public members of nonpublic types?
    • Is this exported?
    • Is there a "library" / "application" distinction?
  • Too hard to define what the entry point surface of a compilation unit is
  • AMF
• Use generic defaults for "empty" constructors of Array, Map, Set #29786
  • An error is the desired behavior
  • Depends on what's in lib.d.ts
  • Why does this work on Ryan's machine??
• Skip typechecking; only emit (support --transpileOnly in tsc, re-open of #4176) #29651
  • Long discussion of syntax vs "grammar" vs semantics errors
  • Ryan wants syntax errors to block (his) emit
  • Is this just piping errors to /dev/null ?
    • No
    • This user clearly would want syntactic errors to appear
  • Long backstory of which phase reports which errors and why
  • We could move "grammatical" errors from check to bind
    • Would pay a responsiveness penalty
  • Wait, what does transpileModule do with grammatical errors?
  • Why is this user's project so slow?
  • Is this a global project or a module project?
• Mapped Types should distribute over union types #28339
  • Pick is not homomorphic, so this doesn't distribute
    • It is "sub" homomorphic though
      • Should this suffice?
      • If so, how?
        • Unclear how to relate keyof results after they're already resolved on a non-generic
  • Unclear how to fix
  • Pick / Omit / etc with their identity-providing inputs (keyof ,never) are not true identities

declare function fn(x: MappedFooOrBar): void;
// Desired: Not OK
fn({ x: true, foo: undefined });
// Desired: OK
fn({ x: false });

• Potential: `Pick<T, K extends keyof T> = T extends unknown ? { ...}
• See what breaks in RWC