Unused Function Parameters

The Problem

doSomething((unused1, unused2, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

doSomething((_, __, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

Solutions

Elisions

doSomething(( , , somethingUseful) => {
  doSomethingWith(somethingUseful);
});

• Matches with existing destructuring
  • ([, c]) is already valid
• Some might say it looks weird

Placeholder Syntax

doSomething((?, ?, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

doSomething((*, *, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

// etc.

• Most explicit, clearly "using up" a parameter without binding it
• Requires more syntax

Placeholder Identifier

doSomething((_, _, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

doSomething((_, _, somethingUseful) => {
  print(_); // IdentifierReference : `_` early error?
  doSomethingWith(somethingUseful);
});

• Arguably most natural, other languages use this (C#, Rust, etc.)
• Any valid identifiers are already valid identifiers, could conflict with existing code