TODOs

[getify]

Keeping notes of TODOs for TypVal. This list will be updated as progress occurs.

• Embedded External Annotations: allow annotating types/signatures for external

  "#extern foo" < int;
  var x = foo;   // x implied as 'int'
  
  "#extern SomeUtil" < func`(string, number) => bool`;
  var y = SomeUtil("hello","world");   // error on "world" not being 'number', y implied as 'bool'
  

  Also, we need to define a (huge) set of these external annotations (to be imported via JSON, perhaps?) for all the built-ins and natives, such as encodeURI(..), console.log(..), JSON.stringify(..), etc.

• Cross-typing: option to collect global types/signatures from non-modules, and exported types/signatures from modules, and "export" them possibly as JSON, and then "import" them for a file as "external annotations". Allows checking multiple files together in a group.

• Generic types for function params/signatures, by allowing signature overloading

  function foo(x = generic) {
     return x;
  }
  
  var a = foo(3);   // `a` is type 'number'
  var b = foo("abc");   // no error, since signature is overloaded, `b` is type 'string'
  

• Enforce TDZ for var, as well as (separately) TDZ for let / const, as well as (separately) TDZ for function declarations

• Function typed-shorthand:

  func`(int,string) => bool`;
  // returns a function like:
  // (x,y) => { x = int`${x}`; y = string`${y}`; return bool`false`; }
  

  function bar(cb = func`int => string`) {
     var x = int`0`;
     x = cb("hello");
     // reports error with "hello" not matching `int` param
     // reports error with `x` being an `int` but trying to assign a `string` to it
  }
  
  var b = func`int => string`;
  

• Custom types (via scope-hoisted pragmas)

  “#define FancyArray”;
  var x = FancyArray`1,2,3`;
  

  Sub types:

  “#define Automobile” < “#define Car”;
  “#define Automobile” < “#define Truck”;
  var y = Automobile``;
  y = Car``;
  y = Truck``;