elm-optimize-level-2/transformations.md

Overview of Possible Transformations

This is an overview of the transformations that could be interesting for elm-optimize

First, we can start with [Robin's article](explored by Robin in this dev.to post)

Making type representation isomorphic

Implemented as variantShapes.ts

Currently the Elm compiler will generate objects that match the shape of a given type.

So, Maybe looks like this:

var elm$core$Maybe$Just = function(a) {
  return { $: 0, a: a };
};

var elm$core$Maybe$Nothing = { $: 1 };

However, the V8 engine is likely better able to optimize these objects if they have the same shape.

So, this transformation fills out the rest of the variants with field: null so that they have the same shape.

var elm$core$Maybe$Just = function(a) {
  return { $: 0, a: a };
};

var elm$core$Maybe$Nothing = { $: 1, a: null };

This does require information from the Elm code itself, which we're currently getting through elm-tree-sitter.

Inlining literal list constructors

initial

_List_fromArray(['a', 'b', 'c']);

with InlineMode.UsingConsFunc

_List_cons('a', _List_cons('b', _List_cons('c', _List_Nil)));

with InlineMode.UsingLiteralObjects(Mode.Prod)

({ $: 1, a: 'a', b: { $: 1, a: 'b', b: { \$: 1, a: 'c', b: _List_Nil } } });

with InlineMode.UsingLiteralObjects(Mode.Dev)

({
  $: '::',
  a: 'a',
  b: { $: '::', a: 'b', b: { \$: '::', a: 'c', b: _List_Nil } },
});

Applying Functions Directly

Separating Type and Payload Data

we usually have this shape for a variant

{ "$": "typename", "a": a, "b": b }

I wonder if this shape would improve representations

{ "$": "typename", "vals": { "a": a, "b": b } }

This would mean that the standardized object form would be passed around {$,vals}, and also that the object in vals has the same shape based on the value of $.