Suggestion: shorthand syntax for annotating function with type

I like to define types for my functions by separating the type out from the value:

type id = <A>(a: A) => A;
const id: id = a => a;

This helps particularly for longer functions where the parameter list often spans many columns and multiple lines.

However, compared to Elm/Haskell, this code is quite boilerplate-y. I wonder if there is some shorthand syntax we could add to make this pattern more concise. For example, the same code in Elm/Haskell:

id : a -> a
id a = a

The boilerplate in the current TypeScript syntax is:

• Manual annotation of value (id) with type of same name (id). Could this be automatic, e.g. matched by name?
• TypeScript requires parameter names for the function type, but are these always required? Could the function type simply by A => A, omitting the parameter names? Or would this cause problems?

Commencez par comparer la notation abrégée TypeScript proposée avec les exemples Elm et Haskell de l’issue. Définissez la syntaxe acceptée et son comportement lors de la vérification des types avant d’identifier les emplacements de l’implémentation et des tests ; l’issue ne spécifie ni fichiers, ni points d’entrée, ni critère concret d’achèvement.