Suggestion: shorthand syntax for annotating function with type

[OliverJAsh]

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?

[thorn0]

For a discussion about parameter names, see #13152,