allow type declarations inside objects

[zpdDG4gta8XKpMCd]

interface W<X, Y, Z> { x: X; y: Y; z: Z; }

function toModule<X, Y, Z>()  {
     type $W = W<X, Y, Z>;
     return {
        W: $W // <-- wish could do that
     };
}

const m = toModule<string, number, boolean>();
const w : m.W = { // <-- wish could do that
   x: '',
   y: 0,
   z: false
};

[mhegazy]

so namespace expressions, a la class expressions?

[zpdDG4gta8XKpMCd]

please allow either of the following:

• either namespaces that can be parametrized with types and values Suggestion: Allow type and value parameters for modules #2625
• or, which is mostly equivalent, allow types in the position of object properties like in the example above

[mhegazy]

here is a sample:

function toModule<X, Y, Z>()  {
     return namespace {
        export interface W { x: X; y: Y; z: Z; }
    }
}

const m = toModule<string, number, boolean>();
const w : m.W = { // <-- wish could do that
   x: '',
   y: 0,
   z: false
};

[mhegazy]

both approach has issues with the current implementations that assumes an expression can only be a value, and not a namespace. we will need a proposal for this one.

[zpdDG4gta8XKpMCd]

Workaround

This is the workaround that I have to use now:

interface W<X, Y, Z> { x: X; y: Y; z: Z; }

function toModule<X, Y, Z>()  {
     const $W : W<X, Y, Z>;
     return {
        W: $W
     };
}

const m = toModule<string, number, boolean>();
const w : typeof m.W = {
   x: '',
   y: 0,
   z: false
};

[aluanhaddad]

👍

[zpdDG4gta8XKpMCd]

@mhegazy

here is a sample:

that would be super great

[zpdDG4gta8XKpMCd]

I am afraid that alone returning a namespace isn't enough. It needs to be also passed as an argument and taken as a parameter. In order to declare it it has to have a type. Do namespaces have a type per se? Doubt so. Anyway, I believe that the difference between namespaces and objects is a made up. It would be great to see namepaces unified with objects because to JavaScript they are the same.

[zpdDG4gta8XKpMCd]

closing in favor of #8358