Prototype assignment should take the type of the initializer and not require a literal

This is a feature request based on actual VS customer code.

TypeScript Version: 3.9.2

Search Terms: ES5 class javascript prototype assignment constructor function

Expected behavior: In the example below, the prototype for test.class should include properties from testPrototype.

Actual behavior: Per @sandersn this pattern is recognized in the binder and only uses syntactic information, therefore does not use the type information from testPrototype .

Related Issues: #39167 from same user code. Also #33454 maybe?

Code

var test = {};
test.testPrototype = {
    add: function (i) {
    }
}

test.class = function (name) {

    function getName() {
        return name;
    }

    this.name = getName();
}

test.class.prototype = test.testPrototype; 

var t = new test.class("test");
t.name
t.add // EXPECTED: Binds to `add` from the prototype, ACTUAL: doesn't


//
// Same pattern works when a literal is assigned to the prototype:
//

var test2 = {};

test2.class = function (name) {

    function getName() {
        return name;
    }

    this.name = getName();
}

// replaced `test.testPrototype` with a literal 
test2.class.prototype = {
    add: function (i) {
    }
}; 

var t2 = new test2.class("test");
t2.name
t2.add // ACTUAL: `add` bound correctly

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "checkJs": true,
    "allowJs": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

Commencez par la reproduction fournie dans TypeScript Playground et le comportement du binder décrit dans l’issue, en comparant l’affectation du prototype du littéral d’objet avec l’affectation depuis test.testPrototype. Le travail est terminé lorsque le type de l’initialiseur fournit les propriétés du prototype afin que t.add soit reconnu dans l’exemple, tandis que le cas de littéral existant continue de fonctionner.