具有TypeScript的ExtJS，未捕获错误

Question

I'm trying out TypeScript with Sencha ExtJS:

/// <reference path="../ExtJS.d.ts" />

Ext.define("CompanyGridPanel", <Ext.grid.IPanel>{
    extend: "Ext.grid.Panel",

    config: {
        companyStore: null
    },

    initComponent: function () {
        this.myFunction(10, 52);

        return this.callParent(arguments);
    },

    myFunction : (a:number, b:Ext.IPanel, ...args) => {

    }
});

Function MyFunction accepts object of type Ext.IPanel as second parameter but is called with number instead. TS compiler does not catch this error, but WebStorm IDE does catch it correctly.

Why TS don't catch it and how can it be fixed?

Using ExtJS 4.2 and TS 0.9.5.0.

Answer 1

The TypeScript compiler will attempt to infer the type of the object in question (b:Ext.IPanel) based on the function call.

Consider the following code: TypeScript will infer that the variable foo is a string, as the return value of the getValue() function is a string, therefore the var foo becomes a string.

In your sample above, this.myFunction(10,52) succeeds, because the compiler is able to match Ext.IPanel to a number, thereby inferring b as a number.

class Test {
   constructor() {
      var foo = getValue();
   }
   getValue() {
      return "bar";
   }
}