getCompletionsAtPosition fails when importing module from definition

[RReverser]

Consider example from http://www.typescriptlang.org/Handbook#modules-pitfalls-of-modules:

myModules.d.ts:

// In a .d.ts file or .ts file that is not an external module:
declare module "SomeModule" {
    export function fn(): string;
}

myOtherModule.ts:

/// <reference path="myModules.d.ts" />
import m = require("SomeModule");

Current TypeScript master doesn't handle autocompletion in myOtherModule.ts since it fails when synchronizing host data, specifically calling

synchronizeHostData ->
createProgram ->
... ->
processImportedModules

which in order finds require("SomeModule") node and tries to call

findModuleSourceFile ->
findSourceFile ->
CompilerHost::getSourceFile

which fails due to assertion that sourceFile is found (which is not for the case of locally declared modules).

[RyanCavanaugh]

Verified w/ test

// @Filename: myModules.d.ts
//// declare module "SomeModule" {
////     export function fn(): string;
//// }

// @Filename: consumer.ts
//// /// <reference path="myModules.d.ts" />
//// import m = require("SomeModule");
//// m./**/

goTo.file(1);
verify.completionListContains('fn');

[RReverser]

Thanks, @RyanCavanaugh!