Report error if code precedes /// reference

a.ts:

'use strict'
/// <reference path='b.d.ts'/>

var x: Foo;

b.d.ts:

interface Foo { x: string; }
declare module "b" {
        export = Foo;
}

D:\test\refs\a> tsc a.ts
a.ts(4,8): error TS2304: Cannot find name 'Foo'.

There's no mention in section 11.1.1 of the spec that /// references must be the first thing in a file in order to work, although I do remember us deciding that was the case at one point. If that is the rule we should update the spec appropriately. We should also add an error to the compiler or else you may spend awhile trying to figure this out since we don't provide much (read: anything) in the way of diagnostics for debugging reference resolution.

Reproduce el caso con a.ts, b.d.ts y tsc a.ts, después lee la sección 11.1.1 de la especificación y los diagnósticos de resolución de referencias del compilador. Determina si la regla documentada exige que las referencias aparezcan primero y define done como actualizar la especificación y/o informar de un error claro del compilador para el error de orden.