Failed assertion when going to definition on constructor when namespace precedes class

[DanielRosenwasser]

namespace Foo {
    export var x;
}

class Foo {
    /*definition*/constructor() {
    }
}

var x = new /*usage*/Foo();

1. Go to definition at the usage marker

Expected: Cursor lands on position of definition marker.
Actual:

getDefinitionAtPosition('C:\Users\drosen\AppData\Local\Temp\~vsFC8F.ts', 99)

StackTrace:

Error: Debug Failure. False expression: 
   at assert (:1558:17)
   at tryAddConstructSignature (:45157:25)
   at getDefinitionFromSymbol (:45143:13)
   at getDefinitionAtPosition (:45254:13)
   at Anonymous function (:48860:17)
   at simpleForwardCall (:48657:9)
   at forwardJSONCall (:48673:13)
   at forwardJSONCall (:48719:13)
   at getDefinitionAtPosition (:48859:13)

Related to #4478.