facebook/esprima — pull request #62 by gabelevi (2014-10-24 00:07:44+00:00)
Title: Parse object type indexer properties

This is a syntax for declaring the types of keys and values when you index into unknown properties on objects and interfaces.

var string_to_int_map: { [index: string]: number } = {};

[This syntax comes from typescript](http://www.typescriptlang.org/Handbook#interfaces-array-types)