function addParameter(id) {
    if (!/^\w+(-+\w+)*$/.test(id)) throw new Error("Invalid parameter name '" + id + "' in pattern '" + pattern + "'");
    if (names[id]) throw new Error("Duplicate parameter name '" + id + "' in pattern '" + pattern + "'");
    names[id] = true;
    params.push(id);
  }
@ngdoc object
@name ui.router.util.type:UrlMatcher

@description
Matches URLs against patterns and extracts named parameters from the path or the search
part of the URL. A URL pattern consists of a path pattern, optionally followed by '?' and a list
of search parameters. Multiple search parameter names are separated by '&'. Search parameters
do not influence whether or not a URL is matched, but their values are passed through into
the matched parameters returned by {@link ui.router.util.type:UrlMatcher#methods_exec exec}.

Path parameter placeholders can be specified using simple colon/catch-all syntax or curly brace
syntax, which optionally allows a regular expression for the parameter to be specified:

* `':'` name - colon placeholder
* `'*'` name - catch-all placeholder
* `'{' name '}'` - curly placeholder
* `'{' name ':' regexp '}'` - curly placeholder with regexp. Should the regexp itself contain
  curly braces, they must be in matched pairs or escaped with a backslash.

Parameter names may contain only word characters (latin letters, digits, and underscore) and
must be unique within the pattern (across both path and search parameters). For colon 
placeholders or curly placeholders without an explicit regexp, a path parameter matches any
number of characters other than '/'. For catch-all placeholders the path parameter matches
any number of characters.

Examples:

* `'/hello/'` - Matches only if the path is exactly '/hello/'. There is no special treatment for
  trailing slashes, and patterns have to match the entire path, not just a prefix.
* `'/user/:id'` - Matches '/user/bob' or '/user/1234!!!' or even '/user/' but not '/user' or
  '/user/bob/details'. The second path segment will be captured as the parameter 'id'.
* `'/user/{id}'` - Same as the previous example, but using curly brace syntax.
* `'/user/{id:[^/]*}'` - Same as the previous example.
* `'/user/{id:[0-9a-fA-F]{1,8}}'` - Similar to the previous example, but only matches if the id
  parameter consists of 1 to 8 hex digits.
* `'/files/{path:.*}'` - Matches any URL starting with '/files/' and captures the rest of the
  path into the parameter 'path'.
* `'/files/*path'` - ditto.

@param {string} pattern  the pattern to compile into a matcher.

@property {string} prefix  A static prefix of this pattern. The matcher guarantees that any
  URL matching this matcher (i.e. any string for which {@link ui.router.util.type:UrlMatcher#methods_exec exec()} returns
  non-null) will start with this prefix.

@property {string} source  The pattern that was passed into the contructor

@property {string} sourcePath  The path portion of the source property

@property {string} sourceSearch  The search portion of the source property

@property {string} regex  The constructed regex that will be used to match against the url when 
  it is time to determine which url will match.

@returns {Object}  New UrlMatcher object