Description:
------------
When a match() statement finds no matching arm, it throws an exception. The exception's error message text, however, is very generic. Specifically, it reads "Unhandled match value of type $type_of_the_match_var".  The type of the variable is rarely useful in that case.  The *value* of the variable is what didn't match, so that's what should be in the message.  However, it's not even in the thrown object at all.

Test script:
---------------
try {
  $v = match('float') {
    'string' => 's',
    'int' => 'i',
  };
  var_dump($v);
} catch (UnhandledMatchError $e) {
  var_dump($e);
}

Expected result:
----------------
An exception thrown with a less misleading error message string, including the value of the variable, not its type.

Actual result:
--------------
object(UnhandledMatchError)#1 (7) {
  ["message":protected]=>
  string(36) "Unhandled match value of type string"
  ["string":"Error":private]=>
  string(0) ""
  ["code":protected]=>
  int(0)
  ["file":protected]=>
  string(9) "/in/U4Ns2"
  ["line":protected]=>
  int(4)
  ["trace":"Error":private]=>
  array(0) {
  }
  ["previous":"Error":private]=>
  NULL
}