InputDefinition: corrected grammar mistakes and added a @throws declaration

Author: nanocom

src/Symfony/Component/Console/Input/InputDefinition.php

@@ -113,7 +113,7 @@ public function addArguments($arguments = array())
  public function addArgument(InputArgument $argument)
  {
  if (isset($this->arguments[$argument->getName()])) {
- throw new \LogicException(sprintf('An argument with name "%s" already exist.', $argument->getName()));
+ throw new \LogicException(sprintf('An argument with name "%s" already exists.', $argument->getName()));
  }
 
  if ($this->hasAnArrayArgument) {
@@ -262,9 +262,9 @@ public function addOptions($options = array())
  public function addOption(InputOption $option)
  {
  if (isset($this->options[$option->getName()]) && !$option->equals($this->options[$option->getName()])) {
- throw new \LogicException(sprintf('An option named "%s" already exist.', $option->getName()));
+ throw new \LogicException(sprintf('An option named "%s" already exists.', $option->getName()));
  } elseif (isset($this->shortcuts[$option->getShortcut()]) && !$option->equals($this->options[$this->shortcuts[$option->getShortcut()]])) {
- throw new \LogicException(sprintf('An option with shortcut "%s" already exist.', $option->getShortcut()));
+ throw new \LogicException(sprintf('An option with shortcut "%s" already exists.', $option->getShortcut()));
  }
 
  $this->options[$option->getName()] = $option;
@@ -280,6 +280,8 @@ public function addOption(InputOption $option)
  *
  * @return InputOption A InputOption object
  *
+ * @throws \InvalidArgumentException When option given doesn't exist
+ *
  * @api
  */
  public function getOption($name)