This method is called to report a syntax error which requires the removal
of a token from the input stream. At the time this method is called, the
erroneous symbol is current {@code LT(1)} symbol and has not yet been
removed from the input stream. When this method returns,
{@code recognizer} is in error recovery mode.
<p>This method is called when {@link #singleTokenDeletion} identifies
single-token deletion as a viable recovery strategy for a mismatched
input error.</p>
<p>The default implementation simply returns if the handler is already in
error recovery mode. Otherwise, it calls {@link #beginErrorCondition} to
enter error recovery mode, followed by calling
{@link Parser#notifyErrorListeners}.</p>
This method is called to report a syntax error which requires the removal of a token from the input stream. At the time this method is called, the erroneous symbol is current {@code LT(1)} symbol and has not yet been removed from the input stream. When this method returns, {@code recognizer} is in error recovery mode.
<p>This method is called when {@link #singleTokenDeletion} identifies single-token deletion as a viable recovery strategy for a mismatched input error.</p>
<p>The default implementation simply returns if the handler is already in error recovery mode. Otherwise, it calls {@link #beginErrorCondition} to enter error recovery mode, followed by calling {@link Parser#notifyErrorListeners}.</p>
@param recognizer the parser instance