Nearly all special errors are now handled gracefully, i.e. the
parser will be able to continue after encountering them. In some
cases the associated error range has been improved using the new
end attribute stack.
To achieve this the error handling code has been moved out of the
node constructors and into special methods in the parser.
A Nop statement will be inserted into statement lists if there are
any trailing comments in the list (which would otherwise not be
associated with any node).
The pretty printer output currently still contains a superfluous
newline.
Adding only a single recovery rule for now.
The API is now:
* throwOnError parser option must be disabled.
* List of Errors is available through $parser->getErrors(). This
method is available either way.
* If no recovery is possible $parser->parse() will return null.
(Obviously only if throwOnError is disabled).
This adds an additional "returnType" subnode to Stmt\Function_,
Stmt\ClassMethod and Expr\Closure, as well as the corresponding
support in the name resolver and pretty printer.
