--- /dev/null
+Upgrading from PHP-Parser 2.x to 3.0
+====================================
+
+The backwards-incompatible changes in this release may be summarized as follows:
+
+ * The specific details of the node representation have changed in some cases, primarily to
+ accomodate new PHP 7.1 features.
+ * There have been significant changes to the error recovery implementation. This may affect you,
+ if you used the error recovery mode or have a custom lexer implementation.
+ * A number of deprecated methods were removed.
+
+### PHP version requirements
+
+PHP-Parser now requires PHP 5.5 or newer to run. It is however still possible to *parse* PHP 5.2,
+5.3 and 5.4 source code, while running on a newer version.
+
+### Changes to the node structure
+
+The following changes are likely to require code changes if the respective nodes are used:
+
+ * The `List` subnode `vars` has been renamed to `items` and now contains `ArrayItem`s instead of
+ plain variables.
+ * The `Catch` subnode `type` has been renamed to `types` and is now an array of `Name`s.
+ * The `TryCatch` subnode `finallyStmts` has been replaced with a `finally` subnode that holds an
+ explicit `Finally` node.
+ * The `type` subnode on `Class`, `ClassMethod` and `Property` has been renamed to `flags`. The
+ `type` subnode has retained for backwards compatibility and is populated to the same value as
+ `flags`. However, writes to `type` will not update `flags` and use of `type` is discouraged.
+
+The following changes are unlikely to require code changes:
+
+ * The `ClassConst` constructor changed to accept an additional `flags` subnode.
+ * The `Trait` constructor now has the same form as the `Class` and `Interface` constructors: It
+ takes an array of subnodes. Unlike classes/interfaces, traits can only have a `stmts` subnode.
+ * The `Array` subnode `items` may now contain `null` elements (due to destructuring).
+ * `void` and `iterable` types are now stored as strings if the PHP 7 parser is used. Previously
+ these would have been represented as `Name` instances.
+
+### Changes to error recovery mode
+
+Previously, error recovery mode was enabled by setting the `throwOnError` option to `false` when
+creating the parser, while collected errors were retrieved using the `getErrors()` method:
+
+```php
+$lexer = ...;
+$parser = (new ParserFactory)->create(ParserFactor::ONLY_PHP7, $lexer, [
+ 'throwOnError' => true,
+]);
+
+$stmts = $parser->parse($code);
+$errors = $parser->getErrors();
+if ($errors) {
+ handleErrors($errors);
+}
+processAst($stmts);
+```
+
+Both the `throwOnError` option and the `getErrors()` method have been removed in PHP-Parser 3.0.
+Instead an instance of `ErrorHandler\Collecting` should be passed to the `parse()` method:
+
+```php
+$lexer = ...;
+$parser = (new ParserFactory)->create(ParserFactor::ONLY_PHP7, $lexer);
+
+$errorHandler = new ErrorHandler\Collecting;
+$stmts = $parser->parse($code, $errorHandler);
+if ($errorHandler->hasErrors()) {
+ handleErrors($errorHandler->getErrors());
+}
+processAst($stmts);
+```
+
+#### Multiple parser fallback in error recovery mode
+
+As a result of this change, if a `Multiple` parser is used (e.g. through the `ParserFactory` using
+`PREFER_PHP7` or `PREFER_PHP5`), it will now return the result of the first *non-throwing* parse. As
+parsing never throws in error recovery mode, the result from the first parser will always be
+returned.
+
+The PHP 7 parser is a superset of the PHP 5 parser, with the exceptions that `=& new` and
+`global $$foo->bar` are not supported (other differences are in representation only). The PHP 7
+parser will be able to recover from the error in both cases. For this reason, this change will
+likely pass unnoticed if you do not specifically test for this syntax.
+
+It is possible to restore the precise previous behavior with the following code:
+
+```php
+$lexer = ...;
+$parser7 = new Parser\Php7($lexer);
+$parser5 = new Parser\Php5($lexer);
+
+$errors7 = new ErrorHandler\Collecting();
+$stmts7 = $parser7->parse($code, $errors7);
+if ($errors7->hasErrors()) {
+ $errors5 = new ErrorHandler\Collecting();
+ $stmts5 = $parser5->parse($code, $errors5);
+ if (!$errors5->hasErrors()) {
+ // If PHP 7 parse has errors but PHP 5 parse has no errors, use PHP 5 result
+ return [$stmts5, $errors5];
+ }
+}
+// If PHP 7 succeeds or both fail use PHP 7 result
+return [$stmts7, $errors7];
+```
+
+#### Error handling in the lexer
+
+In order to support recovery from lexer errors, the signature of the `startLexing()` method changed
+to optionally accept an `ErrorHandler`:
+
+```php
+// OLD
+public function startLexing($code);
+// NEW
+public function startLexing($code, ErrorHandler $errorHandler = null);
+```
+
+If you use a custom lexer with overriden `startLexing()` method, it needs to be changed to accept
+the extra parameter. The value should be passed on to the parent method.
+
+#### Error checks in node constructors
+
+The constructors of certain nodes used to contain additional checks for semantic errors, such as
+creating a try block without either catch or finally. These checks have been moved from the node
+constructors into the parser. This allows recovery from such errors, as well as representing the
+resulting (invalid) AST.
+
+This means that certain error conditions are no longer checked for manually constructed nodes.
+
+### Removed methods, arguments, options
+
+The following methods, arguments or options have been removed:
+
+ * `Comment::setLine()`, `Comment::setText()`: Create new `Comment` instances instead.
+ * `Name::set()`, `Name::setFirst()`, `Name::setLast()`, `Name::append()`, `Name::prepend()`:
+ Use `Name::concat()` in combination with `Name::slice()` instead.
+ * `Error::getRawLine()`, `Error::setRawLine()`. Use `Error::getStartLine()` and
+ `Error::setStartLine()` instead.
+ * `Parser::getErrors()`. Use `ErrorHandler\Collecting` instead.
+ * `$separator` argument of `Name::toString()`. Use `strtr()` instead, if you really need it.
+ * `$cloneNodes` argument of `NodeTraverser::__construct()`. Explicitly clone nodes in the visitor
+ instead.
+ * `throwOnError` parser option. Use `ErrorHandler\Collecting` instead.
+
+### Miscellaneous
+
+ * The `NameResolver` will now resolve unqualified function and constant names in the global
+ namespace into fully qualified names. For example `foo()` in the global namespace resolves to
+ `\foo()`. For names where no static resolution is possible, a `namespacedName` attribute is
+ added now, containing the namespaced variant of the name.
+ * All methods on `PrettyPrinter\Standard` are now protected. Previoulsy most of them were public.
+ The pretty printer should only be invoked using the `prettyPrint()`, `prettyPrintFile()` and
+ `prettyPrintExpr()` methods.
+ * The node dumper now prints numeric values that act as enums/flags in a string representation.
+ If node dumper results are used in tests, updates may be needed to account for this.
+ * The constants on `NameTraverserInterface` have been moved into the `NameTraverser` class.
+ * The emulative lexer now directly postprocesses tokens, instead of using `~__EMU__~` sequences.
+ This changes the protected API of the emulative lexer.
+ * The `Name::slice()` method now returns `null` for empty slices, previously `new Name([])` was
+ used. `Name::concat()` now also supports concatenation with `null`.
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