GeneratorNodeScopeResolver kick-off

Author: ondrejmirtes

src/Analyser/Generator/GeneratorNodeScopeResolver.php

@@ -0,0 +1,44 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Analyser\Generator;
+
+/**
+ * Work In Progress.
+ *
+ * This is next-get NodeScopeResolver. It aims to solve several problems:
+ *
+ * 1) Many expressions are processed multiple times. For example, resolving type
+ *    of BooleanAnd has to process left side in order to accurately get the type
+ *    of the right side. For things like MethodCall, even dynamic return type extensions
+ *    and ParametersAcceptorSelector are called multiple times.
+ * 2) For complicated scope-changing expressions like assigns happening inside other expressions,
+ *    the current type inference is imprecise. Take $foo->doFoo($a = 1, $a);
+ *    When a rule hooks onto MethodCall and iterates over its args, the type of `$a`
+ *    in the second argument should be `int`, but currently it's often `mixed` because
+ *    the assignment in the first argument hasn't been processed yet in the context
+ *    where the rule is checking.
+ *
+ * This class (I will refer to it as GNSR from now on) aims to merge the tasks currently handled
+ * by NodeScopeResolver, MutatingScope and TypeSpecifier all into one, because they are very similar
+ * and their work should happen all at once without duplicit processing.
+ *
+ * This rewrite should fix 1) to improve performance and 2) to improve type inference precision.
+ *
+ * Architecture:
+ * - Uses generators (with `yield`) for internal analysis code to handle recursive traversal
+ *   without deep call stacks and to explicitly manage when sub-expressions are analyzed
+ * - Uses Fibers when calling custom extension code (rules, dynamic return type extensions, etc.)
+ *   to preserve backward compatibility
+ * - Calls to `$scope->getType()` in custom extensions do not need to be preceded with `yield`.
+ *   Instead, if the type is not yet available, the call will transparently suspend the current
+ *   Fiber and resume once the type has been computed
+ * - All computed types and analysis results are stored during traversal so that subsequent
+ *   lookups (from rules or other extensions) hit cached values with no duplicate work
+ * - Synthetic/virtual expressions (e.g., a rule constructing `new MethodCall(...)` to query
+ *   a hypothetical method call) are analyzed on-demand when requested, with the Fiber
+ *   suspending until analysis completes
+ */
+final class GeneratorNodeScopeResolver
+{
+
+}