ReflectionContext for imports and namespace

TLDR: I propose to introduce a new class \ReflectionContext (or perhaps \ReflectionScope?), to give information about imported aliases and the namespace. ## Background / motivation Some libraries that parse doc comment annotations, e.g. phpDocumentor, need to know the class aliases and the namespace that are active in the place (scope) where the class, function or method is declared. E.g. phpDocumentor has this class: https://github.com/phpDocumentor/TypeResolver/blob/552bf401d264a443819a66233932be6a23f59d78/src/Types/Context.php To get this information, they parse the PHP file where the class is defined: https://github.com/phpDocumentor/TypeResolver/blob/552bf401d264a443819a66233932be6a23f59d78/src/Types/ContextFactory.php It would be much more pleasant if PHP would provide this information through the reflection API. A custom library should not need to do an expensive and fragile parsing job for information that is already known. Also, this external parsing might not cover all cases, depending how it is implemented. E.g. local namespace scopes in curly brackets. (Who uses those, btw?) ## Proposal Make information about class aliases (imported through use statements) and the active namespace available through the reflection API. $reflClass = new \ReflectionClass(C::class); $reflContext = $reflClass->getContext(); $aliases = $reflContext->getAliases(); ## Details class ReflectionContext { function getNamespace() : string {..} /** * @return string[] * Format: $[$alias] = $qcn */ function getAliases() : string[] {..} /** * @return string|null * The qcn of the class, or null if it is a built-in type like "string". */ function resolveAlias($alias) : ?string {..} } The $reflClass->getContext()->getNamespace() is the same as $reflClass->getNamespace(). But having it all in the $context object allows this object to be passed around to components that need it. ## Open questions In a method doc comment, we also want to resolve the "self" keyword. For this, the class name is needed as well, not just external imports and namespace. Maybe also introduce \RefllectionMethod::getContext()? Not sure. Should it be "context" or "scope"? It is not the same. Maybe "scope" leads to the wrong expectations.