diff --git a/composer.json b/composer.json
index a21535bb..acb4ae6c 100644
--- a/composer.json
+++ b/composer.json
@@ -44,7 +44,8 @@
         "files" : [
             "src/utils.php",
             "src/FqnUtilities.php",
-            "src/ParserHelpers.php"
+            "src/ParserHelpers.php",
+            "src/Scope/GetScopeAtNode.php"
         ]
     },
     "autoload-dev": {
diff --git a/src/CompletionProvider.php b/src/CompletionProvider.php
index 8b5b5c00..8c39c776 100644
--- a/src/CompletionProvider.php
+++ b/src/CompletionProvider.php
@@ -14,6 +14,7 @@
     CompletionContext,
     CompletionTriggerKind
 };
+use function LanguageServer\Scope\getScopeAtNode;
 use Microsoft\PhpParser;
 use Microsoft\PhpParser\Node;
 use Generator;
@@ -193,15 +194,22 @@ public function provideCompletion(PhpDocument $doc, Position $pos, CompletionCon
             //
             //    $|
             //    $a|
+            //
+            // TODO: Superglobals
 
-            // Find variables, parameters and use statements in the scope
             $namePrefix = $node->getName() ?? '';
-            foreach ($this->suggestVariablesAtNode($node, $namePrefix) as $var) {
+            $prefixLen = strlen($namePrefix);
+            $scope = getScopeAtNode($this->definitionResolver, $node);
+            $variables = $scope->variables;
+            foreach ($variables as $name => $var) {
+                if (substr($name, 0, $prefixLen) !== $namePrefix) {
+                    continue;
+                }
                 $item = new CompletionItem;
                 $item->kind = CompletionItemKind::VARIABLE;
-                $item->label = '$' . $var->getName();
-                $item->documentation = $this->definitionResolver->getDocumentationFromNode($var);
-                $item->detail = (string)$this->definitionResolver->getTypeFromNode($var);
+                $item->label = '$' . $name;
+                $item->documentation = $this->definitionResolver->getDocumentationFromNode($var->definitionNode);
+                $item->detail = (string)$var->type;
                 $item->textEdit = new TextEdit(
                     new Range($pos, $pos),
                     stripStringOverlap($doc->getRange(new Range(new Position(0, 0), $pos)), $item->label)
@@ -408,111 +416,4 @@ private function expandParentFqns(array $fqns) : Generator
             }
         }
     }
-
-    /**
-     * Will walk the AST upwards until a function-like node is met
-     * and at each level walk all previous siblings and their children to search for definitions
-     * of that variable
-     *
-     * @param Node $node
-     * @param string $namePrefix Prefix to filter
-     * @return array <Node\Expr\Variable|Node\Param|Node\Expr\ClosureUse>
-     */
-    private function suggestVariablesAtNode(Node $node, string $namePrefix = ''): array
-    {
-        $vars = [];
-
-        // Find variables in the node itself
-        // When getting completion in the middle of a function, $node will be the function node
-        // so we need to search it
-        foreach ($this->findVariableDefinitionsInNode($node, $namePrefix) as $var) {
-            // Only use the first definition
-            if (!isset($vars[$var->name])) {
-                $vars[$var->name] = $var;
-            }
-        }
-
-        // Walk the AST upwards until a scope boundary is met
-        $level = $node;
-        while ($level && !($level instanceof PhpParser\FunctionLike)) {
-            // Walk siblings before the node
-            $sibling = $level;
-            while ($sibling = $sibling->getPreviousSibling()) {
-                // Collect all variables inside the sibling node
-                foreach ($this->findVariableDefinitionsInNode($sibling, $namePrefix) as $var) {
-                    $vars[$var->getName()] = $var;
-                }
-            }
-            $level = $level->parent;
-        }
-
-        // If the traversal ended because a function was met,
-        // also add its parameters and closure uses to the result list
-        if ($level && $level instanceof PhpParser\FunctionLike && $level->parameters !== null) {
-            foreach ($level->parameters->getValues() as $param) {
-                $paramName = $param->getName();
-                if (empty($namePrefix) || strpos($paramName, $namePrefix) !== false) {
-                    $vars[$paramName] = $param;
-                }
-            }
-
-            if ($level instanceof Node\Expression\AnonymousFunctionCreationExpression && $level->anonymousFunctionUseClause !== null &&
-                $level->anonymousFunctionUseClause->useVariableNameList !== null) {
-                foreach ($level->anonymousFunctionUseClause->useVariableNameList->getValues() as $use) {
-                    $useName = $use->getName();
-                    if (empty($namePrefix) || strpos($useName, $namePrefix) !== false) {
-                        $vars[$useName] = $use;
-                    }
-                }
-            }
-        }
-
-        return array_values($vars);
-    }
-
-    /**
-     * Searches the subnodes of a node for variable assignments
-     *
-     * @param Node $node
-     * @param string $namePrefix Prefix to filter
-     * @return Node\Expression\Variable[]
-     */
-    private function findVariableDefinitionsInNode(Node $node, string $namePrefix = ''): array
-    {
-        $vars = [];
-        // If the child node is a variable assignment, save it
-
-        $isAssignmentToVariable = function ($node) {
-            return $node instanceof Node\Expression\AssignmentExpression;
-        };
-
-        if ($this->isAssignmentToVariableWithPrefix($node, $namePrefix)) {
-            $vars[] = $node->leftOperand;
-        } elseif ($node instanceof Node\ForeachKey || $node instanceof Node\ForeachValue) {
-            foreach ($node->getDescendantNodes() as $descendantNode) {
-                if ($descendantNode instanceof Node\Expression\Variable
-                    && ($namePrefix === '' || strpos($descendantNode->getName(), $namePrefix) !== false)
-                ) {
-                    $vars[] = $descendantNode;
-                }
-            }
-        } else {
-            // Get all descendent variables, then filter to ones that start with $namePrefix.
-            // Avoiding closure usage in tight loop
-            foreach ($node->getDescendantNodes($isAssignmentToVariable) as $descendantNode) {
-                if ($this->isAssignmentToVariableWithPrefix($descendantNode, $namePrefix)) {
-                    $vars[] = $descendantNode->leftOperand;
-                }
-            }
-        }
-
-        return $vars;
-    }
-
-    private function isAssignmentToVariableWithPrefix(Node $node, string $namePrefix): bool
-    {
-        return $node instanceof Node\Expression\AssignmentExpression
-            && $node->leftOperand instanceof Node\Expression\Variable
-            && ($namePrefix === '' || strpos($node->leftOperand->getName(), $namePrefix) !== false);
-    }
 }
diff --git a/src/DefinitionResolver.php b/src/DefinitionResolver.php
index 990c1965..d4b9ffd8 100644
--- a/src/DefinitionResolver.php
+++ b/src/DefinitionResolver.php
@@ -5,6 +5,8 @@
 
 use LanguageServer\Index\ReadableIndex;
 use LanguageServer\Protocol\SymbolInformation;
+use LanguageServer\Scope\Scope;
+use function LanguageServer\Scope\getScopeAtNode;
 use Microsoft\PhpParser;
 use Microsoft\PhpParser\Node;
 use Microsoft\PhpParser\FunctionLike;
@@ -175,10 +177,15 @@ private function getDocBlock(Node $node)
      *
      * @param Node $node
      * @param string $fqn
+     * @param Scope|null $scope Scope at the point of Node. If not provided, will be computed from $node.
      * @return Definition
      */
-    public function createDefinitionFromNode(Node $node, string $fqn = null): Definition
+    public function createDefinitionFromNode(Node $node, string $fqn = null, Scope $scope = null): Definition
     {
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $node);
+        }
+
         $def = new Definition;
         $def->fqn = $fqn;
 
@@ -221,7 +228,7 @@ public function createDefinitionFromNode(Node $node, string $fqn = null): Defini
         if ($node instanceof Node\Statement\ClassDeclaration &&
             // TODO - this should be better represented in the parser API
             $node->classBaseClause !== null && $node->classBaseClause->baseClass !== null) {
-            $def->extends = [(string)$node->classBaseClause->baseClass->getResolvedName()];
+            $def->extends = [$scope->getResolvedName($node->classBaseClause->baseClass)];
         } elseif (
             $node instanceof Node\Statement\InterfaceDeclaration &&
             // TODO - this should be better represented in the parser API
@@ -229,20 +236,20 @@ public function createDefinitionFromNode(Node $node, string $fqn = null): Defini
         ) {
             $def->extends = [];
             foreach ($node->interfaceBaseClause->interfaceNameList->getValues() as $n) {
-                $def->extends[] = (string)$n->getResolvedName();
+                $def->extends[] = $scope->getResolvedName($n);
             }
         }
 
         $def->symbolInformation = SymbolInformation::fromNode($node, $fqn);
 
         if ($def->symbolInformation !== null) {
-            $def->type = $this->getTypeFromNode($node);
+            $def->type = $this->getTypeFromNode($node, $scope);
             $def->declarationLine = $this->getDeclarationLineFromNode($node);
             $def->documentation = $this->getDocumentationFromNode($node);
         }
 
         if ($node instanceof FunctionLike) {
-            $def->signatureInformation = $this->signatureInformationFactory->create($node);
+            $def->signatureInformation = $this->signatureInformationFactory->create($node, $scope);
         }
 
         return $def;
@@ -252,56 +259,62 @@ public function createDefinitionFromNode(Node $node, string $fqn = null): Defini
      * Given any node, returns the Definition object of the symbol that is referenced
      *
      * @param Node $node Any reference node
+     * @param Scope|null $scope Scope at the point of Node. If not provided, will be computed from $node.
      * @return Definition|null
      */
-    public function resolveReferenceNodeToDefinition(Node $node)
+    public function resolveReferenceNodeToDefinition(Node $node, Scope $scope = null)
     {
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $node);
+        }
+
         $parent = $node->parent;
         // Variables are not indexed globally, as they stay in the file scope anyway.
         // Ignore variable nodes that are part of ScopedPropertyAccessExpression,
         // as the scoped property access expression node is handled separately.
         if ($node instanceof Node\Expression\Variable &&
             !($parent instanceof Node\Expression\ScopedPropertyAccessExpression)) {
+            $name = $node->getName();
             // Resolve $this to the containing class definition.
-            if ($node->getName() === 'this' && $fqn = $this->getContainingClassFqn($node)) {
+            if ($name === 'this') {
+                if ($scope->currentSelf === null) {
+                    return null;
+                }
+                $fqn = substr((string)$scope->currentSelf->type->getFqsen(), 1);
                 return $this->index->getDefinition($fqn, false);
             }
 
             // Resolve the variable to a definition node (assignment, param or closure use)
-            $defNode = $this->resolveVariableToNode($node);
-            if ($defNode === null) {
+            if (!isset($scope->variables[$name])) {
                 return null;
             }
-            return $this->createDefinitionFromNode($defNode);
+            return $this->createDefinitionFromNode($scope->variables[$name]->definitionNode, null, $scope);
         }
         // Other references are references to a global symbol that have an FQN
         // Find out the FQN
-        $fqn = $this->resolveReferenceNodeToFqn($node);
-        if (!$fqn) {
-            return null;
-        }
+        $fqn = $this->resolveReferenceNodeToFqn($node, $scope);
 
         if ($fqn === 'self' || $fqn === 'static') {
             // Resolve self and static keywords to the containing class
             // (This is not 100% correct for static but better than nothing)
-            $classNode = $node->getFirstAncestor(Node\Statement\ClassDeclaration::class);
-            if (!$classNode) {
-                return;
-            }
-            $fqn = (string)$classNode->getNamespacedName();
-            if (!$fqn) {
-                return;
+            if ($scope->currentSelf === null) {
+                return null;
             }
+            $fqn = substr((string)$scope->currentSelf->type->getFqsen(), 1);
         } else if ($fqn === 'parent') {
-            // Resolve parent keyword to the base class FQN
-            $classNode = $node->getFirstAncestor(Node\Statement\ClassDeclaration::class);
-            if (!$classNode || !$classNode->classBaseClause || !$classNode->classBaseClause->baseClass) {
-                return;
+            if ($scope->currentSelf === null) {
+                return null;
             }
-            $fqn = (string)$classNode->classBaseClause->baseClass->getResolvedName();
-            if (!$fqn) {
-                return;
+            // Resolve parent keyword to the base class FQN
+            $classNode = $scope->currentSelf->definitionNode;
+            if (!$classNode->classBaseClause || !$classNode->classBaseClause->baseClass) {
+                return null;
             }
+            $fqn = $scope->getResolvedName($classNode->classBaseClause->baseClass);
+        }
+
+        if (!$fqn) {
+            return;
         }
 
         // If the node is a function or constant, it could be namespaced, but PHP falls back to global
@@ -319,15 +332,19 @@ public function resolveReferenceNodeToDefinition(Node $node)
      * May also return "static", "self" or "parent"
      *
      * @param Node $node
+     * @param Scope|null $scope Scope at the point of Node. If not provided, will be computed from $node.
      * @return string|null
      */
-    public function resolveReferenceNodeToFqn(Node $node)
+    public function resolveReferenceNodeToFqn(Node $node, Scope $scope = null)
     {
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $node);
+        }
         // TODO all name tokens should be a part of a node
         if ($node instanceof Node\QualifiedName) {
-            return $this->resolveQualifiedNameNodeToFqn($node);
+            return $this->resolveQualifiedNameNodeToFqn($node, $scope);
         } else if ($node instanceof Node\Expression\MemberAccessExpression) {
-            return $this->resolveMemberAccessExpressionNodeToFqn($node);
+            return $this->resolveMemberAccessExpressionNodeToFqn($node, $scope);
         } else if (ParserHelpers\isConstantFetch($node)) {
             return (string)($node->getNamespacedName());
         } else if (
@@ -335,18 +352,18 @@ public function resolveReferenceNodeToFqn(Node $node)
             $node instanceof Node\Expression\ScopedPropertyAccessExpression
             && !($node->memberName instanceof Node\Expression\Variable)
         ) {
-            return $this->resolveScopedPropertyAccessExpressionNodeToFqn($node);
+            return $this->resolveScopedPropertyAccessExpressionNodeToFqn($node, $scope);
         } else if (
             // A\B::$c - static property access expression
             $node->parent instanceof Node\Expression\ScopedPropertyAccessExpression
         ) {
-            return $this->resolveScopedPropertyAccessExpressionNodeToFqn($node->parent);
+            return $this->resolveScopedPropertyAccessExpressionNodeToFqn($node->parent, $scope);
         }
 
         return null;
     }
 
-    private function resolveQualifiedNameNodeToFqn(Node\QualifiedName $node)
+    private function resolveQualifiedNameNodeToFqn(Node\QualifiedName $node, Scope $scope)
     {
         $parent = $node->parent;
 
@@ -385,7 +402,7 @@ private function resolveQualifiedNameNodeToFqn(Node\QualifiedName $node)
         }
 
         // For extends, implements, type hints and classes of classes of static calls use the name directly
-        $name = (string) ($node->getResolvedName() ?? $node->getNamespacedName());
+        $name = $scope->getResolvedName($node) ?? (string)$node->getNamespacedName();
 
         if ($node->parent instanceof Node\Expression\CallExpression) {
             $name .= '()';
@@ -393,14 +410,14 @@ private function resolveQualifiedNameNodeToFqn(Node\QualifiedName $node)
         return $name;
     }
 
-    private function resolveMemberAccessExpressionNodeToFqn(Node\Expression\MemberAccessExpression $access)
+    private function resolveMemberAccessExpressionNodeToFqn(Node\Expression\MemberAccessExpression $access, Scope $scope)
     {
         if ($access->memberName instanceof Node\Expression) {
             // Cannot get definition if right-hand side is expression
             return null;
         }
         // Get the type of the left-hand expression
-        $varType = $this->resolveExpressionNodeToType($access->dereferencableExpression);
+        $varType = $this->resolveExpressionNodeToType($access->dereferencableExpression, $scope);
 
         if ($varType instanceof Types\Compound) {
             // For compound types, use the first FQN we find
@@ -423,14 +440,18 @@ private function resolveMemberAccessExpressionNodeToFqn(Node\Expression\MemberAc
             || $varType instanceof Types\Self_
         ) {
             // $this/static/self is resolved to the containing class
-            $classFqn = self::getContainingClassFqn($access);
+            if ($scope->currentSelf === null) {
+                return null;
+            }
+            $classFqn = substr((string)$scope->currentSelf->type->getFqsen(), 1);
         } else if (!($varType instanceof Types\Object_) || $varType->getFqsen() === null) {
             // Left-hand expression could not be resolved to a class
             return null;
         } else {
             $classFqn = substr((string)$varType->getFqsen(), 1);
         }
-        $memberSuffix = '->' . (string)($access->memberName->getText() ?? $access->memberName->getText($access->getFileContents()));
+        $memberSuffix = '->' . (string)($access->memberName->getText()
+            ?? $access->memberName->getText($access->getFileContents()));
         if ($access->parent instanceof Node\Expression\CallExpression) {
             $memberSuffix .= '()';
         }
@@ -460,23 +481,25 @@ private function resolveMemberAccessExpressionNodeToFqn(Node\Expression\MemberAc
         return $classFqn . $memberSuffix;
     }
 
-    private function resolveScopedPropertyAccessExpressionNodeToFqn(Node\Expression\ScopedPropertyAccessExpression $scoped)
-    {
+    private function resolveScopedPropertyAccessExpressionNodeToFqn(
+        Node\Expression\ScopedPropertyAccessExpression $scoped,
+        Scope $scope
+    ) {
         if ($scoped->scopeResolutionQualifier instanceof Node\Expression\Variable) {
-            $varType = $this->getTypeFromNode($scoped->scopeResolutionQualifier);
+            $varType = $this->getTypeFromNode($scoped->scopeResolutionQualifier, $scope);
             if ($varType === null) {
                 return null;
             }
             $className = substr((string)$varType->getFqsen(), 1);
         } elseif ($scoped->scopeResolutionQualifier instanceof Node\QualifiedName) {
-            $className = (string)$scoped->scopeResolutionQualifier->getResolvedName();
+            $className = $scope->getResolvedName($scoped->scopeResolutionQualifier);
         } else {
             return null;
         }
 
         if ($className === 'self' || $className === 'static' || $className === 'parent') {
             // self and static are resolved to the containing class
-            $classNode = $scoped->getFirstAncestor(Node\Statement\ClassDeclaration::class);
+            $classNode = $scope->currentSelf->definitionNode ?? null;
             if ($classNode === null) {
                 return null;
             }
@@ -485,12 +508,12 @@ private function resolveScopedPropertyAccessExpressionNodeToFqn(Node\Expression\
                 if (!isset($classNode->extends)) {
                     return null;
                 }
-                $className = (string)$classNode->extends->getResolvedName();
+                $className = $scope->getResolvedName($classNode->extends);
             } else {
-                $className = (string)$classNode->getNamespacedName();
+                $className = substr((string)$scope->currentSelf->type->getFqsen(), 1);
             }
         } elseif ($scoped->scopeResolutionQualifier instanceof Node\QualifiedName) {
-            $className = $scoped->scopeResolutionQualifier->getResolvedName();
+            $className = $scope->getResolvedName($scoped->scopeResolutionQualifier);
         }
         if ($scoped->memberName instanceof Node\Expression\Variable) {
             if ($scoped->parent instanceof Node\Expression\CallExpression) {
@@ -510,146 +533,20 @@ private function resolveScopedPropertyAccessExpressionNodeToFqn(Node\Expression\
         return $name;
     }
 
-    /**
-     * Returns FQN of the class a node is contained in
-     * Returns null if the class is anonymous or the node is not contained in a class
-     *
-     * @param Node $node
-     * @return string|null
-     */
-    private static function getContainingClassFqn(Node $node)
-    {
-        $classNode = $node->getFirstAncestor(Node\Statement\ClassDeclaration::class);
-        if ($classNode === null) {
-            return null;
-        }
-        return (string)$classNode->getNamespacedName();
-    }
-
-    /**
-     * Returns the type of the class a node is contained in
-     * Returns null if the class is anonymous or the node is not contained in a class
-     *
-     * @param Node $node The node used to find the containing class
-     *
-     * @return Types\Object_|null
-     */
-    private function getContainingClassType(Node $node)
-    {
-        $classFqn = $this->getContainingClassFqn($node);
-        return $classFqn ? new Types\Object_(new Fqsen('\\' . $classFqn)) : null;
-    }
-
-    /**
-     * Returns the assignment or parameter node where a variable was defined
-     *
-     * @param Node\Expression\Variable|Node\Expression\ClosureUse $var The variable access
-     * @return Node\Expression\Assign|Node\Expression\AssignOp|Node\Param|Node\Expression\ClosureUse|null
-     */
-    public function resolveVariableToNode($var)
-    {
-        $n = $var;
-        // When a use is passed, start outside the closure to not return immediately
-        // Use variable vs variable parsing?
-        if ($var instanceof Node\UseVariableName) {
-            $n = $var->getFirstAncestor(Node\Expression\AnonymousFunctionCreationExpression::class)->parent;
-            $name = $var->getName();
-        } else if ($var instanceof Node\Expression\Variable || $var instanceof Node\Parameter) {
-            $name = $var->getName();
-        } else {
-            throw new \InvalidArgumentException('$var must be Variable, Param or ClosureUse, not ' . get_class($var));
-        }
-        if (empty($name)) {
-            return null;
-        }
-
-        $shouldDescend = function ($nodeToDescand) {
-            // Make sure not to decend into functions or classes (they represent a scope boundary)
-            return !($nodeToDescand instanceof PhpParser\FunctionLike || $nodeToDescand instanceof PhpParser\ClassLike);
-        };
-
-        // Traverse the AST up
-        do {
-            // If a function is met, check the parameters and use statements
-            if ($n instanceof PhpParser\FunctionLike) {
-                if ($n->parameters !== null) {
-                    foreach ($n->parameters->getElements() as $param) {
-                        if ($param->getName() === $name) {
-                            return $param;
-                        }
-                    }
-                }
-                // If it is a closure, also check use statements
-                if ($n instanceof Node\Expression\AnonymousFunctionCreationExpression &&
-                    $n->anonymousFunctionUseClause !== null &&
-                    $n->anonymousFunctionUseClause->useVariableNameList !== null) {
-                    foreach ($n->anonymousFunctionUseClause->useVariableNameList->getElements() as $use) {
-                        if ($use->getName() === $name) {
-                            return $use;
-                        }
-                    }
-                }
-                break;
-            }
-
-            // Check each previous sibling node and their descendents for a variable assignment to that variable
-            // Each previous sibling could contain a declaration of the variable
-            while (($prevSibling = $n->getPreviousSibling()) !== null && $n = $prevSibling) {
-
-                // Check the sibling itself
-                if (self::isVariableDeclaration($n, $name)) {
-                    return $n;
-                }
-
-                // Check descendant of this sibling (e.g. the children of a previous if block)
-                foreach ($n->getDescendantNodes($shouldDescend) as $descendant) {
-                    if (self::isVariableDeclaration($descendant, $name)) {
-                        return $descendant;
-                    }
-                }
-            }
-        } while (isset($n) && $n = $n->parent);
-        // Return null if nothing was found
-        return null;
-    }
-
-    /**
-     * Checks whether the given Node declares the given variable name
-     *
-     * @param Node $n The Node to check
-     * @param string $name The name of the wanted variable
-     * @return bool
-     */
-    private static function isVariableDeclaration(Node $n, string $name)
-    {
-        if (
-            // TODO - clean this up
-            ($n instanceof Node\Expression\AssignmentExpression && $n->operator->kind === PhpParser\TokenKind::EqualsToken)
-            && $n->leftOperand instanceof Node\Expression\Variable && $n->leftOperand->getName() === $name
-        ) {
-            return true;
-        }
-
-        if (
-            ($n instanceof Node\ForeachValue || $n instanceof Node\ForeachKey)
-            && $n->expression instanceof Node\Expression\Variable
-            && $n->expression->getName() === $name
-        ) {
-            return true;
-        }
-
-        return false;
-    }
-
     /**
      * Given an expression node, resolves that expression recursively to a type.
      * If the type could not be resolved, returns Types\Mixed_.
      *
-     * @param Node\Expression $expr
+     * @param Node|Token $expr
+     * @param Scope|null $scope Scope at the point of Node. If not provided, will be computed from $node.
      * @return \phpDocumentor\Reflection\Type|null
      */
-    public function resolveExpressionNodeToType($expr)
+    public function resolveExpressionNodeToType($expr, Scope $scope = null)
     {
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $expr);
+        }
+
         // PARENTHESIZED EXPRESSION
         // Retrieve inner expression from parenthesized expression
         while ($expr instanceof Node\Expression\ParenthesizedExpression) {
@@ -666,20 +563,10 @@ public function resolveExpressionNodeToType($expr)
         //   $this -> Type\this
         //   $myVariable -> type of corresponding assignment expression
         if ($expr instanceof Node\Expression\Variable || $expr instanceof Node\UseVariableName) {
-            if ($expr->getName() === 'this') {
-                return new Types\Object_(new Fqsen('\\' . $this->getContainingClassFqn($expr)));
-            }
-            // Find variable definition (parameter or assignment expression)
-            $defNode = $this->resolveVariableToNode($expr);
-            if ($defNode instanceof Node\Expression\AssignmentExpression || $defNode instanceof Node\UseVariableName) {
-                return $this->resolveExpressionNodeToType($defNode);
-            }
-            if ($defNode instanceof Node\ForeachKey || $defNode instanceof Node\ForeachValue) {
-                return $this->getTypeFromNode($defNode);
-            }
-            if ($defNode instanceof Node\Parameter) {
-                return $this->getTypeFromNode($defNode);
-            }
+            $name = $expr->getName();
+            return isset($scope->variables[$name])
+                ? $scope->variables[$name]->type
+                : new Types\Mixed_;
         }
 
         // FUNCTION CALL
@@ -691,18 +578,18 @@ public function resolveExpressionNodeToType($expr)
         ) {
             // Find the function definition
             if ($expr->callableExpression instanceof Node\Expression) {
-                // Cannot get type for dynamic function call
                 return new Types\Mixed_;
             }
 
             if ($expr->callableExpression instanceof Node\QualifiedName) {
-                $fqn = $expr->callableExpression->getResolvedName() ?? $expr->callableExpression->getNamespacedName();
+                $fqn = $scope->getResolvedName($expr->callableExpression) ?? $expr->callableExpression->getNamespacedName();
                 $fqn .= '()';
                 $def = $this->index->getDefinition($fqn, true);
                 if ($def !== null) {
                     return $def->type;
                 }
             }
+            return new Types\Mixed_;
         }
 
         // TRUE / FALSE / NULL
@@ -716,6 +603,7 @@ public function resolveExpressionNodeToType($expr)
             if ($token === PhpParser\TokenKind::NullReservedWord) {
                 return new Types\Null_;
             }
+            return new Types\Mixed_;
         }
 
         // CONSTANT FETCH
@@ -726,6 +614,7 @@ public function resolveExpressionNodeToType($expr)
             if ($def !== null) {
                 return $def->type;
             }
+            return new Types\Mixed_;
         }
 
         // MEMBER CALL EXPRESSION/SCOPED PROPERTY CALL EXPRESSION
@@ -735,7 +624,7 @@ public function resolveExpressionNodeToType($expr)
             $expr->callableExpression instanceof Node\Expression\MemberAccessExpression ||
             $expr->callableExpression instanceof Node\Expression\ScopedPropertyAccessExpression)
         ) {
-            return $this->resolveExpressionNodeToType($expr->callableExpression);
+            return $this->resolveExpressionNodeToType($expr->callableExpression, $scope);
         }
 
         // MEMBER ACCESS EXPRESSION
@@ -746,16 +635,19 @@ public function resolveExpressionNodeToType($expr)
             $var = $expr->dereferencableExpression;
 
            // Resolve object
-            $objType = $this->resolveExpressionNodeToType($var);
+            $objType = $this->resolveExpressionNodeToType($var, $scope);
+            if ($objType === null) {
+                return null;
+            }
             if (!($objType instanceof Types\Compound)) {
                 $objType = new Types\Compound([$objType]);
             }
             for ($i = 0; $t = $objType->get($i); $i++) {
                 if ($t instanceof Types\This) {
-                    $classFqn = self::getContainingClassFqn($expr);
-                    if ($classFqn === null) {
+                    if ($scope->currentSelf === null) {
                         return new Types\Mixed_;
                     }
+                    $classFqn = substr((string)$scope->currentSelf->type->getFqsen(), 1);
                 } else if (!($t instanceof Types\Object_) || $t->getFqsen() === null) {
                     return new Types\Mixed_;
                 } else {
@@ -782,7 +674,7 @@ public function resolveExpressionNodeToType($expr)
 
         // SCOPED PROPERTY ACCESS EXPRESSION
         if ($expr instanceof Node\Expression\ScopedPropertyAccessExpression) {
-            $classType = $this->resolveClassNameToType($expr->scopeResolutionQualifier);
+            $classType = $this->resolveClassNameToType($expr->scopeResolutionQualifier, $scope);
             if (!($classType instanceof Types\Object_) || $classType->getFqsen() === null) {
                 return new Types\Mixed_;
             }
@@ -805,19 +697,19 @@ public function resolveExpressionNodeToType($expr)
         //   new A() => resolves to the type of the class type designator (A)
         //   TODO: new $this->a => resolves to the string represented by "a"
         if ($expr instanceof Node\Expression\ObjectCreationExpression) {
-            return $this->resolveClassNameToType($expr->classTypeDesignator);
+            return $this->resolveClassNameToType($expr->classTypeDesignator, $scope);
         }
 
         // CLONE EXPRESSION
         //   clone($a) => resolves to the type of $a
         if ($expr instanceof Node\Expression\CloneExpression) {
-            return $this->resolveExpressionNodeToType($expr->expression);
+            return $this->resolveExpressionNodeToType($expr->expression, $scope);
         }
 
         // ASSIGNMENT EXPRESSION
         //   $a = $myExpression => resolves to the type of the right-hand operand
         if ($expr instanceof Node\Expression\AssignmentExpression) {
-            return $this->resolveExpressionNodeToType($expr->rightOperand);
+            return $this->resolveExpressionNodeToType($expr->rightOperand, $scope);
         }
 
         // TERNARY EXPRESSION
@@ -827,14 +719,14 @@ public function resolveExpressionNodeToType($expr)
             // ?:
             if ($expr->ifExpression === null) {
                 return new Types\Compound([
-                    $this->resolveExpressionNodeToType($expr->condition), // TODO: why?
-                    $this->resolveExpressionNodeToType($expr->elseExpression)
+                    $this->resolveExpressionNodeToType($expr->condition, $scope), // TODO: why?
+                    $this->resolveExpressionNodeToType($expr->elseExpression, $scope)
                 ]);
             }
             // Ternary is a compound of the two possible values
             return new Types\Compound([
-                $this->resolveExpressionNodeToType($expr->ifExpression),
-                $this->resolveExpressionNodeToType($expr->elseExpression)
+                $this->resolveExpressionNodeToType($expr->ifExpression, $scope),
+                $this->resolveExpressionNodeToType($expr->elseExpression, $scope)
             ]);
         }
 
@@ -843,8 +735,8 @@ public function resolveExpressionNodeToType($expr)
         if ($expr instanceof Node\Expression\BinaryExpression && $expr->operator->kind === PhpParser\TokenKind::QuestionQuestionToken) {
             // ?? operator
             return new Types\Compound([
-                $this->resolveExpressionNodeToType($expr->leftOperand),
-                $this->resolveExpressionNodeToType($expr->rightOperand)
+                $this->resolveExpressionNodeToType($expr->leftOperand, $scope),
+                $this->resolveExpressionNodeToType($expr->rightOperand, $scope)
             ]);
         }
 
@@ -902,8 +794,8 @@ public function resolveExpressionNodeToType($expr)
             )
         ) {
             if (
-                $this->resolveExpressionNodeToType($expr->leftOperand) instanceof Types\Integer
-                && $this->resolveExpressionNodeToType($expr->rightOperand) instanceof Types\Integer
+                $this->resolveExpressionNodeToType($expr->leftOperand, $scope) instanceof Types\Integer
+                && $this->resolveExpressionNodeToType($expr->rightOperand, $scope) instanceof Types\Integer
             ) {
                 return new Types\Integer;
             }
@@ -954,8 +846,8 @@ public function resolveExpressionNodeToType($expr)
             $keyTypes = [];
             if ($expr->arrayElements !== null) {
                 foreach ($expr->arrayElements->getElements() as $item) {
-                    $valueTypes[] = $this->resolveExpressionNodeToType($item->elementValue);
-                    $keyTypes[] = $item->elementKey ? $this->resolveExpressionNodeToType($item->elementKey) : new Types\Integer;
+                    $valueTypes[] = $this->resolveExpressionNodeToType($item->elementValue, $scope);
+                    $keyTypes[] = $item->elementKey ? $this->resolveExpressionNodeToType($item->elementKey, $scope) : new Types\Integer;
                 }
             }
             $valueTypes = array_unique($valueTypes);
@@ -981,7 +873,7 @@ public function resolveExpressionNodeToType($expr)
         // $myArray[3]
         // $myArray{"hello"}
         if ($expr instanceof Node\Expression\SubscriptExpression) {
-            $varType = $this->resolveExpressionNodeToType($expr->postfixExpression);
+            $varType = $this->resolveExpressionNodeToType($expr->postfixExpression, $scope);
             if (!($varType instanceof Types\Array_)) {
                 return new Types\Mixed_;
             }
@@ -996,7 +888,7 @@ public function resolveExpressionNodeToType($expr)
         }
 
         if ($expr instanceof Node\QualifiedName) {
-            return $this->resolveClassNameToType($expr);
+            return $this->resolveClassNameToType($expr, $scope);
         }
 
         return new Types\Mixed_;
@@ -1010,9 +902,9 @@ public function resolveExpressionNodeToType($expr)
      * @param Node|PhpParser\Token $class
      * @return Type
      */
-    public function resolveClassNameToType($class): Type
+    public function resolveClassNameToType($class, Scope $scope = null): Type
     {
-        if ($class instanceof Node\Expression) {
+        if ($class instanceof Node\Expression || $class instanceof PhpParser\MissingToken) {
             return new Types\Mixed_;
         }
         if ($class instanceof PhpParser\Token && $class->kind === PhpParser\TokenKind::ClassKeyword) {
@@ -1023,23 +915,28 @@ public function resolveClassNameToType($class): Type
             // `new static`
             return new Types\Static_;
         }
-        $className = (string)$class->getResolvedName();
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $class);
+        }
+        $className = $scope->getResolvedName($class);
 
-        if ($className === 'self' || $className === 'parent') {
-            $classNode = $class->getFirstAncestor(Node\Statement\ClassDeclaration::class);
-            if ($className === 'parent') {
-                if ($classNode === null || $classNode->classBaseClause === null) {
-                    return new Types\Object_;
-                }
-                // parent is resolved to the parent class
-                $classFqn = (string)$classNode->classBaseClause->baseClass->getResolvedName();
-            } else {
-                if ($classNode === null) {
-                    return new Types\Self_;
-                }
-                // self is resolved to the containing class
-                $classFqn = (string)$classNode->getNamespacedName();
+        if ($className === 'self') {
+            if ($scope->currentSelf === null) {
+                return new Types\Self_;
             }
+            return $scope->currentSelf->type;
+        } else if ($className === 'parent') {
+            if ($scope->currentSelf === null) {
+                return new Types\Object_;
+            }
+            $classNode = $scope->currentSelf->definitionNode;
+            if (empty($classNode->classBaseClause)
+                || !$classNode->classBaseClause->baseClass instanceof Node\QualifiedName
+            ) {
+                return new Types\Object_;
+            }
+            // parent is resolved to the parent class
+            $classFqn = $scope->getResolvedName($classNode->classBaseClause->baseClass);
             return new Types\Object_(new Fqsen('\\' . $classFqn));
         }
         return new Types\Object_(new Fqsen('\\' . $className));
@@ -1057,14 +954,19 @@ public function resolveClassNameToType($class): Type
      * Returns null if the node does not have a type.
      *
      * @param Node $node
+     * @param Scope|null $scope Scope at the point of Node. If not provided, will be computed from $node.
      * @return \phpDocumentor\Reflection\Type|null
      */
-    public function getTypeFromNode($node)
+    public function getTypeFromNode($node, Scope $scope = null)
     {
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $node);
+        }
+
         if (ParserHelpers\isConstDefineExpression($node)) {
             // constants with define() like
             // define('TEST_DEFINE_CONSTANT', false);
-            return $this->resolveExpressionNodeToType($node->argumentExpressionList->children[2]->expression);
+            return $this->resolveExpressionNodeToType($node->argumentExpressionList->children[2]->expression, $scope);
         }
 
         // PARAMETERS
@@ -1078,10 +980,12 @@ public function getTypeFromNode($node)
             //  * @param MyClass $myParam
             //  */
             //  function foo($a)
-            $functionLikeDeclaration = ParserHelpers\getFunctionLikeDeclarationFromParameter($node);
             $variableName = $node->getName();
+            if (isset($scope->variables[$variableName])) {
+                return $scope->variables[$variableName]->type;
+            }
+            $functionLikeDeclaration = ParserHelpers\getFunctionLikeDeclarationFromParameter($node);
             $docBlock = $this->getDocBlock($functionLikeDeclaration);
-
             $parameterDocBlockTag = $this->tryGetDocBlockTagForParameter($docBlock, $variableName);
             if ($parameterDocBlockTag !== null && ($type = $parameterDocBlockTag->getType())) {
                 // Doc block comments supercede all other forms of type inference
@@ -1095,12 +999,12 @@ public function getTypeFromNode($node)
                     // Resolve a string like "bool" to a type object
                     $type = $this->typeResolver->resolve($node->typeDeclaration->getText($node->getFileContents()));
                 } else {
-                    $type = new Types\Object_(new Fqsen('\\' . (string)$node->typeDeclaration->getResolvedName()));
+                    $type = new Types\Object_(new Fqsen('\\' . $scope->getResolvedName($node->typeDeclaration)));
                 }
             }
             // function foo($a = 3)
             if ($node->default !== null) {
-                $defaultType = $this->resolveExpressionNodeToType($node->default);
+                $defaultType = $this->resolveExpressionNodeToType($node->default, $scope);
                 if (isset($type) && !is_a($type, get_class($defaultType))) {
                     // TODO - verify it is worth creating a compound type
                     return new Types\Compound([$type, $defaultType]);
@@ -1121,15 +1025,11 @@ public function getTypeFromNode($node)
             if (
                 $docBlock !== null
                 && !empty($returnTags = $docBlock->getTagsByName('return'))
-                && $returnTags[0]->getType() !== null
+                && ($returnType = $returnTags[0]->getType()) !== null
             ) {
                 // Use @return tag
-                $returnType = $returnTags[0]->getType();
-                if ($returnType instanceof Types\Self_) {
-                    $selfType = $this->getContainingClassType($node);
-                    if ($selfType) {
-                        return $selfType;
-                    }
+                if ($returnType instanceof Types\Self_ && null !== $scope->currentSelf) {
+                    return $scope->currentSelf->type;
                 }
                 return $returnType;
             }
@@ -1138,13 +1038,10 @@ public function getTypeFromNode($node)
                 if ($node->returnType instanceof PhpParser\Token) {
                     // Resolve a string like "bool" to a type object
                     return $this->typeResolver->resolve($node->returnType->getText($node->getFileContents()));
-                } elseif ($node->returnType->getResolvedName() === 'self') {
-                    $selfType = $this->getContainingClassType($node);
-                    if ($selfType !== null) {
-                        return $selfType;
-                    }
+                } else if ($scope->currentSelf !== null && $scope->getResolvedName($node->returnType) === 'self') {
+                    return $scope->currentSelf->type;
                 }
-                return new Types\Object_(new Fqsen('\\' . (string)$node->returnType->getResolvedName()));
+                return new Types\Object_(new Fqsen('\\' . $scope->getResolvedName($node->returnType)));
             }
             // Unknown return type
             return new Types\Mixed_;
@@ -1153,7 +1050,7 @@ public function getTypeFromNode($node)
         // FOREACH KEY/VARIABLE
         if ($node instanceof Node\ForeachKey || $node->parent instanceof Node\ForeachKey) {
             $foreach = $node->getFirstAncestor(Node\Statement\ForeachStatement::class);
-            $collectionType = $this->resolveExpressionNodeToType($foreach->forEachCollectionName);
+            $collectionType = $this->resolveExpressionNodeToType($foreach->forEachCollectionName, $scope);
             if ($collectionType instanceof Types\Array_) {
                 return $collectionType->getKeyType();
             }
@@ -1165,7 +1062,7 @@ public function getTypeFromNode($node)
             || ($node instanceof Node\Expression\Variable && $node->parent instanceof Node\ForeachValue)
         ) {
             $foreach = $node->getFirstAncestor(Node\Statement\ForeachStatement::class);
-            $collectionType = $this->resolveExpressionNodeToType($foreach->forEachCollectionName);
+            $collectionType = $this->resolveExpressionNodeToType($foreach->forEachCollectionName, $scope);
             if ($collectionType instanceof Types\Array_) {
                 return $collectionType->getValueType();
             }
@@ -1196,12 +1093,12 @@ public function getTypeFromNode($node)
             if ($declarationNode instanceof Node\PropertyDeclaration) {
                 // TODO should have default
                 if (isset($node->parent->rightOperand)) {
-                    return $this->resolveExpressionNodeToType($node->parent->rightOperand);
+                    return $this->resolveExpressionNodeToType($node->parent->rightOperand, $scope);
                 }
             } else if ($node instanceof Node\ConstElement) {
-                return $this->resolveExpressionNodeToType($node->assignment);
+                return $this->resolveExpressionNodeToType($node->assignment, $scope);
             } else if ($node instanceof Node\Expression\AssignmentExpression) {
-                return $this->resolveExpressionNodeToType($node->rightOperand);
+                return $this->resolveExpressionNodeToType($node->rightOperand, $scope);
             }
             // TODO: read @property tags of class
             // TODO: Try to infer the type from default value / constant value
@@ -1218,9 +1115,10 @@ public function getTypeFromNode($node)
      * Returns null if the node does not declare any symbol that can be referenced by an FQN
      *
      * @param Node $node
+     * @param Scope|null $scope Scope at the point of Node. If not provided, will be computed from $node.
      * @return string|null
      */
-    public static function getDefinedFqn($node)
+    public function getDefinedFqn($node, Scope $scope = null)
     {
         $parent = $node->parent;
         // Anonymous classes don't count as a definition
@@ -1251,6 +1149,10 @@ public static function getDefinedFqn($node)
             return $name === "" ? null : $name . '()';
         }
 
+        if ($scope === null) {
+            $scope = getScopeAtNode($this, $node);
+        }
+
         // INPUT                        OUTPUT
         // namespace A\B;
         // class C {
@@ -1259,18 +1161,18 @@ public static function getDefinedFqn($node)
         // }
         if ($node instanceof Node\MethodDeclaration) {
             // Class method: use ClassName->methodName() as name
-            $class = $node->getFirstAncestor(
-                Node\Expression\ObjectCreationExpression::class,
-                PhpParser\ClassLike::class
-            );
-            if (!isset($class->name)) {
+            if ($scope->currentSelf === null) {
+                return;
+            }
+            $className = substr((string)$scope->currentSelf->type->getFqsen(), 1);
+            if (!$className) {
                 // Ignore anonymous classes
                 return null;
             }
             if ($node->isStatic()) {
-                return (string)$class->getNamespacedName() . '::' . $node->getName() . '()';
+                return $className . '::' . $node->getName() . '()';
             } else {
-                return (string)$class->getNamespacedName() . '->' . $node->getName() . '()';
+                return $className . '->' . $node->getName() . '()';
             }
         }
 
@@ -1282,20 +1184,18 @@ public static function getDefinedFqn($node)
         // }
         if (
             ($propertyDeclaration = ParserHelpers\tryGetPropertyDeclaration($node)) !== null &&
-            ($classDeclaration =
-                $node->getFirstAncestor(
-                    Node\Expression\ObjectCreationExpression::class,
-                    PhpParser\ClassLike::class
-                )
-            ) !== null && isset($classDeclaration->name)) {
+            $scope->currentSelf !== null &&
+            isset($scope->currentSelf->definitionNode->name)
+        ) {
+            $className = substr((string)$scope->currentSelf->type->getFqsen(), 1);
             $name = $node->getName();
             if ($propertyDeclaration->isStatic()) {
                 // Static Property: use ClassName::$propertyName as name
-                return (string)$classDeclaration->getNamespacedName() . '::$' . $name;
+                return $className . '::$' . $name;
             }
 
             // Instance Property: use ClassName->propertyName as name
-            return (string)$classDeclaration->getNamespacedName() . '->' . $name;
+            return $className . '->' . $name;
         }
 
         // INPUT                        OUTPUT
@@ -1310,16 +1210,13 @@ public static function getDefinedFqn($node)
                 return (string)$node->getNamespacedName();
             }
 
-            // Class constant: use ClassName::CONSTANT_NAME as name
-            $classDeclaration = $constDeclaration->getFirstAncestor(
-                Node\Expression\ObjectCreationExpression::class,
-                PhpParser\ClassLike::class
-            );
-
-            if (!isset($classDeclaration->name)) {
+            if ($scope->currentSelf === null || !isset($scope->currentSelf->definitionNode->name)
+            ) {
+                // Class constant: use ClassName::CONSTANT_NAME as name
                 return null;
             }
-            return (string)$classDeclaration->getNamespacedName() . '::' . $node->getName();
+            $className = substr((string)$scope->currentSelf->type->getFqsen(), 1);
+            return $className . '::' . $node->getName();
         }
 
         if (ParserHelpers\isConstDefineExpression($node)) {
diff --git a/src/Scope/GetScopeAtNode.php b/src/Scope/GetScopeAtNode.php
new file mode 100644
index 00000000..d7dc2da3
--- /dev/null
+++ b/src/Scope/GetScopeAtNode.php
@@ -0,0 +1,57 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer\Scope;
+
+use LanguageServer\DefinitionResolver;
+use Microsoft\PhpParser\ClassLike;
+use Microsoft\PhpParser\Node;
+use Microsoft\PhpParser\Node\SourceFileNode;
+use Microsoft\PhpParser\Node\Statement\FunctionDeclaration;
+
+/**
+ * Returns the scope at the start of $node.
+ */
+function getScopeAtNode(DefinitionResolver $definitionResolver, Node $targetNode): Scope
+{
+    /** @var SourceFileNode The source file. */
+    $sourceFile = $targetNode->getRoot();
+    /** @var FunctionDeclaration|null The first function declaration met, excluding anonymous functions. */
+    $nearestFunctionDeclarationParent = $targetNode->getFirstAncestor(FunctionDeclaration::class);
+    /** @var ClassLike|null The first class met. */
+    $nearestClassLike = $targetNode->getFirstAncestor(ClassLike::class);
+
+    $traverser = new TreeTraverser($definitionResolver);
+    $resultScope = null;
+    $traverser->traverse(
+        $sourceFile,
+        function (
+            $nodeOrToken,
+            Scope $scope
+        ) use (
+            &$resultScope,
+            $targetNode,
+            $nearestFunctionDeclarationParent,
+            $nearestClassLike
+        ): int {
+            if ($nodeOrToken instanceof FunctionDeclaration && $nodeOrToken !== $nearestFunctionDeclarationParent) {
+                // Skip function declarations which do not contain the target node.
+                return TreeTraverser::ACTION_SKIP;
+            }
+
+            if ($nodeOrToken instanceof ClassLike && $nodeOrToken !== $nearestClassLike) {
+                // Skip classes which are not the nearest parent class.
+                return TreeTraverser::ACTION_SKIP;
+            }
+
+            if ($nodeOrToken === $targetNode) {
+                $resultScope = $scope;
+                return TreeTraverser::ACTION_END;
+            }
+
+            return TreeTraverser::ACTION_CONTINUE;
+        }
+    );
+
+    return $resultScope;
+}
diff --git a/src/Scope/Scope.php b/src/Scope/Scope.php
new file mode 100644
index 00000000..f3ad37de
--- /dev/null
+++ b/src/Scope/Scope.php
@@ -0,0 +1,45 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer\Scope;
+
+use Microsoft\PhpParser\Node\QualifiedName;
+
+/**
+ * Contains information about variables at a point.
+ */
+class Scope
+{
+    /**
+     * @var Variable|null "Variable" representing this/self
+     */
+    public $currentSelf;
+
+    /**
+     * @var Variable[] Variables in the scope, indexed by their names (without the dollar) and excluding $this.
+     */
+    public $variables = [];
+
+    /**
+     * @var string[] Maps unqualified names to fully qualified names.
+     */
+    public $resolvedNameCache = [];
+
+    public function clearResolvedNameCache()
+    {
+        $this->resolvedNameCache = [];
+    }
+
+    /**
+     * @return string|null
+     */
+    public function getResolvedName(QualifiedName $name)
+    {
+        $nameStr = (string)$name;
+        if (array_key_exists($nameStr, $this->resolvedNameCache)) {
+            return $this->resolvedNameCache[$nameStr];
+        }
+        $resolvedName = $name->getResolvedName();
+        return $this->resolvedNameCache[$nameStr] = $resolvedName ? (string)$resolvedName : null;
+    }
+}
diff --git a/src/Scope/TraversingEndedException.php b/src/Scope/TraversingEndedException.php
new file mode 100644
index 00000000..10951a51
--- /dev/null
+++ b/src/Scope/TraversingEndedException.php
@@ -0,0 +1,8 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer\Scope;
+
+class TraversingEndedException extends \Exception
+{
+}
diff --git a/src/Scope/TreeTraverser.php b/src/Scope/TreeTraverser.php
new file mode 100644
index 00000000..bafc4768
--- /dev/null
+++ b/src/Scope/TreeTraverser.php
@@ -0,0 +1,193 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer\Scope;
+
+use LanguageServer\DefinitionResolver;
+use Microsoft\PhpParser\ClassLike;
+use Microsoft\PhpParser\FunctionLike;
+use Microsoft\PhpParser\MissingToken;
+use Microsoft\PhpParser\Node;
+use Microsoft\PhpParser\Node\Expression;
+use Microsoft\PhpParser\Token;
+use Microsoft\PhpParser\TokenKind;
+use phpDocumentor\Reflection\Fqsen;
+use phpDocumentor\Reflection\Types;
+
+/**
+ * Traversers AST with Scope information.
+ */
+class TreeTraverser
+{
+    /**
+     * Descend into the node being parsed. The default action.
+     */
+    const ACTION_CONTINUE = 0;
+
+    /**
+     * Do not descend into the node being parsed. Traversal will continue after the node.
+     */
+    const ACTION_SKIP = 1;
+
+    /**
+     * Stop parsing entirely. `traverse` will return immediately.
+     */
+    const ACTION_END = 2;
+
+    private $definitionResolver;
+
+    public function __construct(DefinitionResolver $definitionResolver)
+    {
+        $this->definitionResolver = $definitionResolver;
+    }
+
+    /**
+     * Calls visitor for each node or token with the node or token and the scope at that point.
+     *
+     * @param Node|Token $node Node or token to traverse.
+     * @param callable $visitor function(Node|Token, Scope). May return one of the ACTION_ constants.
+     */
+    public function traverse($node, callable $visitor)
+    {
+        try {
+            $this->traverseRecursive($node, $visitor, new Scope);
+        } catch (TraversingEndedException $e) {
+        }
+    }
+
+    private function traverseRecursive($node, callable $visitor, Scope $scope)
+    {
+        $visitorResult = $visitor($node, $scope);
+        if ($visitorResult === self::ACTION_END) {
+            throw new TraversingEndedException;
+        }
+        if (!$node instanceof Node || $visitorResult === self::ACTION_SKIP) {
+            return;
+        }
+
+        foreach ($node::CHILD_NAMES as $childName) {
+            $child = $node->$childName;
+
+            if ($child === null) {
+                continue;
+            }
+
+            $childScope = $this->getScopeInChild($node, $childName, $scope);
+
+            if (\is_array($child)) {
+                foreach ($child as $actualChild) {
+                    $this->traverseRecursive($actualChild, $visitor, $childScope);
+                }
+            } else {
+                $this->traverseRecursive($child, $visitor, $childScope);
+            }
+        }
+
+        $this->modifyScopeAfterNode($node, $scope);
+    }
+
+    /**
+     * E.g. in function body, gets the scope consisting of parameters and used names.
+     *
+     * @return Scope
+     *   The new scope, or the same scope instance if the child does not has its own scope.
+     */
+    private function getScopeInChild(Node $node, string $childName, Scope $scope): Scope
+    {
+        if ($node instanceof FunctionLike
+            && $childName === 'compoundStatementOrSemicolon'
+            && $node->compoundStatementOrSemicolon instanceof Node\Statement\CompoundStatementNode
+        ) {
+            $childScope = new Scope;
+            $childScope->currentSelf = $scope->currentSelf;
+            $childScope->resolvedNameCache = $scope->resolvedNameCache;
+            $isStatic = $node instanceof Node\MethodDeclaration ? $node->isStatic() : !empty($node->staticModifier);
+            if (!$isStatic && isset($scope->variables['this'])) {
+                $childScope->variables['this'] = $scope->variables['this'];
+            }
+
+            if ($node->parameters !== null) {
+                foreach ($node->parameters->getElements() as $param) {
+                    $childScope->variables[$param->getName()] = new Variable(
+                        // Pass the child scope when getting parameters - the outer scope cannot affect
+                        // any parameters of the function declaration.
+                        $this->definitionResolver->getTypeFromNode($param, $childScope),
+                        $param
+                    );
+                }
+            }
+
+            if ($node instanceof Node\Expression\AnonymousFunctionCreationExpression
+                && $node->anonymousFunctionUseClause !== null
+                && $node->anonymousFunctionUseClause->useVariableNameList !== null) {
+                foreach ($node->anonymousFunctionUseClause->useVariableNameList->getElements() as $use) {
+                    $name = $use->getName();
+                    // Used variable in an anonymous function. Same as parent type, Mixed if not defined in parent.
+                    $childScope->variables[$name] = new Variable(
+                        isset($scope->variables[$name]) ? $scope->variables[$name]->type : new Types\Mixed_,
+                        $use
+                    );
+                }
+            }
+
+            return $childScope;
+        }
+
+        if ($node instanceof ClassLike
+            && (in_array($childName, ['classMembers', 'interfaceMembers','traitMembers'], true))
+        ) {
+            $childScope = new Scope;
+            $childScope->resolvedNameCache = $scope->resolvedNameCache;
+            $thisVar = new Variable(
+                new Types\Object_(new Fqsen('\\' . (string)$node->getNamespacedName())),
+                $node
+            );
+            $childScope->variables['this'] = $thisVar;
+            $childScope->currentSelf = $thisVar;
+            return $childScope;
+        }
+
+        return $scope;
+    }
+
+    /**
+     * Adds any variables declared by $node to $scope.
+     *
+     * Note that functions like extract and parse_str are not handled.
+     *
+     * @return void
+     */
+    private function modifyScopeAfterNode(Node $node, Scope $scope)
+    {
+        if ($node instanceof Expression\AssignmentExpression) {
+            if ($node->operator->kind !== TokenKind::EqualsToken
+                || !$node->leftOperand instanceof Expression\Variable
+                || $node->rightOperand === null
+                || $node->rightOperand instanceof MissingToken
+            ) {
+                return;
+            }
+            $scope->variables[$node->leftOperand->getName()] = new Variable(
+                $this->definitionResolver->resolveExpressionNodeToType($node->rightOperand, $scope),
+                $node
+            );
+        } else if (($node instanceof Node\ForeachValue || $node instanceof Node\ForeachKey)
+            && $node->expression instanceof Node\Expression\Variable
+        ) {
+            $scope->variables[$node->expression->getName()] = new Variable(
+                $this->definitionResolver->getTypeFromNode($node, $scope),
+                $node
+            );
+        } else if ($node instanceof Node\Statement\NamespaceDefinition) {
+            // After a new namespace A\B;, the current alias table is flushed.
+            $scope->clearResolvedNameCache();
+        }
+
+
+        // TODO: Handle use (&$x) when $x is not defined in scope.
+        // TODO: Handle list(...) = $a; and [...] = $a;
+        // TODO: Handle foreach ($a as list(...)) and foreach ($a as [...])
+        // TODO: Handle unset($var)
+        // TODO: Handle global $var
+    }
+}
diff --git a/src/Scope/Variable.php b/src/Scope/Variable.php
new file mode 100644
index 00000000..19939714
--- /dev/null
+++ b/src/Scope/Variable.php
@@ -0,0 +1,29 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer\Scope;
+
+use phpDocumentor\Reflection\Type;
+use Microsoft\PhpParser\Node;
+
+/**
+ * Contains information about a single variable.
+ */
+class Variable
+{
+    /**
+     * @var Type
+     */
+    public $type;
+
+    /**
+     * @var Node
+     */
+    public $definitionNode;
+
+    public function __construct(Type $type, Node $definitionNode)
+    {
+        $this->type = $type;
+        $this->definitionNode = $definitionNode;
+    }
+}
diff --git a/src/Server/TextDocument.php b/src/Server/TextDocument.php
index 371ad361..b5cbedc2 100644
--- a/src/Server/TextDocument.php
+++ b/src/Server/TextDocument.php
@@ -214,7 +214,7 @@ public function references(
                 }
             } else {
                 // Definition with a global FQN
-                $fqn = DefinitionResolver::getDefinedFqn($node);
+                $fqn = $this->definitionResolver->getDefinedFqn($node);
 
                 // Wait until indexing finished
                 if (!$this->index->isComplete()) {
@@ -277,7 +277,7 @@ public function definition(TextDocumentIdentifier $textDocument, Position $posit
                 return [];
             }
             // Handle definition nodes
-            $fqn = DefinitionResolver::getDefinedFqn($node);
+            $fqn = $this->definitionResolver->getDefinedFqn($node);
             while (true) {
                 if ($fqn) {
                     $def = $this->index->getDefinition($fqn);
@@ -318,7 +318,7 @@ public function hover(TextDocumentIdentifier $textDocument, Position $position):
             if ($node === null) {
                 return new Hover([]);
             }
-            $definedFqn = DefinitionResolver::getDefinedFqn($node);
+            $definedFqn = $this->definitionResolver->getDefinedFqn($node);
             while (true) {
                 if ($definedFqn) {
                     // Support hover for definitions
@@ -392,7 +392,7 @@ public function xdefinition(TextDocumentIdentifier $textDocument, Position $posi
                 return [];
             }
             // Handle definition nodes
-            $fqn = DefinitionResolver::getDefinedFqn($node);
+            $fqn = $this->definitionResolver->getDefinedFqn($node);
             while (true) {
                 if ($fqn) {
                     $def = $this->index->getDefinition($fqn);
diff --git a/src/SignatureHelpProvider.php b/src/SignatureHelpProvider.php
index aba02b4d..92728252 100644
--- a/src/SignatureHelpProvider.php
+++ b/src/SignatureHelpProvider.php
@@ -126,7 +126,7 @@ private function getCallingInfo(Node $node)
             }
 
             // Now find the definition of the call
-            $fqn = $fqn ?: DefinitionResolver::getDefinedFqn($callingNode);
+            $fqn = $fqn ?: $this->definitionResolver->getDefinedFqn($callingNode);
             while (true) {
                 if ($fqn) {
                     $def = $this->index->getDefinition($fqn);
diff --git a/src/SignatureInformationFactory.php b/src/SignatureInformationFactory.php
index 6b8a1f04..f6fa5a01 100644
--- a/src/SignatureInformationFactory.php
+++ b/src/SignatureInformationFactory.php
@@ -4,6 +4,7 @@
 namespace LanguageServer;
 
 use LanguageServer\Protocol\{SignatureInformation, ParameterInformation};
+use LanguageServer\Scope\Scope;
 use Microsoft\PhpParser\FunctionLike;
 
 class SignatureInformationFactory
@@ -28,9 +29,9 @@ public function __construct(DefinitionResolver $definitionResolver)
      *
      * @return SignatureInformation
      */
-    public function create(FunctionLike $node): SignatureInformation
+    public function create(FunctionLike $node, Scope $scope = null): SignatureInformation
     {
-        $params = $this->createParameters($node);
+        $params = $this->createParameters($node, $scope);
         $label = $this->createLabel($params);
         return new SignatureInformation(
             $label,
@@ -46,12 +47,12 @@ public function create(FunctionLike $node): SignatureInformation
      *
      * @return ParameterInformation[]
      */
-    private function createParameters(FunctionLike $node): array
+    private function createParameters(FunctionLike $node, Scope $scope = null): array
     {
         $params = [];
         if ($node->parameters) {
             foreach ($node->parameters->getElements() as $element) {
-                $param = (string) $this->definitionResolver->getTypeFromNode($element);
+                $param = (string) $this->definitionResolver->getTypeFromNode($element, $scope);
                 $param .= ' ';
                 if ($element->dotDotDotToken) {
                     $param .= '...';
diff --git a/src/TreeAnalyzer.php b/src/TreeAnalyzer.php
index 465f5bb1..0ceda734 100644
--- a/src/TreeAnalyzer.php
+++ b/src/TreeAnalyzer.php
@@ -5,6 +5,8 @@
 
 use LanguageServer\Protocol\{Diagnostic, DiagnosticSeverity, Range, Position, TextEdit};
 use LanguageServer\Index\Index;
+use LanguageServer\Scope\Scope;
+use LanguageServer\Scope\TreeTraverser;
 use phpDocumentor\Reflection\DocBlockFactory;
 use Sabre\Uri;
 use Microsoft\PhpParser;
@@ -56,7 +58,16 @@ public function __construct(PhpParser\Parser $parser, string $content, DocBlockF
 
         // TODO - docblock errors
 
-        $this->traverse($this->sourceFileNode);
+        $traverser = new TreeTraverser($definitionResolver);
+        $traverser->traverse(
+            $this->sourceFileNode,
+            function ($nodeOrToken, Scope $scope) {
+                $this->collectDiagnostics($nodeOrToken, $scope);
+                if ($nodeOrToken instanceof Node) {
+                    $this->collectDefinitionsAndReferences($nodeOrToken, $scope);
+                }
+            }
+        );
     }
 
     /**
@@ -66,7 +77,7 @@ public function __construct(PhpParser\Parser $parser, string $content, DocBlockF
      * @param Node|Token $node
      * @return void
      */
-    private function collectDiagnostics($node)
+    private function collectDiagnostics($node, Scope $scope)
     {
         // Get errors from the parser.
         if (($error = PhpParser\DiagnosticsProvider::checkDiagnostics($node)) !== null) {
@@ -95,52 +106,17 @@ private function collectDiagnostics($node)
         }
 
         // Check for invalid usage of $this.
-        if ($node instanceof Node\Expression\Variable && $node->getName() === 'this') {
-            // Find the first ancestor that's a class method. Return an error
-            // if there is none, or if the method is static.
-            $method = $node->getFirstAncestor(Node\MethodDeclaration::class);
-            if ($method && $method->isStatic()) {
-                $this->diagnostics[] = new Diagnostic(
-                    "\$this can not be used in static methods.",
-                    Range::fromNode($node),
-                    null,
-                    DiagnosticSeverity::ERROR,
-                    'php'
-                );
-            }
-        }
-    }
-
-    /**
-     * Recursive AST traversal to collect definitions/references and diagnostics
-     *
-     * @param Node|Token $currentNode The node/token to process
-     */
-    private function traverse($currentNode)
-    {
-        $this->collectDiagnostics($currentNode);
-
-        // Only update/descend into Nodes, Tokens are leaves
-        if ($currentNode instanceof Node) {
-            $this->collectDefinitionsAndReferences($currentNode);
-
-            foreach ($currentNode::CHILD_NAMES as $name) {
-                $child = $currentNode->$name;
-
-                if ($child === null) {
-                    continue;
-                }
-
-                if (\is_array($child)) {
-                    foreach ($child as $actualChild) {
-                        if ($actualChild !== null) {
-                            $this->traverse($actualChild);
-                        }
-                    }
-                } else {
-                    $this->traverse($child);
-                }
-            }
+        if ($node instanceof Node\Expression\Variable &&
+            !isset($scope->variables['this']) &&
+            $node->getName() === 'this'
+        ) {
+            $this->diagnostics[] = new Diagnostic(
+                "\$this can not be used in static methods.",
+                Range::fromNode($node),
+                null,
+                DiagnosticSeverity::ERROR,
+                'php'
+            );
         }
     }
 
@@ -149,13 +125,13 @@ private function traverse($currentNode)
      *
      * @param Node $node
      */
-    private function collectDefinitionsAndReferences(Node $node)
+    private function collectDefinitionsAndReferences(Node $node, Scope $scope)
     {
-        $fqn = ($this->definitionResolver)::getDefinedFqn($node);
+        $fqn = $this->definitionResolver->getDefinedFqn($node, $scope);
         // Only index definitions with an FQN (no variables)
         if ($fqn !== null) {
             $this->definitionNodes[$fqn] = $node;
-            $this->definitions[$fqn] = $this->definitionResolver->createDefinitionFromNode($node, $fqn);
+            $this->definitions[$fqn] = $this->definitionResolver->createDefinitionFromNode($node, $fqn, $scope);
         } else {
 
             $parent = $node->parent;
@@ -165,7 +141,7 @@ private function collectDefinitionsAndReferences(Node $node)
                     ($node instanceof Node\Expression\ScopedPropertyAccessExpression ||
                     $node instanceof Node\Expression\MemberAccessExpression)
                     && !(
-                        $node->parent instanceof Node\Expression\CallExpression ||
+                        $parent instanceof Node\Expression\CallExpression ||
                         $node->memberName instanceof PhpParser\Token
                     ))
                 || ($parent instanceof Node\Statement\NamespaceDefinition && $parent->name !== null && $parent->name->getStart() === $node->getStart())
@@ -173,7 +149,7 @@ private function collectDefinitionsAndReferences(Node $node)
                 return;
             }
 
-            $fqn = $this->definitionResolver->resolveReferenceNodeToFqn($node);
+            $fqn = $this->definitionResolver->resolveReferenceNodeToFqn($node, $scope);
             if (!$fqn) {
                 return;
             }
@@ -181,21 +157,22 @@ private function collectDefinitionsAndReferences(Node $node)
             if ($fqn === 'self' || $fqn === 'static') {
                 // Resolve self and static keywords to the containing class
                 // (This is not 100% correct for static but better than nothing)
-                $classNode = $node->getFirstAncestor(Node\Statement\ClassDeclaration::class);
-                if (!$classNode) {
-                    return;
-                }
-                $fqn = (string)$classNode->getNamespacedName();
-                if (!$fqn) {
+                if (!$scope->currentSelf) {
                     return;
                 }
+                $fqn = substr((string)$scope->currentSelf->type->getFqsen(), 1);
             } else if ($fqn === 'parent') {
                 // Resolve parent keyword to the base class FQN
-                $classNode = $node->getFirstAncestor(Node\Statement\ClassDeclaration::class);
-                if (!$classNode || !$classNode->classBaseClause || !$classNode->classBaseClause->baseClass) {
+                if ($scope->currentSelf === null) {
+                    return;
+                }
+                $classNode = $scope->currentSelf->definitionNode;
+                if (empty($classNode->classBaseClause)
+                    || !$classNode->classBaseClause->baseClass instanceof Node\QualifiedName
+                ) {
                     return;
                 }
-                $fqn = (string)$classNode->classBaseClause->baseClass->getResolvedName();
+                $fqn = $scope->getResolvedName($classNode->classBaseClause->baseClass);
                 if (!$fqn) {
                     return;
                 }
diff --git a/tests/Validation/cases/constantsInFunctionParamDefault.php.expected.json b/tests/Validation/cases/constantsInFunctionParamDefault.php.expected.json
index 0a34c36e..468ccc94 100644
--- a/tests/Validation/cases/constantsInFunctionParamDefault.php.expected.json
+++ b/tests/Validation/cases/constantsInFunctionParamDefault.php.expected.json
@@ -45,11 +45,11 @@
             "declarationLine": "function b ($a = MY_CONSTANT);",
             "documentation": null,
             "signatureInformation": {
-                "label": "(\\MY_CONSTANT $a = MY_CONSTANT)",
+                "label": "(mixed $a = MY_CONSTANT)",
                 "documentation": null,
                 "parameters": [
                     {
-                        "label": "\\MY_CONSTANT $a = MY_CONSTANT",
+                        "label": "mixed $a = MY_CONSTANT",
                         "documentation": null
                     }
                 ]
diff --git a/tests/Validation/cases/verifyFqsenOnClassProperty.php.expected.json b/tests/Validation/cases/verifyFqsenOnClassProperty.php.expected.json
index a434cf25..314596b1 100644
--- a/tests/Validation/cases/verifyFqsenOnClassProperty.php.expected.json
+++ b/tests/Validation/cases/verifyFqsenOnClassProperty.php.expected.json
@@ -43,7 +43,7 @@
                 },
                 "containerName": "Foo"
             },
-            "type__tostring": "\\",
+            "type__tostring": "mixed",
             "type": {},
             "declarationLine": "protected $bar;",
             "documentation": null,