diff --git a/composer.json b/composer.json
index 268a989..b29c1ee 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,7 @@
         "phpdocumentor/reflection-docblock": "^3.0",
         "sabre/event": "^5.0",
         "felixfbecker/advanced-json-rpc": "^2.0",
-        "squizlabs/php_codesniffer" : "^3.0",
+        "squizlabs/php_codesniffer" : "3.0.0RC3",
         "netresearch/jsonmapper": "^1.0",
         "webmozart/path-util": "^2.3",
         "webmozart/glob": "^4.1",
diff --git a/src/DefinitionResolver.php b/src/DefinitionResolver.php
index 3a8393a..ec295a5 100644
--- a/src/DefinitionResolver.php
+++ b/src/DefinitionResolver.php
@@ -12,7 +12,7 @@ use LanguageServer\Index\ReadableIndex;
 class DefinitionResolver
 {
     /**
-     * @var \LanguageServer\Index
+     * @var \LanguageServer\Index\ReadableIndex
      */
     private $index;
 
@@ -48,6 +48,7 @@ class DefinitionResolver
             // Properties and constants can have multiple declarations
             // Use the parent node (that includes the modifiers), but only render the requested declaration
             $child = $node;
+            /** @var Node */
             $node = $node->getAttribute('parentNode');
             $defLine = clone $node;
             $defLine->props = [$child];
@@ -363,7 +364,7 @@ class DefinitionResolver
      * Returns the assignment or parameter node where a variable was defined
      *
      * @param Node\Expr\Variable|Node\Expr\ClosureUse $var The variable access
-     * @return Node\Expr\Assign|Node\Param|Node\Expr\ClosureUse|null
+     * @return Node\Expr\Assign|Node\Expr\AssignOp|Node\Param|Node\Expr\ClosureUse|null
      */
     public static function resolveVariableToNode(Node\Expr $var)
     {
@@ -415,7 +416,7 @@ class DefinitionResolver
      * If the type could not be resolved, returns Types\Mixed.
      *
      * @param \PhpParser\Node\Expr $expr
-     * @return \phpDocumentor\Type
+     * @return \phpDocumentor\Reflection\Type
      */
     public function resolveExpressionNodeToType(Node\Expr $expr): Type
     {
@@ -539,7 +540,7 @@ class DefinitionResolver
             ]);
         }
         if (
-            $expr instanceof Node\Expr\InstanceOf_
+            $expr instanceof Node\Expr\Instanceof_
             || $expr instanceof Node\Expr\Cast\Bool_
             || $expr instanceof Node\Expr\BooleanNot
             || $expr instanceof Node\Expr\Empty_
@@ -559,19 +560,18 @@ class DefinitionResolver
             return new Types\Boolean;
         }
         if (
-            $expr instanceof Node\Expr\Concat
-            || $expr instanceof Node\Expr\Cast\String_
+            $expr instanceof Node\Expr\Cast\String_
             || $expr instanceof Node\Expr\BinaryOp\Concat
             || $expr instanceof Node\Expr\AssignOp\Concat
-            || $expr instanceof Node\Expr\Scalar\String_
-            || $expr instanceof Node\Expr\Scalar\Encapsed
-            || $expr instanceof Node\Expr\Scalar\EncapsedStringPart
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Class_
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Dir
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Function_
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Method
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Namespace_
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Trait_
+            || $expr instanceof Node\Scalar\String_
+            || $expr instanceof Node\Scalar\Encapsed
+            || $expr instanceof Node\Scalar\EncapsedStringPart
+            || $expr instanceof Node\Scalar\MagicConst\Class_
+            || $expr instanceof Node\Scalar\MagicConst\Dir
+            || $expr instanceof Node\Scalar\MagicConst\Function_
+            || $expr instanceof Node\Scalar\MagicConst\Method
+            || $expr instanceof Node\Scalar\MagicConst\Namespace_
+            || $expr instanceof Node\Scalar\MagicConst\Trait_
         ) {
             return new Types\String_;
         }
@@ -580,23 +580,35 @@ class DefinitionResolver
             || $expr instanceof Node\Expr\BinaryOp\Plus
             || $expr instanceof Node\Expr\BinaryOp\Pow
             || $expr instanceof Node\Expr\BinaryOp\Mul
-            || $expr instanceof Node\Expr\AssignOp\Minus
-            || $expr instanceof Node\Expr\AssignOp\Plus
-            || $expr instanceof Node\Expr\AssignOp\Pow
-            || $expr instanceof Node\Expr\AssignOp\Mul
         ) {
             if (
-                $this->resolveExpressionNodeToType($expr->left) instanceof Types\Integer_
-                && $this->resolveExpressionNodeToType($expr->right) instanceof Types\Integer_
+                $this->resolveExpressionNodeToType($expr->left) instanceof Types\Integer
+                && $this->resolveExpressionNodeToType($expr->right) instanceof Types\Integer
             ) {
                 return new Types\Integer;
             }
             return new Types\Float_;
         }
+
+        if (
+            $expr instanceof Node\Expr\AssignOp\Minus
+            || $expr instanceof Node\Expr\AssignOp\Plus
+            || $expr instanceof Node\Expr\AssignOp\Pow
+            || $expr instanceof Node\Expr\AssignOp\Mul
+        ) {
+            if (
+                $this->resolveExpressionNodeToType($expr->var) instanceof Types\Integer
+                && $this->resolveExpressionNodeToType($expr->expr) instanceof Types\Integer
+            ) {
+                return new Types\Integer;
+            }
+            return new Types\Float_;
+        }
+
         if (
             $expr instanceof Node\Scalar\LNumber
             || $expr instanceof Node\Expr\Cast\Int_
-            || $expr instanceof Node\Expr\Scalar\MagicConst\Line
+            || $expr instanceof Node\Scalar\MagicConst\Line
             || $expr instanceof Node\Expr\BinaryOp\Spaceship
             || $expr instanceof Node\Expr\BinaryOp\BitwiseAnd
             || $expr instanceof Node\Expr\BinaryOp\BitwiseOr
@@ -606,7 +618,7 @@ class DefinitionResolver
         }
         if (
             $expr instanceof Node\Expr\BinaryOp\Div
-            || $expr instanceof Node\Expr\DNumber
+            || $expr instanceof Node\Scalar\DNumber
             || $expr instanceof Node\Expr\Cast\Double
         ) {
             return new Types\Float_;
@@ -702,7 +714,7 @@ class DefinitionResolver
      * Returns null if the node does not have a type.
      *
      * @param Node $node
-     * @return \phpDocumentor\Type|null
+     * @return \phpDocumentor\Reflection\Type|null
      */
     public function getTypeFromNode(Node $node)
     {
@@ -720,6 +732,7 @@ class DefinitionResolver
                     }
                 }
             }
+            $type = null;
             if ($node->type !== null) {
                 // Use PHP7 return type hint
                 if (is_string($node->type)) {
@@ -792,7 +805,7 @@ class DefinitionResolver
                 }
             } else if ($node instanceof Node\Const_) {
                 return $this->resolveExpressionNodeToType($node->value);
-            } else if ($node instanceof Node\Expr\Assign || $node instanceof Node\Expr\AssignOp) {
+            } else {
                 return $this->resolveExpressionNodeToType($node);
             }
             // TODO: read @property tags of class
diff --git a/src/LanguageServer.php b/src/LanguageServer.php
index 62b8400..6eb68e4 100644
--- a/src/LanguageServer.php
+++ b/src/LanguageServer.php
@@ -256,6 +256,7 @@ class LanguageServer extends AdvancedJsonRpc\Dispatcher
             }
             if ($this->workspace === null) {
                 $this->workspace = new Server\Workspace(
+                    $this->client,
                     $this->projectIndex,
                     $dependenciesIndex,
                     $sourceIndex,
diff --git a/src/Protocol/FileEvent.php b/src/Protocol/FileEvent.php
index b4ed833..015044d 100644
--- a/src/Protocol/FileEvent.php
+++ b/src/Protocol/FileEvent.php
@@ -20,4 +20,14 @@ class FileEvent
      * @var int
      */
     public $type;
+
+    /**
+     * @param string $uri
+     * @param int $type
+     */
+    public function __construct(string $uri, int $type)
+    {
+        $this->uri = $uri;
+        $this->type = $type;
+    }
 }
diff --git a/src/Server/Workspace.php b/src/Server/Workspace.php
index fb3807d..1f35134 100644
--- a/src/Server/Workspace.php
+++ b/src/Server/Workspace.php
@@ -5,7 +5,15 @@ namespace LanguageServer\Server;
 
 use LanguageServer\{LanguageClient, Project, PhpDocumentLoader, Options, Indexer};
 use LanguageServer\Index\{ProjectIndex, DependenciesIndex, Index};
-use LanguageServer\Protocol\{SymbolInformation, SymbolDescriptor, ReferenceInformation, DependencyReference, Location};
+use LanguageServer\Protocol\{
+    FileChangeType,
+    FileEvent,
+    SymbolInformation,
+    SymbolDescriptor,
+    ReferenceInformation,
+    DependencyReference,
+    Location
+};
 use Sabre\Event\Promise;
 use function Sabre\Event\coroutine;
 use function LanguageServer\{waitForEvent, getPackageName};
@@ -15,6 +23,11 @@ use function LanguageServer\{waitForEvent, getPackageName};
  */
 class Workspace
 {
+    /**
+     * @var LanguageClient
+     */
+    public $client;
+
     /**
      * The symbol index for the workspace
      *
@@ -53,6 +66,7 @@ class Workspace
     public $documentLoader;
 
     /**
+     * @param LanguageClient    $client            LanguageClient instance used to signal updated results
      * @param ProjectIndex      $index             Index that is searched on a workspace/symbol request
      * @param DependenciesIndex $dependenciesIndex Index that is used on a workspace/xreferences request
      * @param DependenciesIndex $sourceIndex       Index that is used on a workspace/xreferences request
@@ -61,8 +75,9 @@ class Workspace
      * @param Indexer           $indexer
      * @param Options            $options
      */
-    public function __construct(ProjectIndex $index, DependenciesIndex $dependenciesIndex, Index $sourceIndex, \stdClass $composerLock = null, PhpDocumentLoader $documentLoader, \stdClass $composerJson = null, Indexer $indexer = null, Options $options = null)
+    public function __construct(LanguageClient $client, ProjectIndex $index, DependenciesIndex $dependenciesIndex, Index $sourceIndex, \stdClass $composerLock = null, PhpDocumentLoader $documentLoader, \stdClass $composerJson = null, Indexer $indexer = null, Options $options = null)
     {
+        $this->client = $client;
         $this->sourceIndex = $sourceIndex;
         $this->index = $index;
         $this->dependenciesIndex = $dependenciesIndex;
@@ -96,6 +111,21 @@ class Workspace
         });
     }
 
+    /**
+     * The watched files notification is sent from the client to the server when the client detects changes to files watched by the language client.
+     *
+     * @param FileEvent[] $changes
+     * @return void
+     */
+    public function didChangeWatchedFiles(array $changes)
+    {
+        foreach ($changes as $change) {
+            if ($change->type === FileChangeType::DELETED) {
+                $this->client->textDocument->publishDiagnostics($change->uri, []);
+            }
+        }
+    }
+
     /**
      * The workspace references request is sent from the client to the server to locate project-wide references to a symbol given its description / metadata.
      *
diff --git a/tests/Server/ServerTestCase.php b/tests/Server/ServerTestCase.php
index 1a45c64..7bee051 100644
--- a/tests/Server/ServerTestCase.php
+++ b/tests/Server/ServerTestCase.php
@@ -51,9 +51,9 @@ abstract class ServerTestCase extends TestCase
 
     public function setUp()
     {
-        $sourceIndex       = new Index;
-        $dependenciesIndex = new DependenciesIndex;
-        $this->projectIndex      = new ProjectIndex($sourceIndex, $dependenciesIndex);
+        $sourceIndex        = new Index;
+        $dependenciesIndex  = new DependenciesIndex;
+        $this->projectIndex = new ProjectIndex($sourceIndex, $dependenciesIndex);
         $this->projectIndex->setComplete();
 
         $rootPath    = realpath(__DIR__ . '/../../fixtures/');
@@ -61,14 +61,15 @@ abstract class ServerTestCase extends TestCase
         $filesFinder = new FileSystemFilesFinder;
         $cache       = new FileSystemCache;
 
-        $this->input = new MockProtocolStream;
+        $this->input  = new MockProtocolStream;
         $this->output = new MockProtocolStream;
+
         $definitionResolver   = new DefinitionResolver($this->projectIndex);
         $client               = new LanguageClient($this->input, $this->output);
         $this->documentLoader = new PhpDocumentLoader(new FileSystemContentRetriever, $this->projectIndex, $definitionResolver);
         $this->textDocument   = new Server\TextDocument($this->documentLoader, $definitionResolver, $client, $this->projectIndex);
         $indexer              = new Indexer($filesFinder, $rootPath, $client, $cache, $dependenciesIndex, $sourceIndex, $this->documentLoader, null, null, $options);
-        $this->workspace      = new Server\Workspace($this->projectIndex, $dependenciesIndex, $sourceIndex, null, $this->documentLoader, null, $indexer, $options);
+        $this->workspace      = new Server\Workspace($client, $this->projectIndex, $dependenciesIndex, $sourceIndex, null, $this->documentLoader, null, $indexer, $options);
 
         $globalSymbolsUri    = pathToUri(realpath(__DIR__ . '/../../fixtures/global_symbols.php'));
         $globalReferencesUri = pathToUri(realpath(__DIR__ . '/../../fixtures/global_references.php'));
diff --git a/tests/Server/Workspace/DidChangeWatchedFilesTest.php b/tests/Server/Workspace/DidChangeWatchedFilesTest.php
new file mode 100644
index 0000000..1074c58
--- /dev/null
+++ b/tests/Server/Workspace/DidChangeWatchedFilesTest.php
@@ -0,0 +1,41 @@
+<?php
+declare(strict_types = 1);
+
+namespace LanguageServer\Tests\Server\Workspace;
+
+use LanguageServer\ContentRetriever\FileSystemContentRetriever;
+use LanguageServer\{DefinitionResolver, LanguageClient, PhpDocumentLoader, Server};
+use LanguageServer\Index\{DependenciesIndex, Index, ProjectIndex};
+use LanguageServer\Protocol\{FileChangeType, FileEvent, Message};
+use LanguageServer\Tests\MockProtocolStream;
+use LanguageServer\Tests\Server\ServerTestCase;
+use LanguageServer\Server\Workspace;
+use Sabre\Event\Loop;
+
+class DidChangeWatchedFilesTest extends ServerTestCase
+{
+    public function testDeletingFileClearsAllDiagnostics()
+    {
+        $client = new LanguageClient(new MockProtocolStream(), $writer = new MockProtocolStream());
+        $projectIndex = new ProjectIndex($sourceIndex = new Index(), $dependenciesIndex = new DependenciesIndex());
+        $definitionResolver = new DefinitionResolver($projectIndex);
+        $loader = new PhpDocumentLoader(new FileSystemContentRetriever(), $projectIndex, $definitionResolver);
+        $workspace = new Server\Workspace($client, $projectIndex, $dependenciesIndex, $sourceIndex, null, $loader, null);
+
+        $fileEvent = new FileEvent('my uri', FileChangeType::DELETED);
+
+        $isDiagnosticsCleared = false;
+        $writer->on('message', function (Message $message) use ($fileEvent, &$isDiagnosticsCleared) {
+            if ($message->body->method === "textDocument/publishDiagnostics") {
+                $this->assertEquals($message->body->params->uri, $fileEvent->uri);
+                $this->assertEquals($message->body->params->diagnostics, []);
+                $isDiagnosticsCleared = true;
+            }
+        });
+
+        $workspace->didChangeWatchedFiles([$fileEvent]);
+        Loop\tick(true);
+
+        $this->assertTrue($isDiagnosticsCleared, "Deleting file should clear all diagnostics.");
+    }
+}