diff --git a/.gitattributes b/.gitattributes
index 63babab..3f3d483 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -10,6 +10,7 @@
 /.gitignore export-ignore
 /.gitmodules export-ignore
 /.npmrc export-ignore
+/.phan export-ignore
 /.travis.yml export-ignore
 /appveyor.yml export-ignore
 /codecov.yml export-ignore
diff --git a/.phan/config.php b/.phan/config.php
new file mode 100644
index 0000000..a3beb49
--- /dev/null
+++ b/.phan/config.php
@@ -0,0 +1,308 @@
+<?php
+
+use Phan\Issue;
+
+/**
+ * This configuration file was automatically generated by 'phan --init --init-level=1'
+ *
+ * TODOs (added by 'phan --init'):
+ *
+ * - Go through this file and verify that there are no missing/unnecessary files/directories.
+ *   (E.g. this only includes direct composer dependencies - You may have to manually add indirect composer dependencies to 'directory_list')
+ * - Look at 'plugins' and add or remove plugins if appropriate (see https://github.com/phan/phan/tree/master/.phan/plugins#plugins)
+ * - Add global suppressions for pre-existing issues to suppress_issue_types (https://github.com/phan/phan/wiki/Tutorial-for-Analyzing-a-Large-Sloppy-Code-Base)
+ *
+ * This configuration will be read and overlayed on top of the
+ * default configuration. Command line arguments will be applied
+ * after this file is read.
+ *
+ * @see src/Phan/Config.php
+ * See Config for all configurable options.
+ *
+ * A Note About Paths
+ * ==================
+ *
+ * Files referenced from this file should be defined as
+ *
+ * ```
+ *   Config::projectPath('relative_path/to/file')
+ * ```
+ *
+ * where the relative path is relative to the root of the
+ * project which is defined as either the working directory
+ * of the phan executable or a path passed in via the CLI
+ * '-d' flag.
+ */
+return [
+
+    // Supported values: '7.0', '7.1', '7.2', null.
+    // If this is set to null,
+    // then Phan assumes the PHP version which is closest to the minor version
+    // of the php executable used to execute phan.
+    // Automatically inferred from composer.json requirement for "php" of "^7.0"
+    'target_php_version' => '7.0',
+
+    // If enabled, missing properties will be created when
+    // they are first seen. If false, we'll report an
+    // error message if there is an attempt to write
+    // to a class property that wasn't explicitly
+    // defined.
+    'allow_missing_properties' => false,
+
+    // If enabled, null can be cast as any type and any
+    // type can be cast to null. Setting this to true
+    // will cut down on false positives.
+    'null_casts_as_any_type' => false,
+
+    // If enabled, allow null to be cast as any array-like type.
+    // This is an incremental step in migrating away from null_casts_as_any_type.
+    // If null_casts_as_any_type is true, this has no effect.
+    'null_casts_as_array' => false,
+
+    // If enabled, allow any array-like type to be cast to null.
+    // This is an incremental step in migrating away from null_casts_as_any_type.
+    // If null_casts_as_any_type is true, this has no effect.
+    'array_casts_as_null' => false,
+
+    // If enabled, scalars (int, float, bool, string, null)
+    // are treated as if they can cast to each other.
+    // This does not affect checks of array keys. See scalar_array_key_cast.
+    'scalar_implicit_cast' => false,
+
+    // If enabled, any scalar array keys (int, string)
+    // are treated as if they can cast to each other.
+    // E.g. array<int,stdClass> can cast to array<string,stdClass> and vice versa.
+    // Normally, a scalar type such as int could only cast to/from int and mixed.
+    'scalar_array_key_cast' => false,
+
+    // If this has entries, scalars (int, float, bool, string, null)
+    // are allowed to perform the casts listed.
+    // E.g. ['int' => ['float', 'string'], 'float' => ['int'], 'string' => ['int'], 'null' => ['string']]
+    // allows casting null to a string, but not vice versa.
+    // (subset of scalar_implicit_cast)
+    'scalar_implicit_partial' => [],
+
+    // If true, seemingly undeclared variables in the global
+    // scope will be ignored. This is useful for projects
+    // with complicated cross-file globals that you have no
+    // hope of fixing.
+    'ignore_undeclared_variables_in_global_scope' => false,
+
+    // Backwards Compatibility Checking. This is slow
+    // and expensive, but you should consider running
+    // it before upgrading your version of PHP to a
+    // new version that has backward compatibility
+    // breaks.
+    'backward_compatibility_checks' => false,
+
+    // If true, check to make sure the return type declared
+    // in the doc-block (if any) matches the return type
+    // declared in the method signature.
+    'check_docblock_signature_return_type_match' => true,
+
+    // (*Requires check_docblock_signature_param_type_match to be true*)
+    // If true, make narrowed types from phpdoc params override
+    // the real types from the signature, when real types exist.
+    // (E.g. allows specifying desired lists of subclasses,
+    //  or to indicate a preference for non-nullable types over nullable types)
+    // Affects analysis of the body of the method and the param types passed in by callers.
+    'prefer_narrowed_phpdoc_param_type' => true,
+
+    // (*Requires check_docblock_signature_return_type_match to be true*)
+    // If true, make narrowed types from phpdoc returns override
+    // the real types from the signature, when real types exist.
+    // (E.g. allows specifying desired lists of subclasses,
+    //  or to indicate a preference for non-nullable types over nullable types)
+    // Affects analysis of return statements in the body of the method and the return types passed in by callers.
+    'prefer_narrowed_phpdoc_return_type' => true,
+
+    'ensure_signature_compatibility' => true,
+
+    // Set to true in order to attempt to detect dead
+    // (unreferenced) code. Keep in mind that the
+    // results will only be a guess given that classes,
+    // properties, constants and methods can be referenced
+    // as variables (like `$class->$property` or
+    // `$class->$method()`) in ways that we're unable
+    // to make sense of.
+    'dead_code_detection' => false,
+
+    // If true, this run a quick version of checks that takes less
+    // time at the cost of not running as thorough
+    // an analysis. You should consider setting this
+    // to true only when you wish you had more **undiagnosed** issues
+    // to fix in your code base.
+    //
+    // In quick-mode the scanner doesn't rescan a function
+    // or a method's code block every time a call is seen.
+    // This means that the problem here won't be detected:
+    //
+    // ```php
+    // <?php
+    // function test($arg):int {
+    //     return $arg;
+    // }
+    // test("abc");
+    // ```
+    //
+    // This would normally generate:
+    //
+    // ```sh
+    // test.php:3 TypeError return string but `test()` is declared to return int
+    // ```
+    //
+    // The initial scan of the function's code block has no
+    // type information for `$arg`. It isn't until we see
+    // the call and rescan test()'s code block that we can
+    // detect that it is actually returning the passed in
+    // `string` instead of an `int` as declared.
+    'quick_mode' => false,
+
+    // If true, then before analysis, try to simplify AST into a form
+    // which improves Phan's type inference in edge cases.
+    //
+    // This may conflict with 'dead_code_detection'.
+    // When this is true, this slows down analysis slightly.
+    //
+    // E.g. rewrites `if ($a = value() && $a > 0) {...}`
+    // into $a = value(); if ($a) { if ($a > 0) {...}}`
+    'simplify_ast' => true,
+
+    // Enable or disable support for generic templated
+    // class types.
+    'generic_types_enabled' => true,
+
+    // Override to hardcode existence and types of (non-builtin) globals in the global scope.
+    // Class names should be prefixed with '\\'.
+    // (E.g. ['_FOO' => '\\FooClass', 'page' => '\\PageClass', 'userId' => 'int'])
+    'globals_type_map' => [],
+
+    // The minimum severity level to report on. This can be
+    // set to Issue::SEVERITY_LOW, Issue::SEVERITY_NORMAL or
+    // Issue::SEVERITY_CRITICAL. Setting it to only
+    // critical issues is a good place to start on a big
+    // sloppy mature code base.
+    'minimum_severity' => Issue::SEVERITY_LOW,
+
+    // Add any issue types (such as 'PhanUndeclaredMethod')
+    // to this black-list to inhibit them from being reported.
+    'suppress_issue_types' => [
+        'PhanTypeMismatchDeclaredParamNullable',
+        'PhanUndeclaredProperty',  // 66 occurence(s) (e.g. not being specific enough about the subclass)
+        'PhanUndeclaredMethod',  // 32 occurence(s) (e.g. not being specific enough about the subclass of Node)
+        'PhanTypeMismatchArgument',  // 21 occurence(s)
+        'PhanTypeMismatchProperty',  // 13 occurence(s)
+        'PhanUnreferencedUseNormal',  // 10 occurence(s) TODO: Fix
+        'PhanTypeMismatchDeclaredReturn',  // 8 occurence(s)
+        'PhanUndeclaredTypeProperty',  // 7 occurence(s)
+        'PhanTypeMismatchReturn',  // 6 occurence(s)
+        'PhanUndeclaredVariable',  // 4 occurence(s)
+        'PhanUndeclaredTypeReturnType',  // 4 occurence(s)
+        'PhanParamTooMany',  // 3 occurence(s)
+        'PhanUndeclaredTypeParameter',  // 2 occurence(s)
+        'PhanUndeclaredClassProperty',  // 2 occurence(s)
+        'PhanTypeSuspiciousStringExpression',  // 2 occurence(s)
+        'PhanTypeMismatchArgumentInternal',  // 2 occurence(s)
+        'PhanUnextractableAnnotationElementName',  // 1 occurence(s)
+        'PhanUndeclaredClassMethod',  // 1 occurence(s)
+        'PhanUndeclaredClassInstanceof',  // 1 occurence(s)
+        'PhanTypeSuspiciousNonTraversableForeach',  // 1 occurence(s)
+        'PhanTypeMismatchDimAssignment',  // 1 occurence(s)
+        'PhanTypeMismatchDeclaredParam',  // 1 occurence(s)
+        'PhanTypeInvalidDimOffset',  // 1 occurence(s)
+    ],
+
+    // A regular expression to match files to be excluded
+    // from parsing and analysis and will not be read at all.
+    //
+    // This is useful for excluding groups of test or example
+    // directories/files, unanalyzable files, or files that
+    // can't be removed for whatever reason.
+    // (e.g. '@Test\.php$@', or '@vendor/.*/(tests|Tests)/@')
+    'exclude_file_regex' => '@^vendor/.*/(tests?|Tests?)/@',
+
+    // A file list that defines files that will be excluded
+    // from parsing and analysis and will not be read at all.
+    //
+    // This is useful for excluding hopelessly unanalyzable
+    // files that can't be removed for whatever reason.
+    'exclude_file_list' => [],
+
+    // A directory list that defines files that will be excluded
+    // from static analysis, but whose class and method
+    // information should be included.
+    //
+    // Generally, you'll want to include the directories for
+    // third-party code (such as "vendor/") in this list.
+    //
+    // n.b.: If you'd like to parse but not analyze 3rd
+    //       party code, directories containing that code
+    //       should be added to the `directory_list` as
+    //       to `excluce_analysis_directory_list`.
+    'exclude_analysis_directory_list' => [
+        'vendor/',
+    ],
+
+    // The number of processes to fork off during the analysis
+    // phase.
+    'processes' => 1,
+
+    // List of case-insensitive file extensions supported by Phan.
+    // (e.g. php, html, htm)
+    'analyzed_file_extensions' => [
+        'php',
+    ],
+
+    // You can put paths to stubs of internal extensions in this config option.
+    // If the corresponding extension is **not** loaded, then phan will use the stubs instead.
+    // Phan will continue using its detailed type annotations,
+    // but load the constants, classes, functions, and classes (and their Reflection types)
+    // from these stub files (doubling as valid php files).
+    // Use a different extension from php to avoid accidentally loading these.
+    // The 'tools/make_stubs' script can be used to generate your own stubs (compatible with php 7.0+ right now)
+    'autoload_internal_extension_signatures' => [],
+
+    // A list of plugin files to execute
+    // Plugins which are bundled with Phan can be added here by providing their name (e.g. 'AlwaysReturnPlugin')
+    // Alternately, you can pass in the full path to a PHP file with the plugin's implementation (e.g. 'vendor/phan/phan/.phan/plugins/AlwaysReturnPlugin.php')
+    'plugins' => [
+        'AlwaysReturnPlugin',
+        'DollarDollarPlugin',
+        'DuplicateArrayKeyPlugin',
+        'PregRegexCheckerPlugin',
+        'PrintfCheckerPlugin',
+        'UnreachableCodePlugin',
+    ],
+
+    // A list of directories that should be parsed for class and
+    // method information. After excluding the directories
+    // defined in exclude_analysis_directory_list, the remaining
+    // files will be statically analyzed for errors.
+    //
+    // Thus, both first-party and third-party code being used by
+    // your application should be included in this list.
+    'directory_list' => [
+        'src',
+        'vendor/composer/xdebug-handler/src',
+        'vendor/felixfbecker/advanced-json-rpc/lib',
+        'vendor/felixfbecker/language-server-protocol/src/',
+        'vendor/microsoft/tolerant-php-parser/src',
+        'vendor/netresearch/jsonmapper/src',
+        'vendor/phpdocumentor/reflection-common/src',
+        'vendor/phpdocumentor/reflection-docblock/src',
+        'vendor/phpdocumentor/type-resolver/src',
+        'vendor/phpunit/phpunit/src',
+        'vendor/psr/log/Psr',
+        'vendor/sabre/event/lib',
+        'vendor/sabre/uri/lib',
+        'vendor/webmozart/glob/src',
+        'vendor/webmozart/path-util/src',
+    ],
+
+    // A list of individual files to include in analysis
+    // with a path relative to the root directory of the
+    // project
+    'file_list' => [
+        'bin/php-language-server.php',
+    ],
+];
diff --git a/.travis.yml b/.travis.yml
index 3d03dcf..da1f118 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -16,8 +16,11 @@ cache:
 
 install:
   - composer install --prefer-dist --no-interaction
+  - pecl install ast-1.0.0
+
 script:
   - vendor/bin/phpcs -n
+  - vendor/bin/phan
   - vendor/bin/phpunit --coverage-clover=coverage.xml --colors=always
   - bash <(curl -s https://codecov.io/bash)
 
diff --git a/composer.json b/composer.json
index ffa5971..f63bf3a 100644
--- a/composer.json
+++ b/composer.json
@@ -37,6 +37,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^6.3",
+        "phan/phan": "1.1.4",
         "squizlabs/php_codesniffer": "^3.1"
     },
     "autoload": {