update dependencies; phpstan integration; types correction

Author: mmasiukevich

.travis.yml

@@ -26,6 +26,7 @@ install:
 script:
   - ./vendor/bin/phpunit --configuration ./phpunit.xml --coverage-clover=coverage.clover
   - if [ "$TRAVIS_PHP_VERSION" == "7.2" ]; then ./vendor/bin/psalm --config=psalm.xml; fi
+  - if [ "$TRAVIS_PHP_VERSION" == "7.2" ]; then ./vendor/bin/phpstan analyse src --level 7; fi
   - if [ "$TRAVIS_PHP_VERSION" == "7.2" ]; then ./vendor/bin/php-cs-fixer fix --allow-risky=yes --dry-run; fi
 
 after_script:

CONTRIBUTING.md

@@ -22,9 +22,9 @@ For a simple check of the code standard, there is a command:
 composer cs-check
 ```
 ## Static analysis
-To improve the quality of the code used static analysis (via `psalm`). You can start it with the command:
+To improve the quality of the code used static analysis (via `psalm` and `phpstan`). You can start it with the command:
 ```bash
-composer psalm
+composer psalm && composer phpstan
 ```
 ## Running the tests
 The following tests must pass before we will accept a pull request. If any of these do not pass, it will result in a complete build failure.

composer.json

@@ -37,17 +37,19 @@
     "php-service-bus/code-style-config": "^v0.1",
     "phpunit/phpunit": "^8",
     "ext-iconv": "*",
-    "vimeo/psalm": "^v3"
+    "vimeo/psalm": "^v3",
+    "phpstan/phpstan": "^0.11.5"
   },
   "prefer-stable": true,
   "minimum-stability": "stable",
   "scripts": {
     "psalm": "./vendor/bin/psalm --config=psalm.xml",
+    "phpstan": "./vendor/bin/phpstan analyse src --level 7",
     "tests": "./vendor/bin/phpunit --configuration phpunit.xml --verbose",
     "coverage": "./vendor/bin/phpunit --configuration phpunit.xml --coverage-html ./coverage --verbose",
     "cs-check": "./vendor/bin/php-cs-fixer fix --allow-risky=yes --dry-run",
     "cs-fix": "./vendor/bin/php-cs-fixer fix --allow-risky=yes",
-    "pre-commit": "PHP_CS_FIXER_IGNORE_ENV=1 ./vendor/bin/php-cs-fixer fix --allow-risky=yes && ./vendor/bin/psalm --config=psalm.xml && ./vendor/bin/phpunit --configuration phpunit.xml --verbose"
+    "pre-commit": "PHP_CS_FIXER_IGNORE_ENV=1 ./vendor/bin/php-cs-fixer fix --allow-risky=yes && ./vendor/bin/psalm --config=psalm.xml && ./vendor/bin/phpstan analyse src --level 7 && ./vendor/bin/phpunit --configuration phpunit.xml --verbose"
   },
   "config": {
     "optimize-autoloader": true