Add interface inheritance test

tests/InterfaceTest.php

@@ -0,0 +1,84 @@
+<?php
+
+namespace Psalm\Tests;
+
+use PhpParser;
+use PhpParser\ParserFactory;
+use PHPUnit_Framework_TestCase;
+use Psalm\Context;
+use Psalm\Checker\TypeChecker;
+use Psalm\Type;
+
+class InterfaceTest extends PHPUnit_Framework_TestCase
+{
+    protected static $_parser;
+
+    public static function setUpBeforeClass()
+    {
+        self::$_parser = (new ParserFactory)->create(ParserFactory::PREFER_PHP7);
+
+        $config = \Psalm\Config::getInstance();
+        $config->throw_exception = true;
+        $config->use_docblock_types = true;
+    }
+
+    public function setUp()
+    {
+        \Psalm\Checker\FileChecker::clearCache();
+    }
+
+    public function testExtends()
+    {
+        $stmts = self::$_parser->parse('<?php
+        interface a
+        {
+            /**
+             * @return string
+             */
+            public function foo();
+        }
+
+        interface b
+        {
+            public function bar() {
+
+            }
+        }
+
+        interface c extends a, b
+        {
+            /**
+             * @return string
+             */
+            public function baz() {
+
+            }
+        }
+
+        class d implements c
+        {
+            public function foo()
+            {
+            }
+
+            public function bar()
+            {
+            }
+
+            public function baz()
+            {
+            }
+        }
+
+        $cee = (new d())->baz();
+        $dee = (new d())->foo();
+        ?>
+        ');
+
+        $file_checker = new \Psalm\Checker\FileChecker('somefile.php', $stmts);
+        $context = new Context('somefile.php');
+        $file_checker->check(true, true, $context);
+        $this->assertEquals('string', (string) $context->vars_in_scope['$cee']);
+        $this->assertEquals('string', (string) $context->vars_in_scope['$dee']);
+    }
+}