From 16e89a8c1c8bcac83d62d0b8872e59e2ff1c00da Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Fri, 16 Dec 2016 17:59:27 -0500
Subject: [PATCH] Fix #26 - Allow refinement via type intersection

Not just via explict subsets
---
 src/Psalm/Checker/TypeChecker.php |  4 +++-
 tests/TypeTest.php                | 15 +++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/Psalm/Checker/TypeChecker.php b/src/Psalm/Checker/TypeChecker.php
index a16fbb91b..0fbaf9452 100644
--- a/src/Psalm/Checker/TypeChecker.php
+++ b/src/Psalm/Checker/TypeChecker.php
@@ -1253,7 +1253,9 @@ class TypeChecker
             return $new_type;
         }
 
-        if (!TypeChecker::isContainedBy($new_type, $existing_var_type) && $code_location) {
+        if (!TypeChecker::isContainedBy($new_type, $existing_var_type) &&
+            !TypeChecker::isContainedBy($existing_var_type, $new_type) &&
+            $code_location) {
             if (IssueBuffer::accepts(
                 new TypeDoesNotContainType(
                     'Cannot resolve types for ' . $key . ' - ' . $existing_var_type . ' does not contain ' . $new_type,
diff --git a/tests/TypeTest.php b/tests/TypeTest.php
index 61bfb5c95..59b513adb 100644
--- a/tests/TypeTest.php
+++ b/tests/TypeTest.php
@@ -1660,4 +1660,19 @@ class TypeTest extends PHPUnit_Framework_TestCase
         $context = new Context('somefile.php');
         $file_checker->check();
     }
+
+    public function testTypeRefinementWithIsNumeric()
+    {
+        $stmts = self::$parser->parse('<?php
+        function foo(string $a) : void {
+            if (is_numeric($a)) {
+
+            }
+        }
+        ');
+
+        $file_checker = new FileChecker('somefile.php', $stmts);
+        $context = new Context('somefile.php');
+        $file_checker->check();
+    }
 }