From 08e305cbead8d822e431a707b00baf2d4e62e990 Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Wed, 27 Jan 2021 12:48:32 -0500
Subject: [PATCH] =?UTF-8?q?Fix=20#4010=20=E2=80=93=20don=E2=80=99t=20creat?=
 =?UTF-8?q?e=20interface=20intersections=20unless=20there=E2=80=99s=20no?=
 =?UTF-8?q?=20overlap?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../Internal/Type/AssertionReconciler.php     | 21 ++++--------
 .../Type/Comparator/AtomicTypeComparator.php  | 15 +++-----
 .../Type/Comparator/UnionTypeComparator.php   |  6 ++--
 tests/InterfaceTest.php                       | 34 +++++++++++++++++++
 4 files changed, 49 insertions(+), 27 deletions(-)

diff --git a/src/Psalm/Internal/Type/AssertionReconciler.php b/src/Psalm/Internal/Type/AssertionReconciler.php
index c931f9713..adeed8a7e 100644
--- a/src/Psalm/Internal/Type/AssertionReconciler.php
+++ b/src/Psalm/Internal/Type/AssertionReconciler.php
@@ -390,22 +390,13 @@ class AssertionReconciler extends \Psalm\Type\Reconciler
         }
 
         if ($new_type_part instanceof TNamedObject
-            && ((
-                $new_type_has_interface
-                    && !UnionTypeComparator::isContainedBy(
-                        $codebase,
-                        $existing_var_type,
-                        $new_type
-                    )
+            && ($new_type_has_interface || $old_type_has_interface)
+            && !UnionTypeComparator::canExpressionTypesBeIdentical(
+                $codebase,
+                $new_type,
+                $existing_var_type,
+                false
             )
-                || (
-                    $old_type_has_interface
-                    && !UnionTypeComparator::isContainedBy(
-                        $codebase,
-                        $new_type,
-                        $existing_var_type
-                    )
-                ))
         ) {
             $acceptable_atomic_types = [];
 
diff --git a/src/Psalm/Internal/Type/Comparator/AtomicTypeComparator.php b/src/Psalm/Internal/Type/Comparator/AtomicTypeComparator.php
index f31bc97e0..f64710493 100644
--- a/src/Psalm/Internal/Type/Comparator/AtomicTypeComparator.php
+++ b/src/Psalm/Internal/Type/Comparator/AtomicTypeComparator.php
@@ -639,7 +639,8 @@ class AtomicTypeComparator
     public static function canBeIdentical(
         Codebase $codebase,
         Type\Atomic $type1_part,
-        Type\Atomic $type2_part
+        Type\Atomic $type2_part,
+        bool $allow_interface_equality = true
     ) : bool {
         if ((get_class($type1_part) === TList::class
                 && $type2_part instanceof Type\Atomic\TNonEmptyList)
@@ -673,11 +674,11 @@ class AtomicTypeComparator
         $first_comparison_result = new TypeComparisonResult();
         $second_comparison_result = new TypeComparisonResult();
 
-        $either_contains = (AtomicTypeComparator::isContainedBy(
+        return (AtomicTypeComparator::isContainedBy(
             $codebase,
             $type1_part,
             $type2_part,
-            true,
+            $allow_interface_equality,
             false,
             $first_comparison_result
         )
@@ -686,7 +687,7 @@ class AtomicTypeComparator
             $codebase,
             $type2_part,
             $type1_part,
-            true,
+            $allow_interface_equality,
             false,
             $second_comparison_result
         )
@@ -694,11 +695,5 @@ class AtomicTypeComparator
         ) || ($first_comparison_result->type_coerced
             && $second_comparison_result->type_coerced
         );
-
-        if ($either_contains) {
-            return true;
-        }
-
-        return false;
     }
 }
diff --git a/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php b/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php
index 1474c1188..2120328ac 100644
--- a/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php
+++ b/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php
@@ -352,7 +352,8 @@ class UnionTypeComparator
     public static function canExpressionTypesBeIdentical(
         Codebase $codebase,
         Type\Union $type1,
-        Type\Union $type2
+        Type\Union $type2,
+        bool $allow_interface_equality = true
     ): bool {
         if ($type1->hasMixed() || $type2->hasMixed()) {
             return true;
@@ -367,7 +368,8 @@ class UnionTypeComparator
                 $either_contains = AtomicTypeComparator::canBeIdentical(
                     $codebase,
                     $type1_part,
-                    $type2_part
+                    $type2_part,
+                    $allow_interface_equality
                 );
 
                 if ($either_contains) {
diff --git a/tests/InterfaceTest.php b/tests/InterfaceTest.php
index d382ce0cc..c9fd1ac1f 100644
--- a/tests/InterfaceTest.php
+++ b/tests/InterfaceTest.php
@@ -941,6 +941,40 @@ class InterfaceTest extends TestCase
                     }',
                 'error_message' => 'MissingParamType'
             ],
+            'reconcileAfterClassInstanceof' => [
+                '<?php
+                    interface Base {}
+
+                    class E implements Base {
+                        public function bar() : void {}
+                    }
+
+                    function foobar(Base $foo) : void {
+                        if ($foo instanceof E) {
+                            $foo->bar();
+                        }
+
+                        $foo->bar();
+                    }',
+                'error_message' => 'UndefinedInterfaceMethod - src' . \DIRECTORY_SEPARATOR . 'somefile.php:13:31',
+            ],
+            'reconcileAfterInterfaceInstanceof' => [
+                '<?php
+                    interface Base {}
+
+                    interface E extends Base {
+                        public function bar() : void;
+                    }
+
+                    function foobar(Base $foo) : void {
+                        if ($foo instanceof E) {
+                            $foo->bar();
+                        }
+
+                        $foo->bar();
+                    }',
+                'error_message' => 'UndefinedInterfaceMethod - src' . \DIRECTORY_SEPARATOR . 'somefile.php:13:31',
+            ],
         ];
     }
 }