Fix #677 - handle get_class checks more accurately

src/Psalm/Checker/Statements/Expression/AssertionFinder.php

@@ -342,7 +342,7 @@ class AssertionFinder
                     // fall through
                 } else {
                     if ($var_name && $var_type) {
-                        $if_types[$var_name] = $var_type;
+                        $if_types[$var_name] = 'getclass-' . $var_type;
                     }
                 }
 
@@ -614,7 +614,7 @@ class AssertionFinder
                     // fall through
                 } else {
                     if ($var_name && $var_type) {
-                        $if_types[$var_name] = '!' . $var_type;
+                        $if_types[$var_name] = '!getclass-' . $var_type;
                     }
                 }
 

src/Psalm/Type/Reconciler.php

@@ -479,6 +479,8 @@ class Reconciler
             ) {
                 $existing_var_type->removeType('iterable');
                 $existing_var_type->addType(new TNamedObject('Traversable'));
+            } elseif (substr($negated_type, 0, 9) === 'getclass-') {
+                $negated_type = substr($negated_type, 9);
             } else {
                 $existing_var_type->removeType($negated_type);
             }
@@ -795,6 +797,10 @@ class Reconciler
             } else {
                 $new_type = Type::getMixed();
             }
+        } elseif (substr($new_var_type, 0, 9) === 'getclass-') {
+            $new_var_type = substr($new_var_type, 9);
+            $new_type = Type::parseString($new_var_type);
+            $is_strict_equality = true;
         } else {
             $new_type = Type::parseString($new_var_type);
         }
@@ -850,7 +856,10 @@ class Reconciler
         } elseif ($code_location && !$new_type->isMixed()) {
             $has_match = true;
 
-            if ($key && $new_type->getId() === $existing_var_type->getId() && !$is_strict_equality) {
+            if ($key
+                && $new_type->getId() === $existing_var_type->getId()
+                && !$is_strict_equality
+            ) {
                 self::triggerIssueForImpossible(
                     $existing_var_type,
                     $old_var_type_string,

tests/TypeAlgebraTest.php

@@ -571,6 +571,25 @@ class TypeAlgebraTest extends TestCase
                         }
                     }',
             ],
+            'getClassComparison' => [
+                '<?php
+                    class Foo {
+                        public function bar() : void {}
+                    }
+                    class Bar extends Foo{
+                        public function bar() : void {}
+                    }
+
+                    class Baz {
+                        public function test(Foo $foo) : void {
+                            if (get_class($foo) !== Foo::class) {
+                                // do nothing
+                            } else {
+                                $foo->bar();
+                            }
+                        }
+                    }',
+            ],
         ];
     }