Add automatic inheritance to properties

Fixes #1210

src/Psalm/Internal/Analyzer/ClassAnalyzer.php

@@ -982,19 +982,28 @@ class ClassAnalyzer extends ClassLikeAnalyzer
 
             $codebase = $this->getCodebase();
 
+            $property_id = $fq_class_name . '::$' . $property_name;
+
             $declaring_property_class = $codebase->properties->getDeclaringClassForProperty(
-                $fq_class_name . '::$' . $property_name
+                $property_id
             );
 
             if (!$declaring_property_class) {
                 throw new \UnexpectedValueException(
-                    'Cannot get declaring class for ' . $fq_class_name . '::$' . $property_name
+                    'Cannot get declaring class for ' . $property_id
                 );
             }
 
             $fq_class_name = $declaring_property_class;
 
-            $message = 'Property ' . $fq_class_name . '::$' . $property_name . ' does not have a declared type';
+            // gets inherited property type
+            $class_property_type = $codebase->properties->getPropertyType($property_id);
+
+            if ($class_property_type) {
+                return;
+            }
+
+            $message = 'Property ' . $property_id . ' does not have a declared type';
 
             $class_storage = $codebase->classlike_storage_provider->get($fq_class_name);
 

src/Psalm/Internal/Analyzer/Statements/Expression/Assignment/PropertyAssignmentAnalyzer.php

@@ -86,9 +86,7 @@ class PropertyAssignmentAnalyzer
 
             $declaring_property_class = $codebase->properties->getDeclaringClassForProperty($property_id);
 
-            $class_storage = $codebase->classlike_storage_provider->get((string)$declaring_property_class);
-
-            $class_property_type = $class_storage->properties[$prop_name]->type;
+            $class_property_type = $codebase->properties->getPropertyType($property_id);
 
             $class_property_types[] = $class_property_type ? clone $class_property_type : Type::getMixed();
 
@@ -450,7 +448,7 @@ class PropertyAssignmentAnalyzer
                     }
                 }
 
-                $class_property_type = $property_storage->type;
+                $class_property_type = $codebase->properties->getPropertyType($property_id);
 
                 if (!$class_property_type) {
                     $class_property_type = Type::getMixed();
@@ -797,7 +795,7 @@ class PropertyAssignmentAnalyzer
             $context->vars_in_scope[$var_id] = $assignment_value_type;
         }
 
-        $class_property_type = $property_storage->type;
+        $class_property_type = $codebase->properties->getPropertyType($property_id);
 
         if (!$class_property_type) {
             $class_property_type = Type::getMixed();

src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/PropertyFetchAnalyzer.php

@@ -488,7 +488,7 @@ class PropertyFetchAnalyzer
                 }
             }
 
-            $class_property_type = $property_storage->type;
+            $class_property_type = $codebase->properties->getPropertyType($property_id);
 
             if (!$class_property_type) {
                 if (IssueBuffer::accepts(

src/Psalm/Internal/Codebase/Properties.php

@@ -4,6 +4,7 @@ namespace Psalm\Internal\Codebase;
 use Psalm\CodeLocation;
 use Psalm\Internal\Provider\ClassLikeStorageProvider;
 use Psalm\Internal\Provider\FileReferenceProvider;
+use Psalm\Type;
 
 /**
  * @internal
@@ -150,4 +151,49 @@ class Properties
 
         throw new \UnexpectedValueException('Property ' . $property_id . ' should exist');
     }
+
+    /**
+     * @param  string $property_id
+     * @return  ?Type\Union
+     */
+    public function getPropertyType($property_id)
+    {
+        // remove trailing backslash if it exists
+        $property_id = preg_replace('/^\\\\/', '', $property_id);
+
+        list($fq_class_name, $property_name) = explode('::$', $property_id);
+
+        $class_storage = $this->classlike_storage_provider->get($fq_class_name);
+
+        if (isset($class_storage->declaring_property_ids[$property_name])) {
+            $declaring_property_class = $class_storage->declaring_property_ids[$property_name];
+            $declaring_class_storage = $this->classlike_storage_provider->get($declaring_property_class);
+
+            if (isset($declaring_class_storage->properties[$property_name])) {
+                $storage = $declaring_class_storage->properties[$property_name];
+            } else {
+                throw new \UnexpectedValueException('Property ' . $property_id . ' should exist');
+            }
+        } else {
+            throw new \UnexpectedValueException('Property ' . $property_id . ' should exist');
+        }
+
+        if ($storage->type) {
+            return $storage->type;
+        }
+
+        if (!isset($class_storage->overridden_property_ids[$property_name])) {
+            return null;
+        }
+
+        foreach ($class_storage->overridden_property_ids[$property_name] as $overridden_property_id) {
+            $overridden_storage = $this->getStorage($overridden_property_id);
+
+            if ($overridden_storage->type) {
+                return $overridden_storage->type;
+            }
+        }
+
+        return null;
+    }
 }

tests/PropertyTypeTest.php

@@ -1174,6 +1174,30 @@ class PropertyTypeTest extends TestCase
                 [],
                 'error_levels' => []
             ],
+            'inheritDocPropertyTypes' => [
+                '<?php
+                    class X {
+                        /**
+                         * @var string|null
+                         */
+                        public $a;
+
+                        /**
+                         * @var string|null
+                         */
+                        public static $b;
+                    }
+
+                    class Y extends X {
+                        public $a = "foo";
+                        public static $b = "foo";
+                    }
+
+                    (new Y)->a = "hello";
+                    echo (new Y)->a;
+                    Y::$b = "bar";
+                    echo Y::$b;',
+            ],
         ];
     }
 
@@ -1867,6 +1891,41 @@ class PropertyTypeTest extends TestCase
                     }',
                 'error_message' => 'UndefinedThisPropertyFetch',
             ],
+            'inheritDocPropertyTypesIncorrectAssignmentToInstanceProperty' => [
+                '<?php
+                    class X {
+                        /**
+                         * @var string|null
+                         */
+                        public $a;
+                    }
+
+                    class Y extends X {
+                        public $a = "foo";
+                    }
+
+                    (new Y)->a = 5;
+                    echo (new Y)->a;
+                    Y::$b = "bar";
+                    echo Y::$b;',
+                'error_message' => 'InvalidPropertyAssignmentValue',
+            ],
+            'inheritDocPropertyTypesIncorrectAssignmentToStaticProperty' => [
+                '<?php
+                    class X {
+                        /**
+                         * @var string|null
+                         */
+                        public static $b;
+                    }
+
+                    class Y extends X {
+                        public static $b = "foo";
+                    }
+
+                    Y::$b = 5;',
+                'error_message' => 'InvalidPropertyAssignmentValue',
+            ],
         ];
     }
 }