Added InvalidParent issue (#2320)

Refs vimeo/psalm#2304

config.xsd

@@ -208,6 +208,7 @@
             <xs:element name="InvalidMethodCall" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidNullableReturnType" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidOperand" type="IssueHandlerType" minOccurs="0" />
+            <xs:element name="InvalidParent" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidPassByReference" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidPropertyAssignment" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidPropertyAssignmentValue" type="IssueHandlerType" minOccurs="0" />

docs/running_psalm/issues.md

@@ -717,6 +717,15 @@ Emitted when a function parameter default clashes with the type Psalm expects th
 function foo(int $i = false) : void {}
 ```
 
+### InvalidParent
+
+Emitted when a function return type is `parent`, but there's no parent class
+```php
+class Foo {
+    public function f(): parent {}
+}
+```
+
 ### InvalidPassByReference
 
 Emitted when passing a non-variable to a function that expects a by-ref variable

src/Psalm/Internal/Analyzer/FunctionLike/ReturnTypeAnalyzer.php

@@ -20,6 +20,7 @@ use Psalm\Context;
 use Psalm\Internal\FileManipulation\FunctionDocblockManipulator;
 use Psalm\Issue\InvalidFalsableReturnType;
 use Psalm\Issue\InvalidNullableReturnType;
+use Psalm\Issue\InvalidParent;
 use Psalm\Issue\InvalidReturnType;
 use Psalm\Issue\InvalidToString;
 use Psalm\Issue\LessSpecificReturnType;
@@ -657,6 +658,23 @@ class ReturnTypeAnalyzer
         }
 
         if (!$storage->signature_return_type || $storage->signature_return_type === $storage->return_type) {
+            foreach ($storage->return_type->getTypes() as $type) {
+                if ($type instanceof Type\Atomic\TNamedObject
+                    && 'parent' === $type->value
+                    && null === $parent_class
+                ) {
+                    if (IssueBuffer::accepts(
+                        new InvalidParent(
+                            'Cannot use parent as a return type when class has no parent',
+                            $storage->return_type_location
+                        ),
+                        $storage->suppressed_issues
+                    )) {
+                        return false;
+                    }
+                    return null;
+                }
+            }
             $fleshed_out_return_type = ExpressionAnalyzer::fleshOutType(
                 $codebase,
                 $storage->return_type,

src/Psalm/Issue/InvalidParent.php

@@ -0,0 +1,7 @@
+<?php
+namespace Psalm\Issue;
+
+class InvalidParent extends CodeIssue
+{
+
+}

tests/MethodSignatureTest.php

@@ -1007,6 +1007,36 @@ class MethodSignatureTest extends TestCase
                     }',
                 'error_message' => 'ImplementedParamTypeMismatch',
             ],
+            'returnsParentWithNoParent' => [
+                '<?php
+                    class Foo {
+                        public function f(): parent {}
+                    }
+                ',
+                'error_message' => 'InvalidParent',
+            ],
+            'returnsParentWithNoParentAndInvalidParentSuppressed' => [
+                '<?php
+                    class Foo {
+                        public function f(): parent {
+                        }
+                    }
+                ',
+                'error_message' => 'InvalidReturnType',
+                2 => ['InvalidParent'],
+            ],
+            // not sure how to handle it
+            'SKIPPED-returnsParentWithNoParentAndInvalidParentSuppressedMismatchingReturn' => [
+                '<?php
+                    class Foo {
+                        public function f(): parent {
+                            return false;
+                        }
+                    }
+                ',
+                'error_message' => 'InvalidReturnType',
+                2 => ['InvalidParent'],
+            ],
         ];
     }
 }