Fix #71 - prevent instantiation of abstract classes

config.xsd

@@ -72,6 +72,7 @@
 
     <xs:complexType name="IssueHandlersType">
         <xs:choice minOccurs="0" maxOccurs="unbounded">
+            <xs:element name="AbstractInstantiation" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="ContinueOutsideLoop" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="DeprecatedMethod" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="DuplicateParam" type="IssueHandlerType" minOccurs="0" />

src/Psalm/Checker/ClassLikeChecker.php

@@ -314,6 +314,8 @@ abstract class ClassLikeChecker extends SourceChecker implements StatementsSourc
         $config = Config::getInstance();
 
         if ($this instanceof ClassChecker && $this->class instanceof PhpParser\Node\Stmt\Class_) {
+            $storage->abstract = (bool)$this->class->isAbstract();
+
             foreach (ClassChecker::getInterfacesForClass(
                 $this->fq_class_name
             ) as $interface_id => $interface_name) {
@@ -1093,6 +1095,7 @@ abstract class ClassLikeChecker extends SourceChecker implements StatementsSourc
         $reflected_parent_class = $reflected_class->getParentClass();
 
         $storage = self::$storage[$class_name_lower] = new ClassLikeStorage();
+        $storage->abstract = $reflected_class->isAbstract();
 
         self::$class_extends[$class_name] = [];
 

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

@@ -15,6 +15,7 @@ use Psalm\CodeLocation;
 use Psalm\Config;
 use Psalm\Context;
 use Psalm\FunctionLikeParameter;
+use Psalm\Issue\AbstractInstantiation;
 use Psalm\Issue\ForbiddenCode;
 use Psalm\Issue\ImplicitToStringCast;
 use Psalm\Issue\InvalidArgument;
@@ -301,6 +302,8 @@ class CallChecker
 
         $file_checker = $statements_checker->getFileChecker();
 
+        $late_static = false;
+
         if ($stmt->class instanceof PhpParser\Node\Name) {
             if (!in_array($stmt->class->parts[0], ['self', 'static', 'parent'])) {
                 $fq_class_name = ClassLikeChecker::getFQCLNFromNameObject(
@@ -336,6 +339,7 @@ class CallChecker
                     case 'static':
                         // @todo maybe we can do better here
                         $fq_class_name = $context->self;
+                        $late_static = true;
                         break;
                 }
             }
@@ -351,9 +355,24 @@ class CallChecker
 
             if (strtolower($fq_class_name) !== 'stdclass' &&
                 $context->check_classes &&
-                ClassChecker::classExists($fq_class_name, $file_checker) &&
-                MethodChecker::methodExists($fq_class_name . '::__construct')
+                ClassChecker::classExists($fq_class_name, $file_checker)
             ) {
+                $storage = ClassLikeChecker::$storage[strtolower($fq_class_name)];
+
+                // if we're not calling this constructor via new static()
+                if ($storage->abstract && !$late_static) {
+                    if (IssueBuffer::accepts(
+                        new AbstractInstantiation(
+                            'Unable to instantiate a abstract class ' . $fq_class_name,
+                            new CodeLocation($statements_checker->getSource(), $stmt)
+                        ),
+                        $statements_checker->getSuppressedIssues()
+                    )) {
+                        return false;
+                    }
+                }
+
+                if (MethodChecker::methodExists($fq_class_name . '::__construct')) {
                     $method_id = $fq_class_name . '::__construct';
 
                     $method_params = FunctionLikeChecker::getMethodParamsById($method_id, $stmt->args, $file_checker);
@@ -432,6 +451,7 @@ class CallChecker
                     }
                 }
             }
+        }
 
         return null;
     }

src/Psalm/Issue/AbstractInstantiation.php

@@ -0,0 +1,6 @@
+<?php
+namespace Psalm\Issue;
+
+class AbstractInstantiation extends CodeError
+{
+}

src/Psalm/Storage/ClassLikeStorage.php

@@ -89,6 +89,11 @@ class ClassLikeStorage
      */
     public $line_number;
 
+    /**
+     * @var bool
+     */
+    public $abstract = false;
+
     /**
      * @var array<string, bool>
      */

tests/ClassTest.php

@@ -515,4 +515,21 @@ class ClassTest extends PHPUnit_Framework_TestCase
         $context = new Context();
         $file_checker->visitAndAnalyzeMethods($context);
     }
+
+    /**
+     * @expectedException        \Psalm\Exception\CodeException
+     * @expectedExceptionMessage AbstractInstantiation
+     * @return                   void
+     */
+    public function testAbstractClassInstantiation()
+    {
+        $stmts = self::$parser->parse('<?php
+        abstract class A {}
+        new A();
+        ');
+
+        $file_checker = new FileChecker('somefile.php', $this->project_checker, $stmts);
+        $context = new Context();
+        $file_checker->visitAndAnalyzeMethods($context);
+    }
 }