Add support for $a::class

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

@@ -90,9 +90,9 @@ class ConstFetchAnalyzer
     ) {
         $codebase = $statements_analyzer->getCodebase();
 
-        if (($context->check_consts
+        if ($stmt->class instanceof PhpParser\Node\Name) {
-                || ($stmt->name instanceof PhpParser\Node\Identifier && $stmt->name->name === 'class'))
+            if ($context->check_consts
-            && $stmt->class instanceof PhpParser\Node\Name
+                || ($stmt->name instanceof PhpParser\Node\Identifier && $stmt->name->name === 'class')
             ) {
                 $first_part_lc = strtolower($stmt->class->parts[0]);
 
@@ -258,6 +258,16 @@ class ConstFetchAnalyzer
 
                 return null;
             }
+        } elseif ($stmt->name instanceof PhpParser\Node\Identifier && $stmt->name->name === 'class') {
+            ExpressionAnalyzer::analyze($statements_analyzer, $stmt->class, $context);
+            $lhs_type = $stmt->class->inferredType;
+
+            $stmt->inferredType = new Type\Union([
+                new Type\Atomic\TClassString('object', $lhs_type)
+            ]);
+
+            return;
+        }
 
         $stmt->inferredType = Type::getMixed();
 

tests/ClassStringTest.php

@@ -311,6 +311,47 @@ class ClassStringTest extends TestCase
 
                     foo(AChild::class);',
             ],
+            'returnClassConstantClassStringParameterized' => [
+                '<?php
+                    class A {}
+
+                    /**
+                     * @return class-string<A> $s
+                     */
+                    function foo(A $a) : string {
+                        return $a::class;
+                    }',
+            ],
+            'returnGetClassClassStringParameterized' => [
+                '<?php
+                    class A {}
+
+                    /**
+                     * @return class-string<A> $s
+                     */
+                    function foo(A $a) : string {
+                        return get_class($a);
+                    }',
+            ],
+            'createClassOfTypeFromString' => [
+                '<?php
+                    class A {}
+
+                    /**
+                     * @return class-string<A> $s
+                     */
+                    function foo(string $s) : string {
+                        if (!class_exists($s)) {
+                            throw new \UnexpectedValueException("bad");
+                        }
+
+                        if (!is_a($s, A::class, true)) {
+                            throw new \UnexpectedValueException("bad");
+                        }
+
+                        return $s;
+                    }',
+            ],
         ];
     }
 
@@ -428,6 +469,27 @@ class ClassStringTest extends TestCase
                     foo(AChild::class);',
                 'error_message' => 'InvalidArgument',
             ],
+            'createClassOfWrongTypeFromString' => [
+                '<?php
+                    class A {}
+                    class B {}
+
+                    /**
+                     * @return class-string<A> $s
+                     */
+                    function foo(string $s) : string {
+                        if (!class_exists($s)) {
+                            throw new \UnexpectedValueException("bad");
+                        }
+
+                        if (!is_a($s, B::class, true)) {
+                            throw new \UnexpectedValueException("bad");
+                        }
+
+                        return $s;
+                    }',
+                'error_message' => 'InvalidReturnStatement',
+            ],
         ];
     }
 }