From 470885e4f1c366d769660471a60d25f64902cd87 Mon Sep 17 00:00:00 2001
From: someniatko <someniatko@gmail.com>
Date: Tue, 12 Jul 2022 13:43:53 +0300
Subject: [PATCH] #8200 - improve inferring the "final" `static` type when
 calling static methods inside a different class

differentiate between `static` defined in a class which CALLS a given static method, and `static` defined in the method which IS CALLED.
---
 .../ExistingAtomicStaticCallAnalyzer.php      | 34 +++++++++++
 tests/Template/Issue8200Test.php              | 58 +++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 tests/Template/Issue8200Test.php

diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/StaticMethod/ExistingAtomicStaticCallAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/StaticMethod/ExistingAtomicStaticCallAnalyzer.php
index 7855200e95e..d8af9168d55 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/StaticMethod/ExistingAtomicStaticCallAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/StaticMethod/ExistingAtomicStaticCallAnalyzer.php
@@ -551,6 +551,18 @@ private static function getMethodReturnType(
             ) {
                 $static_type = $context->self;
                 $context_final = $codebase->classlike_storage_provider->get($context->self)->final;
+            } elseif ($context->calling_method_id !== null) {
+                $self_method_return = $codebase->methods->getMethodReturnType(
+                    MethodIdentifier::fromMethodIdReference($context->calling_method_id),
+                    $context->self
+                );
+                // differentiate between these cases:
+                //   1. "static" in return type comes from return type of the
+                //   method CALLING the currently analyzed static method - use $context->self.
+                //   2. "static" comes from the CALLED static method - use $fq_class_name.
+                $static_type = $self_method_return !== null && self::hasStaticInType($self_method_return)
+                    ? $context->self
+                    : $fq_class_name;
             } else {
                 $static_type = $fq_class_name;
             }
@@ -613,4 +625,26 @@ private static function getMethodReturnType(
 
         return $return_type_candidate;
     }
+
+    /**
+     * Dumb way to determine whether a type contains "static" somewhere inside.
+     */
+    private static function hasStaticInType(Union $union_type): bool
+    {
+        foreach ($union_type->getAtomicTypes() as $atomic_type) {
+            if ($atomic_type instanceof Atomic\TGenericObject) {
+                foreach ($atomic_type->type_params as $type_param) {
+                    if (self::hasStaticInType($type_param)) {
+                        return true;
+                    }
+                }
+            } elseif ($atomic_type instanceof TNamedObject) {
+                if ($atomic_type->value === 'static') {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
 }
diff --git a/tests/Template/Issue8200Test.php b/tests/Template/Issue8200Test.php
new file mode 100644
index 00000000000..a20b5fa7507
--- /dev/null
+++ b/tests/Template/Issue8200Test.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace Psalm\Tests\Template;
+
+use Psalm\Tests\TestCase;
+use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
+
+class Issue8200Test extends TestCase
+{
+    use ValidCodeAnalysisTestTrait;
+
+    /**
+     * @return iterable<string,array{string,assertions?:array<string,string>,error_levels?:string[]}>
+     */
+    public function providerValidCodeParse(): iterable
+    {
+        return [
+            'return TemplatedClass<static>' => [
+                '<?php
+
+                /**
+                 * @template-covariant A
+                 * @psalm-immutable
+                 */
+                final class Maybe
+                {
+                    /**
+                     * @param null|A $value
+                     */
+                    public function __construct(private $value = null) {}
+
+                    /**
+                     * @template B
+                     * @param B $value
+                     * @return Maybe<B>
+                     *
+                     * @psalm-pure
+                     */
+                    public static function just($value): self
+                    {
+                        return new self($value);
+                    }
+                }
+
+                abstract class Test
+                {
+                    final private function __construct() {}
+
+                    /** @return Maybe<static> */
+                    final public static function create(): Maybe
+                    {
+                        return Maybe::just(new static());
+                    }
+                }',
+            ],
+        ];
+    }
+}