add stubs for min/max (#5353)

src/Psalm/Internal/Provider/FunctionReturnTypeProvider.php

@@ -68,6 +68,7 @@ class FunctionReturnTypeProvider
         $this->registerClass(ReturnTypeProvider\GetClassMethodsReturnTypeProvider::class);
         $this->registerClass(ReturnTypeProvider\FirstArgStringReturnTypeProvider::class);
         $this->registerClass(ReturnTypeProvider\HexdecReturnTypeProvider::class);
+        $this->registerClass(ReturnTypeProvider\MinMaxReturnTypeProvider::class);
     }
 
     /**

src/Psalm/Internal/Provider/ReturnTypeProvider/MinMaxReturnTypeProvider.php

@@ -0,0 +1,57 @@
+<?php declare(strict_types=1);
+
+namespace Psalm\Internal\Provider\ReturnTypeProvider;
+
+use Psalm\Plugin\EventHandler\Event\FunctionReturnTypeProviderEvent;
+use Psalm\Plugin\EventHandler\FunctionReturnTypeProviderInterface;
+use function count;
+use Psalm\Internal\Type\ArrayType;
+use Psalm\Type;
+
+class MinMaxReturnTypeProvider implements FunctionReturnTypeProviderInterface
+{
+    /**
+     * @return array<lowercase-string>
+     */
+    public static function getFunctionIds(): array
+    {
+        return ['min', 'max'];
+    }
+
+    public static function getFunctionReturnType(FunctionReturnTypeProviderEvent $event): ?Type\Union
+    {
+        $call_args = $event->getCallArgs();
+        if (count($call_args) === 0) {
+            return null;
+        }
+
+        $statements_source = $event->getStatementsSource();
+        $nodeTypeProvider = $statements_source->getNodeTypeProvider();
+
+        if (count($call_args) === 1
+            && ($array_arg_type = $nodeTypeProvider->getType($call_args[0]->value))
+            && $array_arg_type->isSingle()
+            && $array_arg_type->hasArray()
+            && ($array_type = ArrayType::infer($array_arg_type->getAtomicTypes()['array']))
+        ) {
+            return $array_type->value;
+        }
+
+        $atomics = [];
+        foreach ($call_args as $arg) {
+            if ($array_arg_type = $nodeTypeProvider->getType($arg->value)) {
+                foreach ($array_arg_type->getAtomicTypes() as $atomicType) {
+                    $atomics[] = $atomicType;
+                }
+            } else {
+                return Type::getMixed();
+            }
+        }
+
+        if ($atomics === []) {
+            return Type::getMixed();
+        }
+
+        return new Type\Union($atomics);
+    }
+}

tests/FunctionCallTest.php

@@ -1530,6 +1530,29 @@ class FunctionCallTest extends TestCase
                 [],
                 '8.0'
             ],
+            'maxWithFloats' => [
+                '<?php
+                    function foo(float $_float): void
+                    {}
+
+                    foo(max(1.1, 1.2));',
+            ],
+            'maxWithObjects' => [
+                '<?php
+                    function foo(DateTimeImmutable $fooDate): string
+                    {
+                        return $fooDate->format("Y");
+                    }
+
+                    foo(max(new DateTimeImmutable(), new DateTimeImmutable()));',
+            ],
+            'maxWithMisc' => [
+                '<?php
+                    $a = max(new DateTimeImmutable(), 1.2);',
+                [
+                    '$a' => 'DateTimeImmutable|float',
+                ],
+            ],
         ];
     }
 
@@ -2055,6 +2078,13 @@ class FunctionCallTest extends TestCase
                     }',
                 'error_message' => 'InvalidReturnStatement'
             ],
+            'maxWithMixed' => [
+                '<?php
+                    /** @var mixed $b */;
+                    /** @var mixed $c */;
+                    $a = max($b, $c);',
+                'error_message' => 'MixedAssignment'
+            ],
         ];
     }
 }