Do not let method_exists() check fall through to general logic when object type contains template types

- When the specific `method_exists` handling in `ImpossibleCheckTypeHelper` cannot
  determine the result (no concrete class names, no GenericClassStringType), it falls
  through to the general type specifier logic
- The general logic uses `HasMethodType::isSuperTypeOf()` which calls `hasMethod()` on
  the argument type; for `object&T` where T is a TemplateMixedType, this returns Yes
  (inherited from MixedType), causing a false positive "will always evaluate to true"
- Add early `return null` when `$objectType->hasTemplateOrLateResolvableType()` is true,
  preventing the general logic from running on types where method existence is uncertain
- Verified analogous cases: `property_exists` is not affected (its type specifying
  extension returns empty SpecifiedTypes for non-native properties); `is_callable` is
  not affected; `class-string<T>` template bounds are correctly handled by the existing
  GenericClassStringType block

Author: VincentLanglet

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -242,6 +242,10 @@ public function findSpecifiedType(
 								return false;
 							}
 						}
+
+						if ($objectType->hasTemplateOrLateResolvableType()) {
+							return null;
+						}
 					}
 				}
 			}

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -1224,4 +1224,10 @@ public function testBug12063(): void
 		$this->analyse([__DIR__ . '/data/bug-12063.php'], []);
 	}
 
+	public function testBug8217(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-8217.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-8217.php

@@ -0,0 +1,18 @@
+<?php declare(strict_types = 1);
+
+namespace Bug8217;
+
+class HelloWorld
+{
+	/**
+	 * @template T
+	 *
+	 * @param T $object
+	 */
+	public static function check($object): void
+	{
+		if (is_object($object) && method_exists($object, 'method')) {
+			echo 1;
+		}
+	}
+}