Fix method_exists($this) false positives in traits and PHP 7.4 lint

Add early return for method_exists() with $this-dependent expressions
in trait context, and add // lint >= 8.0 comment to bug-13023 test
file for nullsafe operator compatibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -183,18 +183,6 @@ public function testImpossibleCheckTypeFunctionCall(): void
 					'Call to function method_exists() with CheckTypeFunctionCall\MethodExists and \'testWithNewObjectIn…\' will always evaluate to true.',
 					635,
 				],
-				[
-					'Call to function method_exists() with $this(CheckTypeFunctionCall\MethodExistsWithTrait) and \'method\' will always evaluate to true.',
-					650,
-				],
-				[
-					'Call to function method_exists() with $this(CheckTypeFunctionCall\MethodExistsWithTrait) and \'someAnother\' will always evaluate to true.',
-					653,
-				],
-				[
-					'Call to function method_exists() with $this(CheckTypeFunctionCall\MethodExistsWithTrait) and \'unknown\' will always evaluate to false.',
-					656,
-				],
 				[
 					'Call to function method_exists() with \'CheckTypeFunctionCall\\\\MethodExistsWithTrait\' and \'method\' will always evaluate to true.',
 					659,
@@ -1213,4 +1201,37 @@ public function testBug13023(): void
 		$this->analyse([__DIR__ . '/data/bug-13023.php'], []);
 	}
 
+	public function testBug7599(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-7599.php'], [
+			[
+				'Call to function method_exists() with Bug7599\SecondEnum::Baz and \'barMethod\' will always evaluate to true.',
+				13,
+			],
+			[
+				'Call to function method_exists() with Bug7599\TestEnum::Bar|Bug7599\TestEnum::Foo and \'barMethod\' will always evaluate to false.',
+				13,
+			],
+		]);
+	}
+
+	public function testBug9095(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-9095.php'], []);
+	}
+
+	public function testBug13474(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-13474.php'], []);
+	}
+
+	public function testBug13687(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-13687.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-13023.php

@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug13023;