Still report method_exists($this) as always true when method is defined in the trait

When a trait defines a method itself, method_exists($this, 'method') will
always be true regardless of which class uses the trait. Only suppress the
report when the method is NOT defined in the trait, since then the result
depends on the using class.

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

Author: phpstan-bot

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -200,7 +200,16 @@ public function findSpecifiedType(
 					$objectArg = $args[0]->value;
 
 					if ($scope->isInTrait() && ExpressionDependsOnThisHelper::isExpressionDependentOnThis($objectArg)) {
-						return null;
+						$traitReflection = $scope->getTraitReflection();
+						$methodArgValue = $args[1]->value;
+						$methodArgType = $this->treatPhpDocTypesAsCertain ? $scope->getType($methodArgValue) : $scope->getNativeType($methodArgValue);
+						$constantMethodNames = $methodArgType->getConstantStrings();
+						if (
+							count($constantMethodNames) !== 1
+							|| !$traitReflection->hasNativeMethod($constantMethodNames[0]->getValue())
+						) {
+							return null;
+						}
 					}
 					$objectType = $this->treatPhpDocTypesAsCertain ? $scope->getType($objectArg) : $scope->getNativeType($objectArg);
 

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -183,6 +183,10 @@ 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 \'CheckTypeFunctionCall\\\\MethodExistsWithTrait\' and \'method\' will always evaluate to true.',
 					659,