Suppress property.nonObject and method.nonObject errors when property_exists()/method_exists() guard is present

[phpstan-bot]

Summary

When property_exists($mixed, 'prop') is used as a guard and then $mixed->prop is accessed, PHPStan incorrectly reported "Cannot access property $prop on class-string|object." This happened because property_exists() narrows mixed to class-string|(object&hasProperty(prop)), and the class-string member of the union causes canAccessProperties() to return maybe(), triggering the property.nonObject error. The same issue existed for method_exists() with canCallMethods().

PR #5544 added property_exists() guard handling in AccessStaticPropertiesCheck but missed the instance property access case in AccessPropertiesCheck, and also missed the analogous method_exists() case in MethodCallCheck.

Changes

• src/Type/Php/PropertyExistsTypeSpecifyingExtension.php: In the !isObject()->yes() branch, also store the property_exists() call result as true (via createFuncCallSpec) in addition to narrowing the argument type. This enables synthetic call checks to find the stored specification.
• src/Type/Php/MethodExistsTypeSpecifyingExtension.php: Same fix for the generic (non-string) branch.
• src/Rules/Properties/AccessPropertiesCheck.php: Add a synthetic property_exists() call check before the canAccessProperties() error (line 122). Also extend the existing property_exists() guard check for undefined properties (previously only handled Expr names) to also handle Identifier names by constructing a String_ node.
• src/Rules/Methods/MethodCallCheck.php: Add a synthetic method_exists() call check before the canCallMethods() error. Also extend the existing method_exists() guard check for undefined methods to handle Identifier names.
• tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php: Remove the assertion for the now-suppressed false positive "Cannot call method foo() on class-string|object."

Analogous cases probed

• Static property access (AccessStaticPropertiesCheck): Already fixed by PR Suppress undefined static property error when property_exists() guard is present #5544. Verified no regression.
• Property access in assignment (AccessPropertiesInAssignRule): Uses AccessPropertiesCheck, automatically covered. Added dedicated test.
• Object-type branch in type specifiers: When the first argument IS already an object, the narrowed type is object&hasProperty(prop) (no class-string union), so canAccessProperties() returns yes() and no false positive occurs. No fix needed.
• Static method calls (CallStaticMethodsRule): Not affected — static method calls on class-strings are valid PHP and handled differently.

Root cause

Two independent issues combined to produce the false positive:

1. PropertyExistsTypeSpecifyingExtension (and MethodExistsTypeSpecifyingExtension) narrowed the argument type for mixed to class-string|(object&hasProperty(…)) but did NOT store the function call result as true. This meant synthetic property_exists()/method_exists() call checks in rule code could not detect the guard.

2. AccessPropertiesCheck (and MethodCallCheck) did not check for property_exists()/method_exists() guards before reporting the canAccessProperties()/canCallMethods() error. The existing guard checks only applied to the "undefined property/method" errors and only for dynamic (Expr) names.

Test

• tests/PHPStan/Rules/Properties/data/bug-14667.php — Tests instance property access after property_exists() with mixed, explicit mixed, object|string, object, $this, self, and chained conditions.
• tests/PHPStan/Rules/Properties/data/bug-14667-assign.php — Tests property assignment after property_exists() with mixed, explicit mixed, and object|string.
• tests/PHPStan/Analyser/nsrt/bug-14667.php — Verifies type narrowing produces class-string|(object&hasProperty(prop)) for mixed.
• tests/PHPStan/Rules/Methods/data/bug-14667.php — Tests method call after method_exists() with mixed, explicit mixed, object|string, object, and chained conditions.

Fixes phpstan/phpstan#14667