Report abstract method overriding non-abstract method in OverridingMethodRule and OverridingPropertyRule

[phpstan-bot]

Summary

PHP forbids making a non-abstract method abstract in a child class (it's a fatal error), but PHPStan did not report this. This PR adds the check in both OverridingMethodRule (for regular methods and constructors) and OverridingPropertyRule (for property hooks).

Changes

• src/Rules/Methods/OverridingMethodRule.php: Added abstract-overriding-non-abstract check in two places:
  • In the main prototype check path (handles regular methods, static methods, protected methods, multi-level inheritance)
  • In the constructor-specific $prototypeData === null path, since MethodPrototypeFinder intentionally skips non-abstract constructor prototypes
• src/Rules/Properties/OverridingPropertyRule.php: Added per-hook abstract-overriding-non-abstract check within the supportsPropertyHooks() block. When a child property is declared abstract and the prototype property has concrete hooks, each matching hook type is reported individually (matching PHP's per-hook error behavior).
• Both errors use ->nonIgnorable() as instructed in the issue comments.
• New error identifiers: method.abstractOverridingNonAbstract and property.abstractOverridingNonAbstractHook

Root cause

OverridingMethodRule checked for final methods, static/non-static mismatches, visibility changes, parameter contravariance, and return type covariance — but never checked whether an abstract method was trying to override a non-abstract one. The same gap existed in OverridingPropertyRule for property hooks.

Analogous cases probed

• Constructors: PHP also forbids abstract constructors overriding non-abstract ones. MethodPrototypeFinder skips non-abstract constructor prototypes (by design, for signature compatibility), so the check was added separately in the constructor handling branch. ✅ Fixed
• Trait abstract methods: PHP allows a trait's abstract method to coexist with a concrete inherited method — no error needed. ✅ Verified (no fix needed)
• Interface methods: All interface methods are abstract, so an interface extending another interface can't trigger this. ✅ Verified (not applicable)
• Non-hooked properties overridden by abstract hooked properties: PHP allows public int $x; to be overridden by abstract public int $x { get; } — no error needed. ✅ Verified (no fix needed)

Test

• tests/PHPStan/Rules/Methods/data/bug-14457.php — Regression test for abstract method overriding non-abstract, covering: basic case, static methods, protected methods, multi-level inheritance, constructors, and OK cases (abstract→abstract, concrete→concrete, concrete→abstract).
• tests/PHPStan/Rules/Properties/data/bug-14457.php — Regression test for abstract property hooks overriding non-abstract hooks, covering: get hook, set hook, both hooks, and OK cases (abstract→abstract, concrete→abstract, concrete→concrete).

Fixes phpstan/phpstan#14457

[ondrejmirtes]

1. tests/PHPStan/Rules/Properties/data/bug-14457.php needs to be excluded from make lint in Makefile
2. There are escaped mutants https://github.com/phpstan/phpstan-src/actions/runs/26278594657/job/77349482802?pr=5730 which means more tests have to be added

[phpstan-bot]

Pushed. Here's what was done to address the review:

1. Lint exclusion: Added --exclude tests/PHPStan/Rules/Properties/data/bug-14457.php to the Makefile lint target, since that file uses PHP 8.4 property hooks syntax that parallel-lint can't parse.

2. Escaped mutant fix: Changed !$prototype->isAbstract()->yes() to $prototype->isAbstract()->no() in OverridingPropertyRule.php:181. The TrinaryLogicMutator was mutating !->yes() to ->no() — which is semantically identical for PhpPropertyReflection (it always returns Yes or No, never Maybe), making the mutant unkillable by tests. With ->no() as the base code, the mutator will flip it to ->yes(), which IS distinguishable: when the prototype is abstract, ->yes() returns true (incorrectly entering the error branch), caught by the abstract→abstract test case.