Do not remember readonly properties' constructor-narrowed types in other methods when clone with is available (PHP 8.5)

[phpstan-bot]

Summary

On PHP 8.5, the new clone with syntax (clone($obj, ['prop' => $value])) can
reinitialize readonly properties. PHPStan reported a false positive
Strict comparison using !== between null and null will always evaluate to false
for a readonly property that was assigned null in the constructor but later
reinitialized through clone with:

readonly class CoffeeBreak
{
    public ?int $durationInMinutes;

    public function __construct(public string $name) {
        $this->durationInMinutes = null;
    }

    public function setDuration(): self {
        return clone($this, ['durationInMinutes' => 15]);
    }

    public function hasDuration(): bool {
        return $this->durationInMinutes !== null; // wrongly reported as always false
    }
}

The fix stops remembering a readonly property's constructor-narrowed value in
other methods when clone with is available, so the property widens back to its
declared type (?int here).

Changes

• src/Analyser/MutatingScope.php — rememberConstructorExpressions() no longer
  carries readonly PropertyFetch types into other methods when
  getPhpVersion()->supportsCloneWith() is not no(). The check uses the
  scope-narrowable Scope::getPhpVersion() so it honors an enclosing
  if (PHP_VERSION_ID >= 80500).
• src/Php/PhpVersions.php — added supportsCloneWith(): TrinaryLogic (>= 8.5).
• tests/PHPStan/Analyser/nsrt/bug-14838.php — new regression test (the issue's
  reproducer).
• Updated existing tests that relied on readonly constructor remembering to
  assert the widened types under PHP 8.5 via PHP_VERSION_ID branches:
  bug-12902.php, bug-12902-non-strict.php,
  remember-non-nullable-property-non-strict.php,
  remember-readonly-constructor-narrowed.php,
  remember-readonly-constructor-narrowed-hooks.php.

Root cause

MutatingScope::rememberConstructorExpressions() keeps the constructor's
narrowed types of readonly property fetches (e.g. null, 4|10,
class-string) and makes them visible in every other method, because before PHP
8.5 a readonly property could not change after construction.

clone with breaks that invariant: clone($obj, ['prop' => $value])
reinitializes the property and produces a new instance. That instance can be
returned and have its methods called, so inside any instance method $this may
be a clone-modified object whose readonly property differs from the constructor
value. This is true even for private readonly properties, since the
declaring class itself can run clone with on them. Remembering the constructor
value is therefore unsound on PHP 8.5, and the fix widens readonly properties
back to their declared type there. Pre-8.5 behavior is unchanged.

Probed but intentionally out of scope

A __clone() method that reinitializes a readonly property (allowed since PHP
8.3) can produce the same kind of stale narrowing on 8.3/8.4. Fixing that
soundly would require either widening all readonly remembering on 8.3+
(a large precision regression — there are deliberate tests asserting narrowed
readonly values from 8.2 onward) or per-property analysis of __clone bodies at
remember-time (a much larger change). Since clone with makes the unsoundness
universal and unconditional on 8.5, this PR scopes the fix to 8.5, where the
trade-off is unambiguous. The sibling closure-capture and
method-call-invalidation paths for readonly properties were also checked and are
sound on 8.5 (they reason about the current $this, which clone with does not
mutate).

Test

• nsrt/bug-14838.php (// lint >= 8.5) reproduces the report: on PHP 8.5
  $this->durationInMinutes is int|null (not null), so the comparison is no
  longer reported as always-false.
• The updated remember-* / bug-12902* tests assert, via
  if (PHP_VERSION_ID >= 80500) { … } else { … }, that readonly properties
  widen to their declared type on PHP 8.5 while keeping the narrowed type on
  older versions. These branches are exercised and were confirmed to fail
  without the source fix.

Fixes phpstan/phpstan#14838