avoid SpecifiedTypes allocation in setRootExpr when unchanged

[SanderMuller]

Problem

SpecifiedTypes::setRootExpr() is called on the return value of nearly every specifyTypesInCondition() call in TypeSpecifier. Each call allocates a new SpecifiedTypes object, even when the root expression is already the same object.

Since specifyTypesInCondition recurses through the AST and calls setRootExpr($expr) at each level, inner calls often set the root to a node that an outer call then overwrites with the same node again. The same Expr object reference is passed down and back up the call chain, so identity (===) is the right check here.

Solution

public function setRootExpr(?Expr $rootExpr): self
{
    if ($this->rootExpr === $rootExpr) {
        return $this;
    }
    // ... existing allocation
}

Impact

CI benchmark results to follow.

[phpstan-bot]

You've opened the pull request against the latest branch 2.2.x. PHPStan 2.2 is not going to be released for months. If your code is relevant on 2.1.x and you want it to be released sooner, please rebase your pull request and change its target to 2.1.x.